ISJCIE V1I1

ISJCIE is dedicated to the publication of cutting-edge research in the following scope:

1. Structural loading, health monitoring, and strengthening area:

• Design of civil infrastructure and lifelines to withstand wind, tropical cyclones, thunderstorms, and tornadoes.

• Construction material behaviour at high temperatures and analysis of whole structure behaviour under fire impacts

• Foundation design for earthquake loading and Lifelines earthquake engineering.

• Monitoring of structural repairs and development of self-repairable structures

• Condition assessments and condition-based maintenance and performance;

• Sensor network design, data transmission, wired and wireless communication; Self-powered and low power sensors technology and management.

• Seismic response of buildings, bridges, and other special structures; Rehabilitation of the constructed heritage, Rehabilitation of coastal structures

• Structural pathologies and diagnostic methodological approach; In-situ sensors, corrosion sensors, and sensors for local damage detection

• Integration of structural health monitoring and control, Fire risk analysis, numerical modeling, and protection systems

• Advanced inspection, testing, and non-destructive methodologies; Performance assessment, safety evaluation, and scour indicators

• Advanced signal processing and interpretation techniques, Multi-functional materials and new sensor materials

• Monitoring of aging structures and infrastructure, Adaptive rehabilitation, and rehabilitation technologies

• Seismic retrofitting, repair, and strengthening methods, Load capacity ratings and service life estimations.

• Building performance simulation and durability, Sensor/structure integration technology

• Optical fibre sensors for health monitoring, Monitoring of high-rise buildings and bridges

• Passive, active, and semi-active controls, Remote control of monitoring systems

• Implementation of structural monitoring, Seismic vulnerability, and loss assessment

• Durability issues in harsh environments, Sensors for high-temperature applications

• Dynamic stability and progressive collapse, Data mining and data management

• Vibration and wave propagation methods, Artificial intelligence tools, Solidification, and stabilization

• FRP composites, Codes of Practice and Design, Facade material and design, Case studies

2. Advanced concrete technology area:

• Concrete waste management, recycling, and environmental aspects, Material properties and development of new materials

• Failure mechanism and concrete health monitoring, Microstructural characterization of concrete

• Concrete admixtures, mixers, and sealers, Fibre-reinforced concrete technology, Fresh and hardened concrete

• High-performance concrete, Aesthetics of concrete, Durability, and repair, LCC, SDC, and SCC, Cement accelerator

• Concrete cancer, Concrete leveling, Test methods, Case studies.

3. Advanced geotechnical engineering area:

• Finite element modeling of saturated/unsaturated geotechnical systems/materials

• Soil improvement techniques and modification by inclusions and confinement; Dynamic soil-structure interaction and pipeline-soil interaction

• Underground structures, tunnels, and trenchless construction, Soil classification, exploration, and laboratory testing

• Soil dynamics and geotechnical earthquake engineering, Geotechnical site investigation and instrumentation

• Numerical simulation of multiphase porous media, Computer applications in geotechnical engineering

• Geotechnics for road and railway transportation, Computer applications in geotechnical engineering

• Slope stability, landslides, and retaining walls, Recycled wastes & lightweight geomaterials.

• Earthquake-resistant design of foundations, Numerical analysis of suction caissons

• Sensor-Enabled Geosynthetics (SEG), Seepage and dewatering systems; Soil bearing capacity and foundation settlements.

• Limit state design of foundations, Erosion and deterioration, Deep foundations / Pile foundation

• Unsaturated soil mechanics, Geotechnical aspects of landfills, Geo-environmental engineering

• Computational geomechanics, Constitutive modeling, Dam, and marine geotechnics

• Computational poromechanics, Soft soil engineering, Liquefaction analysis, Soil-Bio interactions

• Creep of clayey soils, Probabilistic approaches, Geohazards, Offshore Foundations, Centrifuge model tests

• Reliability design for foundations, Local site effects, microzonation, Field seismic testing, Rock mechanics; Cemented soils, Expansive soils, Case studies.

4. Offsite manufacturing and digital construction area:

• Sustainable construction, Construction issues in modular systems and planning of modular building

• Types of modular construction and application of modular systems; Environmental concerns, Renovation of buildings, Case studies

• Smart construction (3D printing, artificial intelligence, robotics); Precast concrete modules and hybrid modular construction systems

• Prefabrication forms, designing, process, and formwork systems; Factory production of modules, automation, and field factory.

• Technological forecasting and strategic planning, Intelligent decision support systems

• Information technologies in construction and BIM, Constructions management and technology

• Construction law and legal issues in construction, Construction life cycle / Construction materials

• Construction economics and cost control, procurement and equipment; Acoustic insulation and structural design of modular construction

• Tolerances; related codes and standards, Built environment, Inspection methods, Contract administration

• Specifications and quality control, Scheduling and estimating, Value engineering and optimization.

Welcome to the "International Scientific Journal of Civil and Infrastructure Engineering (ISJCIE)" This journal is a quarterly international peer-reviewed openaccess journal that publishes high-quality single-blind peer-reviewed papers in the civil and infrastructure engineering field. We publish the latest international research studies as fast as possible and encourage postgraduate students and top researchers to publish their experimental and numerical studies with us.

When we receive a paper, it is checked for originality and the contents to ensure the work is not published under similar titles. Then chief editor sends the article to one of the editorial board members, who are responsible for finding two reviewers for review. After receiving reviewers' comments, if some corrections are needed, reviewers' comments are sent to the author(s) to make corrections within the specified time. This process continues until the article is either rejected or approved. Once a paper is accepted, its online version will be published quickly. Any online paper would have a unique DOI number to ensure other researchers can cite it. Authors keep possession of the copyright for their papers but permit anyone to download, reuse, reprint, modify, distribute, and copy the content as long as the original authors and source are cited. Everybody can access the full text of the published articles in PDF format without restriction. The "International Scientific Journal of Civil and Infrastructure Engineering (ISJCIE)" is dedicated to the publication of cutting-edge research in all civil engineering scopes.

Dr. Saeed Nemati Coordinator Chief Editor and Founder

in this issue:

• Combined Effects of Waste Glass and Nano-Silica Powder on Workability, Durability, and Mechanical Properties of Fiber-Reinforced Self-Compacting Mortar …1

• Durability Plan for Coastline Concrete Structures and Design Considerations under Aggressive Environment Conditions……………………………………………………………….………………14

• ANN Model to Damage Detection of Steel Bridge Based on Signal Processing…………….35

• Numerical and Experimental Study on a Creative Concrete Pressure Reduction System (CPRS)……………………………………………………………………………………………………………………..…….46

• Optimisation of In-Vessel Composting of Municipal Solid Wastes (MSW) 59

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International Scientific Journal of Civil and Infrastructure Engineering (ISJCIE)

ISSN 2298-8168 https://doi.org/10.56601/ISJCIE

Board of Chief Editors:

• Superior Chief Editor: Prof. Bijan Samali, Western Sydney University, Australia

• Coordinator Chief Editor and Founder: Dr. Saeed Nemati, CIVILICOM, Australia

• Chief Editor, Geotechnical Eng Discipline: Prof. Hadi Khabbaz, University of Technology, Sydney, Australia

• Chief Editor, Structural Eng Discipline: A/Prof. Shami Nejadi, University of Technology, Sydney, Australia

• Chief Editor, Manufacturing and Cons Discipline: Dr. Pejman Sharafi, Western Sydney University, Australia

Editorial Board Members (alphabetical order):

• Dr. Yahya Aliabadizadeh, The Catholic University of America, USA

• Dr. Alireza Ahangar Asr, University of Salford, UK

• A/Prof. Farhad Aslani, University of Western Australia, Australia

• Dr. Hoss Bineshian, Amberg Engineering, Australia

• Prof. Domenico Brigante, OLYMPUS, Italy

• Dr. Mostafa B. Jelodar, Massey University, New Zealand

• Dr. Ali Delnavaz, QAI University, IR

• Prof. Hormoz Family, University of Science and Technology, IR

• A/Prof. Amirhosein Ghaffarian Hoseini, Auckland University of Technology, New Zealand

• Dr. Shahin Ghanooni, ABuild Consulting Engineers, New Zealand

• Prof. Yaghoob Gholipour, Tehran University, IR

• Dr. Sadegh Ghourchian, Concrefy, Netherlands

• Prof. S. Mohsen Haeri, Sharif University of Technology, IR

• Dr. Farzad Hatami, Amirkabir University of Technology, IR

• A/Prof. Farshid J. Alaee, Shahrood University of Technology (SUT), IR

• Dr. Nima Khorsandnia, Van der Meer Consulting, Australia

• A/Prof. Mahdi Kioumarsi, Oslo Metropolitan University, Norway

• A/Prof. Nicolas A. Libre, University of Missouri, USA

• Dr. Mojtaba Mahmoodian, RMIT University, Australia

• A/Prof. Iraj H.P. Mamaghani, University of North Dakota, USA

• A/Prof. Abdoreza S. Moghadam, International Institute of Earthquake Engineering and Seismology, IR

• Dr. Masoud Moghaddasi, AECOM, Australia

• Emeritus Prof. Hamid Nikraz, Curtin University, Australia

• Dr. Ehsan Noroozinejad Farsangi, The University of British Columbia (UBC), CA

• A/Prof. Gozde Basak Ozturk, Aydin Adnan Menderes University, Turkey

• Eng. Pierre Palmberg, Northvolt AB, Sweden

• Dr. Francesco Pittau, Polytechnic University of Milan, Italy

• Prof. Alireza Rahai, Amirkabir University of Technology, IR

• Dr. Allen Rejaie, T.Y. Lin International, USA

• Dr. Cyrus Sadr Nafisi, K. N. Toosi University of Technology, IR

• Dr. Amin Sarang, Value Analysis Canada, CA

• Dr. Matthias Schueller, Parsons Corporation, CA

• Dr. Farzaneh Tahmoorian, Central Queensland University (CQU), Australia

• Dr. Mojtaba Tajziehchi, BMT, Australia

• Prof. Fariborz M. Tehrani, California State University, USA

• Dr. Efi Tzoura, Ferrovial, UK

• Prof. Konstantinos D. Tsavdaridis, City University of London, UK

• A/Professor Hamid Reza V. Goudarzi, University of New South Wales, Australia

• Dr. Ezgi (Yurdakul) Wilson, Transport for NSW, Australia

Combined Effects of Waste Glass and Nano-Silica Powder on Workability, Durability and Mechanical Properties of Fiber-Reinforced Self-Compacting Mortar

Maryam Monazami, Shahrood University of Technology, Iran

Farshid Jandaghi Alaee*, Shahrood University of Technology, Iran Ashkan Abedian, Shahrood University of Technology, Iran

* CorrespondingAuthor, fjalaee@shahroodut.ac.ir, Received: Aug 2022, Accepted: Sep 2022

ABSTRACT: This research aims to combine the effects of waste glass and Nano-silica powder on the properties of fiber-reinforced self- compacting mortar. A detailed study was undertaken to investigate the effect of different glass powder contents as cement replacement on the behavior of mortar. For this purpose, Portland cement was partially replaced by 10%, 15%, and 20% waste glass powder alone, and then in combination with 2% substitution levels for Nano-silica. The amount of water-binder ratio and cementitious materials content were considered constant. Fresh properties of specimens were determined using slump flow, and vfunnel flow time tests, mechanical properties were determined by compressive strength, and tensile strength tests, and durability characteristics evaluated by water absorption, and resistance to sulfuric acid attack. Microstructural morphology of specimens was also assessed by scanning electron microscopy. It was observed that the workability slightly decreased and improved mechanical and durability properties could be achieved. The SEM micrographs illustrated more densified pore structure of the mortars containing waste glass powder which leads to increase in strength and durability of specimens.

Keywords: Waste glass; Nano-silica; Durability; Mechanical properties; Workability; Selfcompacting mortar

1. Introduction

Glass waste is representing environmental problems all over the world. These materials occupy huge parts of the landfill spaces, due to the non-biodegradable nature of glass, and causing seriousenvironmentalpollutions. Also, the lackofspaces for new landfills is aproblem facing the dense population cities in different countries. The best solution to overcome over the environmentalimpact oftheseglasswastesistoreusethem.Thechemical compositionofwaste glass shows that glass has a large quantity of silicon and calcium and with amorphous structure; glass has the ability to be a pozzolanic or even a cementitious material [1].

Different studies have been made for the use of waste glass in cement and concrete industries. Some of these studies used waste glass as an aggregate; others used it as a cement replacement and some studies used it as aggregate and as a cement replacement in the same mixture. The use of waste glass as a coarse and fine aggregate in the production of concrete was very limited and did not show satisfactory results because of the alkali-silica destructive reaction between the cement and the waste glass aggregate and the low performance of the

Infrastructure, Construction, Concrete, Geotechnic, Earthquake, Environment.

produced concrete. It was found that the particle size of the waste glass aggregate is playing a vital role in alkali-silica harmful reaction [1].

Thepozzolanicproperties ofglassarousedtheidea ofusing thewasteglass as acementitious material or as partial replacement of cement in the production of concrete. The pozzolanic properties of glass are highly affected by the particle sizes of glass [2]. Different studies have been done to investigate the optimum particle size and percentage of waste glass that can be used as a partial replacement to cement to produce concrete. Table 1 shows a summary of some research for the use of waste glass as a partial replacement to cement.

