Professorial Inaugural Lecture Series BUILDING COLLAPSE AND BUILDERS IN SHACKLES:
RESEARCH EFFORTS ON POLYMER CONCRETE AS ‘WAY OUT’
INAUGURAL LECTURE By
PROFESSOR BALA MUHAMMAD Dean, Faculty of Environmental Sciences
Professorial Inaugural Lecture Series BUILDING COLLAPSE AND BUILDERS IN SHACKLES:
RESEARCH EFFORTS ON POLYMER CONCRETE AS ‘WAY OUT’
INAUGURAL LECTURE By
PROFESSOR BALA MUHAMMAD Dean, Faculty of Environmental Sciences
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PROFESSOR BALA MUHAMMAD
In every research undertaking there is joy to every single novel ﬁnding: The absolute joy is in the usefulness of the novel ﬁndings
TOAST At childhood, I was involved in the construction of residential buildings using naturally found traditional building materials. Interestingly, the actions performed during the involvements were all under the mentorship of my father. The lessons learnt, though mainly basics, inspired a keen interest in me, which later galvanized into high inquisitiveness in both traditional and modern ‘building materials’ sciences as well as construction techniques especially those of great relevance to our environment. Since then, I begin to realize the fact that ‘building basically consists of several elements made from materials of different natural origins’. The inquisitiveness grew much higher after I attended Polytechnic as well as University where I studied ‘building’ in both institutions. In fact, it was then I realized that in modern perspectives ‘every single material found as a component in building is a result of extensive search and intensive research’ involving possibly many professional investigators. In fact, investigations on building materials, guided by various ‘National and International Standards’ are normally carried out within the laboratories as well as real situations. In real situations for instance, the potential material could be assessed for performance capacities in ‘short-term’, ‘medium-term’ and ‘long-term’ periods under various service conditions. The assessment is usually carried out diligently and of course so rigorously simply because optimum quality, safety, economy and harmony must be ensured. Indeed, by the time the material is recommended to serve within the building envelop, its properties and performance capacities must have been fully observed and wholly documented. In this respect, the necessary technical knowhow in the materials production, construction methods and maintenance strategies are usually spelt out and equally disseminated over years of higher educational learning and trainings on students who - at the end of their graduations - emerge as ‘Builders-to-be’. The young graduates will then embark on the accumulation of practical knowledge through participations in project executions under highly experienced professionals. Eventually, they will be screened by elder statesmen in the profession before earning their recognition as BUILDERS. Surprisingly, upon all these diligent and rigorous measures towards ensuring desired satisfaction in qualitative material’s production, fully functional buildings and minimal maintenance activities, regretfully many buildings are composed of substandard materials, poor workmanship, as well as persistent maintenance challenges. “What would you expect in the event of building materials’ production by those lacking the knowledge of the required material’s properties? What would you expect in the event of construction handled by those who neither have the proper knowledge nor correct training to 5
build? What would you expect in the event of an attempt to maintain existing building by employing the services of quarks”? No wonder, substantial numbers of buildings are collapsing so much so that one may conclude; the buildings are on ‘collapse rampage’. Imagine, fifty-four (54) reported ‘building collapse’ cases within a period of forty-eight (48) months [PUNCH; 27th August, 2017]. Therefore, based on this report, at least a building is surely going to collapse within our territorial boundaries in every twenty-seven (27) days. In fact, it may not be a surprise if the rate of ‘building collapse’ in our nation has doubled over the last two years. This lecture expounds on years of research journey towards making our buildings a better and safer place to live.
Yes, es, to make BUILDINGS BUILDINGS better & safer places places for MANKIND!
INTRODUCTION RIVER OF LIFE I started my career in the field of environmental issues as a student at ‘Government Secondary Technical School (GSTS) Mashi, Katsina (1978 1983). During my five (5) years stay in the Technical School, I developed much interest in ‘Building’. I believed the keen interest was a result of meticulous lessons from our competent teachers most especially in the areas of ‘Technical Drawings’ and ‘Workshop Practices’. In fact, at the end of completion, I received my first ‘Honour Roll Award’ for reaching the academic standard required by the school. Actually, my interest in the field of ‘building’ grew much higher after I attended the renowned Kaduna Polytechnic (1983 - 1986) where I obtained ‘National Diploma’ in building (ND Building). Similarly, at the end of the ND programme, I received a prestigious prize; ‘Best Student - ND 2 Building’. The practical experience gathered from chain of rigorous trainings in the well equipped workshops and laboratories of the polytechnic as well as the experience gained during industrial training fund (ITF) schemes have contributed immensely to my understanding of ‘building’. I then attended the famous Ahmadu Bello University (ABU) Zaria (1987 – 1990) where I obtained Bachelor of Science Degree in Building (B. Sc. Building). Indeed, it was during the degree programme that I understood most of the concepts in building science. In fact, it was at this transient moment of intense learning that I conceived a bursting vision of the conceptual entities involved in the field of building construction. It is still thrilling to me whenever I recalled the days I took survey of the ABU main gate for the purpose of analysis and design of a proposed pedestrian crossover which I submitted to the Building Department as my final year project. Although, ‘National Youth Service Corp (NYSC)’ scheme (1990 - 1991) temporarily took me away from the grooming exercise, but, this added a wonderful experience in my career. For instance, once I was requested by the NYSC state office to inspect and give advice on remedial actions to persistent roof leakages in a Jumu’ah Mosque building at Normans Land. Upon reaching the building, while in the process of examining the genesis of the leakages, I perceived two of the greatest dangers to any workforce in the construction industry; possible collapse while at work and that of falling down from the roof or scaffold. After NYSC scheme, I then joined academic line and at the same time I embarked on M. Sc. Degree in Civil Engineering at ABU which ended with a research on polymeric substance as an additive in cement mix. Although, positive results were obtained, but lack of suitable equipment for proper chemical analysis hindered thorough investigation. Until several years later 7
when an opportunity came through PhD programme, the research was thoroughly and extensively carried out (2006). It was at this juncture that the ‘river of life’ migrated from ‘learning intensive’ to ‘research intensive’. Therefore, I marked this point as the beginning of the ‘Scientific Research Journey’. Meanwhile, the genesis leading to the circumstances surrounding the building industry which necessitated general overhauling through research actions was briefly highlighted below. The Building Industry Today, the global building industry is already in a new era where technological advancements have been witnessed in many cities. Indeed, global technological advancement has evolved infrastructural transformations through newly developed construction materials, highly harmonized designs, advanced construction techniques and remarkable maintenance methods. The technological advancement was however a result of numerous interests in the expansion of mankind’s frontiers in conjunction to the need for a harmonious co-existence with the eco-sphere, so that a healthy life in harmony with nature is fully enforced. At national level however, the building industry has been facing cumulative challenges over this period of global technological advancements, especially in the sectors of ‘construction materials’, ‘project executions’ and ‘maintenance practices’. While substandard building materials appear to be on the increase in our markets, the construction industry further suffers from unavailability of modern construction equipment as well as poor workmanship and barely little to none maintenance capabilities. As a result, the much desired ‘economically viable’, ‘structurally safe’ and ‘serviceably durable’ buildings are never achieved in many executed projects. Consequently, both properties and most importantly human lives are periodically wasted through incessant partial or complete building collapse. This situation needs to be examined and equally corrected so that lives and properties can be saved.
