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IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) e-ISSN: 2278-1684,p-ISSN: 2320-334X, Volume 7, Issue 2 (May. - Jun. 2013), PP 17-23 www.iosrjournals.org

Tie Confined Glass Fiber Reinforced Self Compacting Recycled Aggregate Concrete Mr.N.Venkat Rao1, Dr.T.Muralidhara Rao2, Dr.M.L.V.Prasad3, Dr.P.Rathish Kumar4 1 2

Assoc.Professor, Dept.of Civil Engg., Vardhaman College of Engg., Hyderabad-501218. A.P., India. Professor& Head, Dept.of Civil Engg., Vardhaman College of Engg., Hyderabad-501218. A.P., India. 3 A.E.E, Irrigation Dept, o/o the SEIC, Kurnool-518002. A.P, India 4 Assoc.Professor, Dept of Civil Engg, NIT Warangal506004. A.P, India,

Abstract:Conventional concrete used in building and civil engineering applications requires compaction to achieve strength, durability and homogeneity. The typical method of compaction, vibration, generates delays and additional costs in projects and moreover is a serious health hazard in and around construction sites. The development of Self-Compacting Concrete (SCC) marks an important milestone in improving the product quality and efficiency of the building industry. The typical methods of compaction and vibration of normal concrete generates delays and additional costs in concrete. A structural reinforced concrete member can be theoretically analyzed if the stress-strain behavior of its constituent material is known. Preservation of the environment and conservation of the rapidly diminishing natural resources should be the essence of sustainable development. The enormous amounts of demolished concrete produced from deteriorated and obsolete structures create severe ecological and environmental problems. One of the ways to solve this problem is to use this Building Demolished Waste (BDW) concrete as aggregates in new concrete. This paper aims to develop stress-strain relationship for M40 grade Glass Fiber Reinforced Self Compacting Recycled Aggregate Concrete (GFRSCRAC). The results of specimens tested under strain control rate of loading are presented. The behavior of tie confined GFRSCRAC is used in formulating a constitutive relationship. Keywords: Building Demolished Waste, Self Compacting Concrete, Recycled Aggregate, Glass Fiber, Confinement, Stress–Strain Curves.

I.

Introduction

Self-Compacting Concrete (SCC) is considered as a concrete which can be placed and compacted under its self-weight with little or no vibration effort, and which is at the same time, cohesive enough to be handled without segregation or bleeding[1]. The working environment is significantly enhanced through avoidance of vibration induced damages, reduced noise and improved safety [2]. Additionally, the technology is improving performance in terms of hardened material properties like surface quality, strength and durability. It is used to facilitate and ensure proper filling and good structural performance of restricted areas and heavily reinforced structural members [3]. The enormous amounts of demolished concrete produced from deteriorated and obsolete structures create severe ecological and environmental problems[4]. One of the ways to solve this problem is to use this Building Demolished Waste (BDW) concrete as aggregates in new concrete [5]. Addition of fibers enhances the ductility of an otherwise brittle recycled aggregate concrete. Concrete is brittle under tensile loading and the mechanical properties of concrete may be improved by randomly oriented short discrete fibers which prevent or control initiation and propagation or coalescence of cracks. Ductility of Concrete is provided with fiber reinforced cementitious composites, because fibers bridge crack surfaces and delay the onset of the extension of localized crack [6]. Self-Compacting Concrete (SCC) has gained wide usage for placement in congested reinforced concrete structures with difficult casting conditions. For such applications, the fresh concrete must possess high fluidity and good cohesiveness. Fiber is a small piece of reinforcing material possessing certain characteristic properties. They can be circular or flat. The fiber is often described by some convenient parameter called “aspect ratio (l/d)”. The aspect ratio of the fiber is the ratio of its length to its diameter [7]. Some of the fibers that are commonly used are steel fibers, nylons, glass, polypropylene and carbon. Each type of fiber has its characteristics properties and limitations. The main objective of the study here is to develop a stress-strain model for Glass Fiber Reinforced Self compacting Concrete (GFRSCRAC). The main parameters involved in the investigation are the strength, spacing and diameter of lateral ties, dosage of fiber, strength of concrete and core dimensions of the specimen. These parameters controls the behaviour of tie confined GFRSCRAC. The non-dimensional parameters called Confinement index (Ci) and Fiber index (Fi) are identified involving all the parameters influencing the behavior of FRSCC. The Confinement Index is defined as: www.iosrjournals.org