Although considerable research has been devoted to the use of waste glass as an aggregate or as a cement replacement in traditional vibrated concrete (TVC), rather less attention has been paid to the use of waste glass in self-compacting concrete (SCC). Self-compacting concrete or self-consolidating concrete is highly flowable, non-segregating concrete that can spread into place, fill the formwork, and encapsulate the reinforcement without any mechanical consolidation [9]. Originally developed in Japan with the first significant applications in early 1990s, it has rapidly been adopted worldwide in construction [10].

SCC is composed of Portland cement, fine aggregate, coarse aggregate, water, chemical admixtures, and typically supplementary cementitious materials such as fly ash, slag, silica fume, and metakaolin. In some cases, mineral fillers such as limestone powder or very fine sands are used to increase the mixture's powder or fine material content. Aside from mineral fillers, the materials used to produce SCC are the same as those common to the production of conventional concrete [11]. In various parts of the world, different concepts might be followed for the proportioning of SCC and are referred to as 'powder-type SCC', 'viscosity-modifying admixture (VMA)-type SCC', or 'mixed-type SCC' [12].

It is the fresh, plastic properties of SCC that differentiate the material from conventional concrete. Workability of SCC is described in terms of filling ability (unconfined flowability), passing ability (confined flowability), and stability (segregation resistance), and is characterized by specific testing methods. For SCC, it is important to seek a combination of constituents that provide the mortar the appropriate yield stress for the application while maintaining adequate viscosity to ensure passing ability and segregation resistance [9]. As a result, it is attractive to consider the extent to which waste materials with suitable particle sizes can be incorporated.

Table 1 Summary of all the research for the use of waste glass as a partial replacement to cement [1]

In an attempt to enhance the knowledge of using waste materials in SCC, a detailed study was undertaken to investigate the effect of different glass powder contents as cement replacement on the behavior of mortar. The mechanical, physical and microstructural performances of mortars were investigated based on 10%, 15%, and 20% substitution levels for waste glass alone, and then in combination with 2% substitution levels for Nano- silica.

2. Experimental Program

2.1 Materials

The materials used in this study will be discussed in the following sections.

2.1.1

An ordinary type II Portland cement that complies with the requirements of specification

ASTM C150 [13] was used as a testing cement. Table 2 shows the chemical composition and physical properties of cement, as supplied by the manufactures.

2.1.2 Fine aggregate

The natural fine aggregate used in this study was river sand from a local source. A series of laboratory tests were conducted to assess the properties of fine aggregate. Table 3 shows the results of these tests. Fine aggregate gradation shall meet the requirements of ASTM C33 [17] as illustrated in Figure 1

2.1.3

Mixed color ground glass supplied by a local source was used in this study without any

Portland cement

Table 2 Chemical and physical characteristics of Portland cement

Glass powder

treatment, washing or sorting. The distribution of glass particles was determined by using a particle-size analyzer device. Figure 2 shows the variation between the normalized particle amounts versus particle diameter. It can be realized from this figure that the particle diameters are in the range of 0.297-153.42 μm

Silicon dioxide Nanoparticle (Nano-SiO2) in dispersed suspension form with an average particle size of 11- 13 nm, specific surface area of 200 m2/g and purity of higher than 99% was used in this study.

2.1.4 Nano-silica

Table 3 Review of laboratory tests for fine aggregate Test method

Fig.1 Fine aggregate diameter size based on the sieve analysis

2.1.5 Superplasticizer

A polycarboxylate type super plasticizer (SP) with trademark of Vand Super Plast PCE according to ASTM C494 [18] type F with specific gravity of 1.03 g/cm3 was utilized to achieve the desired workability in all mortar mixtures

Polypropylene fibers (PPF) were added to the mixture to determine whether improved mechanical properties and durability could be achieved. Table 4 shows the properties of these fibers

2.2 Mixture proportions

Laboratory trails used to verify properties of the initial mix composition with respect to the specified characteristics. A control mix (named CO) was proportioned with reference to EFNARC [19] and modified with various glass and Nano-silica particle contents as listed in table 5. A total of eleven mixtures were designed to have constant water/binder ratio of 0.4, a total binder content of 700 kg/m3 and 0.3% polypropylene fibers by mix volume. The purpose was to determine the following effects on mixed mortar:

• The effect of glass powder as a cement replacement material at 10, 15, and 20% dosage rates.

Fig.2 Glass powder particle size distribution

2.1.6 Fiber

Table 4 Properties of polypropylene fibers

• Combined effect of glass and Nano-silica powder as cement replacement material.

Table 5

Mix design and basic properties of mortars

2.3 Specimens

Fresh mortar was cast into 50⨯50⨯50 mm cubes for compressive strength and water absorption tests and in briquet gang mold for tensile strength tests. The specimens were demolded 24 hours after casting and cured in water at a constant temperature of 23 ± 3 °C until they were tested.

2.4 Test Methods

Each mixture was tested for fresh and hardened concrete properties. The fresh concrete properties were measured to judge the flow and self-compactibility behavior of the concrete.

2.4.1 Slump flow test

The slump flow test is a common procedure used to determine the horizontal free-flow characteristics of each mixture. In performing this test, the standard Abrams cone is filled in a single lift without rodding. Once filled, the cone is raised and the diameter of resulting concrete paddy is measured as described by ENFARC [19].

2.4.2 V-funnel flow time test

The V-funnel test was used to access the viscosity and filling ability of each mixture. A V shaped funnel was filled with fresh concrete and the time taken for the concrete to flow out of the funnel is measured and recorded as the V-funnel flow time as described by ENFARC [19].

2.4.3 Compressive strength test

Compressive strength test was conducted in accordance with ASTM C109 [20] to evaluate the strength development of mortars containing various glass and Nano-silica content at the age of 7, 14 and 28 days, respectively.

2.4.4 Tensile strength test

Tensilestrength test was performed with reference to ASTM C307[21]at theageof28 days.

2.4.5 Water absorption test

The water absorption test was carried out at 28 days of age in accordance with ASTM C642 [22]. Saturated surface dry specimens were kept in an oven at 110 °C for 48 hours. After the determination of initial weight, the specimens were immersed in water for 48 hours. The final weight was then determined, and the absorption was calculated to assess the permeability of the mortar specimens.

2.4.6 Chemical resistance test

The chemical resistance was studied by immersing the specimens in a sulfuric and hydrochloric acid solutions. After 28 days of curing, the specimens were removed from water tank and the compressive strength and mass were measured. After the initial weight was recorded, the specimen was immersed in a 3%, and 5% H2SO4 solution for 56 days. After 56 days of immersion, the specimens were removed from the solutions, rinsed with tap water and brushed before the testing of compressive strength and mass changes were measured.

2.4.7 Microstructure analysis

The microstructure of the concrete mixes was analyzed using Scanning Electron Microscope (SEM) which helps to visualize the microstructure of hydrated cement paste.

3. Results and Discussion

3.1 Fresh properties of SCM

The test results from slump flow diameter and V-funnel flow time are presented in table 5. All of mixtures were designed to give a slump flow diameter of 25 ± 1 cm with reference to EFNARC [19] by adjusting the amount of SP content. As shown in Table 5, the incorporation of Nano-silica made the mortars less flowable and more viscose, causing a significant decrease in workability. The workability of mortars was slightly decreased with an increase in glass powder content.

Fresh

Table 6

properties of SCMs

3.2 Mechanical properties of hardened SCM

3.2.1 Compressive strength

The average compressive strength of specimens at different curing ages are shown in figure 3. The addition of glass powder shows a decrease in compressive strength of samples for early ages of curing. However, after 28 days the compressive strength evidently develops in comparison with control sample. It's due the fact that both hydration and pozzolanic reaction affect mortar strength development at late ages.

It can also be observed that the incorporation of Nano-silica has a beneficial effect on the improvement of compressive strength of cement mortars at early ages. The Nano-silica exhibits a high pozzolanic activityresulting in the productionof additionalstrength giving C-S-Hphase. In addition, Nano-silica exhibits a pore- filling effect and compacts the microstructure which contributes to the strength improvement.

3.2.2 Tensile strength

The average tensile strength of specimens at 28 days of curing are shown in figure 4. It can be seen that the mixes with glass powder alone and in combination with Nano-silica showed highervaluesin comparisonwiththatofthecontrolsample.Theseparticlesstrengthentheweak regions that is between cement paste and polypropylene fibers. Also, tensile strength of specimens incorporating Nano-silica in most cases was higher than that of the glass powder samples. The nanoparticles fill the pores especially porous Portland crystals which array in the interfacial transition zone between the cement matrix and polypropylene fibers.

Fig.3 Compressive strength values of samples at 7, 14, and 28 days of curing

3.2.3 Water absorption

The experimentally obtained results are presented in figure 5. In general, the results showed increased values of water absorption when glass powder was added. However, incorporation of Nano-silica, due to high specific surface area, reduced the water absorption content of mortar. The Nano-silica contained some free water on the surface, which is resulted in continuous hydration that made the matrix more compacted.

3.2.4 Resistance to sulfuric acid attack

The loss of mass and compressive strength of the specimens upon immersing in a 3%, and 5% H2SO4 solution after 56 days are shown in Tables 7, and 8.

Fig.4 Tensile strength values of samples at 28 days of curing

Fig.5 Water absorption values of samples at 28 days of curing

3.2.5 Microstructural observations

The microstructures of cement paste at the interfacial transition zone (ITZ) were captured by SEM, as seen in Figure 6. The porous paste structures at ITZ in CO mixture, are shown in Figure 6, where CH, ettringite, and amorphous calcium-silicate-hydrates (C-S-H) can be recognized. Among the solids, pores of varying sizes are also noticeable. In contrast, the pozzolanic reaction densified the microstructures by turning CH into secondary C-S-H, and produced a more homogeneous microstructure, as shown in Figure 7 and 8 for 10G and 15G samples, respectively. Therefore, it is expected that the mechanical and durable properties of concrete could be improved due to this densified ITZ, which is normally the weakest phase in concrete composites.

Table 7 Results of compressive strength and mass change of specimen immersed in 3% H2SO4 solution

Table 8 Results of compressive strength and mass change of specimen immersed in 5% H2SO4 solution

Fig.6.a SEM micrograph of CO sample – 20 μm

Fig.6.b SEM micrograph of CO sample – 2 μm

4. Conclusions

This study was conducted to assess the effect of combined waste glass and Nano-silica powder on the properties of fiber-reinforced self-compacting mortar. The following results can be obtained from the present study:

1. Incorporating Nano-silica powder in mortar mixtures decreased the fluidity, and hence increased the superplasticizer dosage to maintain workability.

2. The workability of mortars was slightly decreased with an increase in glass powder content, and it can be compensated by increased dosage of superplasticizer.

3. The addition of waste glass powder up to 20%, slightly increased the compressive strength of specimens, however combined waste glass and Nano-silica powder would significantly increase the mechanical properties of mortar mixtures.

4. According to the SEM micrographs, smaller pores achieved by addition of waste glass powder,which canimprovethemechanical, durability, andmicrostructural properties ofmortar mixtures.

5. References

[1] Y.JaniandW.Hogland,"Wasteglassintheproductionofcement andconcrete -Areview," JournalofEnvironmentalandChemicalEgineering,vol.2,no.3,pp.1767-1775,September

Fig.7.a SEM micrograph of 10G sample – 20 μm

Fig.7.b SEM micrograph of 10G sample – 2 μm

Fig.8.a SEM micrograph of 15G sample – 20 μm

Fig.8.b SEM micrograph of 15G sample – 20 μm

2014.

[2] Y. Shao, T. Lefort, S. Moras and D. Rodriguez, "Studies on Concrete Containing Ground Waste Glass," Cement and Concrete Research, vol. 30, no. 1, pp. 91-100, January 2000.

[3] C. Shi, Y. Wu, C. Riefler and H. Wang, "Characteristics and pozzolanic reactivity of glass powders," Cement and Concrete Research, vol. 35, no. 5, pp. 987-993, May 2005.

[4] N. Schwarz, H. Cam and N. Neithalath, "Influence of a fine glass powder on the durability characteristicsofconcreteanditscomparisontoflyash,"CementandConcreteComposites, vol. 30, no. 6, pp. 486-496, July 2008.

[5] R. Nassar and P. Soroushian, "Strength and durability of recycled aggregate concrete containing milled glass as partial replacement for cement," Construction and Building Materials, vol. 29, pp. 368-377, April 2012.

[6] A. Khmiri, B. Samet and M. Chaabouni, "A cross mixture design to optimise the formulation of aground wasteglass blended cement," Construction and Building Materials, vol. 28, no. 1, pp. 680-686, March 2012.

[7] A. Khmiri, M. Chaabouni and B. Samet, "Chemical behaviour of ground waste glass when used as partial cement replacement in mortars," Construction and Building Materials, vol. 44, pp. 74-80, July 2013.

[8] A. M. Matos and J. Sousa-Coutinho, "Durability of mortar using waste glass powder as cementreplacement,"ConstructionandBuildingMaterials,vol.36,pp.205-215,November 2012.