Therefore, save lives; FIX BUILDINGS! Building Materials The presence of substandard building materials in our markets is perhaps one of the greatest obstacles towards achieving strong, stable, safe and durable buildings. Actually, most of the inferior building materials either contribute directly to the weakening of the elemental parts of the building or promote rapid decline in the overall integrity of the building with consequent effect on mechanical and durability functions. In other words, failure of
building materials to satisfy the required specifications could be an important detrimental factor causing grievous repercussions. Meanwhile, numerous materials could be involved in the construction of any particular building, but products of cement mixes are generally present in most buildings. This makes cement products particularly concrete the most dominant building materials. In fact, while cement is currently the most important construction gel, cement-concrete is the most versatile and preferred construction material on earth with remarkable excelling status as an index signifying the growth and development of a nation. Background of the Challenges The crux of the matter originates from the fact that cement-concrete in its normal condition has quite a number of limitations which inevitably affects its general performance. These include; delayed hardening, intrinsic brittleness, weak tensile capacity, low flexural strength, small failure strain, large drying shrinkage, susceptibility to frost damage, high moisture absorption and most critically low resistance to chemicals. In consequence, not only the desire to coup with the ever changing global modernization was curtailed, but also structural degradations and aesthetic ugliness were manifested on many structures. As if these inherent shortcomings associated with the conventional concrete are not enough, the substandard practice surfaced and this makes the situation even worst. The synergic effect of the duo; performance limitations and substandard practice therefore transforms the situation into catastrophic challenges with consequent eventualities including the relatively rampant building collapse in our society. Remedial Measures â€“ Research Attempts In order to improve on these drawbacks, many research attempts have been made following careful identification of performance requirements and mode of failure mechanisms. The remedial proposals so far employed centered on the various forms of concrete modifications as well as enhanced technology-based production techniques. These include polymer modified concretes (PMC), fiber-reinforced concretes (FRC), ferrocement composites and high performance concrete [Bala M. 2009]. Others include selfcompacting concrete (SCC), self-healing concrete (SHC), just-add-water concrete, bullet-proof concrete (BPC), magic concrete and transparent concrete. This draft of professorial inaugural lecture reveals hurdles, successes, limitations and absolute joys in respect to years of painstaking scientific research activities conducted mainly on a typical polymeric substance and its performance capacities in cement mixes. Thus, the research principally dealt with two main segments; various
forms of the polymeric substance involved and the numerous positive roles this polymer can offer in the modifications of the conventional concrete and mortar. The first segment explores scientific data in respect of a typical polymer; rubber latex through rigorous â€˜Chemical Analysesâ€™, Thermogravimetric Analyses (TGA), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM). The second segment on the other hand, investigated mechanical and durability functions of the polymer modified phases by carrying out experimental tests on compressive, tensile and flexural strengths, water absorption, drying shrinkage, fire resistance, resistance to acids and sulphates as well as TGA, DSC and SEM.
THE SCIENTIFIC RESEARCH JOURNEY PART I The Mind-Game The scientific research journey begins with the ‘mind-game’; in search of ‘research approach’ on the unprecedented circumstances surrounding the building industry particularly the major drawbacks causing manifestations of degradations, aesthetic ugliness and collapse. Although, the mind may never stop thinking about possible link between these drawbacks and ‘corruption’, but only the actual shortcomings within the buildings which might be connected with the possible ‘corruption’ were considered throughout this investigation. Thus, upon careful study of the facts on the state of affairs as it exists, imperative deductions were proposed, followed by pilot surveys which involve several preliminary laboratory experiments. Typically, the critical issue pertaining to the low resistance capacity of the conventional concrete to chemicals is perhaps related to its moisture absorption which serves as the avenue for most of the destructive agents. In this respect, the various options in the mind-game include; possible increase in the compaction of the compositional conglomerate❶, possible inclusion of an additive of nano-size❷, probable application of superficial barrier❸, probable deactivation of the destructive substances❹ and potential promotion of extra chemical activities to engage the destructive agents into productive components❺. In a similar manner, the mind-game examined each of the drawbacks associated with the conventional concrete along with a chain of possible remedial options. Meanwhile, since each of the remedial options may yield positive results, the mind-game must therefore exploit secondary factors such as ‘availability’, ‘applicability’ and ‘capacity’ of each option before a decisive preference can be deduced. Indeed, aided by extensive literature review and highly experienced senior mentors as shown in Figure 1, the mind-game spontaneously drifted into a seemingly endless chain of pondering and counter pondering followed by recommendations and counter recommendations, so much so that it was then that ‘I begin to observe a change in the self natural African black hair turning into white colour’.
Figure 1: Distinguished senior research mentors; 3rd left - Professor Abubakar Adamu Rasheed (Executive Secretary NUC, Principal Mentor), 3rd right – Professor Mohammad Ismail (UTM Faculty of Civil Engineering; Deputy Dean Research and Innovation, Academic Mentor), 1st right – Associate Professor Zaiton Abdul-Majid (UTM Faculty of Science; Deputy Dean Research and Innovation, Chemical Analysis Mentor), 1st left – Associate Professor Muhammad Aamer Rafique Bhutta (Polymer Concrete Expert), 2nd left - Professor Riadh Sahnoun (Quantum Chemistry Expert) and 2nd right – Bala Muhammad (Researcher)
Actually, the mind-game never reached to an end; instead, it was halted by fixing a deadline to stop. By then, based on a vast amount of identified facts and concise contents of scientific proposals the ‘research approach’ has been decided and the potential material of interest was also chosen. Interestingly, the major inherent shortcomings associated with the conventional concrete namely; intrinsic brittleness, weak tensile capacity, low flexural strength, small failure strain, large drying shrinkage, susceptibility to frost damage, high moisture absorption and low resistance to chemicals were discovered to have a common relationship with respect to the existence of voids within the interstices of the hardened phase. Therefore, inclusion of material of nano-size was opted. Indeed, the option of employing polymeric substance with elastomeric qualities into the cement mixes was considered not only a way of enhancing mechanical and durability properties of the hardened phases but also a highly strategic option in respect of sustainability. Polymeric Latexes Following the conclusion that a material of nano-size preferably polymeric in nature with elastomeric qualities should be targeted for enhancing the qualities and general performance of the cement mixes, the research journey then begins to explore the world of polymer latexes. Indeed, polymer latexes are being increasingly used in the building
construction industry as modifiers, especially in hydraulic cement concrete and mortar. Figure 2 presents polymeric latexes used as cement modifiers. Among the different presentations of polymeric latexes, elastomers are the most widely used.
Figure 2: Polymer latexes for concrete and mortar modifications [Ohama 1995] Elastomeric Latexes In practice, there are two basic elastomers applicable to cement mixes and these are NRL and synthetic latex. It is worth noting that Nigeria is blessed with both NRL and synthetic latex. Figure 3 shows some prominent derivatives of these elastomers. Meanwhile, due to the prevailing increase in global awareness on environmental issues, I developed high interest in the use of NRL and its derivatives. Qualities attributed to NRL include its status as a renewable resource, high sticky quality, superior building tack, extremely high resilience, and excellent mechanical characteristics.
Figure 3: Elastomeric latexes for concrete and mortar modifications [Bala M. 2012 - Ohama 1995 Extended]
Natural Rubber Latex NRL is a whitish to off-white milky fluid usually obtained by tapping the bark of Para tree (Hevea Brasiliensis). According to history, the Para rubber tree is indigenous to the Amazon rainforest of Para state, Brazil where it grows wild within 5o of the equator. It was observed that twenty botanical families which consisted of about 12,500 species produce latex. But, few plant species known to produce rubber are capable of producing large amount of high molecular weight rubber [Bradley et al., 2006]. Indeed, the research journey took self into many rubber tree plantations. Figure 4 illustrates typical rubber tree plantation as well as the principal operations involved in the extraction of NRL for cement mortar and concrete modifications. In its fresh state, NRL comprises “30%” ─ “40%” rubber hydrocarbon particles (C5H8) suspended in a serum together with about “6%” non-rubber substances [Ong, 1998; Jitladda, 2006]. The non-rubber substances include proteins, lipids, carbohydrates, sugars and traces of some metals such as zinc, magnesium, copper and iron. Natural rubber is a high molecular weight polymer of isoprene (cis-1,4-polyisoprene). It has a particle diameter of 0.1 ─ 4.0 µm and a chemical structure shown in Figure 5 [Rattana, 2003; David & Richard, 2002].