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Tie Confined Glass Fiber Reinforced Self Compacting Recycled Aggregate Concrete Ci  Pb  Pb  f v f c  

b s

(1)

where, Pb is the ratio of the volume of ties to the volume of concrete, Pb is the ratio of the volume of ties to the volume of concrete corresponding to a limiting pitch (1.2 times the least lateral dimension), b is the breadth of the prism and s is the spacing of ties. The stress in the steel binder is given by f v   v .E s and is always limited to maximum yield strength.  v and E s are the strains and modulus of elasticity of the binder steel. Fiber index (Fi), which indicates the degree of confinement provided by fiber. The Fiber index (Fi) is product of weight fraction (wf) of fiber and the aspect ratio (l/d) of the fiber. Due to the passive confinement of the fibers in the core concrete there will be a good bond with core and cover. The fact that the inclusion of fibers is more beneficial in improving the crack resistance, flexural strength and energy absorption capacity of concrete, rather than other properties, is well-established: (2) Fi  w f l d 

 

where, wf is the ratio of the weight of fiber to weight of concrete, (l/d) is the ratio of length of the fiber to the diameter of the fiber.

II.

Methodology

The construction of heavily reinforced concrete members, such as columns and beams in moment resisting frames in seismic areas, makes the placement of concrete quite difficult. The FRSCRAC is highly flowable, stable concrete which flows readily into place, filling formwork without any compaction and without undergoing any significant segregation. The construction of modern structures calls for the attention of the use of materials with improved properties in respect of strength, stiffness, toughness and durability. The addition of fibers along with the lateral ties was found to improve the deformation characteristics and especially the integrity of concrete. The present paper contributes mainly to the study of confined and unconfined Glass Fiber Reinforced Self Compacting Recycled Aggregate Concrete (GFRSCRAC). The most fundamental requirement in predicting the behaviour of GFRSCRAC is the knowledge of stress-strain behaviour of the constituent materials. This should be of interest to engineers considering the use of GFRSCRAC for various structural applications. In the present study, M40 grade of concrete is taken for developing the GFRSCRAC.

III.

Recycled Aggregate

In recent years, recycling of concrete to produce aggregates suitable for structural and nonstructural concrete applications is emerging as a commercially viable and technically feasible operation. This situation has arisen following well over two decades of intensive research, predominantly centered on laboratory-crushed concrete in lieu of various properties. The need for the production and use of RA is nowadays very urgent. This subject is considered very important, because there are now suitable conditions for construction of big infrastructures. By the production and use of RA, There is an establishment of presuppositions for substantial protection of natural sources of country, which are neither endless nor inexpensive [8]. There is a decrease of high volumes of fresh concrete wastes, which illegally ends up in uncontrolled areas of deposition. Aggregates occupy bulk of the volume of concrete. Their size, grading, shape and surface texture have significant influence on properties of concrete. Moreover, in the present study recycled aggregate from Building Demolished Waste (BDW) was crushed and classified before use. For qualifying the utility of recycled aggregate in concrete, the important parameters like bulk density, voids ratio, specific gravity, water absorption, crushing and impact value, angularity and IAPST were determined based on IS Codal provisions [9]. These properties were determined for RA and compared with NA are shown in the following Table 1. Table 1- Properties of Natural & Recycled Aggregate Properties

Natural Aggregate(NA)

Recycled Aggregate(RA)

Bulk Density % of Voids Void Ratio Specific Gravity Fineness Modulus Water absorption Flakiness Index Elongation Index Aggregate Impact Value (%) Aggregate Crushing Value (%) IAPST Angularity Number

1.46 44.26 0.79 2.78 7.1 1.00 3.56 7.13 32.20 22.77 18.10 10.31

1.28 48.26 0.93 2.55 7.15 5.68 4.6 8.4 34.48 28.16 20.41 13.99

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Tie Confined Glass Fiber Reinforced Self Compacting Recycled Aggregate Concrete IV.