[9] ACI Committee 237, "Self-Consolidating Concrete ACI 237R-07," American Concrete Institute, Detroit, MI, USA, April 2007.

[10] G. D. Schutter, P. J. Bartos, P. Domone and J. Gibbs, "Self-Compacting Concrete", Scotland, UK: Whittles Publishing, 2008.

[11] J. A. Daczko, "Self-Consolidating Concrete - Applying What We Know", New York, USA: Spon Press, 2012.

[12] K. H. Khayat and G. D. Schutter, "Mechanical Properties of Self-Compacting Concrete - State-of-the-Art Report of the RILEM Technical Committee 228-MPS on Mechanical Properties of Self-Compacting Concrete", London: Springer, 2014.

[13] American Society for Testing and Materials, "Standard Specification for Portland Cement ASTM C150-07," ASTM International, PA, USA, 2009.

[14] American Society for Testing and Materials, "Standard Test Method for Density, Relative Density (Specific Gravity), and Absorption of Fine Aggregate ASTM C128-07a," ASTM International, PA, USA, 2009.

[15] American Society for Testing and Materials, "Standard Test Method for Total Evaporable Moisture Content of Aggregate by Drying ASTM C566-97 (Reapproved 2004)," ASTM International, PA, USA, 2009.

[16] American Society for Testing and Materials, "Standard Test Method for Seive Analysis of Fine and Coarse Aggregates ASTM C136- 06," ASTM International, PA, USA, 2009.

[17] American Society for Testing and Materials, "Standard Specification for Concrete Aggregates ASTM C33-08," ASTM International, PA, USA, 2009.

[18] American Society of Testing and Materials, "Standard Specification for Chemical Admixtures for Concrete ASTM C494-08a," ASTM International, PA, USA, 2009.

[19] European Federation of National Associations Representing for Cocrete, "Specification and Guidelines for Self-Compacting Concrete," ENFARC, Farnham, UK, 2002.

[20] American Society for Testing and Materials, "Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in or [50-mm] Specimens) ASTM C10908," ASTM International, PA, USA, 2009.

[21] AmericanSociety forTesting andMaterials,"StandardTest MethodforTensileStrength

of Chemical-Resistant Mortar, Grouts, and Monolithic Surfacings ASTM C307-03 (Reapproved 2008)," ASTM International, PA, USA, 2009.

[22] American Society for Testing and Materials, "Standard Test Method for Density, Absorption, and Voids in Hardened Concrete ASTM C642-06," ASTM International, PA, USA, 2009.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CCBY) License (http://creativecommons.org/licenses/by/4.0/).

Infrastructure, Construction, Concrete, Geotechnic, Earthquake, Environment.

Durability Plan for Coastline Concrete Structures and Design Considerations under Aggressive Environment Conditions

Tamur Salik, University of Technology Sydney, Australia

Hadi Khabbaz*, University of Technology Sydney, Australia

*CorrespondingAuthor, Hadi.khabbaz@uts.edu.au, Received: Sep 2022,Accepted: Oct 2022

ABSTRACT: Concrete durability is the ability of concrete to resist environmental impact or chemical attack in a long time without substantial deterioration. The aim of this study is to provide a durability plan for concrete structures to encompass the 100-year design life. The coastlineconcretestructuredesign requirementsareformulatedconsideringacasestudyoftwin bridges in Ballinaregions,Australia,whichcanbe extendedto othertypeof concretestructures. The proposed durability plan incorporates concrete strength, provided cover thickness and construction methods for each structural component. This paper elaborates the service life design of twin bridges and conducts durability design, employing the first principles for environmental loads affecting structural components. The realistic model for chloride induced corrosion, based on diffusion theory and carbon dioxide diffusion model, are also included in this study. In addition, the specifications of concrete and other preventive measures are described. The chloride modelling of the bridges has been conducted using a realistic model based on diffusion theory. It has been revealed that 100 years of design life can be achieved by using 65% slag in the concrete of bridge deck. The findings suggest that fibre boards and supplementary cementitious materials both are notably effective to maintain a durability of 100 years.

Keywords: Durability; Supplementary cementitious materials; Realistic modelling; Diffusion theory

1. Introduction

Many concrete structures are exposed to various types of aggressive environments. Significant challenges and problems can be experienced by concrete structures in long term. These problems include deteriorating processes such as carbonation, alkali-aggregate reaction, chlorination, freezing, and thawing. Bridges provide an essential platform for better communication and transportation in modern societies. A bridge is a common source to get across a river. It is also a way to get across a busy freeway. Therefore, any onshore concrete bridge structure under consideration is required to be designed in a way to withstand environmental resistance and to allow the traffic flow up to hundred years. In this paper a comprehensive durability plan is presented for twin bridges in Ballina region. It is an exclusive plan to ensure 100 years of durability. These Ballina bridges are located 736 km by road from SydneyCBDinthesouthernside.Bothofthemcontainthesamenumberofpiersandabutments. The details of structural members are also present in the drawings to determine the durability of project. The drawings also include the information related to earthquake loading, wind

loading and flood data of the adjacent areas of these bridges. The bridges are in the region of Ballina, which is 1 km away from the coastline. The probability of environmental attack increases due to the coastline proximity. Durability plan ensures the overall performance and health of concrete structures Therefore, the necessity of durability plan is high to achieve a better performance in a long term. There are certain features that should be incorporated in the scope of the durability plan. The major points are:

• Recognizing the potential environmental loads on the structure,

• Identifying appropriate design practices for construction, and

• Establishing suitable measures to achieve the complete design life.

Design life is the period for which bridge, or any structure is necessary to remain useable. The design life for many bridges is intended to 100 years. The realistic modelling based on diffusion theory and CO2 diffusion model is used to come up with 100 years design life and then comparing with thecode AS 5100:2007. Thedesign life incorporates the intended life with appropriate maintenance. To study the environmental effects, previous reports have been reviewed and accordingly a data set was established.

2. Literature Review

Chloride diffusivity along with its design is a major benchmark to check the quality control in durability planning. Concrete compressive strength and chloride diffusivity are the primary element to for measuring the quality checks. Output of research reflects that safety margins of durability less than 2% for 120 years is safe. Durability quality check happened by changing the design value to laboratory classifications specifically for chloride diffusivity [1] Reinforcement corrosion ratio is high to damage the concrete cover and steel rusting causing cracking, spalling. Corrosion ratio in reinforcement has applied the rule of splash zone, underwater zone and atmospheric zone.

Corroded reinforcements ratio of decreased tropical atolls is higher compared with general marine offshore environment. Chloride concentration of concrete is lower in ordinary Portland cement (OPC) compared with calcium aluminate cement (CAC). To improve the durability in concrete structure lowering the rate of water-to-binder recommended for compressive strength as well. Employing OPC approach is more durable than CAC. The investigations reveal that complicated and harsh environment of tropical atolls corrodes concrete structures severely and the reinforcement corrosion ratio is extensive [2]. Impact of salt spray is moderate on steel (e.g. BSt 420). Focus is required on better engineering to reduce the large losses. There is substantial ductility due to salt spray exposure. The outcomes of accelerated corrosion tests on bare steel bars depicters better qualitative compared with aged concrete steel bars Deterioration of reinforced concrete structure will occur due to alkali-silica chemical reaction [3] The tool to describe the relation of chloride ingress into concrete under two different normal & mock environments, the outcome can be defined by Fick’s diffusion model. To check the connection of chloride in concrete between normal & abnormal environments also required at different level of chloride content surface of convection zone depth that results in concrete characteristic

& environmental issues [4] Analysing the chance of corrosion with the time started when considered two separate classifications of environment severity and with depth of concrete underwater including w/c ratio. Starting of corrosion is subject to different parameters. It has been seen that structural surface and the cover depth values are main factors for probabilistic analysis. To check the material resistance against chloride ingress, coefficient of diffusion has a major role. Durability is linked with true values of cover depth which is not commonly used in many practices. This factor gives more accurate results with probabilistic approaches, keeping in view the inherent randomness present on degradation phenomenon that may disturb structural durability. Optimum values of cover depth totally associated with concrete quality against porosity that can be seen in the water-cement ratio. More deep research is needed to consider the conception, maintenance, and reparation to reach the engineering which align with w/c ratio and the cover depth value which ultimately reaches high structural safety [5] Durability of concrete is not fully linked with design and material; however construction work and quality also does matters. The lower construction quality will be exposed in sever environment in concrete structures. Probability approach of design shall be used to achieve durability. Most of the durability problems can be seen in mismanagement of quality control checks, hence the focus should be given to the quality control to reach desired durability. Experienced based tools to check the quality of concrete construction should be conducted to avoid any quality mismanagement. To reach better controlled durability, proper manual should be issued, explaining the concerns regarding future durability [6,7]

3. Part 1: Structural Members and Environmental Loads

3.1 Identification of

Members

The structural components of twin bridges are identified using drawings and listed in the following Table 1 along with their concrete strength grade, methods of construction and cover thickness.

Table 1 Structural members and their construction details

3.2 Environmental Loads on Structural Members

• To study the environmental effects, previous reports have been reviewed and accordingly a data set was established. This data contains the following details:

• Meteorological data: wind,temperatureandrelativehumidity ofBallinasurroundings were obtained by the local meteorological centre. These reports were important in indicating the kinds of environmental attacks that can potentially harm the bridge [8]. Meteorological details are depicted in Table 2.

• Environmental data: Environmental reports for Ballina region were accessed to study the carbonation-corrosion.

• The rainfall is drastically increasing in that region annually. The Meteorological Bureau of Ballina states that the average rainfall in 2000 was 900 mm, which increased to 1800 mm in 2016. This represents that relative humidity would keep on increasing accordingly in upcoming years [8]

• The air may comprise the 10 billion metric tons by chloride in that region. Out of which 30% may went back to the ground. The chloride content is heading 1450 km (900 miles) away fromtheoceanregion. Andthis is continuouslyincreasing in thewholeregion, which creates an alarming situation [9].

• As per AS 5100.5 the twin bridges are in the temperature zone. As the annual temperature is increasing gradually, so a meticulous approach is to be taken during curing practices. The improper curing can lead to plastic shrinkage.

• Testing of Soil: The client has provided the data of borehole for below-ground interaction of environmental loads and types of material (Table 3)

Table 2 Meteorological data of Ballina region

Table 3 Bore log for Ballina twin bridges

The structural members identified previously from drawings are subjected to environmental loads depending on their location i.e., underground, or above ground. The environmental loads on each structural member are depicted in Table 4

4. Part 2: Service Life Design from First Principle

After identifying the structural members, a durability design is conducted from the first principles for environmental loads. The detailed summary of environmental loads is given in Table 5, which are required prior to commencement of design

4.1 Chloride-Induced Corrosion

The bridge structure is located on the coastline; this closeness of the bridge makes the structure favourable to the chloride attacks. It is given that there is no atmospheric air borne chloride present but there are other parameters responsible for chloride ingress in concrete like mixture proportions, type of cement and existence of reinforcing bars. The carbon dioxide in the presence of moisture reacts with chloride salts and gives free chlorides. These chloride ions diffuse into the concrete and affect its strength. Piles and piers are considered as submerged elements of a bridge structure. Piles have three places where the exposure conditions vary.

Figure 1 depicts the different types of materials by borehole analysis.

Fig.1 Types of materials

Table 4 Environmental loads on structural members

1. Submerged portion in ground

2. Submerged portion in water

3. Portion above sea water

Table 5 Environmental loads summary and their effects [10]

Consequences

1 Underground Chloride in creek water Rate of diffusion is low due to high quantity of Oxygen in creek water

2 Sulphate attack Causes the volume of concrete to expand and contract due to change in its elastic properties. End result is cracking in concrete

3 Alkali Silica Reactions It causes random cracking and deteriorates the surface. High Loss in serviceability

4 Atmospheric or above ground Chloride-induced corrosion

Rate of diffusion of chlorides increase with the increase in concentration of chloride ions in atmosphere

It increases the corrosion rate of steel

5 Corrosion due to Carbonation It decreases the serviceability and strength of structure exposed to atmosphere

Issues In design

Chloride attack mostly occur to the piers due to their exposure

Piers are more vulnerable to sulphate attack

For this bridge structure, it is not accepted to possess visible surface cracking

There is no airborne chloride present in atmosphere as given.

The members of bridge exposed to atmosphere are most effected e.g., bridge deck, pile cap and portion of piles

6 Pollutants Interacts with the surface and delaminates Protective layers to avoid pollutants causing cracking

7 Temperature and moisture Tends to expand and contract the concrete Exposed elements protected by paint

The chloride diffusion for outer exposed parts of the bridge to atmosphere is more than in comparison with submerged components. This happens due to the presence of high concentration of oxygen in water. The submerged elements have higher values of chloride concentration. Concrete having strength of 30 MPa or more has chloride concentration ranging from 1%-2 % by cement weight [11]. Pier 1 on Northbound is experiencing the highest quantities of chlorides with 2280mg/kg. The chloride penetration effect through using SCMs can be decreased by controlling the cover design for the elements of structure submerged in water. The concrete deck is assumed of experiencing the chloride diffusion and the chloride concentration is taken as 2.8 kg in a meter cube for modelling [12]. We have done the chloride induced modelling of concrete using realistic model based on diffusion theory.

