Effect on recycled aggregate on concrete properties
924
International Journal of Earth Sciences and Engineering ISSN 0974-5904, Volume 04, No 06 SPL, October 2011, pp. 924-928
Effect on recycled aggregate on concrete properties Y. V. Akbari Post Graduate Student, Applied Mechanics Department, L. D. College of Engineering, Ahmedabad, Gujarat (India) Email: [email protected]
N. K. Arora Associate Professor, Applied Mechanics Department, L. D. College of Engineering, Ahmedabad, Gujarat (India) Email: [email protected]
M. D. Vakil Lecturer, Applied Mechanics Department, L. D. College of Engineering, Ahmedabad, Gujarat (India) Email: [email protected] ABSTRACT: Use of recycled aggregate in concrete has become compulsion for many countries due to the scarcity of natural aggregates. The use of demolished concrete debris as aggregates in concrete results in significant economical and environmental benefits. In present work, an attempt has been made to study the effect of recycled aggregate on behavior of normal strength concrete. The experimental program includes variation in water cement ratio and replacement of natural aggregates by recycled aggregates. Three different water ratios 0.60, 0.52 and 0.43 and aggregate replacement of 0%, 15% , 30% , 50% were accounted in experimental program. Experimental results shows up to 25% reduction in compressive strength, 23% reduction in flexural strength, 26% reduction in split tensile strength and a noticeable reduction in workability was observed with the increase in percentage of aggregate replacement. KEY WORDS: Recycled aggregate, Natural aggregate, compressive strength, split tensile strength, Flexural strength. INTRODUCTION Concrete is the most favorite choice used in construction industry. This is due to its basic ingredients (cement, coarse aggregate, fine aggregate, water) are easily to find, little maintenance service, easily to handle, most economical material, good in compression, durable and good fire resistance. Because of these factors, there is scarcity that natural sources like coarse aggregate will diminish. Thus, to preserve this source, the application of Recycled Aggregate (RA) for producing concrete is introduced. In Malaysia the concrete which used RA or known as Recycled Aggregate Concrete (RAC) is considered new. However, it is not a new material in South Africa, Netherland, United Kingdom (UK), Germany, France, Russia, Canada and Japan (2002). These countries have gained many experiences on application of RAC in their construction industry. Although RA is becoming a good alternative material, there is still a weakness on its performance in concrete. In fresh concrete performance, it was found that RAC obtained lower in workability compared to concrete using Natural Aggregate or known as Natural Aggregate Concrete (NAC) (Topcu and Sengel, 2004: Limbachiya 2004)[1]. For hardened concrete performance, i.e. compressive strength, it was recognized that RAC obtained lower in strength compared to NAC (Topcu and Sengel 2004: Fraaij et al, 2002: Kenai et al., 2002 and Poon et al., 2004). For improving the performance of RA, the application of new method like Two-Stage Mixing Approach (TSMA) by Tam et al., (2007) and utilization of pozzolanic material like fly ash by Kou, Poon and Chan (2007) has been introduced. Both studies have contributed into improvement IN performance of RAC. This study presents the results of an experimental study on the performance of RAC with utilization of Micronised
Biomass Silica as pozzolanic material. The study is focused on the influence of various percentages of MBS in RAC on the compressive strength and water permeability. Recent research by the Fredonia group has established that the global demand for construction aggregates may exceed 26 billion tones by 2011. Leading this demand, are the single user: China (25%), EU (12%) and the USA (10%). However, because of industrialization and significant infrastructure and construction development, there are expected to be significant increase in use of aggregates in India (which is already one of the major national markets at 3%) beyond 2011[5]. In India, about 14.5 MT of solid wastes are generated annually from construction industries, which include wasted sand, gravel, bitumen, bricks, and masonry, concrete. However, some quantity of such waste is being recycled and utilized in building materials and share of recycled materials varies from 25% in old buildings to as high as 75% in new buildings .Hence the subject of concrete recycling is regarded as very important in the general attempt for sustainable development in our times. In a parallel manner, it is directly connected with (a) increase of demolition structures past out of performance time, (b) demand for new structures and (c) results––of destruction by natural phenomena (earthquakes, tsunami, heavy cyclon etc.).Construction & Demolition (C&D) wastes are normally composed of concrete rubble, bricks and tiles, sand and dust, timber, plastics, cardboard and paper, and metals. Concrete rubble usually constitutes the largest proportion of C&D waste. It has been shown that crushed concrete rubble, after separation from other C&D waste and sieved, can be used as a substitute for natural coarse aggregates in concrete or as a sub-base or a base layer in pavements. This type of recycled material is called recycled aggregate.