Figure 4: Rubber tree plantation and extraction of NRL for concrete and mortar modifications [Bala, 2012]
Figure 5: Chemical structure of cis-,4-polyisoprene [David & Richard, 2002]
Most of the properties of NRL are determined during the process of natural polymerization rather than controlled as normally is the case with emulsion polymerization. This forms the basis for the presence of non-rubber substances. In addition, bacterial activities and coagulation are known to exist in NRL. However, in order to combat bacterial growth as well as coagulation, NRL is usually preserved with ammonia when harvested from the tree and again after concentration [Esah & Paul, 2002]. Preservation is generally achieved through high or low ammonia-tetramethythiuram disulfide/zinc oxide (HA-TZ or LA-TZ). The later is most often preferred as it ensures good color, chemical stability and low toxicity [Bala 2009]. Medium of dispersion in the NRL is greatly reduced after concentration so that density of the rubber hydrocarbons is increased to about “60%”. Digression Point: An Encounter with Road Safety Personnel Based on the fact that LA-TZ is more preferred over HA-TZ for the reasons stated earlier, this scientific research journey decided to give an ammonia-free NRL a trial with the hope of achieving increased performance qualities. However, upon requesting for ammonia-free NRL from the suppliers, the research journey was confronted with unexpected hurdles; it was after several days of delay while waiting for a feasible NRL ‘harvest-day’, and when finally the day came, the vehicle of the research journey was suddenly flagged down by road safety personnel for over speeding. Indeed, the vehicle was carrying ammonia-free NRL thereby hoping to reach laboratory before it coagulates. Earlier before the commencement of this adventurous journey, all issues in respect of transit modalities have been identified, studied and strategized. In fact, in order to meet all ends, the vehicle was moving at the maximum speed limit, except at overtaking points where the radar spotted the car moving at ‘maximum speed limit plus’: Imagine the long uncertain waiting for the ‘harvestday’❶, cost of the specimen❷, transportation strategies in fear of traffic holdups❸, transportation expenses❹, and the prearrangements in the laboratory for immediate specimen preparations as well as various tests❺. Now the research journey was at middle of nowhere facing ‘x-ray eyes’ of road safety personnel. When finally the car was allowed to proceed, the latex is already in coagulation process! Chemical Analysis of NRL The research journey took its first experimental actions on detailed analyses of the NRL. This was aimed at understanding not only the entire chemical constituents present in the NRL but also the relative content of each substance. In this respect, six field lattices and four specialty latexes were obtained and analyzed for various physical and chemical characteristics. ‘Standards’ employed in carrying out the chemical analysis are mainly International Standard Organization (ISO), Malaysian Standards (MS) and British Standards (BS). While the first experimental pilot surveys were
conducted at Ahmadu Bello University (ABU) Zaria, the chemical analyses were jointly carried out in the following research units: Environmental Laboratory UTM, Rubber Research Institute Malaysia (RRIM) and Sime Darby Research Center (SDRC) Malaysia.
Properties of field lattices evaluated include; total solid content (TSC), dry rubber content (DRC), non-rubber content (NRC), alkalinity, volatile fatty acid number (VFA), particle size, molecular weight, polydispersity and mechanical stability time (MST). Others include inorganic constituents specifically zinc, magnesium, copper, iron and manganese. Findings from the scientific research journey eventually yielded the physical and chemical properties presented in Figures 6 and 7. However, this is for the six lattices only. While it is important to note that DRC represents the main hydrocarbon substance targeted in concrete and mortar modifications, other substances were however assessed for positive or negative roles in the modifications. The rubber particles were expected to enhance the concrete and mortar phases mainly through void-filling and latex-film formation.
Figure 6: (a) TSC and DRC (b) Zinc and magnesium contents
Figure 7: (a) Non-rubber contents (b) Copper, iron and manganese Since DRC is an important component, the lattices were classified based on the DRC contents: (1) ‘High’ (> 41%); RRIM 926 with 41.66%. (2) ‘Below average’ (31-34%); RRIM 2015, RRIM 937 and PB 350. (3) ‘Low’ (< 31%); KT 3539 and PB 260. From this it might be postulated that if poly 1-4 isoprene substance is the sole strength determinant in the modified mix, then
concrete modified with RRIM 926 should yield the highest strength. However, contrary to this postulation, the strength results as shown later went against latexes with high DRC contents. Novel Findings: The Joy and the Absolute Happiness 1, 2 & 3 The results from the preceding chemical analyses and the relationship which follow between these results and subsequent observations on their roles in cement mixes, not only got access into ELSEVIER publications (Figure 8), but these findings of novelty successfully gained accessibility into Advances in Engineering Series (Figure 9) through recommendation by a Canadian based ‘Target Selection Team’. Thus, extended findings were invited and the advanced version of this research was listed (along with other worldwide research findings that matters) on the first page of the February (2012) edition of Advances in Engineering. Additionally, the findings to this respect were broadly submitted as a book chapter to INTECH – Open Science / Open Minds: Advanced Elastomers – Technology, Properties and Applications of NRL Elastomers, September, 2012. ISBN 978-953-51-0739-2, Janeza, Trdine 9, 51000 Rijeka, Croatia (Figure 10). The publication caught the attention of quite a large number of researchers across the globe; through cumulative downloads of 1,000 in its first six months after publication and over 2,000 downloads within a year.
Figure 8: Joy and Absolute Happiness – 1
Figure 9: Joy and Absolute Happiness – 2
Figure 10: Joy and Absolute Happiness - 3
THE SCIENTIFIC RESEARCH JOURNEY PART II Optimization, Mechanical and Durability Investigations This part forms the most challenging segment in this adventurous scientific research journey. Six (6) and eight (8) optimization evaluations and property assessments were conducted respectively. Some of the major parameters involved are depicted in Figure 11. Principally, the assessments deliberated on the mechanical and durability properties of the NRL-MC.
Figure 11: Experimental programme; properties of NRL-MC Optimization parameters dealt with include determination of the most appropriate water cement ratio, optimum latex dosage and most effective curing regime. These three parameters were all based on highest compressive strength gain and this is because strength of concrete is one of the major criterions for assessing its qualities. In addition to compressive strength assessments, tensile and flexural strengths of the NRL-MC were also assessed under mechanical property investigations. On the other hand, the durability parameters investigated are fire endurance capacity, water exclusion capability and resistance to sulphuric acid as well as sodium sulphate attacks. Optimization Assessments Effect of NRL on workability and setting The ease with which a freshly mixed NRL-MC flows during mixing, placement and compaction is noticeably impressive and depending on the contents of the latex, this property could be maintained up to a period of about 1 hr Âą 5 min. At lower latex dosage; 1 - 5%, workability increases with 19
increase in latex content. However, further observations revealed that the reverse is the case when latex is increased to higher percentages; say 10% and above. For instance, the workability values for normal mortar (NM), NRLMM 10% and NRL-MM 20% were observed as 154 mm, 87 mm and 55 mm accordingly. Similarly, shorter setting periods were experienced for high latex dosages. Therefore, when the latex dosage is so small to form chains or spongy links, the latex particles aid the workability by “ball bearing” action. In this respect, the ball bearing action could be of further advantage by reducing the actual water/cement ratio for possible increase in strength especially in situations where mechanical property is of greater importance. Most appropriate water cement ratio Due to the fact that the compressive strength of concrete is strongly linked up with water cement ratio and that NRL not only contains water but also influences workability, most appropriate water cement ratio became an important property. Five mixes of ‘Grade 30’ MC-3% ware developed with w/c ranging from 0.4 to 0.6. However, MC-5% is also included in order to ascertain whether change in latex content will cause noticeable impact. The result of the 28 days compressive strength is shown in Figure 12.