4.2 Realistic Model for Chloride Concentration

The realistic model can be used for the twin bridges due to the variability of factors like unified environment, uniform quality and absolute cover which may affect the service life of [13]. As we know the covers from the provide drawings, we can calculate the time required for chloride to pass through that cover by using following modelling relation.

Where: t = Time, x = Depth, ���� = Diffusion coefficient, ���� = Concentration of chloride at surface,

���� = Concentration of chloride, �� = Compressive strength

By using the correction factors for stress, exposure time and temperature as well as microclimatic conditions, we can derive improved model as follow.

Some of the values can be suggested for the various factors mentioned above as shown in table 6.

50 GP concrete

2000).

Crack-freed stress factor ��3 0.70-0.76 for compression members, 1.1 for tension zone in un-cracked flexure member

Limiting crack width to cover

1.2 for crack in tension zone

�� = €θ Cs

θ= 1.0 for crack-freed member such as columns and piles

���� /C ≤0.01

θ

Microclimatic load factor € € = 1.0 for fully submerged zone.

€ = 1.15, 1.08,1.02 for grade 32, 40 and 50 in tidal zone

Limiting value of ���� 1.5, 1.0 and 0.8 for grade 32, 50 and 60 respectively. [14]

Table 6 Suggested factors for realistic model of chloride induced corrosion

4.3 Observations for Chloride Induced Corrosion

By using the borehole data mentioned in Table 3, it can be observed that for piles submerged below the ground the chloride concentration is in the range of 5000-12000 mg/kg according to the depth. It means that the chloride induced corrosion will be more severe in these regions as compared with the rest of the areas.

4.4 Calculations

The Following equation was used to calculate the amount of chloride concentration at a specific location.

In this case the cover above is 60 mm, a check should be performed to figure out the amount ofchloride at 60mm and thencomparethis to the chloridethreshold level (CTL)=0.05,Cs=1.4, α = 0.55.

For chloride, the first step is to calculate the diffusion coefficient for 100 years (D100 years). This can be carried out using the following formula: ��100 =0.90�� 12( 1 100)α (4)

The blinder that is chosen is fly ash with a w/b ratio of 0.4. As seen from Table 4, ��1 =0.90�� 12m2/s, Therefore:

��100 =090�� 12( 1 100)α ��100 = 7.15E -14

The t is 100 years. This need to be converted into seconds.

T = 60 X 60 X 24 X 365 X 100

T – 315360000

Finally,

0.06

Table 7 Observations for chloride induced corrosion

Since the calculated ���� for the piles is less than CTL, the piles is deemed to comply with chloride induced corrosion.

By looking at the initial drawing given, the smallest cover required is the 55mm which is for the concrete planks. After applying the same formula as above, but using a cover of 55mm instead of 60mm:

Thismeansthatthesmallestcoverof55mmisalsosufficientagain chlorideinducedcorrosion. According to this result, it is acceptable to say that all components of the twin bridge will be acceptable to chloride induced corrosion.

4.5 Chloride Modelling

It is established via modelling that choice of concrete and concrete cover compared with chloride ingress is much better, as depicted below in Figure that chloride ingress is at upper layer of concrete cannot reach to reinforcement even after 99.8 years. This slowdown to chloride is established in below graph that chloride ingress percentage is lower as 0.10% after 100 years. Figure 02 shows the effect of chloride concentration on reinforcement with time

Table 8 Chloride concentration against different types of cement

Fig.2 Effect of chloride concentration on reinforcement with time

ReinforcementBars Concrete

GreenArea:Chlorideingressof0.10%after99.8years

4.6 Carbonation-Induced Corrosion

The Carbonation corrosion is witnessed various parts old structures in the region of Ballina. The report issues by environmental authorities have indicated that the carbon induced corrosion may also lead to the expansion of the structure by steel corrosion. These expansions have high impacts on strength and cause cracks in the structure. The following members of the structure will show the possible effects of carbonation-induced corrosion:

• Planks precast: The already formed layer of carbonation will prevent the further carbonation in the affected members of the structure.

• Concrete in deck: Carbonation may slightly affect the deck concrete, although it is not prone to carbonation due to thick 10 mm bitumen fibre board and 75 mm bituminous topping, protecting it underside.

The following materials are taken into consideration to highlight the effects the effects of carbonation induced corrosion in our bridge structure.

• Ordinary Portland cement or GP Cement

• Slag by 65% in replacement with Cement

• Fly Ash (FA) 25% replaced with cement

4.7 CO2 Diffusion Model

Thecarbonation depth ofthemembersthatareproneto thecarbonation iscalculatedbyusing the following relation.

���� =����05 (5)

Where: K is rate of carbonation or coefficient (mm/year0.5),

T = Initial time,

dc = Depth of carbonation

The calculations for concrete plank and abutments by using Ordinary Portland cement or GP Cement, Fly Ash (FA)25%replaced with cementand Slagby65%in replacementwith Cement respectively are shown below.

• By using general purpose cement (GP) in concrete having strength more than 35 MPa and exposed conditions.

• Calculation of depth of carbonation by applying 25% fine aggregates (FA) in concrete having strength more than 35 MPa in exposed conditions.

• Calculation of depth of carbonation by applying 65% slag in concrete having strength more than 35 MPa in exposed conditions.

*This

*This

is sufficient by considering GP cement for Carbonation

This shows that cover of plank is NOT enough, when using 25% fine aggregates for carbonation.

*This shows that cover of abutments is sufficient by using 25% FA for carbonation.

Table 9 Observations for chloride induced corrosion

Table 10 Observations for chloride induced corrosion

*This shows that cover of plank is NOT enough by using 65% slag for carbonation.

*This shows that cover of

is NOT sufficient by using 65% slag for carbonation.

The precast barriers would not undergo carbonation corrosion, as they do not possess any reinforcement. In above calculations, it is clear by carbonation modelling that when concrete is casted by using GP cement with keeping nominal cover for elements, it prevents carbonation. The above calculations show that cover is also not sufficient for 100-year design life by replacing cement with fly ash and slag. Although, the regional and meteorological clearly showed that the carbonation is not a huge issue to the bridge structure, however we would redesign the structure, which would withstand the adversity of slag and fly ash on concrete carbonation induced corrosion [15]. By performing above calculations, it can be observed that cover is not sufficient for some conditions. It is to be noted that by changing cover, we will be changing the structural capacity of the structure so we will prefer not to change the cover. Instead, we will change the concrete mix.

4.8 Reduction of Carbonation

If we want to reduce carbonation without changing cover requirements, then we can suggest following recommendations.

• Concrete should be made by blending cement having a minimum cement content of 240 kg/m3

• The cement used for making concrete should be a shrinkage limited one or the generalpurpose cement which should conform to the specifications.

• If it is desired to prevent carbonation in drier regions of bridge then the compensation of carbonates can be made by increasing general purpose cement proportions.

Observations for chloride induced corrosion

4.9 Sulphate and Acid Sulphate

In the report provided by the Roads and Maritime Services (RMS) acidic sulphate soils is present in Pacific Highway. Along with that the borehole data also confirms Pier 1, Northbound is exposed with sulphate content. Table 12 outlines the content of each member exposed with the sulphate soil in ground.

The mechanism of sulphate ions transport is diffusion. The sulphate ions diffuse into the concrete core and effect the concrete. The diffusion rate of sulphate is 1/100 as compared to the chloride attack. Though the rate is exceedingly small, but the effect of harming the concrete is severe. The ettringite (delayed ettringite formation, DEF) is formed into the concrete due to sulphate attack. This leads to the expansion and concrete expands up to 227% of its original volume. The elastic properties of concrete loss due to the gypsum formation by the sulphate attack. The coastal location of twin bridges makes it vulnerable to both sulphate and chloride, considering this both would also interact with each other. The interaction of chloride and sulphate ions reduces the effects produced by the sulphate ions. In the presence of chloride, the ettringite and gypsum are soluble. These soluble precipitates out of the concrete. Barriers and Planks are other precast member must be put in use after they get dried. This allows protective layer against sulphate attacks to be formed by carbonation [15]. The submerged piers and ground contacted abutment surfaces are discussed further in the report.

4.10 Alkali-Silica Reactivity and Ettringite

In alkali-silica reaction with concrete aggregates wherein, magnesium, sodium, potassium hydroxides react with mineral content in the crack or hole openings of concrete. They form silica gel and cause cracking and expansion. The cracklings can occur in different parts of the structure with different patterns. In lightly loaded elements it occurs as map-cracks, such as in precast barriers. In highly loaded elements like abutments and piers, it occurs in the principal stress direction. The alkali-silica reactivity is considered as a serviceability issue. The use of alkali metals shouldbeonpriorityforbetterdesign. ApartfromthatAustraliais has less content of alkali in cement which makes it less vulnerable to alkali-silica reactivity (ASR). Moreover, the use of Supplementary Cementations Material (SCM) like slag and fly ash are used to diminish the effect of ASR. Along with that the use of nonreactive aggregate eliminates the adverse impact of ASR. The surface abrasion caused by the ASR increases the deterioration of concrete surface and increase serviceability problems. There are procedures and treatments in this report to handle all these issues. The surface abrasion caused by the ASR increases the

Table

Observations for chloride induced corrosion

deterioration of concrete surface and increase serviceability problems. There are procedures and treatments in this report to handle all these issues. The bridges under consideration are S3 category of acceptability of damage due to ASR. It means that the twin bridge must be designed to avoid any visible cracking caused by ASR during the complete Hundred-year design life.

4.11 Preventive Measures

The following preventive measures can be taken to avoid the alkali silica reactions.

• Use of supplementary cementations materials (SCMs) like natural pozzolans, fly ash, fume of silica, and GGBFS. SCM can be used as 25% for fly ash, 10% for silica fume, 40-70% for blast-furnace slag by mass of cement.

• The access of external alkalis and moisture should be controlled by using a sealer which can be paint or any moisture repellent surface. The surface should be re-applied after certain period.

• Use river gravel for this purpose because it consists of minimum reactive aggregates.

• Application of barium and lithium salts in the form of admixtures can be used.

• Use of low water to cement ratio and air entrainment of concrete to control the expansion due to ASR.

4.12 Bacteria-Induced Corrosion

The concrete can be affected by microbial activity in underground surfaces. There are two possibilities of happening this activity. The anaerobic bacteria create corrosive and disruptive sulphuric acid that causes harm to the concrete. Secondly, the bacteria named ‘Thiobacillus ferrooxidans’ oxidize the pyrite. These both create sulphates and corrosive sulphuric acids which have adverse effects on the concrete [16].

5. Part 3: Specifications of Concrete and Other Protection

5.1 Specifications of Materials

5.1.1 Classification of exposure and material design

The exposure of structures is classified in the standards given by Table 4.3 of AS 3600 [17] It states that the structural members that are below water and submerged will be considered in B1 classification. Whereas the structural members outside the water and exposed to external atmosphere are subjected to B2 classification. The structural members of the twin bridges can be analysed for the exposure classification. The piers of the bridges are constantly under chloride and acid sulphates exposure due to chlorides present in soil. In this case, the effect of sulphates is reduced to negligible extent due to presence of chloride because the sulphate salts will be dissolved and come out of the concrete. Hence, the piers will only be subjected to the attack of chlorides and we will analyse this situation and give remedial preventive actions for this situation. The pier headstocks are present in the zone where water will continuously splash on structure, so it is considered in C2 classification. The piles are classified in U due to the

absence of data of exposure. Table 13 gives the classification of exposure for different elements of bridges.

Table 13 Exposure classification of structural components

The exposure classification mentioned above helps in determining the concrete grade for the structural members. For this purpose, AS 5100.5 (Table4.10.3-A)is usedtodetermine concrete grades forcast-in-situconcretemembers [18] Table 14provides thenominal coverfordifferent exposure classifications of cast-in-situ concrete members.

a. Nominal cover where standard formwork and compaction were used

Table 14 Nominal cover for cast-in-situ concrete members Exposure

Nominal Cover for concrete of characteristic compressive strength(fC) not less than (mm)

Note: Increased value is required if Clause 4.10.3 (c) applies

In case of precast concrete members, AS5100.5 provides us with a different table to determine concrete grades for precast concrete members based on their exposure classification. Table 15 provides the nominal cover for different exposure classifications of precast concrete members [18].

b. Nominal cover where rigid formwork and intense compaction were used

Table 15 Nominal cover for precast concrete members

Cover for concrete (TABLE 4.10.3(B)of characteristic compressive strength(fC) not less than (mm)

It is necessary to give special attention while casting the concrete and achieving the required cover. There is provision of allowance of 20mm for cast-in-situ and 5mm for precast members given in Australian Standard AS3600:2009.

