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  • 1. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME TECHNOLOGY (IJCIET) ISSN 0976 – 6308 (Print) ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December, pp. 186-192 © IAEME: www.iaeme.com/ijciet.asp Journal Impact Factor (2013): 5.3277 (Calculated by GISI) www.jifactor.com IJCIET ©IAEME EFFECT OF RECYCLED COARSE AGGREGATES ON CHARACTERISTIC STRENGTH OF DIFFERENT GRADES OF CONCRETE Pinal C. Khergamwala1, Dr. Jagbir Singh2, Dr. Rajesh Kumar3 1 Civil Engineering Department, Indus University, Ahmedabad, India Associate Professor, Department of Civil Engineering, GNDEC, Ludhiana, India. 3 Associate Professor, Department of Civil Engineering, GZS, PTU campus, Bathinda. 2 ABSTRACT Sustainable development of the cement and concrete industry requires the utilization of industrial and agricultural waste components. At present, for a variety of reasons, the concrete construction industry is not sustainable. It consumes huge quantities of virgin materials which can be saved for next generations. So, finding a solution to substitute a practical recycled product for part of the aggregate seems to be desirable for sustainable development. Recycled aggregates are aggregate resulting from the processing of inorganic material previously used in construction, e.g. crushed concrete, masonry, brick. The level of impurities in the construction waste significantly affect the strength and performance of the recycled aggregate when used in concrete; therefore aggregates created from the broad field of construction and demolition waste (C&DW) such as brick-based recycled aggregates and asphalt-based recycled aggregates which contain up to 100% masonry are often used for secondary applications and are of little interest for use in concrete. This study focus on the utilization of aggregates created mainly from laboratory waste and left over fresh concrete, the type of recycled concrete aggregates that contains little or no impurities. The objective of this paper is to investigate physical properties of two different grades of concrete M 20 and M 30 using recycled coarse aggregate. Concrete tested with varying percentage of recycled aggregate i.e. 0, 25, 50, 75 and 100 % of natural aggregates. Compressive strength of concrete after 7 and 28 days were measured and comparative analysis is made. Key Words: Compressive strength, Concrete, Recycled aggregate, Sustainable development 1. INTRODUCTION Concrete is the world’s second most consumed material after water, and its widespread use is the basis for urban development. It is estimated that 25 billion tones of concrete are manufactured each year, twice as much concrete is used in construction around the world when compared to the 186
  • 2. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME total of all other building materials combined. Construction industry cannot survive without its use and applications. Therefore it is required to find alternative and sustainable materials to reduce the cost of concrete. On the other hand, the amount of construction waste has been dramatically increased in the last decade, and social and environmental concerns on the recycling of the waste have consequently been increased. Non- biodegradable construction and demolition waste is creating lots of problem in the environment and its disposal is becoming a great concern. Recent technology has also improved the recycling process. In this rapid industrialized world, recycling construction material plays an important role to preserve the natural resources. Many countries have recycling schemes for C&DW to avoid dumping to landfill, as suitable landfill sites are becoming scarce particularly in heavily populated countries. The greatest users of recycled aggregate in new concrete are the United Kingdom, the Netherlands, Belgium, Switzerland and Germany. Developing countries are still in the process to follow this trend with time. 2. NECESSITY TO USE RCA The protection of the environment is a basic factor, which is directly connected with the survival of the human race. Parameters like environmental consciousness, protection of natural recourses, sustainable development play an important role in modern requirements for construction works. Construction materials play very significant role in our lives. Concrete is a manufactured product, essentially consisting of cement, aggregates, water and admixture(s). Among these, aggregates, i.e. inert granular materials such as sand, crushed stone or gravel form the major part. Aggregates provide about 75 per cent of the body of the concrete and hence its influence is extremely important. As stated by Oikonomou, Construction