Fiber Reinforced Self Compacting Recycled Aggregate Concrete

Fresh SCC must possess the key properties including filling ability, passing ability and resistance to segregation at required level. To satisfy these conditions EFNARC [10] has formulated certain test procedures. The details of mix proportions adopted in the present study are designed as per Nansu method of mix design [11] is shown in Table 2 and the fresh properties of GFRSCRAC are shown in Table 3. Companion cube specimens of standard dimensions 150mm x 150mm were also cast and tested for the strength. The results of the compressive strength are also presented in Table 3. All the concrete mixes were mixed for about 5 minutes as per standards in a rotating drum type mixer. The fresh properties were determined. Table 2: Details of Mix Proportions Designaiton

Grade of Concrete

Cement in Kg

C.A Kg

F.A Kg

Fly–Ash Kg

Glass Fiber (Kg)

Water (Lit)

S.P (lit)

VMA lit

GFRSCRAC

M40

412

707

944

166

1.00

193

16.00

0.48

Table 3: Fresh and Hardened Properties of SCC with Glass Fiber Slump Cone Test Desg.

GFRSCRAC

V Funnel Test

H-Flow (mm)

T50 (time in Sec)

Time for complete discharge Sec

T 5 min in Sec

675

5.12

12.08

15.20

V.

L Box Test Time for 0-200 mm spread 3.22

Time for 0- 400 mm spread

H2/H1

6.41

0.81

Comp. Strength (Mpa) 49.26

Experimental Program

The program consisted of casting and testing of 75 prisms of size 150 x 150 x 300mm cast for examining the stress-strain behavior of M40 grade concrete. The prisms in each batch were divided into five sets. In each set three identical specimens were cast and tested after 28 days curing and the average behaviour was taken to represent the behaviour for that set of three specimens. Some additional 150x150mm cubes were cast as companion specimens for predicting the compressive strength. The details of prisms cast are shown in Table 4. 5.1 Materials used Ordinary Portland cement with a compressive strength not less than 53 MPa [named 53 grade cement], at the end of 28 days was used in the study [12]. The Fine Aggregate (F.A) used was standard river sand confirming to Zone-II [13]. Recycled Aggregate was used as Coarse Aggregate (C.A). The aggregate was properly graded through standard sieves before using in the concrete works. The fly ash available locally was used as a partial replacement for cement, Cem-Fil Anti Crack, alkali resistant glass fiber, has been specially developed for the reinforcement of cementitious mortars and concrete mixes. Some characteristic features of Cem-Fil Anti-Crack HD are, its Specific gravity is 2.6; length of the fiber is close to 12 mm, aspect ratio 857:1, and Specific surface area being 105 m2 /kg. Conplast SP 337 superplasticizer (water reducing admixture) and Viscosity Modifying Agent (VMA) were added in optimum dosages for improving the properties of SCC. The 4mm nominal diameter G.I wire was used as longitudinal reinforcement in the prisms. The steel used as lateral reinforcement was 8 mm nominal diameter mild steel obtained from single lot. The concrete strength Viz., M40 (compressive strength not less than 40 MPa at the end of 28 days) were tested in the study. 5.2 Curing The specimens were cured for 28 days in the curing tank. The water in the curing tank was changed at the end of 14 days. After completion of curing the specimens were kept in shade for one day and then tested. 5.3Testing The cured specimens were capped with plaster of Paris before testing to provide a smooth loading surface, to avoid any stress concentration during the application of load. A Tinius–Olsen testing machine of 1810 KN capacity was used for testing the prisms under axial compression. The prisms were tested under strain rate control, 0.1 mm/min. The same type of test set up followed for studying the stress – strain behaviour of fibers based specimens which was adopted for no fiber concrete specimens. The set up of two square frames along with the compressometer was used for measuring the strains. All the specimens were tested under a strain control of 0.1mm/minute and the load increased rapidly in the initial stage up to about 75 to 80 percent of the peak load and increased at a slower rate until the peak load was reached. Tests were continued until the peak load dropped to about 0.5 times the peak load. Beyond the peak load, the strains increased at a rapid rate and were accomplished with a decrease in the load carrying capacity of the specimen. www.iosrjournals.org

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Tie Confined Glass Fiber Reinforced Self Compacting Recycled Aggregate Concrete VI.