5.2 Concrete Works and Thermal Modelling

Concrete mix design and construction methods inserted in concrete works modelling program along with related site parameters to check the durability of this bridge. The modelling was performed for 100 years’ time to fit the design life supplies. Granulated ground blast furnace slag (GGBFS) is famous to be utilized in lowering the temperature differentiation due to heat in concrete pours by hydration. Along 180mm nominal thickness of bridge deck, it has notbeenthemainaspect. TheeffectivenessofSCMcanbeseeninbelowpictureveryevidently. It can be evidently seen in the Figure 3; temperature differentiation is due to heat of hydration is satisfactory having concrete pour being done in the morning in summer season.

5.3 Concrete Specifications

After specifying the concrete cover for the structural members based on their exposure classification, we can also specify the design requirements of concrete mix design to fulfil durability requirements. For this purpose, we can get assistance from the RMS B80 guide. The durability requirements of concrete based on exposure classification of structural members are given in Table 16

Fig3. Effect of temperature on concrete

Table 16 Requirements of durability for cast-in-situ & precast concrete members

Applying the design requirements of concrete cover and concrete mix design, incorporating environmental loads and exposure classification of structural members, we can suggest design specifications for the durability plan of bridges to satisfy 100-year design life. Details are depicted in Table 17

The suggested concrete grade for deck is 55 MPa and it is conforming the requirement for abrasion which is at least 32 MPa. Similarly, the input for water-cement ratio for chloride modelling is used 0.34 in Life-365 (modelling software), while performing chloride induced corrosion modelling this lies in the range of 0.32-0.40 as indicated above.

5.4 Effect of SCMs and Curing on Durability of Concrete

There will be high heat of hydration due to mass concrete of piers, abutments, and deck slab. For prevention of occurrence of thermal cracks, a suitable amount of supplementary cementitious materials (SCM) are added in the concrete mix but also steps are taken to ensure the effective and proper curing. Loss of moisture is prevented by curing; steam curing is recommended for pre-cast members whereas wet curing for 14 days for cast-in-situ members is recommended. In the region of high wind, moisture loss can also happen. To avoid excessive bleeding wind barriers must be erected as this will make also curing more effective [19]. There are lots of advantages of adding SCMs in the concrete mix design. The negative effect of the

Table 17 Design specifications for 100 years design life

increase in depth of carbonation due to the addition of SMs will be weighed out due to its more beneficial effects. The design life of 100 years will be obtained in aggressive and harsh weather conditions, slag is added up to 65%. Chloride induced corrosion prevented by the addition of fly-ash. Another advantage of SCMs is that the concrete mix will be less permeable and more durable. Further, sulphate attack is prevented by the addition of slag and fly-ash as both will reduce chemical diffusion rate. There will be less alkali-silica reaction due to these supplementary cementitious materials (SCMs) [20]

5.5 Performance Based Specifications

Performance based specifications are required for the bridge to last for 100 years. They are done to help attain design life and their costs for maintenance are generally high. Some of the requirements to meet by using performance-based specifications are compressive strength, water absorption, surface abrasion, chloride diffusion and sorptivity [17]

The Performance based specifications are as follows

• The concrete needs to have a compressive strength of 50MPa

• Diffusion coefficient,

• RTA sorptivity is 14 mm

• Volume of Permeable Voids (%) is 13%

• Rapid Chloride Permeability is 1000 Coulomb

Following are the summary of performance-based specifications required for our bridge.

Table 18 Design specifications for 100 years design life

5.6 Preventive Actions for Corrosion of Concrete

5.6.1 Use of coatings

Polyurethane based exterior weather coating by the trademark of SIKA/FOSROC for additional protection of concrete surface on piers, abutments and deck slab is good prevention from corrosion. This gives a strong and rapid hindrance to the entrance of forceful synthetic chemical substances into the structure while all the while enabling the structure to relax and breath. We can develop the required thickness in micrometres by applying multiples layers of coating of these. During the application procedure, we may use the technical sheets provided by the manufacturers.

5.6.2 Cold and expansion joints treatment

While constructing the bridges, joints are more sensitive and foreseeable. If there is a time gap in concrete placing then joints will form, and these are cold joints. For the accommodation of movements due to contraction and expansion of structural components, expansion joints are formed[21] However,forthediffusion ofharshelements,joints arethemost vulnerablepoints. Surface retarders are used at the end to avoid cold joints. The use of this will avoid forming any joints at next when placing new concrete with old one. It is critical to treat the expansion joints. To seal the expansion joints different sealants of approved trademark (SIKA/FOSROC) are used. The sealants are used to avoid ingress the chemicals into structures through the expansion joints provided in structure of bridge. Hence the movements in the bridge structure due to expansion and contraction are also not compromised [22]

5.7 Preventive Actions for Corrosion of Steel Reinforcements

5.7.1 Control of cracks using AS5100 & AS 3600

Structural integrity is severely damaged if cracks are oriented along with the reinforcement. Shear and bending strength of the structure is adversely affected by these cracks. Alkali-silica reaction can produce the cracks that are in same alignment along the steel reinforcement bars. To achieve the required design life, AS3600 provides the different strategies to reduce and control these cracks. For instance: one technique is provided in Section 8.6 of AS 3600-2009.

5.7.2 Galvanization / cathodic protection

Zinc-Rich epoxy coating on steel reinforcement prevent it from deteriorating and further ingress of chemicals. The manufacturer provides the technical details for these coatings, and theyshouldbeimplemented.Anotheroptionisthe applicationofgalvanizedreinforcement than ordinary reinforcement.

6. Conclusions

After comprehensive literature review and establishing the design requirements through modelling some suggestions are presented for marine structures. Throughout the entirety of the

coastline concrete structure and design specifications for aggressive environments this document should be considered as a living document for alkali-silica reactions. It is suggested that to identify the potential durability risks for members in tidal splash zone and submerged structures, conduct testing of ground water and creek. It is endorsed that due to the marine exposure and acid sulphate conditions, pre-cast reinforced concrete structures tested and inspected before installation. Proper inspection of edge reinforcement detailing is required as per scope and specifications. Construction of coastline concrete structure in aggressive environment conditions demands the quality control and insurance at all the stages. Concrete Works modelling for environmental loads i.e., chloride ingress, thermal effects, and carbonation: has confirmed the design life of 100 years for concrete structures as per given specific design requirements.

7. Disclosure Statement

The authors would like to mention that there is no potential conflict of interest.

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This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CCBY) License (http://creativecommons.org/licenses/by/4.0/).

ANN Model to Damage Detection of Steel Bridge Based on Signal Processing

Farzad Hatami*, Amirkabir University of Technology (Tehran Polytechnic), Iran

*CorrespondingAuthor, hatami@aut.ac.ir, Received: Feb. 2023, Accepted: May 2023

ABSTRACT: Measurement uncertainties were regarded in this study through the overview of Gaussian white noise and axle load error into the numerically modeled accelerations before using them to train the systems. The result was discovered to be noise delicate, as predictable, but the method appears strong and performs well within typical noise levels Furthermore, since white noise is a broadband contribution, construction modes of vibration that are untruth within its necessary bandwidth can be recognized from the output measurements. In this study, two frames, an un-damaged and a damaged steel bridge beam, were modeled to evaluate damage detection methods by white noise excitation. In the damaged frame of a steel bridge, one of the beams of the steel deck was weakened by a decrease in the modulus of elasticity. These frames were analyzed under the comparable record of the Tabas earthquake, and the displacement responses and acceleration of the classes were extracted. The results of the signal analysis and processing showed that the best indicator for evaluating the difference between the dynamic properties of the two frames and the damage detection is the ANN, since any damage, along with significant energy absorption at a specified frequency, can be varied. Also, the natural frequency of both structural was obtained by noise excitation with the ANN algorithm.

Keywords: ANN, Genetic Algorithm (GA), Damage Detection, White Noise Excitation

1. Introduction

There are numerous vibration-based approaches for model updating in the literature. The elementary impression behind these works is that the modal parameters are occupations of the physical assets of the construction. A variation in the physical assets is related to changes in the modal assets, which may be noticed. Natural frequencies and mode shapes are frequently taken as the measured data to identify local damage. An inclusive appraisal has been given on the recognition, position, and description of structural damage via methods based on measured vibration response. Soft computing approaches such as fuzzy logic and neural networks have rewards over the old-style statistical approaches for predicting time series [1]. Soft computing approaches do not need to specify a model construction convent. It is more accessible to approximation complex classifications with these approaches than the simple linear statistical approaches because they are nonlinear [2]. Learning of the recent advances within Structural Health Monitoring (SHM) and damage detection was shown.

2. Research history

Concerning optimum sensor location (OSL), an essential part of any damage detection structures, reference shall be found to the research of Huang et al. [3] using GA, anywhere forthcoming algorithm usages some sensor kinds as contribution and standards about the

Infrastructure, Construction, Concrete, Geotechnic, Earthquake, Environment.

anticipated amount correctness to bring the optimum amount of sensors and their place. A genetic algorithm (GA), enthused by the organic evolutionary procedure, is a universal optimization method that can be used to treasure a nearby optimum explanation to a problem with numerous resident answers. The genetic algorithm, first formal as an optimization technique by Holland [4], is a meta-heuristic optimization method for serious dimensional and nonlinear problems. Genetic programming (GP) [5], as an allowance of GA, was an artificial intelligence method in which the answers are network programs with tree-like structures and can be used to forecast the performance of engineering structures. The developed method can be effortlessly operated in applied conditions, noisy problems, and stochastic search methods based on the apparatus of natural assortment and natural genetics. Gene expression programming (GEP) [6] is a new postponement of GP, which changes network programs with different dimensions and forms programmed in linear chromosomes with a fixed length. Some technical exertions have been in plateful GEP physical and structural engineering responsibilities. The main benefit of the GEP-based method is its ability to make predictive calculations without assuming the previous form of the scientific association. The procedure was genuine, with an experimental study on a single-span steel structure as a case study. So, Li et al. [7] proposed a new structure enciphering and transformation particle group optimization algorithm technique. Consuming a numerical model of a three-span prestressed concrete cablestayed bridge, this method was established to have increased merging rapidity and accuracy compared to the other state-of-the-art approaches (e.g., GA). Still, within the OSL theme, Yi et al. [8] upcoming new sensor location method in multi-dimensional space only promises optimization in a specific structural direction, which results in a useless optimization of the detection grid when retaining multi-axial sensors.So, numerical research was shown on a target structure model. Jin et al. [9] approach an extended screen-based artificial neural network (ANN) method for damage detection in a bridge under unembellished temperature variances. The time-lagged natural frequencies, time-lagged temperature, and period settings are chosen as the contributions for the neural network, which forecasts the natural frequency at the next timestage.Therearenumerousissuedresearches concerningthediscoveryofstructuraldamage with the release of GEP. Still, most of the proposed approaches are based on an achieved information method, which needs information on the damage complaint of the structure to be obtainable. This postures an effort in the practical application of these methods because, as it is recognized, the information in damaged complaints does not typically exist. The technique obtainable in this paper contains an updated mode-free damage detection algorithm using Gene expression programming (GEP) by ANN Toolbox.

3. ANN model

The ANN was developed and trained using the Neural Network Toolbox accessible in some software such as MATLAB. The special of complete construction has essential consequences concerning how well the system will make the forecasts. The ANN algorithm's superiority concluded other procedures in runtime and exercise, and challenging errors were established by applying thegenetic algorithm (GA). In GEP, entitiesareprogrammed as linear threads of fixed size, as shown in Fig. 1, which are advanced as non-linear objects with different dimensions

andshapes.Theseobjects areknownasexpressiontrees(ETs).Typically,entitiesarecomposed of only one chromosome, which, in turn, can have one or more genetic factors separated into head and conclusion portions. ETs are the appearance of a chromosome and experience the collection process, directed by their suitability value, to generate new entities. The structural organization of the GEP genes is better understood in terms of open reading frames (ORFs). In GEP, there are two tongues: the linguistic of the genes and the linguistic of the ETs. In GEP, cheers to the modest rules that control the structure of ETs and their connections, it is likely to conclude the phenotype assumed the arrangement of a gene directly and iniquity versa [10]. Figure 2 illustrates the essential stages of GEP. The procedure commences by randomly generating the chromosomes that form the initial population. Next, these chromosomes are expressed, and each individual's fitness is assessed by evaluating a set of fitness cases (known as the selection environment). Using a roulette wheel sampling approach, individuals are then chosen based on their fitness levels (their performance in that particular environment) to reproduce with alterations, resulting in offspring with new traits. This modification of the population is accomplished by applying one or more genetic operators to selected chromosomes, such as crossover, mutation, and rotation. The resulting new individuals are then subjected to the same developmental process, which involves genome expression, exposure to the selection environment, and reproduction with modification. This entire process is repeated for a set number of generations or until a satisfactory solution is obtained.

Fig.1 Chromosome with 2 genes and its decryption [8]

Fig. 2 Flowchart of a GEP [8]

This comprehensible fluent symbolization is named the Karva linguistic. For sample, a scientific appearance [a×(b+c)]-[√(a-c)] can be signified by a two-gene chromosome or an ET, as shown in Fig. 3. This character displays how two genes are programmed as a linear thread and how it is expressed as an ET [10].