Figure 12: Effect of water cement ratio at 28 days The result shows that least water cement ratio (0.4) yielded the highest compressive strength of 35.56 N/mm2. Addition of water beyond this value indicated negative impact by causing decrease in the strength. Obviously, this finding does not conclude 0.4 ratio as the best content for NRL-MC, rather it only indicates that the less the mixing water, the more advantageous it will be towards strength development. Therefore, going by Abraham’s law [Somayaji, 2001]; 0.35 water cement ratio which is considered as appropriate for complete hydration of cement particles should be noted as the best applicable water content to NRL-MC.
Most effective curing regime Full immersions of specimens in water as well as air curing systems were exercised so that ideal moist condition for the cement hydration as well as coalescences of the hydrocarbon particles present in the latex are motivated accordingly. Thus, specimens were cured in accordance with Japanese Industrial Standards (JIS) A1171:2000 (2M/5W/21A), which signifies 2 days in moist condition, 5 days in water at 20 Âą 3 oC and 21 days in air at 20 Âą 3 o C. However, new modifications were added and these are 2M/3W/23A, 2M/7W/19A and 2M/9W/17A. The new modifications were aimed at evaluating the most favorable curing system for the NRL-MC. The results shown in Figure 13 suggested 2M/7W/19A as the best curing method for NRL-MC. Shortfalls in the first two curing systems revealed the possibilities of retardation in strength development due to loss of water through evaporation during the early air drying process. Further increase in the number of days for specimens to remain in water beyond 2M/7W/19A has indicated a significant fall in strength which signifies lack of sufficient time for latex-film formation to fully develop.
Figure 13: Effect of curing regime The idea of the air curing was to allow for latex-film formation which is necessary to the possible additional strength over that arising from cement hydration. Thus, unlike NC where higher strength is achieved by wet curing alone, MC requires dry curing for optimum strength. Indeed, the result of the air curing process as manifested on the specimens resembles real conditions where most concretes are stripped off formwork and allowed to develop strength in open atmosphere and not necessarily immersed in moisture. Most beneficial latex dosage Laboratory sized investigation revealed gradual increase in compressive strength with increase in field latex content up to about 3% latex/water ratio (Figure 14). However, further increase in latex beyond this content yielded a continuous decrease in the compressive strength. Obviously, as freshly mixed latex modified concrete loses its plasticity, the latex substances are entrapped in the capillaries and possibly in the voids of
the hardened phase also. Thus, depending on the quantity of the latex present in the phase, the hydrocarbon substances may coalesce to form layers of films on cement oxides and aggregate particles.
Figure 14: Effect of latex dosage at 84 days At lower dosages for instance, the latex may end up as filler thereby enhancing the overall density which in turn mitigates increase in strength. Hence, while strength development in normal concrete is mainly a consequence of cement hydration that of the latex modified concrete is usually a combination of both cement hydration and latex-film formation. However, where the quantity of the latex added into the mix is more than sufficient enough to fill in capillaries and possible voids in the hardened specimen, the excess latex tends to prevent the aggregate particles from becoming closer, thereby creating weaker regions for earlier crack developments especially during compressive strength test. Mechanical Properties of NRL-MC Effect of NRL on compressive strength Great emphasis was laid in the choice of suitable mix design for both the conventional concrete which serves as the control sample and the MC. This is due to the fact that good quality concrete stems from the design of the mix, precisely, accurate proportioning of its constituents. For this reason, BRE, a method construed to have a great impact on workability, strength and durability requirements using Portland cements and natural aggregates was chosen. Typical mix-design proportions per m3 for â€˜Grade 30â€™ are presented in Table 1. Table 1: Mix Design Proportions for NRL-MC (Grade 30) 0% Latex (NC) Cement 425 kg/m3 Fine aggregate 780 " Coarse aggregate 915 " Mixing water 230 " Latex 0 "
6% Latex (MC) Cement 425 kg/m3 Fine aggregate 780 " Coarse aggregate 915 " Mixing water 223.1 " Latex 13.8 liters
1% Latex (MC) Cement 425 kg/m3 Fine aggregate 780 " Coarse aggregate 915 " Mixing water 228.9 " Latex 2.3 liters
8% Latex (MC) Cement 425 kg/m3 Fine aggregate 780 " Coarse aggregate 915 " Mixing water 220.8 " Latex 18.4 liters
2% Latex (MC) Cement 425 kg/m3 Fine aggregate 780 " Coarse aggregate 915 " Mixing water 227.7 " Latex 4.6 liters
10% Latex (MC) Cement 425 kg/m3 Fine aggregate 780 " Coarse aggregate 915 " Mixing water 218.5 " Latex 23 liters
3% Latex (MC) Cement 425 kg/m3 Fine aggregate 780 " Coarse aggregate 915 " Mixing water 226.6 " Latex 6.9 liters
12% Latex (MC) Cement 425 kg/m3 Fine aggregate 780 " Coarse aggregate 915 " Mixing water 216.2 " Latex 27.6 liters
4% Latex (MC) Cement 425 kg/m3 Fine aggregate 780 " Coarse aggregate 915 " Mixing water 225.4 " Latex 9.2 liters
15% Latex (MC) Cement 425 kg/m3 Fine aggregate 780 " Coarse aggregate 915 " Mixing water 212.8 " Latex 34.5 liters
5% Latex (MC) Cement 425 kg/m3 Fine aggregate 780 " Coarse aggregate 915 " Mixing water 224.3 " Latex 11.5 liters
20% Latex (MC) Cement 425 kg/m3 Fine aggregate 780 " Coarse aggregate 915 " Mixing water 207 " Latex 46 liters
Inclusion of concentrated latex into the NC mix yielded the compressive strength pattern shown in Figure 15. The optimum strength corresponds to about 1.4% (â‰ˆ1.5%) with an increase of about 4.5% over NC. However, higher strength increase (4.8%) was observed after about three months curing and this is attributed to more beneficial gains on the latex through air curing. This indicates a continuous increase in strength of NRL-MC over that of NC with age.
Figure 15: Compressive strength of NRL-MC Meanwhile, it is worth noting that the optimum latex dosage previously observed which yielded highest strength was twice the value obtained in this case. This is due to differences in the concentrations of the two latexes; field latex and concentrated latex. The former contains about 50% DRC when compared with the later. Effect of NRL on tensile strength Figure 16 presents effect of the NRL on the tensile strength of concrete. In a similar manner to compressive case, 1.5% latex/water was observed as the optimum dosage causing maximum strength gain. However, the percentage increase in the tensile strength of NRL-MC over that of NC was higher (9.7%) when compared with that of the compressive strength. This suggests greater performance by the NRL in tensile than in compressive capacities. This may not be a surprise since failure in concrete is normally associated with some degree of fracture of material and different types of loading give rise to different modes of failure.
Figure 16: Tensile strength of NRL-MC The application of gradual compressive stress on a test piece for instance, leads to initial diminution of the inter-atomic spacing with no indication of fracture at the beginning and this enables the material to withstand more loads before the formation of unacceptable cracks. In the tensile case on the other hand, rapture will occur through development of space between particles and since the force causing rapture is small, the elastic effect of the NRL might contribute better when compared with the situation under compression.
Effect of NRL on flexural strength Unlike in the previous cases; compressive and tensile strengths, in this case 4% yielded the maximum strength (Figure 17). Since failure of plain concrete in terms of resistance to bending is usually a consequence of performance capability in tension, especially in the lower layers of the section under load, the action of LFF is therefore much felt in this situation. In this case, the applied bending stresses are invariably causing elongations most especially in the lowermost layers of the section, and this act synonymous to a direct test on the elasticity of the latex-films. Thus the higher amount of the latex over 1.5% became an advantage as it will provide stronger elastic capabilities.