#020410441 Copyright © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved
Effect On Recycled Aggregate On Concrete Properties
EXPERIMENTAL WORK The main object of this paper is to compare the hardened properties of concrete with different amount of recycled aggregate. The scope of this investigation is limited to target strength of concrete. The experimental work for this study is including the materials used for experimental work, the concrete mixes proportion, testing that has been used for determine the fresh concrete performance and testing that has been conducted for assessing the hardened concrete performance.mix design was designed as per IS-102622009 as control mix with natural coarse aggregate. The mix proportion was found. Finally i tried to three mixes, mix-1, mix-2,mix-3 based on w/c ratio respectively 0.60, 0.52 and 0.43.The control mix was with 100% natural coarse aggregates. Other mixes were also prepared with (85% +15%), (70% +30%) and (50% + 50%) combination of natural coarse aggregates and recycled coarse aggregates respectively as given in Table-1. Table-1: Percentage of aggregate used in 3 batches of each mixes. Batch-1 Mix-1 (0.60 w/c) NCA
100%
85%
70%
50%
RCA
0%
15%
30%
50%
Batch-2
Mix-2 (0.52 w/c)
NCA
100%
85%
70%
50%
RCA
0%
15%
30%
50%
Batch-3
Mix-3 (0.43 w/c)
NCA
100%
85%
70%
50%
RCA
0%
15%
30%
50%
MATERIALS USED Cement In this study, these materials were used for experimental work. There are Ordinary Portland Cement (OPC) of 53 grade confirming to Indian standard IS 12269-1987 was used. Sand Fine aggregate (sand) used for this entire study or investigation for concrete was river sand confirming to zone-1 of IS:383-1970. Coarse aggregate In this investigation, two types of coarse aggregates were used for preparation of concrete, Natural coarse aggregate(NCA) and recycled coarse aggregate(RCA).
925
NCA: Crushed hard granite chips of maximum size 20mm were used in concrete mixes. The bulk density of aggregate was 1470 kg/m3 and specific gravity was found to be 2.87. RCA: Recycled coarse Aggregate (RCA) was prepared by crushing the waste cube which has been thrown away at the outside of Material Laboratory. The waste cubes were broken into smaller pieces by hammer and crushed using a stone crusher after sieved. Maximum size of RCA that has been produced is 20mm and minimum size is 4.75mm. and after found out the physical and mechanical properties of natural coarse aggregate as well as recycled coarse concrete.
Table‐2: Physical properties of NCA & RCA Properties NCA RCA 1470 1451 Bulk Density (Kg/m3) Specific gravity 2.68 2.87 Water Absorption (%) 1.7 7 Water Potable water confirming to IS: 456-2000 was used for casting and curing. MIX DESIGN: Mix is Designed as per water binder ratio 0.60, 0.52 and 0.43 respectively. The control mix was made with 100% natural coarse aggregates(NAC). Other mixes were also prepared with (85% +15%), (70% +30%) and (50% + 50%) combination of natural coarse aggregates and recycled coarse aggregates respectively (RCA) .The various ingredients used in the mixes are as per table-3 Table‐3: Proportion and weight of each mix material by weight. Cement Sand Water 20mm N 20mmR Batch‐1 [kg] [kg] [Litre] [kg] [kg] Mix‐1 (0.60 w/c + 100% NCA + 0% RCA) 14.69 35.77 10.02 34.67 ‐ Mix‐1 (0.60 w/c + 85% NCA + 15% RCA) 14.69 35.77 10.28 28.49 4.90 Mix‐1 (0.60 w/c + 70% NCA + 30% RCA) 14.69 35.77 10.56 23.46 9.79 Mix‐1 (0.60 w/c + 50% NCA + 50% RCA) 14.69 35.77 10.95 16.76 16.32 Batch‐2 Mix‐2 (0.52 w/c + 100% NCA + 0% RCA) 16.95 33.64 10.00 34.84 ‐ Mix‐2 (0.52 w/c + 85% NCA + 15% RCA) 16.95 33.64 10.26 28.64 4.92 Mix‐2 (0.52 w/c + 70% NCA + 30% RCA) 16.95 33.64 10.54 23.58 9.84 Mix‐2 (0.52 w/c + 50% NCA + 50% RCA) 16.95 33.64 10.93 16.84 16.40 Batch‐3 Mix‐3 (0.43 w/c + 100% NCA + 0% RCA) 20.49 31.01 9.96 34.62 ‐ Mix‐3 (0.43 w/c + 85% NCA + 15% RCA) 20.49 31.01 10.22 28.45 4.89 Mix‐3 (0.43 w/c + 70% NCA + 30% RCA) 20.49 31.01 10.50 23.43 9.78 Mix‐3 (0.43 w/c + 50% NCA + 50% RCA) 20.49 31.01 10.89 16.74 16.30
International Journal of Earth Sciences and Engineering ISSN 0974-5904, Volume 04, No 06 SPL, October 2011, pp. 924-928
10mm N [kg] 18.70 13.7 12.65 9.04
10mm R [kg] ‐ 2.56 5.11 8.52
18.79 15.44 12.72 9.08
‐ 2.57 5.14 8.56
18.67 15.35 12.64 9.03
‐ 2.55 5.10 8.51
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Y. V. Akbari, N. K. Arora, M. D. Vakil
CASTING OF SPECIMENS: Casting of Specimens was done by batching of materials, preparation of moulds and placing of concrete in the moulds. BATCHING: The performance of recycled coarse aggregates concrete is influenced by the mixing. This means that a proper and good practice of mixing can lead to concrete for better performance. A proper mix of concrete is essential for the strength of the concrete and better bonding of the cement and aggregate. Before the concreting, all the mix material were weighed as given in Table and kept ready for concreting as per design mix proportions. PREPARATION OF CONCRETE MOULDS: Concrete moulds were oiled for easy stripping. The moulds for conducting tests on fresh concrete were made ready and inner surface were oiled. PREPARATION OF CONCRETE Concrete was prepared in the mixer and dumped in iron tray placed on a flat surface. Again the concrete was manually mixed properly before placing in the moulds. TEST ON FRESH CONCRETE In this study, the workability tests were conducted on fresh concrete. Workability affects the rate of placement and the degree of compaction of concrete. Slump test, compacting factor tests were conducted on fresh concrete and the get results. PREPARATION OF SAMPLES During the placing of fresh concrete into mould, proper care was taken to remove entrapped air by using a table vibrator to attain maximum strength. Vibrators were used after every 1/3 filling of material into the mould and the top surface was properly levelled at the end. DEMOULDING After levelling the fresh concrete in the mould, it was allowed to set for 24 hrs. The identification marks of concrete specimens were done with permanent markers and the specimens were removed from the mould. The moulds were cleaned and kept ready for next batch of concrete mix. CURING Curing is an important process to prevent the concrete specimens from losing their moisture while they are gaining their required strength. Inadequate curing is also the cause of unexpected cracks on the surface of concrete specimen. All concrete specimens were cured in water at room temperature for 28 days. After 28 days curing, concrete specimens were removed from the curing chamber to conduct tests on hardened concrete.