4. Finite Element Model and Model Assessment

In this section, numerical simulation is modeling. The laboratory analysis response consists of 30 lateral-displacement loading cycles, while the numerical analysis response comprises a lateral-displacement loading cycle. The numerical analysis cycle has obtained the coverage of the laboratory analysis cycles. The following figure compares the cyclic response of the numerical simulation with that of the laboratory cycles. The connection response is the forcedisplacement relation. As can be seen, the numerical simulation cyclic response is in good agreement with that of the laboratory cycles. There is an excellent agreement, both in the precompression phase, post-compression phase, and compression phase, whether positive or negative. The best model was chosen on the basis of a multi objective strategy as below:

i. The simplicity of the model, although this was not a predominant factor.

ii. The best fitness value of the model on the training dataset.

iii. The best fitness value of the model on the testing dataset. The first objective was controlled by the user through the parameter settings (e.g., the number of genes or head size which determines the upper limit for the size of the programs encoded in the gene).

5. The deformation and stress distribution

The following figure shows a simulated sample in the Abaqus software. Given that to generate simple connection numerical simulations, the exact dimensions and sizes of components, materials, interactions, and finite element grids are considered to create numerical connectivity simulations, it can be claimed that the numerical analysis results of the sample Simple connection cases are also highly accurate and reliable.

Fig. 3 Sample of a GEP expression tree [8]

Therefore, a simplified model of this frame is created in OPENSEES software, in which the beams and columns are connected by a torsion spring and a short spring. As stated earlier, two damaged and un-damaged beams must be simulated to capture the response under input stimulation and identify the damage's place and extent. For this purpose, the elastic modulus of the target beam was reduced to 0.1E to cause damage, reducing the lateral stiffness of the target frame. In the un-damaged frame (A), the elastic modulus of all beams is considered to be E. This strategy can be implemented in three ways:

1- Reduce the stiffness of the first beams to One-tenth of the stiffness of the second & third lateral beams (frame B)

2- Reduce the stiffness of the second beams to One-tenth of the stiffness of the 1st & third lateral beams (frame C)

3. Reduce the stiffness of the third beams to One-tenth of the stiffness of the 1st & second lateral beams (frame D)

Each of these strategies has been applied separately, and the frame response has been extracted under the scale of the Tabas earthquake. The earthquake was also applied to the undamaged beam, with all beams having an elastic modulus E (un-damaged frame). Finally, the acceleration and displacement response was extracted by OPENSEES software.

Fig. 4 Finite Element Steel Bridge Modeling

Fig. 5 Beam Local Buckling Analyze

A. The damaged frame response (Frame C)

B. The non-damaged frame response (Frame A)

Fig. 7 Comparison of natural frequency Modes: Accelerated Response of Second beam, un-damaged Frame (Frame A), and Damaged Frame (Frame C)

Damage (Frame C) Undamage (Frame A)

Fig. 8 Comparison of first natural frequency Modes: Accelerated Response of un-damaged Frame (Frame A) and Damaged Frame (Frame C)

Fig. 6 TABAS earthquake accelerometer

Damage (Frame C)-C2

Undamage (Frame A)-C2

Fig. 9

of second natural frequency Modes: Accelerated Response of un-damaged Frame (A) and Damaged Frame (C)

Damage (Frame C)-C3

Undamage (Frame A)-C3

Fig. 10 Comparison of third natural frequency Modes: Accelerated Response of un-damaged Frame (Frame A) and Damaged Frame (Frame C)

Damage (Frame C)-C4

Undamage (Frame A)-C4

Fig. 11

of fourth natural frequency Modes: Accelerated Response of un-damaged Frame (Frame A) and Damaged Frame (Frame C)

Comparison

Comparison

Concerning the above relation, the domain and frequency of natural functions can be represented in a 3D graph with time. The domain can be added to the 2D time-frequency diagram in the form of color plots. This spectrum can be represented as a frequency-time function of the natural modes in a graph. This spectrum is called the image plot of the ANN transform. This spectrum for the two un-damaged frames (A) and the damaged frame (C) is shown in figure 13.

To extract the shape of the natural modes of the frame, it uses the recorded acceleration response of the classes, so that the acceleration response of all the classes is first extracted by input stimulation. The intrinsic modes of acceleration response of each class are then extracted by the modal analysis function method.

Fig 12. Comparison of first Mode (C1) Fourier Spectrum with Fourier Spectrum Accelerated Damage Response Frame

Fig.13 Comparison of the 2D time-frequency diagram of the un-damaged frame (A) and the damaged frame (C)

To examine how close, the predicted values were to the compressive strength steel fiber concrete, for indices, mean absolute error (MAE), mean absolute percentage error (MAPE), root mean square error (RMSE), and absolute fraction of variance (R2) were employed to evaluate the performance of models which are defined as follows:

The main reason for defining other statistical parameters was that the R-value alone is not an appropriate indicator of prediction accuracy of a model. This is because R will not change significantly by shifting the output values of a model equally. The statistical parameters of the final GEP model are given in Table 1.

If a model gives R>0.8, a strong correlation exists between the predicted and measured values. In all cases, the error values (e.g., RMSE and MAE) are at the minimum. Therefore, the model can be judged as very good.

Fig.14 Comparison of first Mode Shape of the un-damaged frame (Frame A) and Damaged Frame (Frame C)

6. Model Validity

Table 1 The statistical parameters of the best GEP model

In this study, two frames as un-damaged and a damaged beam of steel bridge were modeled to evaluate damage detection methods. In the damaged frame, one of the beams was weakened by a decrease in the modulus of elasticity. These frames were analyzed under the comparable record of the Tabas earthquake and the displacement responses and acceleration of the classes were extracted. Because of the importance of road communication, bridge was one of the most important principal constructions under development in any country that has many research backgrounds. Checking the condition of bridges before the operation and during operation is important to ensure the proper performance of the bridge according to the design in different periods. Besides, transportation development in many cases, requires the use of an existing route for heavy loads as well as higher speeds. Therefore, it is necessary to study the behavior of the bridge during its lifetime and to consider the necessary arrangements for its maintenance and repair. Detecting breakdowns in early stages in structural systems during their service life has involved the attention of many scientists in recent decades and has been the subject of many research articles in the fields of civil, mechanical, and aerospace engineering. Therefore, the presentarticlepresentsamethodologyforperformingbridgehealthmonitoringinordertoreach the location and severity of the damage, determining the service life-prediction of the bridge. For this purpose, the accessibility cable bridge of Tehran Milad Tower on Sheikh Fazlollah Nouri highway will be investigated, and numerical simulations will be performed, the types of sensors required as well as the sensor layout architecture and the service life-prediction of the bridge will be evaluated.

The results of the signal analysis and processing showed that the best indicator for evaluating the difference between the dynamic properties of the two frames and the damage detection is the ANN, since any damage, along with significant energy absorption at a specified frequency, can be varied. Frequency of structural modulus obtained. Also, the ANN is much more accurate than single-dimensional transforms such as Fourier transforms because it can calculate the instantaneous frequency, since, in one-dimensional transforms, one of the later answers disappears, making it difficult to evaluate the dynamic properties of the system. Also, the empirical decomposition method used in the ANN is well able to separate the output signal into the natural frequency modes, which are equivalent to the natural modes of the frame. It is much easier and more accurate to compare the response of two frames using the natural modes to compare the overall response of two frames. Because the damage is associated with high-

Fig.15 Comparison of experimental results with the predicted results for training set

7. Conclusion

frequency components of the response, therefore, by distinguishing the structural response to natural modes with a specified frequency range, the presence or absence of damage can be identified by using natural modes of high-frequency response. Natural frequency analysis can determine the shape of the natural modes of the structure by responding to the classes because the natural modes of the response correspond to the natural modes of the structure with reasonable accuracy. The results showed that with the event of damage to the structure, the natural frequency of the structure decreases, the period increases, the hardness decreases, the mode governing the response of the structure to the shear mode increases and the contribution of higher modes to the overall response of the structure increases.

8. References

[1] Maddala, Gangadharrao S., and Kajal Lahiri. Introduction to econometrics. Vol. 2. New York: Macmillan, 1992.

[2] Melin, Patricia, Alejandra Mancilla, Miguel Lopez, and Olivia Mendoza. "A hybrid modular neural network architecture with fuzzy Sugeno integration for time series forecasting." Applied Soft Computing 7, no. 4 (2007): 1217-1226.

[3] Huang, Ying, Simone A. Ludwig, and Fodan Deng. "Sensor optimization using a genetic algorithm for structural health monitoring in harsh environments." Journal of Civil Structural Health Monitoring 6 (2016): 509-519.

[4] Goldberg, D. E., and J. H. Holland. "Genetic algorithms and machine learning. 3 (2): 9599." (1988).

[5] Koza, John. "R. 1992 Genetic Programming: on the Programming of Computers by Means of Natural Selection." (1992).

[6] Ferreira, Candida. "Gene expression programming: a new adaptive algorithm for solving problems." arXiv preprint cs/0102027 (2001).

[7] Li, Juelong, Xun Zhang, Jianchun Xing, Ping Wang, Qiliang Yang, and Can He. "Optimal sensor placement for long-span cable-stayed bridge using a novel particle swarm optimization algorithm." Journal of Civil Structural Health Monitoring 5 (2015): 677-685.

[8] Yi, Ting‐Hua, Hong‐Nan Li, and Chuan‐Wei Wang. "Multiaxial sensor placement optimization in structural health monitoring using distributed wolf algorithm." Structural Control and Health Monitoring 23, no. 4 (2016): 719-734.

[9] Jin,Chenhao,ShinaeJang,XiaorongSun,JingchengLi,andRichardChristenson. "Damage detection of a highway bridge under severe temperature changes using extended Kalman filter trained neural network." Journal of Civil Structural Health Monitoring 6 (2016): 545560.

[10] Ferreira, Cândida. "Gene expression programming in problem solving." Soft computing and industry: recent applications (2002): 635-653.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CCBY) License (http://creativecommons.org/licenses/by/4.0/).

Numerical and Experimental Study on a Creative Concrete Pressure Reduction System (CPRS)

Saeed Nemati*, Western Sydney University, Australia

Yahya Aliabadizadeh, University of Maryland, College Park, USA

Farzad Yaghmaei, Almasaze, UAE

*CorrespondingAuthor, Nematiuts@gmail.com, Received: Jan 2023, Accepted: March 2023

ABSTRACT: The lateral pressure exerted on concrete structures formworks is influenced by various factors, including the aggregate content and size, water-to-cement ratio (w/c), type and amount of cement, presence of silica fume, fly ash, slag, ground limestone filler, type and quantity of superplasticizer, configuration of reinforcement steel bars, rate and method of placement, concrete temperature, ambient conditions, set time of concrete, and the dimensions, type, rigidity, and roughness of the formwork. It canbe challenging, andsometimes impossible, to simultaneously control all these parameters. This research introduces an innovative system called the Concrete Pressure Reduction System (CPRS), which incorporates sacrificial perforated sheets. The CPRS effectively manages the lateral pressure exerted by the concrete and mitigates excessive pressure on the formwork. Numerical modeling demonstrated that the utilization of this system can reduce the maximum principal stress, maximum shear stress, and maximum deformation by a minimum of approximately 27%, 30%, and 25%, respectively. Deformation obtained from parametric studies were verified through experimental tests, which displayed reasonable agreement with the outcomes of the study.

Keywords: Concrete Pressure Reduction System (CPRS), sacrificial perforated sheets, formwork.