Stress-Strain Behaviour of GFRSCRAC

A structural reinforced concrete member can be theoretically analyzed if the stress-strain behaviour of its constituent materials is known [14]. Stress-Strain relation of steel is not a big problem as there is very less material variation compared to that of concrete. Concrete being produced at site has very much uncertainty; moreover, there is significant variation in the behaviour of vibrated concrete (VC) and GFRSCRAC. Also, there is much variation in behaviour of confined and unconfined concrete as well. Generally, in practice we use code specified stress-strain relation in the analysis and design, but generally they are recommended for normal vibrated concrete only. Now as the advancement in concrete technology has been promoting the use of GFRSCRAC, the stress-strain relation for GFRSCRAC is to be used in design. The most common practice for confining concrete is by the use of lateral ties and inclusion of fiber in the core concrete. Thus our study is being done for the tie confined fiber reinforced self compacting concrete. Thus the spalling of cover was less in this type of confinement. The addition of fibers along with the lateral ties was found to improve the deformation characteristics and specially the integrity of concrete. Table 4 Details of prisms tested (M40 Grade GFRSCRAC) Long.Steel Sl.No

Designation

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

P00 G01 G02 G03 G04 P10 G11 G12 G13 G14 P20 G21 G22 G23 G24 P30 G31 G32 G33 G34 P40 G41 G42 G43 G44

No (mm) 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

Dia (mm) 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94 3.94

Lateral Steel Dia (mm) 7.96 7.96 7.96 7.96 7.96 7.96 7.96 7.96 7.96 7.96 7.96 7.96 7.96 7.96 7.96 7.96 7.96 7.96 7.96 7.96

Spacing (mm) 150 100 75 50 150 100 75 50 150 100 75 50 150 100 75 50 150 100 75 50

Fi 0.000 0.000 0.000 0.000 0.000 0.089 0.089 0.089 0.089 0.089 0.179 0.179 0.179 0.179 0.179 0.268 0.268 0.268 0.268 0.268 0.357 0.357 0.357 0.357 0.357

Cube Strength (MPa)

Pl.Prism Strength (MPa)

45.83

34.59

46.02

34.98

46.16

35.2

46.28

35.48

46.39

35.78

Total=

Fig 1 Stress Vs Strain for Ci=0.0 (M40)

No. of Prisms 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 75

Fig 2 Stress Vs Strain for Ci=0.03(M40)

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Tie Confined Glass Fiber Reinforced Self Compacting Recycled Aggregate Concrete

Fig 3 Stress Vs Strain for Ci=0.09 (M40)

Fig 4 Stress Vs Strain for Ci=0.09(M40)

Fig 5 Stress Vs Strain for Ci=0.43 (M40)

Fig 6 Prism Specimens after testing

Table 5 Confinement index, Fiber index, Peak Stress, Corresponding Strain, Ductility Factor S.No

Design ation

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

P00 G01 G02 G03 G04 P10 G11 G12 G13 G14 P20 G21 G22 G23 G24 P30 G31 G32 G33 G34 P40 G41 G42 G43 G44

Confinement Index (Ci) 0.00 0.00 0.00 0.00 0.00 0.02 0.02 0.02 0.02 0.02 0.09 0.09 0.09 0.09 0.09 0.19 0.19 0.19 0.19 0.19 0.43 0.43 0.43 0.43 0.43

Fiber Index (Fi)

Peak Strength (fu)

fu/fc'