TEST ON HARDENED CONCRETE: Compressive strength: Compressive strength is defined as the maximum resistance of a concrete cube to axial loading. Three specimens of size 150 mm x 150 mm x 150 mm were used for compression testing for each batch of mix. Testing of specimens was carried out after curing. Specimen dimensions were measured before testing. Clean and surface dried specimens were placed in the testing machine. The platen was lowered and touched the top surface of the specimen. The load was applied at the gradually and maximum load was the recorded. Split Tensile strength Test: Split tensile test was conducted on specimens of size 150mm diameter and 300mm height. The testing of specimens should be carried out as soon as possible after curing. Specimen dimension were measured before the testing. Cleaned and cured specimens placed in the testing machine. The platen was lowered and was allowed to touch the top surface of the specimen. The force was applied and increase continuously. Maximum load at which the specimen failed was recorded. Flexural strength: The prism were tested to evaluate the flexural strength of the concrete. The prism dimensions were measured accurately before testing and marked by a marker for placing in the testing machine. The test results on hardened concrete are in Table No. 4 Table‐4: Test Results of Hardened concrete and Workability
Batch‐1 Mix‐1 (0.60 w/c + 100% NCA + 0% RCA) Mix‐1 (0.60 w/c + 85% NCA + 15% RCA) Mix‐1 (0.60 w/c + 70% NCA + 30% RCA) Mix‐1 (0.60 w/c + 50% NCA + 50% RCA)
compressive Flexural Split Compaction Slump Strength Strength Tensile Factor Value
15.02 14.28 13.07 11.26
3.6 3.4 3.2 2.8
5.24 4.98 4.53 3.87
0.950 0.940 0.931 0.928
80 82 87 89
19.94 19.14 17.13 15.17
4.4 4.2 3.6 3.4
5.56 5.33 4.89 4.22
0.960 0.946 0.929 0.922
98 111 125 132
26.89 25.36 23.91 20.47
4.6 4.2 4.2 3.2
7.11 6.76 6.27 5.42
0.950 0.936 0.927 0.917
70 78 90 93
Batch‐2 Mix‐2 (0.52 w/c + 100% NCA + 0% RCA) Mix‐2 (0.52 w/c + 85% NCA + 15% RCA) Mix‐2 (0.52 w/c + 70% NCA + 30% RCA) Mix‐2 (0.52 w/c + 50% NCA + 50% RCA)
Batch‐3 Mix‐3 (0.43 w/c + 100% NCA + 0% RCA) Mix‐3 (0.43 w/c + 85% NCA + 15% RCA) Mix‐3 (0.43 w/c + 70% NCA + 30% RCA) Mix‐3 (0.43 w/c + 50% NCA + 50% RCA)
INTERPRETATION OF TEST RESULTS: The test results such as compressive strength, split tensile strength and flexural strength with different proportions of recycled coarse aggregate and different mixes are discussed below:
International Journal of Earth Sciences and Engineering ISSN 0974-5904, Volume 04, No 06 SPL, October 2011, pp. 924-928
Effect On Recycled Aggregate On Concrete Properties
Compressive strength: Compressive strength is the major parameter which influences other properties of concrete. Compressive strength of different concrete specimen with different recycled coarse aggregates(0%, 15%, 30%, 50%) was found to be respectively 15.02 Mpa, 14.28 Mpa, 13.07 Mpa and 11.26 Mpa for Mix-1(0.60 w/c ) and 19.94 Mpa, 19.14 Mpa, 17.13 Mpa and 15.17 Mpa for Mix-2 ( 0.52 w/c) and 26.89 Mpa, 25.36 Mpa, 23.91 Mpa and 20.47 Mpa for Mix-3 (0.43 w/c).From the above test results, it is clear that when natural coarse aggregate is substituted with RCA, the compressive strength is found to be reducing. The same was observed by the earlier researchers Prasad, Limbachiya[2] and GC and RK Behera[3]. This may be due to the fact that the failure of normal strength concrete is caused by mortar failure. The bond between mortar and RCA is weaker than that of NCA. But many researchers said on HSC (High strength concrete), the concrete failure is due to aggregate crushing. The RCA posses lesser crushing value than that NCA. Compressive strength with 0%, 15%, 30% and 50% RCA with different mixes are plotted in fig-1.The decrease in compressive strength of 15%, 30% and 50% RCA with respect to 100% NCA were plotted in fig-2.The decrease in compressive strength was found to be very less variation between 0 to 30% replacement of RCA but afterwards an increased RCA gives significant variation seen in compressive strength. Split Tensile strength: Split Tensile strength of different concrete specimen with different recycled coarse aggregates(0%, 15%, 30%, 50%) was found to be respectively 5.24 Mpa, 4.98 Mpa, 4.53 Mpa and 3.87 Mpa for Mix-1(0.60 w/c ) and 5.56 Mpa, 5.33 Mpa, 4.89 Mpa and 4.22 Mpa for Mix-2 ( 0.52 w/c) and 7.11 Mpa, 6.76 Mpa, 6.27 Mpa and 5.42 Mpa for Mix-3 (0.43 w/c). Here also , when natural coarse aggregate is substituted with RCA, the Split tensile strength is found to be decresing. From the above test results, it is clear that when natural coarse aggregate is substituted with RCA, the Split tensile strength is found to be reducing. Split tensile strength with 0%, 15%, 30% and 50% RCA with different mixes are plotted in fig. The decrease in Split tensile strength of 15%, 30% and 50% RCA with respect to 100% NCA were plotted in fig. The decrease in split tensile strength was found to be very less variation between 0 to 30% replacement of but afterwards an increased RCA showed considerable variation seen in spilt tensile strength ,as per fig.5 and Fig-6. The same was observed in this investigation but in this case 26% decreased split tensile strength. Flexural strength: Flexural strength of concrete specimens with different recycled coarse aggregates(0%, 15%, 30%, 50%) was
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found to be respectively 3.6 Mpa, 3.4 Mpa, 3.2 Mpa and 2.8 Mpa for Mix-1(0.60 w/c ) and 4.4 Mpa, 4.2 Mpa, 3.6 Mpa and 3.4 Mpa for Mix-2 ( 0.52 w/c) and 4.6 Mpa, 4.2 Mpa, 4.2 Mpa and 3.2 Mpa for Mix-3 (0.43 w/c). In this test results as same as a reduction of flexural strength. when natural coarse aggregate is replaced with RCA that time flexural strength is found to be reducing. The percentage of reduction of flexural strength with 15%, 30% and 50% of RCA were found to 5.55, 11.11 and 22.22 for Mix-1, 4.54, 18.18 and 22.72 for Mix-2, and 8.69, 8.69 and 30 for Mix-3 respectively and plotted in fig.3 & 4.
Fig -1 Variation of Compressive strength With % of RCA
Fig-2 Decrease in compressive strength with percentage of RCA
Fig-3 Variation of Flexural strength with % of RCA
International Journal of Earth Sciences and Engineering ISSN 0974-5904, Volume 04, No 06 SPL, October 2011, pp. 924-928
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Y. V. Akbari, N. K. Arora, M. D. Vakil
Fig-4 Decrease in Flexural strength with % of RCA
Fig-5 Variation of split tensile strength With % of RCA
CONCLUSION: The percentages of recycled concrete aggregates were varied from 0% to 50%and it was observed to affect following properties of mix: 1. Water absorption of recycled aggregates was found to be greater than natural aggregates, and this needs to be compensated during mix design. 2. Compressive strength showed a decrease of up to 24% as the percentage of recycled concrete aggregates increased. The reduction is not prominent up to 25% replacement of recycled aggreagate. 3. Flexural strength reduces with increase in percentage of recycled aggregate. The reduction is increased with decrese in water-binder ratio. 4. Split tensile strength also reduces with increase in percentage of recycled aggregate upto. 26%. 5. Noticeable reductions in compressive strength is observed with increasing the percentage of recycled aggregate beyond 25%. REFERENCES: [1] Limbachiya M.C.,Leelawat T. And Dhir R.K.,”Use of recycled concrete aggregates in high strength concrete” Materials and structures, Vol33,November-2000, pp.574-580. [2] M C Limbachiya, A Koulouris, J.J. Roberts and A N Fried,” Performance Of Recycled Aggregate Concrete” RILEM International symposium on Environment conscious-materials and system for sustainable development, Pages: 127-136, Year2004. [3] G.C. Behera and R.K. Behera,” Effect of Recycled Aggregate on Normal strength concrete”, Innovative world of structural engineering conference, September-2010. [4] Recommended guide lines for concrete Mix Design IS: 10262-2009. Bureau of Indian standards, New Delhi. [5] Parekh D.N and Dr. Modhera C.D,” Assessment of recycled aggregate concrete”, Journal of engineerring research and studies.