1. Introduction

During the construction of concrete structures, it is crucial to design formworks that can withstand both the ultimate and serviceability limit states. Various loads, including wind, equipment/construction loads, snow, dead and live loads, as well as the lateral pressure exerted by the fillingmaterial, must be considered. For evaluation of lateral pressure, some factors must be checked. These factors can be summarized as follows:

• Materials (aggregate content and size, w/c, cement type and content, silica fume, fly ash, slag, ground limestone filler, superplasticizer type, and content)

• Placement Conditions (placement rate, placement method, the temperature of the concrete, temperature of the ambient, set time of concrete)

• Formwork Characteristics (dimensions, type, rigidity, and roughness)

• Reinforcement steel bars configuration

2. Research History

Ingeneral, researchindicatesthatincreasing thecontentandsizeofaggregatestendsto result in a lower initial lateral pressure in concrete structures. In the context of highly flowable

mixtures, a study conducted by Assaad et al. (2005) revealed that an increase in the volume of coarse aggregates led to a reduction in lateral pressure and an accelerated rate of pressure drop after casting. Increasing the w/c or/and superplasticizer content increases the lateral pressure. It is also shown that addition of Supplementary Cementitious Materials (SCM), such as fly ash (Gardner, 1984), silica fume or granulated blast-furnace slag (ASTM C989, 2014) affect the lateral pressure and more specifically its rate of decay (Khayat et al., 2007). In fact, mixtures with higher cement content develop greater lateral pressure (Ritchie, 1962). Amziane et al. (2000) reported that the use of a discontinuously-graded aggregate with Maximum Size of Aggregate (MSA) of 30mm can lead to higher lateral pressure for conventional vibrated concrete than a continuously-graded aggregate. Ore et al. (1968) reported that the effect of incorporating a water-reducing or set-retarding agent has limited influence on formwork pressure. Also, the effect of adding HRWRA (High-Range Water-Reducing Admixture) to enhance workability increased formwork pressure (Gardner, 1984). Ruiz-Ripoll et al. (2014) have studied the effect of mix design on fresh SCC (Self Consolidating /Compacting Concrete) on formwork pressure. Also. Perrot et al. (2009) studied reinforcement steel bars configuration on the applied lateral pressure of concrete on formworks. On the other hand, concrete pumped into the formwork from its bottom exhibits higher pressures than that placed from above. McCarthy et al. (2012) have shown that maximum concrete pressures with SCC are slightly lower than the full liquid head at any rates of rising in columns and walls. Base-to-top pouring may reduce the effects of impact pressure, as concrete entering formwork is absorbed into the body of the material (Johnston, 2010). The higher initial temperature of the concrete and/or the ambient temperature, will provide the higher lateral pressure and subsequently, a higher rate of pressure decay is recorded (Roby, 1935). In addition, after placement, mixtures with longer setting times display longer lateral pressure cancellation time (Khayat et al., 2007). In most studies, the pressure can be found to decrease slowly before dropping to zero approximately 3h after casting (Khayat et al., 2007). Several studies have established that the rate of casting could have marked effect on formwork pressure (Vanhove et al., 2001, Khayat et al. 2002, Leemann et al. 2003, Assaad 2004, Fedroff et al., 2004, Beitzel et al., 2004, Billberg 2003 and TejedaDominguez et al. 2005). When the casting rate is so fast, formwork pressure could well reach hydrostatic pressure. For SCC placed at relatively moderate-to-high casting rates, Assaad et al. (2006) found the decrease in casting rate from 25 to 5 m/h can reduce the maximum initial pressure by 15%; however, no significant effect was noted on the rate of pressure drop with time. The casting interruption of 10 or 20 min between subsequent lifts at the middle of the placement was reported to lead to a considerable reduction in formwork pressure. Wolfgang et al. (2003) conducted such an investigation on a model wall. As expected, the decrease rate of placement resulted in lower lateral pressure for either the bucket and bottom injection placement methods. Rodin (1952) showed that smaller cross-sections exhibit lower maximum pressure. Gardner (1984) demonstrated that an increase in the formwork dimension will create a larger lateral pressure. Research also has shown that the type of formwork has an effect on formwork pressure. Specifically, rigid and smooth formwork materials result in higher lateral pressure and a lower rate of pressure drop after placement. The roughness of the forms also plays a role due to the dynamic friction that develops upon concrete placement (Djelal, 2001; Djelal et al. 2004, Vanhoveet al. 2000). It was shownthattheapplicationofdemoulding agents,

such as oil, to the formwork, can decrease friction and lead to an increase in lateral pressure (Khayat et al., 2007). On the other hand, Khayat et al. (2005) have shown that the scale effect has an influence on the rate of drop in lateral pressure with time. Arslan et al. (2005) and similarly, Tejeda-Dominguez et al. (2005) have shown the decrease in pressure after casting was dependant on the forming material.

According to above-mentioned studies, there have been several theoretical models to predict formwork pressure, including several input parameters such as rateofcasting,vibrationsystem, setting time, consistency, form permeability and surface texture, form dimensions, coarse aggregate specification, the temperature and concrete unit weight (Proske et al., 2007). In addition to known models such as IS’s model and CAN/CSA model, the most famous of these models are Omran model (Omran et al., 2013), McCarthy model (McCarthy et al., 2012), Models of German Standard (DIN 18218, 2010), Puente model (Puente et al., 2010), Proske model (Proske et al., 2010, 2014), Model of JGJ 162-2008 (Puente et al., 2010), Gregori model (Gregori et al., 2008), Graubner and Proske model (Graubner et al., 2005, 2008), Khayat and Assaad model (Assaad et al., 2006), RousselandOvarlezmodel(Rousselet al., 2005),Vanhove model (Vanhove et al., 2004), ACI model (ACI 347-04, 2004), Model of TGL 33421/01 (Puente et al., 2010), CEB-FIP model, Yu model (Yu, 2000), New Delhi model (Puente et al., 2010), CIRIA model (CIRIA, 1985), Models of French Standard (NF P93-350, 1995) and Tah and Price model (Tah and Price, 1991). Above-mentioned studies and many others in the literature have been the bases of several codes for the general design of formwork as shown in Table 1.

Table 1 Most common standards and regulation for formwork general design

EN12812:2008 ‘‘Falsework Performance Requirements and General Design’’

The European Committee for Standardization (CEN/TC 53 ‘‘Temporary works equipment’’)

EN13670:2011 ‘‘Execution of Concrete Structures’’

Construction Industry Research and Information Association (CIRIA)

The European Union DIN18218: 2010-01

CIB-CEB-FIP

For the highly workable concrete, hydrostatic form pressure over the total formwork height must be assumed (Proske et al., 2014)

For the highly workable concrete, hydrostatic form pressure over the total formwork height must be assumed (Proske et al., 2014) and for the design of the formwork, the bilinear pressure distribution is employed (Figure 2-14)

For the highly workable concrete, hydrostatic form pressure over the total formwork height must be assumed (Proske et al., 2014)

CANADA

The European Federation of Producers and Contractors of Specialist Products for Structures (EFNARC)

Forms higher than 3m are designed for full hydrostatic head (EFNARC, 2002)

The lateral pressure diagram of concrete is assumed to be trapezoidal in shape (Figure 2-13) (SP-4(14), 2014).

American Concrete Institute (ACI) ACI Committee 347 (2004) (ACI 347-04) and SP-4 (2014) ‘‘Formwork for Concrete’’

The significant variables considered in the ACI recommendations are the rate and method of placement, consistency of concrete, coarse aggregate concentration, aggregate nominal size, concrete temperature, smoothness and permeability of the formwork material, size and shape of the formwork, consolidation method, pore-water pressure, content and type of cement, as well as the depth of the concrete placement, or concrete head (Proske et al., 2014).

Occupational Safety and Health Administration (OSHA) (Nawy, 2008)

American National Standards Institute (ANSI) (Nawy, 2008)

Scaffolding, Shoring and Forming Institute (SSFI) (Nawy, 2008)

American Society of Civil Engineering (ASCE) (Nawy, 2008)

Formwork Suppliers (FS) (Nawy, 2008)

Canadian Standards Association (CSA) CSA S269.3 ‘‘Concrete Formwork’’

Unless the rate of placement can be controlled to a design specified rate, column forms shall be designed for full hydrostatic pressure

Canadian Standards Association (CSA) CSA S269.1 ‘‘Falsework for Construction Purposes’’

Unless the rate of placement can be controlled to a design specified rate, column forms shall be designed for full hydrostatic pressure

Canadian Standards Association (CSA) CSA S269-2012 (last version)

3. System Configuration

It considered the same provisions and language described by the ACI 347-12 for determining the formwork pressure of SCC (Khayat et al., 2011)

As can be seen in Figure 1, this system consists of two sacrificial perforated sheets which are connected to each other using some ties. Sacrificial sheets are located between steel bars and the internal surface of the formwork. This system bears the lateral pressure of concrete and prevents a significant pressure on the formwork. The dimensions of the sheets, the diameter of the holes and their arrangement are completely optional. But, any change in any of these parameters can change the performance of the system. The material of these sheets should be

Australia AS3610.1 (2010) “Formwork for concrete” AS3600 (2009) “Concrete structures”

such that they do not react negatively with the concrete and at the same time, they must have the necessary resistance.

Fig.1 The general configuration of presented concrete pressure reduction system (CPRS)

4. Numerical Study

In this study, the PVC perforated plates are selected as sacrificial sheets. The internal width and the height of the formwork are 400 mm and 2,500 mm respectively. The material of the formwork is PVC with a thickness of 4 mm. The formwork has been assumed fixed in the bottom level (at y = 0). The thickness of sacrificial sheets are 3 mm and their height is 1,000 mm too. The diameter of the holes is 20 mm. The rate of the holes to the whole surface of the sheets is 0.3 too. The diameter of cylindrical ties is 10 mm and the distance between them is 700 mm. The used concrete has been modelled as a viscoelastic, homogeneous, and isotropic filler with a density of 2450 kg/m3. Figure 2 shows the distribution of the principal stress the shear stress in the formwork. As can be seen, the maximum principal stress and the maximum shear stress in the formwork are 22.88 MPa and 2.68 MPa respectively. These stresses are created adjacent to the supports.

Then the concrete pressure reduction system (CPRS) was added to the model. Figure 3 shows the distribution of the principal stress the shear stress in the sacrificial sheets. As can be seen, the maximum principal stress and the maximum shear stress in the formwork are about 150 MPa and 36.7 MPa respectively. These stresses are created in the location of the ties.

Fig.2 Principal stress (left) and shear stress (right) distribution in the simple formwork

The deformation pattern of the sacrificial sheets is illustrated in Figure 4. As can be seen, the maximum deformation of the formwork is about 3 mm. This deformation is created in the middle of the locations of the ties.

Fig.3 Principal stress (left) and Shear stress (right) of the sacrificial sheets

Fig.4 Deformation of the sacrificial sheets

Figure 5 shows the distribution of the principal stress the shear stress in the formwork after using the CPRS. As can be seen, the maximum principal stress and the maximum shear stress in the formwork are reduced to 16.7 MPa and 1.87 MPa respectively in compare with 22.88 MPa and 2.68 MPa regarding simple formwork. These stresses are created adjacent to the supports too.

In addition, figure 6 shows a comparison between the deformation pattern of simple formworks and CPRS formworks. As can be seen, the usage of CPRS has reduced the maximum deformation of formwork from 7.18 mm to 5.35 mm. A summary of numerical results are collected in the table 2. Based on this table, usage of CPRS has reduced the maximum principal stress, the maximum shear stress and the maximum deformation of formwork by 27%, 30.2% and 25.5% respectively.

Fig.5 Principal stress (left) and shear stress (right) distribution in the formwork with CPRS

Table 2 A summary of the numerical results

5. Conclusion

• This research introduces an innovative system called the Concrete Pressure Reduction System (CPRS), which incorporates sacrificial perforated sheets.

• The CPRS effectively manages the lateral pressure exerted by the concrete and mitigates excessive pressure on the formwork.

• Numerical modeling demonstrated that the utilization of this system can reduce the maximum principal stress by a minimum of approximately 27%

• Numerical modeling demonstrated CPRS reduces the maximum shear stress, and maximum deformation, 30%, and 25%, respectively.

• Deformation obtained from parametric studies were verified through experimental tests, which displayed reasonable agreement with the outcomes of the study.

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Optimisation of In-Vessel Composting of Municipal Solid Wastes (MSW)

Lida Rafati*, Hamadan University of Medical Sciences, Iran

*CorrespondingAuthor, Lrafati@yahoo.com, Received: Dec 2022, Accepted: April 2023

ABSTRACT: The aim of this study is to recover nutrient resources by optimizing the chemical oxygen demand (COD) through composting Municipal Solid Wastes (MSW). The study involved 84 tests on four sets of samples, focusing on aeration period, percentage of porous materials, and moisture content. The composting process was carried out using an in-vessel system at a temperature of 70 °C for a period of 14 days. The results indicate that the best aeration period is 8 hours. The addition of porous materials should be limited to 10% of the total weight, as exceeding or reducing this amount can have a negative impact on the process. Furthermore, the research demonstrates that COD can be reduced by approximately 50% through this composting approach.

Keywords: Chemical Oxygen Demand (COD), Carbon to Nitrogen Ratio (C/N), Aeration, Composting, Municipal Solid Wastes (MSW)

1. Introduction

The rapid growth of industrial and technological advancements, along with the increasing population, has presented two significant challenges related to urban solid waste. Although several disposal methods have been proposed, each has its drawbacks, necessitating the development of more advanced approaches to address these issues. Furthermore, composting involves important parameters such as chemical oxygen demand (COD), which impact the activities of microorganisms and serve as indicators of maturity. Achieving an optimal level of COD typically leads to other optimal design parameters. Thus, this study aims to propose a sustainable composting solution by determining the optimum parameters. Simultaneously optimizing COD in the composting process, the study focuses on three design parameters: aeration period, percentage of porous material, and moisture content.

2. Research History

Composting is highly valued for its environmental versatility in the stabilization of municipal solid waste (MSW). Composting is considered an ideal technique for managing solid wasteduetoitsabilitytobiologicallyconvertorganicsolidwastesintostabilizedorganicmatter (OM) with high plant nutrient content. In the present time, there is a growing significance and extensive research focused on understanding various indices associated with the composting process. This expanding knowledge base contributes to advancing our understanding and optimizing composting practices. Each year, significant research efforts are dedicated to solid waste management systems, particularly composting systems. Mahapatra et al. [1] summarised

the various bins manufactured around the world that are used for the composting of organic solid waste. A notable example is the work of Shuval et al. [2] between 1981 and 1989, where they conducted a series of cost-effectiveness tests using various composting materials with different ratios. According to their findings, Shuval et al. affirmed the feasibility of cocomposting wastewater sludge with various organic waste materials. However, the selection of primary ratios is significantly influenced by economic factors. Mahapatra et al. [3]

Körner et al. [2] focused on the integration of composting as a viable solution for managing the organic fractions of municipal solid waste (MSW). They highlighted that composting offers a suitable approach for treating the organic waste components within MSW.The research paper discusses various options for the collection and separation of impurities in urban areas. Additionally, it suggests a phased approach to source separation, beginning with the inclusion of hotel and restaurant waste. Furthermore, for rural areas, the implementation of home composting is recommended as a practical solution.