Peak Strain Єu

0 0.089 0.179 0.268 0.357 0 0.089 0.179 0.268 0.357 0 0.089 0.179 0.268 0.357 0 0.089 0.179 0.268 0.357 0 0.089 0.179 0.268 0.357

34.59 34.98 35.20 35.48 35.78 35.98 37.20 37.36 37.56 37.95 36.35 37.70 38.14 38.54 39.95 38.51 39.91 41.30 42.71 43.29 42.19 43.28 44.70 45.10 45.66

1.000 1.011 1.018 1.026 1.034 1.000 1.034 1.038 1.044 1.055 1.000 1.037 1.049 1.060 1.099 1.000 1.036 1.072 1.109 1.124 1.000 1.026 1.059 1.069 1.082

0.00218 0.00248 0.00254 0.00260 0.00270 0.00261 0.00328 0.00341 0.00355 0.00371 0.00340 0.00390 0.00411 0.00427 0.00459 0.00398 0.00470 0.00505 0.00539 0.00588 0.00645 0.00685 0.00710 0.00736 0.00770

Єu/ Єc' 1.000 1.138 1.165 1.193 1.238 1.000 1.257 1.307 1.360 1.421 1.000 1.148 1.209 1.255 1.349 1.000 1.181 1.269 1.355 1.477 1.000 1.062 1.101 1.141 1.194

Є0.85 u Ascend ing x 10^6 1736 1698 1650 1610 1594 2098 1759 1700 1780 1820 2155 2094 1960 1784 1910 2375 2276 2360 2450 2360 2820 2836 2729 2670 2496

Є 0.85 u Descending x 10^6

Ductility Factor

2928 3176 3267 3302 3400 4617 4690 4839 5500 5815 5928 6654 6470 6310 6909 7885 7904 8343 8891 8850 9984 10270 10538 10684 11076

1.69 1.87 1.98 2.05 2.13 2.20 2.67 2.85 3.09 3.20 2.75 3.18 3.30 3.54 3.62 3.32 3.47 3.54 3.63 3.75 3.54 3.62 3.86 4.00 4.44

P=plain prism; G=glass fiber prisms;

VII.

Discussions

a)Confinement index (Ci), Fiber index (Fi) Vs Stress ratio & Strain ratio: Table 5 shows the details of stress ration, strain ratio, ductility factor, confinement index and fiber index for M40 grade concrete. Figs 7(a) and 7(b) shows the relationship between stress ratio Vs confinement index and Strain ratio Vs confinement index. Similarly Fig 8(a) and 8(b) shows the details of stress ratio Vs fiber index www.iosrjournals.org

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Tie Confined Glass Fiber Reinforced Self Compacting Recycled Aggregate Concrete and strain ratio Vs fiber index. The relationships between stress ratio, strain ratio, confinement index, fiber index for FRSCRAC is shown in Equations 3 and 4. 4.50

1.40

y = 4.1417x + 1 R2 = 0.913

4.00

y = 0.5233x + 1 R2 = 0.9777

1.35

3.50

1.30

ec/ec'

3.00

fc/fc'

1.25

2.50

1.20

2.00

1.15

1.50

1.10

1.00

1.05 1.00 0.00000

0.00000

0.20000

0.40000

0.60000

0.20000

0.40000

Ci

0.60000

0.80000

0.80000

Ci

Fig 7(a) Stress ratio Vs Ci, 1.100

Fig 7(b) Strain ratio Vs Ci,

y = 0.2208x + 1 R2 = 0.971

ecf/ec'

fcf/fc'

1.050 1.000 0.950 0.900 0

0.1

0.2

0.3

y = 0.8375x + 1 R2 = 0.8013

1.600 1.400 1.200 1.000 0.800 0.600 0.400 0.200 0.000

0.4

0

0.1

F.I

0.3

0.4

F.I

Fig 8(a) Stress ratio Vs Fi ,

Fig 8(b) Strain ratio Vs Fi

b) From the relations obtained: The Confined Concrete Strength:

The Confined Concrete Strain:

0.2

u '

fu  (1  0.523CiR ) (1  0.221FiR ) f'  (1  4.142CiR ) (1  0.838FiR )

(3)

(4)

c) Confinement index (Ci), Fiber index (Fi) Vs Ductility Factor: The Ductility Factor is defined as the ratio of strains at 85% of the peak strength in the descending portion to that of the ascending portion. The values of the Ductility Factor for concrete made for different tie spacing is shown in Table 5. It can be noted that there is an increase in ductility factor with increase in Confinement index and Fiber index.