Fig-6 Decrease in split tensile strength With % of RCA
International Journal of Earth Sciences and Engineering ISSN 0974-5904, Volume 04, No 06 SPL, October 2011, pp. 924-928
International Journal of Earth Sciences and Engineering ISSN 0974-5904, Volume 04, No 06 SPL, October 2011, pp. 924-928
Effect on recycled aggregate on concrete properties Y. V. Akbari Post Graduate Student, Applied Mechanics Department, L. D. College of Engineering, Ahmedabad, Gujarat (India) Email: [email protected]
N. K. Arora Associate Professor, Applied Mechanics Department, L. D. College of Engineering, Ahmedabad, Gujarat (India) Email: [email protected]
M. D. Vakil Lecturer, Applied Mechanics Department, L. D. College of Engineering, Ahmedabad, Gujarat (India) Email: [email protected] ABSTRACT: Use of recycled aggregate in concrete has become compulsion for many countries due to the scarcity of natural aggregates. The use of demolished concrete debris as aggregates in concrete results in significant economical and environmental benefits. In present work, an attempt has been made to study the effect of recycled aggregate on behavior of normal strength concrete. The experimental program includes variation in water cement ratio and replacement of natural aggregates by recycled aggregates. Three different water ratios 0.60, 0.52 and 0.43 and aggregate replacement of 0%, 15% , 30% , 50% were accounted in experimental program. Experimental results shows up to 25% reduction in compressive strength, 23% reduction in flexural strength, 26% reduction in split tensile strength and a noticeable reduction in workability was observed with the increase in percentage of aggregate replacement. KEY WORDS: Recycled aggregate, Natural aggregate, compressive strength, split tensile strength, Flexural strength. INTRODUCTION Concrete is the most favorite choice used in construction industry. This is due to its basic ingredients (cement, coarse aggregate, fine aggregate, water) are easily to find, little maintenance service, easily to handle, most economical material, good in compression, durable and good fire resistance. Because of these factors, there is scarcity that natural sources like coarse aggregate will diminish. Thus, to preserve this source, the application of Recycled Aggregate (RA) for producing concrete is introduced. In Malaysia the concrete which used RA or known as Recycled Aggregate Concrete (RAC) is considered new. However, it is not a new material in South Africa, Netherland, United Kingdom (UK), Germany, France, Russia, Canada and Japan (2002). These countries have gained many experiences on application of RAC in their construction industry. Although RA is becoming a good alternative material, there is still a weakness on its performance in concrete. In fresh concrete performance, it was found that RAC obtained lower in workability compared to concrete using Natural Aggregate or known as Natural Aggregate Concrete (NAC) (Topcu and Sengel, 2004: Limbachiya 2004)[1]. For hardened concrete performance, i.e. compressive strength, it was recognized that RAC obtained lower in strength compared to NAC (Topcu and Sengel 2004: Fraaij et al, 2002: Kenai et al., 2002 and Poon et al., 2004). For improving the performance of RA, the application of new method like Two-Stage Mixing Approach (TSMA) by Tam et al., (2007) and utilization of pozzolanic material like fly ash by Kou, Poon and Chan (2007) has been introduced. Both studies have contributed into improvement IN performance of RAC. This study presents the results of an experimental study on the performance of RAC with utilization of Micronised
Biomass Silica as pozzolanic material. The study is focused on the influence of various percentages of MBS in RAC on the compressive strength and water permeability. Recent research by the Fredonia group has established that the global demand for construction aggregates may exceed 26 billion tones by 2011. Leading this demand, are the single user: China (25%), EU (12%) and the USA (10%). However, because of industrialization and significant infrastructure and construction development, there are expected to be significant increase in use of aggregates in India (which is already one of the major national markets at 3%) beyond 2011[5]. In India, about 14.5 MT of solid wastes are generated annually from construction industries, which include wasted sand, gravel, bitumen, bricks, and masonry, concrete. However, some quantity of such waste is being recycled and utilized in building materials and share of recycled materials varies from 25% in old buildings to as high as 75% in new buildings .Hence the subject of concrete recycling is regarded as very important in the general attempt for sustainable development in our times. In a parallel manner, it is directly connected with (a) increase of demolition structures past out of performance time, (b) demand for new structures and (c) results––of destruction by natural phenomena (earthquakes, tsunami, heavy cyclon etc.).Construction & Demolition (C&D) wastes are normally composed of concrete rubble, bricks and tiles, sand and dust, timber, plastics, cardboard and paper, and metals. Concrete rubble usually constitutes the largest proportion of C&D waste. It has been shown that crushed concrete rubble, after separation from other C&D waste and sieved, can be used as a substitute for natural coarse aggregates in concrete or as a sub-base or a base layer in pavements. This type of recycled material is called recycled aggregate.