Figure 17: Flexural strength of NRL-MC Novel Findings: The Joy and the Absolute Happiness 4, 5 & 6 Details on the findings of workability, optimization and mechanical properties have been published in the following ‘Scientific Journals’: Performance Optimization of Elastomeric Latexes in Cement Concrete Production. Science, Technology and Development, 34(4): 232-241, 2015 [Bala & Abdullahi, 2015]. Mechanical Capabilities and Fire Endurance of NRL Modified Cement Concrete. Canadian Journal of Civil Engineering, 38 (6) 661-668, 2011 [Mohammad et al., 2011] Making Void-Free Cement-Latex Blend using Morphology and Thermal Degradation Analysis. Indian Concrete Journal (ICJ), Vol. 83(11) 2009 [Bala et al., 2009] Durability Functions of NRL-MC Effect of NRL on drying shrinkage of mortar Drying shrinkage test was in conformity with ASTM C531:2005. Demec readings between 150 mm demec-gauge points were observed on daily basis for two weeks at 23 ± 2°C. Figure 18 presents typical observation on a specimen. The daily operations were followed by consecutive circles of three days drying and an overnight cooling at 60 °C and 23 ± 2°C respectively. The 25
drying shrinkage was recorded each day until constant value was observed for at least two successive days.
Figure 18: Measuring drying shrinkage using demec gauge Three drying stages were observed; initial, intermediate and final stages (Figure 19). While observations made on the third day after casting are considered as drying shrinkage at the initial stage, those marking the end of the controlled atmospheric curing period are taken as intermediate case. Observations conducted at the end of the heating and cooling oscillations were considered as final stage.
Figure 19: Stages of drying shrinkage (NRL-MM) The optimum content of poly(1,4-isoprene) for minimum drying shrinkage was found to be 10% (vol.) isoprene/water ratio and the mortar was observed to be enhanced by 7.5% within a month of normal and heating curing systems. However, differences in drying shrinkage between the normal and modified mixes appeared to be on the increase with time. Meanwhile, subjecting the specimens to heating at 60 °C was observed to have negative effect through softening of the integrated poly(1,4-isoprene) particles with possible consequence to higher shrinkage as the surrounding harder particles presses on the isoprene. Thus, alternative method which does not include heating could be more suitable for cement mixes modified with elastomers. Effect of NRL on water absorption of concrete Measurement of water absorption was conducted in accordance with BS 1881–122: 1983; ‘Method for Determination of Water Absorption’. Cored samples were kept in an oven for 72 h at 105 ± 5 oC followed by subsequent cooling for 24 h in dry airtight vessels (Figure 20). At the end of drying and cooling processes specimens were immersed in water for 30 ± 0.5 min at 20 ±
1 oC and then weighed. Average water absorption of three cored specimens expressed as a percentage of dry samples is considered as the water absorbed in each particular batch.
Figure 20: Water absorption; (a) coring (b) cored (c) drying (d) cooling Figure 21 presents water absorption results. From the results, MC-5% absorbed the least water content, above and below which more water was absorbed. In fact, the more the latex content above this limit the higher the water absorbed. Since NC contains voids as depicted in its structure morphological captions, therefore latex content in mixes below MC-5% is insufficient to fill the voids. Similarly, modifications beyond MC-5% depicted poor water exclusion properties perhaps due to excess latex over that which is sufficient for the most effective voids filling. Indeed, excess latex beyond that which is necessary to fill capillary pores may prevent proper compaction of aggregates by appearing at interface boundaries. Meanwhile, prolonged air curing or heat treatment as in the water absorption test could cause increase in void contents mainly due to higher expulsion of moisture.
Figure 21: Water absorption of NRL-MC Effect of NRL on fire endurance of concrete The scientific research journey noted with serious concern that inclusion of elastomeric substances into concrete aimed at improving performance properties may pose an important threat particularly at high temperatures. The danger could be more pronounced when the co-matrix systems are applied as surfacing materials in tropical regions or in the event of elevated temperatures due to fire outbreaks and nuclear reactor pressure vessels.
In order to establish capacities of the NRL-MC normal and modified concrete specimens were prepared, heated and subsequently tested for compressive strength. Five temperature levels; ambient temperature (27oC), 150, 300, 500 and 800oC were applied. An electric furnace was employed and it has an average heating rate 15.6oC/min. The temperature gradient was evaluated from the ratio (Tf - To)/Mt. Where To and Tf are the initial and final temperatures respectively, and Mt represents minutes taken to raise the temperature from 27oC to 800oC. Heating is terminated once the desired temperature is attained and specimens are allowed to cool in the furnace until room temperature is achieved. Figure 22 portrays some activities involved during the fire endurance investigations.
Figure 22: Fire; (a) before (b) during (c) after (d) crushing after 1,200oC Compressive strength of NRL-MC decreases with increase in temperature at a rate faster than that of NC (Figure 23). In fact, while strength loss in NRL-MC containing 1.5% latex/water ratio could be up to 50.5% at 800 o C, the corresponding loss in NC was observed as 37.8% only at similar temperature. Meanwhile, since at room temperature MC-1.5% exhibited slightly greater strength over that of the NC, the temperature point at which the MC fell below the NC was evaluated and this was found to be 390oC (Figure 24). Thus, inclusion of NRL as a modifier in concrete likely to face elevated temperature below 350oC may not require special safety design precaution measures. However, where the temperature exceeds this limit, additional safety actions to the normal design requirements may be necessary.
Figure 23: Residual compressive strength of NRL-MC after fire
Figure 24: Critical limit of NRL-MC against NC Effect of NRL on chemical resistance of concrete One of the major environmental factors threatening effective performance of concrete is the attack from chemical agents such as acids and sulfates. Deterioration of concrete due to chemical aggression is a serious menace to the two major properties of concrete; strength and durability. Hence, this scientific research journey evaluated performance capacity of NRL-MC in chemically aggressive environments. Two curing mediums containing 5% H2SO4 and 2.5% Na2SO4 each were employed as aggressive environments. In order to understand what really happens when concrete is ‘cast-in-situ’; where concrete is introduced to the service area during its initial age, specimens for H2SO4 were placed into the aggressive curing environment immediately after removal from moulds. However, specimens for Na2SO4 were given one month treatment in ordinary water at 23 oC and 80 ± 5% RH, followed by 72 h air drying at 20 ± 3 oC and 80 ± 5% RH, before exposure to aggressive medium (Figure 25).
Figure 25: Resistance to Na2SO4; (a) before exposure (b) Na2SO4 (c) after exposure Results of compressive strength after aggressive treatment by H2SO4 are presented in Figure 26. The strength values for both NC and MC are low among all immersion periods since specimens were introduced into the aggressive medium immediately after removal from moulds as explained earlier. While NC entertained gradual increase in strength until 56 days where it drops and later pickups at 84 days, MC-1.5% continue to experience reductions until 84 days before it shows signs of strength development. The
other modifications; MC-5% and MC-10% continue to depreciate throughout the 84 days observation period.
Figure 26: Strength performance of NRL-MC in acidic environment In respect to H2SO4 environment, initial strength development in NC was observed to be higher than in MC, perhaps due to lack of favorable condition for the formation of latex-films. However, during the third curing month the rate was higher particularly in MC-1.5%; 33.7% as against 15.1% in NC, which suggests effectiveness of NRL towards blocking internal contact between the aggressive agents and cement paste. Meanwhile, close inspection on specimens subjected to H2SO4 environment discloses some leaching of the cement paste, minute disintegration of fine aggregate particles and slight exposure of gravels. Indeed, this observation was noticed in both NC and MC specimens, especially on the last batch of the specimens. Figure 27 presents compressive strength results for both NC and MC after 84 days immersion in Na2SO4. In this case, initial strengths were relatively high since specimens were cured for 28 days before immersion into the Na2SO4 environment. During the 84 days, all categories of specimens gain strengths at the beginning but suffer strength loss towards the end. However, NC suffers the highest strength loss. In fact, NC with second highest strength value ended up having the least strength among all.