Conclusions 1. 2. 3.

4. 5.

6.

From the structural properties of RA it can be concluded that the coarse aggregate obtained from crushing BDW can be used for structural concrete works. This confirms the fact that RA is in no way inferior to NA. The confinement studies on GFRSCRAC proved that there is an increase in peak stress, strain at peak stress and strain at 85% of peak stress with increase in confinement index and fiber index. The improvement in strength and strain at peak stress was developed. The relationship between stress ratio, strain ratio and the Confinement Index and Fiber Index is: u fu  (1  4.142CiR ) (1  0.838FiR )  (1  0.523CiR ) (1  0.221FiR ) ' f' With the addition of glass fiber the ascending portion of the load-deflection changes very slightly, but the descending portion becomes less steep, which resulted in a higher ductility and toughness of the material. The ductility of concrete improved with the tie confinement and addition of glass fibers. With the increase in the confinement index the stress strain behaviour improved from a brittle behaviour to ductile nature. The curves became flat in the post ultimate portion. The Stress-Strain behaviour can be used to develop the stress block parameters which forms the basis for the design of Tie Confined Glass Fiber Reinforced Self Compacting Recycled Aggregate Concrete. www.iosrjournals.org

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Tie Confined Glass Fiber Reinforced Self Compacting Recycled Aggregate Concrete References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]

Okamura.H & Ozawa.K, Mix design for Self-Compacting concrete library of JSCE, 1995, PP107-120. Brouwers H.J.H. and Radix H.J. Theoretical and experimental study of Self-Compacting Concrete, Cement & Concrete Research, 9, 2005, pp 2116–36. Ouchi Hibino M.M. and Okamura H. Effect of Superplasticizer on Self Compactability of Fresh Concrete, TRR 1574, 1996, pp.37-40. Sagoe-Crentsil K.K. .Brown T .and Taylor A.H Performance of concrete made with commercially produced coarse recycled concrete aggregate, Cement & Concrete Research, 31,2001, 707-712. Topcu Bekir Ilker, Guncan Fuat Nedim, Using waste concrete as aggregate, Cement and Concrete Research; 25(7), 1995, 1385-90. Mustafa Sahmaran and Ozgur Yaman, I. Hybrid fiber reinforced self-compacting concrete with a high-volume coarse fly ash, Elsevier Science Publishers, 2005, PP 109-126. Steffen Grunewald, Parameter-study on the influence of steel fibers and coarse aggregate content on the fresh properties of selfcompacting concrete, Cement and Concrete Research, 21 May 2001, 2001, PP: 1793-1798 . Dhir R, Henderson N, Limbachiya M. Proceedings of International Symposium: Sustainable Construction: Use of Recycled Concrete Aggregate 1998, Thomas Telford. Indian Standard Code IS: 383, Specification for coarse and fine aggregates from natural sources for concrete 1970. Specifications and Guidelines for Self-Compacting Concrete, EFNARC, 2002, Association House, 99 West Street, Farnham, UK. Nan Su, Hsu K.C.,.Chai H.W. A Simple mix design methods for Self compacting concrete, Cement and Concrete Research 2001, PP 1799 – 1807. Indian Standard Code IS: 12269, Specifications for 53 Grade Ordinary Portland cement. Indian Standard Code IS: 2386, Methods of test for Aggregates for Concrete,1997. Saenz, L. P.,Discussion of the paper Equation for the stress-strain curve of concrete, P. Desayi and S. Krishnan, Journal of ACI, 61(9), September, 1964, pp1229-1235.

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Tie Confined Glass Fiber Reinforced Self Compacting Recycled Aggregate Concrete  

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