#020410441 Copyright © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved
Effect On Recycled Aggregate On Concrete Properties
EXPERIMENTAL WORK The main object of this paper is to compare the hardened properties of concrete with different amount of recycled aggregate. The scope of this investigation is limited to target strength of concrete. The experimental work for this study is including the materials used for experimental work, the concrete mixes proportion, testing that has been used for determine the fresh concrete performance and testing that has been conducted for assessing the hardened concrete performance.mix design was designed as per IS-102622009 as control mix with natural coarse aggregate. The mix proportion was found. Finally i tried to three mixes, mix-1, mix-2,mix-3 based on w/c ratio respectively 0.60, 0.52 and 0.43.The control mix was with 100% natural coarse aggregates. Other mixes were also prepared with (85% +15%), (70% +30%) and (50% + 50%) combination of natural coarse aggregates and recycled coarse aggregates respectively as given in Table-1. Table-1: Percentage of aggregate used in 3 batches of each mixes. Batch-1 Mix-1 (0.60 w/c) NCA
100%
85%
70%
50%
RCA
0%
15%
30%
50%
Batch-2
Mix-2 (0.52 w/c)
NCA
100%
85%
70%
50%
RCA
0%
15%
30%
50%
Batch-3
Mix-3 (0.43 w/c)
NCA
100%
85%
70%
50%
RCA
0%
15%
30%
50%
MATERIALS USED Cement In this study, these materials were used for experimental work. There are Ordinary Portland Cement (OPC) of 53 grade confirming to Indian standard IS 12269-1987 was used. Sand Fine aggregate (sand) used for this entire study or investigation for concrete was river sand confirming to zone-1 of IS:383-1970. Coarse aggregate In this investigation, two types of coarse aggregates were used for preparation of concrete, Natural coarse aggregate(NCA) and recycled coarse aggregate(RCA).
925
NCA: Crushed hard granite chips of maximum size 20mm were used in concrete mixes. The bulk density of aggregate was 1470 kg/m3 and specific gravity was found to be 2.87. RCA: Recycled coarse Aggregate (RCA) was prepared by crushing the waste cube which has been thrown away at the outside of Material Laboratory. The waste cubes were broken into smaller pieces by hammer and crushed using a stone crusher after sieved. Maximum size of RCA that has been produced is 20mm and minimum size is 4.75mm. and after found out the physical and mechanical properties of natural coarse aggregate as well as recycled coarse concrete.
Table‐2: Physical properties of NCA & RCA Properties NCA RCA 1470 1451 Bulk Density (Kg/m3) Specific gravity 2.68 2.87 Water Absorption (%) 1.7 7 Water Potable water confirming to IS: 456-2000 was used for casting and curing. MIX DESIGN: Mix is Designed as per water binder ratio 0.60, 0.52 and 0.43 respectively. The control mix was made with 100% natural coarse aggregates(NAC). Other mixes were also prepared with (85% +15%), (70% +30%) and (50% + 50%) combination of natural coarse aggregates and recycled coarse aggregates respectively (RCA) .The various ingredients used in the mixes are as per table-3 Table‐3: Proportion and weight of each mix material by weight. Cement Sand Water 20mm N 20mmR Batch‐1 [kg] [kg] [Litre] [kg] [kg] Mix‐1 (0.60 w/c + 100% NCA + 0% RCA) 14.69 35.77 10.02 34.67 ‐ Mix‐1 (0.60 w/c + 85% NCA + 15% RCA) 14.69 35.77 10.28 28.49 4.90 Mix‐1 (0.60 w/c + 70% NCA + 30% RCA) 14.69 35.77 10.56 23.46 9.79 Mix‐1 (0.60 w/c + 50% NCA + 50% RCA) 14.69 35.77 10.95 16.76 16.32 Batch‐2 Mix‐2 (0.52 w/c + 100% NCA + 0% RCA) 16.95 33.64 10.00 34.84 ‐ Mix‐2 (0.52 w/c + 85% NCA + 15% RCA) 16.95 33.64 10.26 28.64 4.92 Mix‐2 (0.52 w/c + 70% NCA + 30% RCA) 16.95 33.64 10.54 23.58 9.84 Mix‐2 (0.52 w/c + 50% NCA + 50% RCA) 16.95 33.64 10.93 16.84 16.40 Batch‐3 Mix‐3 (0.43 w/c + 100% NCA + 0% RCA) 20.49 31.01 9.96 34.62 ‐ Mix‐3 (0.43 w/c + 85% NCA + 15% RCA) 20.49 31.01 10.22 28.45 4.89 Mix‐3 (0.43 w/c + 70% NCA + 30% RCA) 20.49 31.01 10.50 23.43 9.78 Mix‐3 (0.43 w/c + 50% NCA + 50% RCA) 20.49 31.01 10.89 16.74 16.30
International Journal of Earth Sciences and Engineering ISSN 0974-5904, Volume 04, No 06 SPL, October 2011, pp. 924-928
10mm N [kg] 18.70 13.7 12.65 9.04
10mm R [kg] ‐ 2.56 5.11 8.52
18.79 15.44 12.72 9.08
‐ 2.57 5.14 8.56
18.67 15.35 12.64 9.03
‐ 2.55 5.10 8.51
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Y. V. Akbari, N. K. Arora, M. D. Vakil
CASTING OF SPECIMENS: Casting of Specimens was done by batching of materials, preparation of moulds and placing of concrete in the moulds. BATCHING: The performance of recycled coarse aggregates concrete is influenced by the mixing. This means that a proper and good practice of mixing can lead to concrete for better performance. A proper mix of concrete is essential for the strength of the concrete and better bonding of the cement and aggregate. Before the concreting, all the mix material were weighed as given in Table and kept ready for concreting as per design mix proportions. PREPARATION OF CONCRETE MOULDS: Concrete moulds were oiled for easy stripping. The moulds for conducting tests on fresh concrete were made ready and inner surface were oiled. PREPARATION OF CONCRETE Concrete was prepared in the mixer and dumped in iron tray placed on a flat surface. Again the concrete was manually mixed properly before placing in the moulds. TEST ON FRESH CONCRETE In this study, the workability tests were conducted on fresh concrete. Workability affects the rate of placement and the degree of compaction of concrete. Slump test, compacting factor tests were conducted on fresh concrete and the get results. PREPARATION OF SAMPLES During the placing of fresh concrete into mould, proper care was taken to remove entrapped air by using a table vibrator to attain maximum strength. Vibrators were used after every 1/3 filling of material into the mould and the top surface was properly levelled at the end. DEMOULDING After levelling the fresh concrete in the mould, it was allowed to set for 24 hrs. The identification marks of concrete specimens were done with permanent markers and the specimens were removed from the mould. The moulds were cleaned and kept ready for next batch of concrete mix. CURING Curing is an important process to prevent the concrete specimens from losing their moisture while they are gaining their required strength. Inadequate curing is also the cause of unexpected cracks on the surface of concrete specimen. All concrete specimens were cured in water at room temperature for 28 days. After 28 days curing, concrete specimens were removed from the curing chamber to conduct tests on hardened concrete.