Figure 27: Strength performance of NRL-MC in sulfated environment In respect to Na2SO4, while highest strength loss; 18.9% was observed against NC, the lowest; 2.86% was recorded against MC-5%. On the other hand, considering lowest and highest strength gains against NC and MC-3%
respectively, it follows that increase in strength associated with the modified concrete was 86.2% higher than the corresponding increase in NC. Thus, absence of latex particles in the capillaries and voids of NC might have rendered the matrix vulnerable to attack by the surrounding Na2SO4 ions. Meanwhile, samples cured in Na2SO4 medium showed no sign of leaching or weight loss throughout the curing period. Novel Findings: The Joy and the Absolute Happiness 7, 8 & 9 The foregone assessments on durability properties of NRL-MC appeared in details in the following ‘Flag-ship Journals’:
Figure 28: Joy and Absolute Happiness – 7
Figure 29: Joy and Absolute Happiness – 8
Figure 30: Joy and Absolute Happiness – 9
THE SCIENTIFIC RESEARCH JOURNEY PART III Material Characterization and Morphology The scientific research journey never stopped at the foregone gigantic investigations, material characterizations as well as morphological studies were also involved. In this respect, the main tools employed are ‘Thermogravimetric Analysis’ (TGA), ‘Differential Scanning Calorimetry’ (DSC) and ‘Scanning Electron Microscopy’ (SEM). The findings in this segment truly added much glamour to the overall investigations. In fact, most of the findings under the ‘Scientific Research Journey Parts I and II’ were better understood when analyzed on the basis of the findings in ‘one’ or more of the three sections involved in this segment (Part III). Additionally, the collaborative involvement of ‘Chemical Engineering Exparts’ to this respect has transformed the entire research exercise as an enjoyable session indeed. Yes, scientific RESEARCH is an enjoyable ADVENTURE Thermogravimetric Analysis Thermogravimetric analyzer, Mettler Toledo TGA/STDA 851e was used for the thermal degradation assessments. Mass loss and decomposition temperature (Td) were observed by raising applied temperature from 25 oC to 900 oC, with heating rate and flow of nitrogen at 10 oC/min and 10 ml/min respectively. More than ten test specimens were involved and these were basically obtained from hardened cement paste (HCP), latex film, cementlatex co-matrix and mortar. Typical results on TGA assessments are given in Figure 31. HCP was observed to suffer from two major weight losses at 55-200 oC (about 9%) and 520-770 oC (about 17%). The latex-films however suffer from single sudden similar weight losses (about 95%) at 340-460 oC. Initial weight loss in HCP could be related to the combined evaporations of water vapour, capillary water, interlayer moisture and adsorbed atmospheric moisture. The final weight loss however could be the result of degradations related to calcium oxides (Ca(OH)2) of the cement. This characteristic obviously suggests condition where the cement normally loses its binding properties due to decomposition of its oxides, thereby yielding to a significant lost in strength. Eventually, HCP degraded by about 27% of its original weight during the entire firing process. Thus, its main filler content was about 73%.
On the other hand, lack of weight loss in latex film between initial temperature and 200 oC indicates absence of moisture in the film. However, the high weight loss that follows marked the softening point and the main degradation limit of NRL. The remaining decomposed content (<5%) afterwards represents the filler. Volume change was also observed to be involved in the process as the 1.2 mm film was reduced to a thin dark-purple coat with adhesive qualities upon touch.
Figure 31: Thermal degradations of cement, latex and blend Differential Scanning Calorimetry DSC was carried out using PERKIN ELMER DSC 7. However, prior to loading specimens were weighed on Mettler AE 166 and housed in a pressed aluminium pan. The heating rate and range were 20 oC/min and 30 oC to 550 o C respectively. Nitrogen was also used as a purge gas at 20 ml/min. At least ten specimens were prepared and tested for DSC observations. The specimens include HCP, latex films, cement latex blend and mortar. Typical endothermic patterns during heating as well as cooling of the materials tested for DSC are presented in Figure 32. Except for the two shallow crests indicated by the two downward arrows, the pattern in HCP depicted smooth progress in the heat-absorbed and heat-released graphs. Considering the micro-structural units in a typical cement matrix, the shallow crests at about 100 oC and 460 oC could be related to its water vapour, capillary, adsorbed and interlayer moisture turning into steam. While the steam is expected to be expelled at a temperature of about 100 oC, the chemically combined water require much higher temperature of about 460 oC for its expulsion. On the other hand, endothermic pattern for the latex, yielded major noticeable crest between 100 oC and 200 oC; this suggests softening range. The peak temperature appeared at about 150.33 oC with onset and end at 146.94 oC and 172.33 oC respectively.
Figure 32: Endothermic process; (a) HCP (b) Fresh latex (RRIM 2015)
Scanning Electron Microscopy JEOL Scanning Electron Microscope JSM 6390 LV was used. Morphologies were obtained at a current and working distance of 15 Kv and 9 mm respectively. Specimens were coated with 10 nm platinum in an â€˜Auto Fine Coaterâ€™ before positioning against electron gun. Platinum coating was carried out at 20 mA for about 60 sec. Specimens involved in this section include HCP, latex-films, cement-latex blend, cement-water-latex blend and mortar. Figure 33 presents typical morphologies observed from the ESM captions. The latex-film depicted a continuous membrane without signs of porosity. However, HCP yielded a morphology associated with porously textured surface which is further accompanied by voids or micro particles spacing. Presence of latex can be identified in the cement-latex blend as its morphology looks more cementitious than HCP alone. Thus, upon mixing cement with the water containing latex, the 1-4 isoprene particles gradually coalesced through withdrawal of moisture necessary for cement hydration. Similar effects of the latex could be seen when NM is compared with MM 10% and MM 20%.
Figure 33: SEM; (a) Latex-film (b) HCP (c) Cement-latex blend (d) Normal mortar (e) MM 10% (f) MM 20%
Novel Findings: The Joy and the Absolute Happiness 10 Although, the findings under material characterization and morphology serve as supplementary facts to the results of the investigations explained in the previous sections, some novel findings from this sections dominated another publication in ‘Flag-ship Journal’:
Figure 34: Joy and Absolute Happiness – 10
THE SCIENTIFIC RESEARCH JOURNEY AT PRESENT
There is a popular Arabic saying, ‘Malyanfa’ul ‘ilm, illaa ‘amalunbih’; which could be interpreted as ‘the use of knowledge is in its application’. Thus, research findings should be exploited through applications and this should be the ultimate goal. However, this is not exactly what is happening in our domain. Numerous promising institutional research outcomes have been kept on papers only without converting the theoretical findings into practical applications for the benefit of the general populace. In this situation therefore, the best alternative option, though of little impact is to demonstrate effectiveness of findings through the few available practical opportunities falling along the way. So far, this is exactly what I have been doing in respect to the foregone outcomes of the ‘Scientific Research Journeys; Parts I, II and III’. In addition, much has been done and more is still underway on two parallel research activities; ‘Abandoned Construction Projects’ and ‘Treated Effluents’. These two were also included in this section. The worldwide acceptance for publications of the novel findings from the aforementioned scientific investigations❶; the response by researchers to the published findings through noticeable downloads which erupted❷; the frequent online collaborations between self and global researchers which became a routine❸; the spectacular invitations I have been receiving from scientific journals to be a reviewer or to serve in their editorial boards❹; these collectively gave me the courage and zeal to commence practical applications of the findings. Meanwhile, theoretical findings on construction materials involving laboratory experiments are not sufficient to attract full practical applications. In most cases, small scale implementation follows before full scale implementation. In view of this, I started on small scale applications through building renovation works and in the last five years since the commencement of this exercise the results were surprisingly more than expected. For instance, I was privileged to act as ‘Chairman Direct Labour; Staff Housing Renovations’ in one of my former Universities. Indeed, more than two hundred cases from over fifty buildings have been successfully ‘attended to’ using the principles derived from these findings. In fact, apart from the excellent successes recorded, another interesting part of it is in the financial aspect; where 10 to 40% ONLY of the actual costs for same actions using the conventional approach were recorded. In a remark by the Vice Chancellor (VC) of the University where I headed the renovation exercise, who is currently the Executive Secretary of the ‘National Universities Commission (NUC), he said and I quote “About fifty
million naira (N 50,000,000) was saved to the University on renovation works within a period of twenty monthsâ€?. In respect to these achievements, the academic mentor shown in Figure 1 advised for the writing of concise series of construction books on the newly researched techniques as well as successes observed in the renovation exercise. The books are expected to enrich not only Builders and Estate Managers handling construction and maintenance activities, but also the overall stakeholders in the building sector. Hopefully, this could help in curtailing the present dilemma in both construction and maintenance activities. On the other hand, briefs on the parallel research activities are hereby depicted in the following Figures 35 and 36.