Onwosi et al. [4] put forth a range of composting methods that have been reported to be utilized in waste management. Furthermore, they highlighted the crucial factors such as temperature, pH, C/N ratio, moisture content, and particle size, which are considered relevant in the monitoring of the composting process. The study also delved into the implementation of suitable techniques to enhance and optimize the effectiveness of the composting process. However, certain challenges arose during composting, including the generation of leachate, gas emissions, and the lack of consistent assessment of maturity indices. The researchers addressed these difficulties and proposed strategies for their improvement. Additionally, they highlighted several innovative technologies that have the potential to enhance composting practices. In a separate study, Cofie et al. [5] presented the possibilities and performance of co-composting mixed treatment of fecal sludge (FS) and MSW, exploring the synergies between the two waste streams. The objectives of the study were to investigate the impact of different types of municipal solid waste (MSW), the mixing rate of MSW with fecal sludge (FS), and the frequency of turning on the quality of compost. Samples were collected during each turning process and analyzed for variousparameters, including total solids, electrical conductivity,total volatile solids, total organic carbon, pH, ammonium and nitrate nitrogen, and total Kjeldahl nitrogen. The results indicated that the number of turning repetitions did not significantly influence temperature changes or the quality of the compost. In another study, researchers explored the co-composting performance of sewage sludge (SS) and the organic fraction of municipal solid waste (OFMSW) at different ratios [6]. The findings indicated that a higher proportion of sewage sludge (SS) facilitated the initiation of the composting process, while increasing the organic fraction of municipal solid waste (OFMSW) extended the thermophilic period and enhanced the degree of humification. However, a higher proportion of OFMSW necessitated a longer co-composting duration to ensure optimal compost maturity and quality. In another study, Cai et al. conducted four experimental series on co-composting wastewater sludge with rice husk, observing the removal of a significant portion of semi-volatile organic compounds from the compost after 56 days [7]. In their research, Lannotti et al. [8] investigated the stability of compost generated from municipal solid waste (MSW) using dissolved oxygen respirometry in a pilot-scale system. The study involved examining the changes in stability of samples at different stages of the composting process through chemical and physical tests. This

methodology offers a versatile approach, serving as a straightforward quality control measure or enabling the calculation of rates for comparing efficiency within or among composting facilities. Furthermore, using an anaerobic pilot reactor, some researchers assessed a composting mixture comprising municipal solid waste, wastewater treatment sludge, wood chips, and a series of enzymes [9]. According to their study, the choice of combining materials, composting materials, and their composition ratios significantly affect the quality of the final compost product. Brinton conducted an examination of the historical appreciation of compost and emphasized the growing recognition of the importance of distinguishing compost from other recycled wastes and conventional fertilizers [10].

In a separate investigation, researchers examined the effects of incorporating different bulking waste materials, such as wood shavings, into OFMSW composting, focusing on their influence on microbial enzymatic activity and the quality of the final compost [11]. The results demonstrated that combining OFMSW with wood shavings and a microbial consortium proved to be a beneficial approach, enhancing enzymatic activity and reducing the composting time. In another research endeavor, laboratory tests were conducted using sewage sludge as a base substrate for composting [12]. The study observed characteristic parameters of the composting process, including fat content and lipolytic enzymatic activity, using aerated static lab-scale composters. The results indicated that co-composting with sewage sludge can be considered a viable option for treating solid waste, even at high proportions of up to 40%. However, it may be advisable to limit the maximum ratio to 20% to avoid prolonged composting periods. Tognetti et al. explored the impact of various municipal organic waste (MOW) on the stabilization of organic matter and the quality of compost [13]. The findings indicated that shredded treatments demonstrated faster stabilization of organic matter compared to nonshredded treatments. Addition of wood shavings significantly improved compost quality, although it led to a decrease in total nitrogen and available nutrient concentrations. In their research, Nemati et al. [14] investigated the recovery of nutrient resources through the cocomposting of wastewater treatment plant sludge with Municipal Solid Wastes (MSW). Their study aimed to achieve optimal levels of chemical oxygen demand (COD) and carbon to nitrogen ratio (C/N). The researchers determined that the most favorable waste to sludge ratio for this process is 2:1. Additionally, they found that an 8-hour aeration period yields the best results. To maintain the desired composting conditions, the addition of porous materials was limited to a maximum of 15% of the total weight. Interestingly, the study indicated that sludge dewatering is unnecessary in such co-composting processes. Furthermore, Nemati et al. [14] observed that the efficiency of reducing both COD and C/N levels reached approximately 40%.

Bian et al. [15] examined the influence of matured sewage sludge (MSS) amendment on N2O emissions during aerobic co-composting of MSW. The results confirmed that MSW composting with MSS amendments increased N2O emissions during the initial stage. Zhanga et al. [16] focused on the physicochemical characteristics, such as pH and electrical conductivity (EC), in the co-composting of pine sawdust with fresh solid swine manure. The results suggested that nitrogen and phosphorus decomposition primarily occurred during the mesophilic phase, while organic carbon degradation took place during the thermophilic phase. A mixture of 30% swine manure with an initial C/N ratio of approximately 40 was found to be optimal for composting organic substrates. In a similar study, Millán [17] conducted a field trial

involving the co-composting of municipal solid organic waste with wastewater treatment plants (WWTP) sludge in a municipality in Boyacá. The study aimed to identify the optimal proportion of these materials and characterize their respective properties. Yang et al. [18] investigated the composting of yard trimmings (YT) and food waste (FW), with the goal of determining the appropriate mixing ratio between the two. The results indicated that a 1:1 mixing ratio was optimal, resulting in a C/N ratio of 14.15.

3. Method

The study utilized a "Composting Optimization Laboratory Reactor" as the experimental setup. This reactor system consisted of a closed chamber housing four cylindrical vessels. To ensure precise temperature control, automatic elements and digital sensors were employed to continuously monitor the ambient temperature. The frame of the system was constructed using fiberglass sandwich panels with double galvanized facings, providing excellent insulation and minimizing heat exchange. The temperature regulation was achieved through a digital heating system, where the sensors would activate and cut off the electricity flow to the elements as the desired temperature was reached. However, due to the efficient insulation system, it took a significant amount of time for the temperature to decrease. The heat loss could be adjusted between zero to ten Celsius degrees, depending on the desired accuracy. The pilot system was equipped with a central switch, fuse, and function indicator for operational safety. Additionally, two external fans were installed in the reactor to serve as air blowers and heat-gas exhaust. This allowed the operator to select various aeration types, and the fan could be activated or deactivated using a digital timer along with a thermal sensor or its functional interval. Manual control of these fans was also possible when specific programs were not in place. In the study, the initial phase involved source separation of the municipal solid waste (MSW). The separated waste material then underwent milling to achieve an approximate size of 4 cm, which was considered suitable for composting and contributed to the rapid reduction of organic carbon content. Small wood chips, measuring approximately 1200 mm2 in area, were added to create the necessary porosity in the composting material. Additionally, flexible PVC parts with a length of approximately 20 mm were used to further enhance the porosity. The pH value of the waste used in the study was measured to be 6.3.

4. Test series

In this study, three series of tests were designed and conducted as follows:

4 1 Series 1: Constant parameters: Temperature, Amount of additives for increasing porosity (20%), Moisture content of waste (no dewatering)

• Constant parameters: temperature: 70 °C, initial COD

• Variable parameters: aeration frequency and duration (times of aeration)

• Sampling period: every 2 days

• Test duration: 14 days

• Controlling parameters: COD variation

Aeration frequency and duration are shown in the Table 1 Table

4.2 Series 2: Determination of optimum amount of additives for increasing porosity

• Constant parameters: temperature, times of aeration, Moisture content of waste (no dewatering), initial COD

• Variable parameters: amount of additives for increasing porosity

• Sampling period: every 2 days

• Test duration: 14 days

• Controlling parameters: COD variation

In this series, different amount of additives were added to the samples in order to determine the optimum amount for the best level of porosity. The evaluated ratios are shown in Table 2

Series 3: Optimum moisture determination

• Constant parameters: temperature, times of aeration, amount of additives for increasing porosity, initial COD

• Variable parameters: moisture content of waste

• Sampling period: every 2 days

• Test duration: 14 days

• Controlling parameters: COD, and weight variation

At this stage, the optimum moisture content was determined by varying the water content of waste. The considered moisture contents are shown in Table 3.

Table 2 Amount of additives in each tank

3 Moisture content in each tank

4 Results

In the initial test series focusing on continuous aeration, tank 1 was continuously supplied with air by keeping its door open. Since maintaining continuous humidity control was challenging, the initial moisture level was used as the determining factor. Based on Figure 1, it was observed that tank 2 achieved a 35% reduction in COD. This indicates that extending the aeration intervals by 8 hours resulted in a 20% decrease in system efficiency due to a reduction in available oxygen for the microorganisms. Interestingly, although the aeration intervals increased linearly, the efficiency reduction process was non-linearly affected. The efficiency reduction was comparable to that achieved with continuous aeration. In other words, when extended aeration was applied, biological processes were hindered due to rapid moisture loss, with a maximum reduction of 25% observed. Therefore, the optimal aeration period was determined to be 8 hours in this scenario. Figure 1 illustrates the highest rate of COD removal during 15 days of system operation occurring in tank 2, after which the rate remained relatively constant. The observed COD reduction was 50%. Any percentage of porosity-enhancing additives exceeding 10% led to a decrease in the COD removal rate. Hence, it is recommended to apply this recommended level of porosity-enhancing additives in real-scale applications. Furthermore, the addition of 20% of this material, due to its high porosity, resulted in early moisture evaporation and a reduction in system efficiency by approximately 40%.

The optimum reduction of COD was found to be 50%. Dewatering up to 60% caused a decrease in system efficiency by up to 20%. Similarly, dewatering to 40% resulted in another 27% reduction in system efficiency. This indicates the high moisture requirements of the microorganisms involved in the composting process. Notably, tank 4 exhibited the highest rate of compost COD reduction (as shown in Figure 2).

Figure 1 illustrates the results of COD control in all series of tests in a 14-day period.

Fig.1 Variation in COD levels across different tanks after a duration of 14 days in the initial (left), second (middle) and third (right) series of tests.

5 Conclusion

Based on the research findings, the in-vessel composting of municipal wastes yields the following results:

• Municipal wastes should not undergo dewatering during the composting process.

• When maintaining a temperature of 65 °C and applying an 8-hour aeration period, the maximum Chemical Oxygen Demand (COD) reduction in the municipal solid waste (MSW) is 50%.

• Extending the aeration intervals by 8 hours leads to a decrease in system efficiency by 20%.

• To achieve optimal results at a temperature of 65 degrees, it is recommended to include porosity producing additives in the mixture volume, accounting for 10% of the total volume.

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This article is an open-access article distributed under theterms and conditions of the Creative Commons Attribution (CCBY) License (http://creativecommons.org/licenses/by/4.0/).

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Our partner journal is open to submit papers in the Road and Pavement Engineering

SCOPE

•

• Accident analysis and traffic psychology

• Airport pavement systems

• Bounded and unbounded pavement design

• Crack and fracture mechanic

• Transportation network design

• Environmental impacts of transportation

• Intelligent and E-Transportation

• Innovative laboratory testing

• Logistics and supply-chain

• Material characterization and behaviour

• Non-destructive tests

• Numerical simulations of pavements

• Pavement construction techniques

• Pavement damage analysis

• Life cycle assessment and cost analysis

• Pavement management systems

• Pavement structural integrity evaluation

• Road and pavement maintenance

• Road construction, marking, safety

Chief Editor:

• Dr. Farzaneh Tahmoorian, Central Queensland University (CQU), Australia

Members (alphabetical order):

• Dr. Yahya Aliabadizadeh, The Catholic University of America, USA

• Prof. Ehsan Forootan, Aalborg University, Denmark

• Prof. Mahmoud Ameri, University of Science and Technology, Iran

• Dr. Hossein Asadi, Senior Manager (Pavements) at Transport for NSW, Australia

• Eng. Russell Crabb, Managing Director of Asphalt Consulting Company, Australia

• Eng. Ryan Jansz, National Technical Manager of Boral asphalt, Australia

• Dr. Shahab Khakpour, University of Oulu, Finland

• Prof. Arash Massoudieh, The Catholic University of America, USA

• Dr. Saeed Nemati (Founder), CIVILICOM, Australia

• Emeritus Prof. Hamid Nikraz, Curtin University, Australia

• Dr. Pejoohan Tavassoti, University of Waterloo, Canada

• Prof. John Yeaman, University of the Sunshine Coast, Australia

• Dr. Ali Ghavidel, APAC, New Zealand

• Load-bearing capacity of pavements

• Sustainable transportation

• Transportation economic policy

• Fatigue-Creep interaction in the pavements

• Transportation infrastructures

• Case studies

doi.org/10.56601/AJMRPE