TEST ON HARDENED CONCRETE: Compressive strength: Compressive strength is defined as the maximum resistance of a concrete cube to axial loading. Three specimens of size 150 mm x 150 mm x 150 mm were used for compression testing for each batch of mix. Testing of specimens was carried out after curing. Specimen dimensions were measured before testing. Clean and surface dried specimens were placed in the testing machine. The platen was lowered and touched the top surface of the specimen. The load was applied at the gradually and maximum load was the recorded. Split Tensile strength Test: Split tensile test was conducted on specimens of size 150mm diameter and 300mm height. The testing of specimens should be carried out as soon as possible after curing. Specimen dimension were measured before the testing. Cleaned and cured specimens placed in the testing machine. The platen was lowered and was allowed to touch the top surface of the specimen. The force was applied and increase continuously. Maximum load at which the specimen failed was recorded. Flexural strength: The prism were tested to evaluate the flexural strength of the concrete. The prism dimensions were measured accurately before testing and marked by a marker for placing in the testing machine. The test results on hardened concrete are in Table No. 4 Table‐4: Test Results of Hardened concrete and Workability
Batch‐1 Mix‐1 (0.60 w/c + 100% NCA + 0% RCA) Mix‐1 (0.60 w/c + 85% NCA + 15% RCA) Mix‐1 (0.60 w/c + 70% NCA + 30% RCA) Mix‐1 (0.60 w/c + 50% NCA + 50% RCA)
compressive Flexural Split Compaction Slump Strength Strength Tensile Factor Value
15.02 14.28 13.07 11.26
3.6 3.4 3.2 2.8
5.24 4.98 4.53 3.87
0.950 0.940 0.931 0.928
80 82 87 89
19.94 19.14 17.13 15.17
4.4 4.2 3.6 3.4
5.56 5.33 4.89 4.22
0.960 0.946 0.929 0.922
98 111 125 132
26.89 25.36 23.91 20.47
4.6 4.2 4.2 3.2
7.11 6.76 6.27 5.42
0.950 0.936 0.927 0.917
70 78 90 93
Batch‐2 Mix‐2 (0.52 w/c + 100% NCA + 0% RCA) Mix‐2 (0.52 w/c + 85% NCA + 15% RCA) Mix‐2 (0.52 w/c + 70% NCA + 30% RCA) Mix‐2 (0.52 w/c + 50% NCA + 50% RCA)
Batch‐3 Mix‐3 (0.43 w/c + 100% NCA + 0% RCA) Mix‐3 (0.43 w/c + 85% NCA + 15% RCA) Mix‐3 (0.43 w/c + 70% NCA + 30% RCA) Mix‐3 (0.43 w/c + 50% NCA + 50% RCA)
INTERPRETATION OF TEST RESULTS: The test results such as compressive strength, split tensile strength and flexural strength with different proportions of recycled coarse aggregate and different mixes are discussed below:
International Journal of Earth Sciences and Engineering ISSN 0974-5904, Volume 04, No 06 SPL, October 2011, pp. 924-928
Effect On Recycled Aggregate On Concrete Properties
Compressive strength: Compressive strength is the major parameter which influences other properties of concrete. Compressive strength of different concrete specimen with different recycled coarse aggregates(0%, 15%, 30%, 50%) was found to be respectively 15.02 Mpa, 14.28 Mpa, 13.07 Mpa and 11.26 Mpa for Mix-1(0.60 w/c ) and 19.94 Mpa, 19.14 Mpa, 17.13 Mpa and 15.17 Mpa for Mix-2 ( 0.52 w/c) and 26.89 Mpa, 25.36 Mpa, 23.91 Mpa and 20.47 Mpa for Mix-3 (0.43 w/c).From the above test results, it is clear that when natural coarse aggregate is substituted with RCA, the compressive strength is found to be reducing. The same was observed by the earlier researchers Prasad, Limbachiya[2] and GC and RK Behera[3]. This may be due to the fact that the failure of normal strength concrete is caused by mortar failure. The bond between mortar and RCA is weaker than that of NCA. But many researchers said on HSC (High strength concrete), the concrete failure is due to aggregate crushing. The RCA posses lesser crushing value than that NCA. Compressive strength with 0%, 15%, 30% and 50% RCA with different mixes are plotted in fig-1.The decrease in compressive strength of 15%, 30% and 50% RCA with respect to 100% NCA were plotted in fig-2.The decrease in compressive strength was found to be very less variation between 0 to 30% replacement of RCA but afterwards an increased RCA gives significant variation seen in compressive strength. Split Tensile strength: Split Tensile strength of different concrete specimen with different recycled coarse