Figure 35: Top-left; Abandoned prototype structure, Top-right; Depreciation in compressive strength of concrete after 6 years exposure using UPV, RH and core methods, Bottom-left; Ultimate strength loss in exposed reinforcement with age, Bottom-right; Performancedepreciation with age for various grades in abandoned reinforced concrete structure (Stage1; level of strength increase, Stage-2; level of reverse in strength, Stage-3; level of strength depreciation, Stage-4; level of appreciable strength depreciation, Stage-5; level of critical strength depreciation)
Novel Findings: The Joy and the Absolute Happiness 11 and 12 At least two publications were made into â€˜Flag-ship Journalâ€™ and these are presented below. In fact, the second paper is currently awaiting a potential PhD Student who can tackle programming of the data involved so that a software appliance can be modeled for smart and quick assessments purposes.
Figure 36: Joy and Absolute Happiness – 11 and 12 The research on treated effluents was based on the observations that concrete production requires a lot of water and only fresh-water is used in most of its production. For instance, in the year 2010 alone, the quantity of water used in the production of concrete at an average of 250kg of cement per 1m3 and 0.5 w/c was estimated as 825 billion liters (Tony and Jenn, 2008). On the other hand, there is an alarming increase in the demand for fresh-water mainly due to global population growth and industrialization. In order to find alternatives to the use of fresh-water in concrete production, a team of researchers including self took a look at possible utilization of treated effluents (TE) from heavy industry (TEHI), palm-oil mill (TEPM) and domestic sewage (TEDS). The results have been successfully published in yet another ‘Flag-ship Journal! Novel Findings: The Joy and the Absolute Happiness 13
Figure 37: Joy and Absolute Happiness – 13
THE SCIENTIFIC RESEARCH JOURNEY AHEAD Background This segment of the scientific research journey summarizes the progress so far in the evolution of the NRL-MC, before presenting an already programmed research actions ahead. The two; research journey so far and research journey ahead are strongly interconnected. Full utilization of the achievements from the research journey so far and the tasks ahead were both aimed at tackling the inherent shortcomings associated with cement mixes particularly concrete and mortar through the utilization of NRL as an integrated part in the hardened phases. In the meantime, the following have been addressed: Application of NRL in cement mortar was first studied by self at local level (ABU Zaria) and the results were quite promising. In this case, mortar of two different mix proportions were prepared and tested for mechanical capacities. Several latex clones (LC) and timber latex clones (TLC) were then studied at international level (UTM Malaysia) aimed at finding best clones applicable to cement mixes. In this case, chemical analysis and performance capacities were involved. Findings of novelty were published in many â€˜Flagship Journalsâ€™ and these include Construction and Building Materials (ELSEVIER), American Society for Civil Engineers (ASCE), Canadian Journal of Civil Engineering (CJCE), Indian Journal of Concrete (IJC), Malaysian Journal for Civil Engineering (MJCE) and Pakistan Journal of Science, Technology and Development. There is a large response by researchers to the published findings through noticeable downloads and frequent online collaborations between self and global researchers. This reflects level of significance of the findings to the bulk of knowledge. Practical applications of the principal findings have gone a long way with remarkable success in performance effectiveness and huge financial savings when compared with conventional methods. Thus, the main task ahead is to explore possible similarities as well as differences between the latexes used at international level and the natural rubber latexes commonly found in Nigeria. This is aimed at evaluating local latexes of the most suitable quality for cement mixes, so that optimum application can be applied on prototype structures or medium scale buildings with the hope of extending applications to large scale structures for the benefit of the wider society. Indeed, elastomeric concrete as well as
elastomeric mortar suitable for Nigerian situations could be a reasonable option in tackling the present building dilemma in Nigeria. The Main Objectives - Research Ahead 1. To study natural rubber tree clones locally produced in Nigeria particularly the LC and TLC in a similar manner to those involved in the research conducted at international level. 2. To investigate the performance capacities of NRL found in Nigeria applicable to concrete and mortar. The specific objectives to this regard include; (a) Identifying, by chemical analysis, natural rubber clonal species that yield minimum content of non-required organic and mineral substances, such as sludge and proteins in the B-serum and C-serum phases of the latex. (b) Determining the properties of the most recommended clonal species, such as; rubber, protein and total solid contents (TSC), sludge content, molecular weight, particle size, alkalinity and water content. (c) Assessing latex mechanical stability time (MST) for the various clones involved in the investigations. (d) Identifying, by studying chemical composition, the best method of preservation in relation to strength development in concrete and mortar. (e) Investigating the degree of miscibility with hydraulic cement minerals for optimum strength values. (f) Finding the chemical bonding capacity of the NRL with the cement particles. (g) Evaluating effect of NRL on bonding between NRL-MC and steel reinforcement. (h) Identifying the desirability of blending latex with cement mixes. 3. To investigate property-improvements of NRL-MC and NRL-MM in terms of physical and mechanical qualities. (a) Maximum safe volume of NRL to be added in concrete (b) Compressive, tensile and flexural strengths tests (c) Compressive strength test at elevated temperatures (d) Drying shrinkage (e) Waterproofing qualities (i.e. improvement on moisture exclusion) 4. To categorize NRL-MC as a material for protection and repair against deterioration of concrete by determining; (a) Effectiveness of NRL in concrete against acid based environments. (b) Effectiveness of NRL in concrete against sulphate based environments
5. To identify factors influencing the performance of NRL in the modified elements using; (a) TGA and DSC of separate and proportionate mixes for thermal stability. (b) Morphological compatibility between cement and latex particles SEM. 6. To design, construct and monitor prototype buildings consisting of roof slab, reinforced floors, etc. Parameters to be studied include; (a) Structural integrity; compressive strength through coring, UPV, etc. (b) Durability functions; cracks, water absorption, corrosion, etc. Long Term Benefits â€“ Research Ahead The long term impact of this project could be viewed in several perspectives and these include; social, economic and technological impact. Social Impact Synthetic latex is practically scarce, expensive and need vigorous chemical processing for its production. Thus, it is seldom employed for large-scale works, except in maintenance and laboratory experiments. Since NRL is naturally found, and there are no sophistications in its production and applications, rubber tree farmers and traders across the country could be engaged. Thus, research on the NRL aimed at its utilization in cement mixes could be viewed as a socially-motivated booster through job creation. Economic Impact Considering the fact that concrete is the highest man made product on earth, inclusion of NRL is its production will attract a lot of economic benefit to the producers, traders and most importantly the stakeholders of the constructions since structural integrity of the infrastructures will be elevated and maintenance cost will also diminish drastically. Technological Impact Undertaking research on elastomeric concrete and mortar will surely create more openings for further research in the areas of other global rubber tree species as well as hydraulic cements falling outside the scope of this research. This could strengthen the efforts towards rescuing reinforced concrete from the present dilemma of degradation and aesthetic ugliness. Indeed, the emergence of elastomeric concrete as a technological solution to the disgraceful situation of building collapse and huge cost on maintenance could in addition to safety be a pride to all Nigerians. It is worth noting that the â€˜Research Aheadâ€™ has been strategized to involve three full-time PhD Students (by research), six full-time M. Sc. Students (by research) and at least nine Undergraduate Students.