aggregates(0%, 15%, 30%, 50%) was found to be respectively 5.24 Mpa, 4.98 Mpa, 4.53 Mpa and 3.87 Mpa for Mix-1(0.60 w/c ) and 5.56 Mpa, 5.33 Mpa, 4.89 Mpa and 4.22 Mpa for Mix-2 ( 0.52 w/c) and 7.11 Mpa, 6.76 Mpa, 6.27 Mpa and 5.42 Mpa for Mix-3 (0.43 w/c). Here also , when natural coarse aggregate is substituted with RCA, the Split tensile strength is found to be decresing. From the above test results, it is clear that when natural coarse aggregate is substituted with RCA, the Split tensile strength is found to be reducing. Split tensile strength with 0%, 15%, 30% and 50% RCA with different mixes are plotted in fig. The decrease in Split tensile strength of 15%, 30% and 50% RCA with respect to 100% NCA were plotted in fig. The decrease in split tensile strength was found to be very less variation between 0 to 30% replacement of but afterwards an increased RCA showed considerable variation seen in spilt tensile strength ,as per fig.5 and Fig-6. The same was observed in this investigation but in this case 26% decreased split tensile strength. Flexural strength: Flexural strength of concrete specimens with different recycled coarse aggregates(0%, 15%, 30%, 50%) was
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found to be respectively 3.6 Mpa, 3.4 Mpa, 3.2 Mpa and 2.8 Mpa for Mix-1(0.60 w/c ) and 4.4 Mpa, 4.2 Mpa, 3.6 Mpa and 3.4 Mpa for Mix-2 ( 0.52 w/c) and 4.6 Mpa, 4.2 Mpa, 4.2 Mpa and 3.2 Mpa for Mix-3 (0.43 w/c). In this test results as same as a reduction of flexural strength. when natural coarse aggregate is replaced with RCA that time flexural strength is found to be reducing. The percentage of reduction of flexural strength with 15%, 30% and 50% of RCA were found to 5.55, 11.11 and 22.22 for Mix-1, 4.54, 18.18 and 22.72 for Mix-2, and 8.69, 8.69 and 30 for Mix-3 respectively and plotted in fig.3 & 4.
Fig -1 Variation of Compressive strength With % of RCA
Fig-2 Decrease in compressive strength with percentage of RCA
Fig-3 Variation of Flexural strength with % of RCA
International Journal of Earth Sciences and Engineering ISSN 0974-5904, Volume 04, No 06 SPL, October 2011, pp. 924-928
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Y. V. Akbari, N. K. Arora, M. D. Vakil
Fig-4 Decrease in Flexural strength with % of RCA
Fig-5 Variation of split tensile strength With % of RCA
CONCLUSION: The percentages of recycled concrete aggregates were varied from 0% to 50%and it was observed to affect following properties of mix: 1. Water absorption of recycled aggregates was found to be greater than natural aggregates, and this needs to be compensated during mix design. 2. Compressive strength showed a decrease of up to 24% as the percentage of recycled concrete aggregates increased. The reduction is not prominent up to 25% replacement of recycled aggreagate. 3. Flexural strength reduces with increase in percentage of recycled aggregate. The reduction is increased with decrese in water-binder ratio. 4. Split tensile strength also reduces with increase in percentage of recycled aggregate upto. 26%. 5. Noticeable reductions in compressive strength is observed with increasing the percentage of recycled aggregate beyond 25%. REFERENCES: [1] Limbachiya M.C.,Leelawat T. And Dhir R.K.,”Use of recycled concrete aggregates in high strength concrete” Materials and structures, Vol33,November-2000, pp.574-580. [2] M C Limbachiya, A Koulouris, J.J. Roberts and A N Fried,” Performance Of Recycled Aggregate Concrete” RILEM International symposium on Environment conscious-materials and system for sustainable development, Pages: 127-136, Year2004. [3] G.C. Behera and R.K. Behera,” Effect of Recycled Aggregate on Normal strength concrete”, Innovative world of structural engineering conference, September-2010. [4] Recommended guide lines for concrete Mix Design IS: 10262-2009. Bureau of Indian standards, New Delhi. [5] Parekh D.N and Dr. Modhera C.D,” Assessment of recycled aggregate concrete”, Journal of engineerring research and studies.
Fig-6 Decrease in split tensile strength With % of RCA
International Journal of Earth Sciences and Engineering ISSN 0974-5904, Volume 04, No 06 SPL, October 2011, pp. 924-928