CONCLUSION An attempt to counteract most shortcomings associated with concrete through the development of elastomeric concrete (Elasto-concrete) and elastomeric mortar (Elasto-mortar) is underway. In this respect, while much has been done, more is needed. These initiatives could pave way towards achieving buildings with greater certainty in durability and security against undue collapse. In addition, not only properties and innocent lives could be saved through these developments, but nations yarning for the ‘provision of shelter for all’ could be fully strengthened since huge savings have been observed from little practical applications of the new techniques. Rampant ‘Building Collapse’ in our society has been responsible for immense material wastages as well as several casualties involving innocent citizens some of which have lost parts of their limbs and many others have already lost their lives completely. The main questions could be: ‘Until when will these predicaments last? Why should educational stakeholders spend huge amount of money in training builders but eventually ending up in shackles? Who is responsible for depriving the builders from serving the entire nation when it comes to building constructions? Where is the real solution hiding? Please beware! The custodians of buildings (BUILDERS) must be allowed to shoulder construction responsibilities; otherwise BUILDING COLLAPSE will never ever stop! Finally, I profusely thanked the All-Mighty for ‘His’ uncountable bounties from the first second to the last second of my research journey. I then wish to thank my ‘Majestic Parents’ who sent me unto the path of knowledge, my ‘Humble Teachers’ who thought me the basics, my ‘Seasoned Lecturers’ who lectured me through the hard ways, my ‘Super Supervisors’ who pushed me into the river of research, my ‘Caring Family Members’ who have been extra patient with me during my seclusions, my ‘Extra Experienced Technologists’, my ‘Criticizing Colleagues’, my ‘Serious Students’, and the ‘Group of Seven’ (G7) for their immense contributions throughout. I also wish to extent ‘Special Reserved Thanks’ to BAZE University Giants; ProChancellor, Vice Chancellor, Deputy Vice Chancellors, Registrar, Bursar, Librarian, Deans of Faculties, Directors, Chief Security Officer and in particular, the Director Strategy and Special Duties for their unprecedented input in making this Professorial Inaugural Lecture a reality.
REFERENCES ASTM (2005). Standard Test Method for Linear Shrinkage and Coefficient of Thermal Expansion of Chemical-Resistant Mortars, Grouts, Monolithic Surfacing and Polymer Concretes; C531 - 00 Bala Muhammad (2012). Advanced Elastomers - Technology, Properties and Application of Natural Rubber Latex, Book Chapter, ISBN: 979-953-307-5. InTech Croatia Bala Muhammad and Abdullahi S. Performance Optimization of Elastomeric Latexes in Cement Concrete Production: Science, Technology and Development, 34(4): 232-241, 2015. ISSN 0254-6418/DOI: 10.3923/std.2015.232.241 Council for Science and Technology. Bala Muhammad, A. A. Yussuf and Mohammad I. (2009). Making Void-Free Cement-Latex Blend using Morphology and Thermal Degradation Analysis. Indian Concrete Journal (ICJ). 83(11):32-39. Bala Muhammad, Mohammad I., A. A. Yussuf and M. A. R. Bhutta (2011) Elastomeric Influence of Natural Rubber Latex on Cement Mortar at High Temperatures using Thermal Degradation Analysis. Construction & Building Materials 25: 2223-2227. ELSEVIER Bala Muhammad and Mohammad Ismail. Performance of Hydrocarbon Particles on the Drying Shrinkage of Cement Mortar – Building and Construction Materials 24, 868–873, 2013. ELSEVIER Bala Muhammad, Mohammad I., Muhammad A. R. B. and Zaiton A. (2012). Influence of non-hydrocarbon substances on the compressive strength of natural rubber latex-modified concrete. Construction & Building Materials 27: 241-247. ELSEVIER Bala Muhammad, Mohammad Ismail, Aamer Rafique Bhutto and Zaiton AbdulMajid. Influence of Non-Hydrocarbon Substances on the Compressive Strength of Natural Rubber Latex-Modified Concrete - Advanced. Advances in ENGINEERING. May, 2012. Bala Muhammad, Mohammad, .I, Zaiton H. and A. A. Yusuf (2011) Elastomeric Effect of Natural Rubber Latex on Compressive Strength of Concrete at High Temperatures. Journal of Materials in Civil Engineering (JMCEASCE). Online Production, 5; 2011 Bala Muhammad and Mohammad I. (2012). Performance of natural rubber latex modified concrete in acidic and sulfated environments. Construction and Building Materials 31 129–134. ELSEVIER Bala Muhammad (2009), Impact of natural rubber latex on engineering properties of concrete. PhD thesis: Universiti Teknologi Malaysia. BS 1881-122:1983. Testing concrete; Part 122 – Method for determination of water absorption. London: BSI Publications.
BS EN 12390:2002. Testing hardened concrete; Part 3 - Compressive strength of test specimens. London: BSI Publications. Bradley S., Andrew A., Katrina C., Deborah J., Jenny L., John C., Oswaldo O., Richard W., David K., and Steven J. (2006). Identification and comparison of Natural Rubber from two Lactuca Species. Phytochemistry, 67(2006), 2590-2596. David J. D. and Richard H. D. (2002). Natural and Synthetic Latex Polymers. UK: Rapra Technology Limited. Esah Y. and Paul C. (2002). The Manufacture of Gloves from Natural Rubber Latex. Malaysian Rubber Export Promotion Council, 110(2), S3-S14. Illston J. M., Dinwoodie J. M., and Smith A. A. (1979). Concrete Timber and Metals - the Nature and Behavior of Structural Materials. Van Nostrand, Berkshire, England: Reinhold Company. Japan Industrial Standards JIS1171:2000. Test materials for polymer-modified mortar. Tokyo: Japanese Standard Association. Jitladda T. S. (2006). Structural characterization of natural rubber based on recent evidence from selective enzymatic treatments. Journal of Bioscience and Bioengineering, 103, 287-292. Lech C. (2006). Concrete-polymer composite: Overview. 5th Asian Symposium on Polymers in Concrete (ASPIC) September, 11-12. Chennai, India. Allied Publishers Pvt. Ltd., 87-104. Mohammad Ismail, Bala Muhammad, Abdirahman Ali Yussuf, Zaiton Majid and Mohamed El-Gelany Ismail. Mechanical capabilities and fire endurance of natural rubber latex-modified cement concrete (NRLMCC). Canadian J of Civil Engineering, 38 (6) 661-668, 2011. Ohama Y. (1995). Handbook of polymer-modified concrete and mortars. New Jersey (USA): Noyes Publications. Ong E. L. (1998). Latex Protein Allergy and Your Gloves. Kuala Lumpur, Malaysia: Malaysian Rubber Board. PUNCH Newspapers: FMPWR Communiqué, 6th Meeting of the Council. Theme; ‘Building for Inclusion, Growth and Prosperity’, Building Collapse in Nigeria between 2012 and 2016. 27th August 2017. Rattana T. (2003). Reinforcement of Natural Rubber Latex by Nanosize Montmorillonite Clay. PhD Thesis. The Pennsylvania State University. Schneider M., Pith T. and Lambla M. (1997). Toughening of polystyrene by natural rubber-based composite particles. Part I: Impact reinforcement by PMMA and PS grafted core-shell particles. Journal of Materials Science, 32 6331-6342. Somayaji S., 2001. Civil Engineering Materials. New Jersey, United States of America (USA): Prentice Hall. 44
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TITLE OF LECTURE- BUILDING COLLAPSE AND BUILDERS IN SHACKLES: RESEARCH EFFORTS ON POLYMER MODIFIED CONCRETE AS A WAY OUT by Bala MUHAMMAD (...
Published on Jun 20, 2019
TITLE OF LECTURE- BUILDING COLLAPSE AND BUILDERS IN SHACKLES: RESEARCH EFFORTS ON POLYMER MODIFIED CONCRETE AS A WAY OUT by Bala MUHAMMAD (...