sector is responsible for environmental degradation because it: • • • Takes 50% of raw materials from nature; aggregates for the production of cement and concrete, which results in the decrease of available natural resources which is continuously sub-graded. Consumes 40% of total energy; for the production, transport, use of raw materials and final ones, as cement and concrete. Creates 50% of total waste from old construction works (demolition wastes). The main reasons for the increase of this volume of demolition concrete waste are: (i) (ii) (iii) Many old buildings and other structures have overcome their limit of use and need to be demolished; Structures, even fit for use, are under demolition, because there are new requirements and necessities; Creation of building wastes which result from natural destructive phenomena like earthquakes, storms etc. The use of RCA on a large scale may help to reduce the effects of the construction on these factors by reusing waste materials and preventing more NA from being queried. Mostly crushed concrete is used as a sub-base material for pavements and for low grade applications in civil engineering projects, this study can be a positive step towards its use as a higher grade resource - as aggregate in new concrete. 187
  • 3. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME 3. MATERIALS The concrete test specimens were cast using cement, fly ash, fine aggregate, conventional and recycled coarse aggregate and water. The materials, in general, conformed to the specification laid down in the relevant Indian Standard Codes. The characteristics of the materials were as follows. 3.1 Cement Ordinary Portland cement 43 grade, from a single source had been used throughout the investigation. The physical properties of the cement which conformed to Indian Standard IS 8112: 1989 are listed in Table 1. All the tests on the cement samples were carried out as per recommendations of IS 4031: 1988. The cement was carefully stored in air tight silos to prevent deterioration in its properties due to atmospheric effects. Table 1. Physical properties of the cement (OPC 43 grade) IS 8112:1989 requirement Characteristic Units Results Blaine's fineness cm2/gm 3007 ≥2250 Specific gravity Soundness (Le Chatelier’s test) Autoclave expansion Normal consistency (% of cement by weight) Initial Setting time Final Setting time Compressive strength 3-day 7-days 28-days mm % % 3.14 1.9 0.07 29 42 410 25.65 35.12 45.36 3.14 ≤10 ≤0.80 30 ≥ 30 ≤ 600 ≥23 ≥33 ≥43 minutes MPa 3.2 Fly-ash A low-calcium fly ash obtained from the combined fields of the electrostatic precipitator of the thermal power plant was used. The 45 micron passing fraction in the unprocessed fly ash was more than 90 percent. The physical and chemical characteristics of the fly ash given in Table 2 satisfy the requirements of IS 3812: 1981 for fly ash. Fly ash was carefully stored in airtight silos in the laboratory to prevent deterioration in their properties due to exposure to the ambient conditions. Table 2. Physical and chemical properties of the fly ash Property Fly ash 2 Blaine's fineness, cm /gm 3462 Specific gravity 2.24 Silicon dioxide, SiO2, percent by mass 57.50 SiO2 + Al2O3 + Fe2O3, by mass 91.00 Loss on ignition, percent by mass 0.57 188
  • 4. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME 3.3 Fine Aggregate Locally available river sand having a specific gravity of 2.61, water absorption of 0.90 % and a fineness modulus of 2.65 was used as fine aggregate. The sand was sieved through a 75 micron sieve to make it free from lumps of clay and other foreign matter in the laboratory before being used for casting. The physical properties of the fine aggregate are listed in Table 3. The fine aggregate confirmed to Zone II of IS 383: 1987. Table 3. Physical properties of the fine aggregates Characteristics Result Grading Zone II (IS:383-1987) Fineness modulus 2.65 Specific gravity 2.61 Density (loose) kN/m3 15.10 Water absorption (%) 0.90 Moisture content (%) 0.45 3.4 Coarse Aggregates Natural aggregates (NA) and recycled concrete aggregates (RCA) were used as the coarse aggregates in the concrete mixtures. A locally available crushed granite was used as the natural coarse aggregate. The source of recycled aggregate was crushed concrete from laboratory waste and left over fresh concrete. To improve the quality of RCA treatment process in terms of washing was given. Recycled and natural coarse aggregates used had the same nominal size 10 mm and 20 mm. To compare the physical properties of RCA with natural aggregates various tests has been done. Table 4 shows the comparison between NA and RCA. Table 4. Physical properties of Natural and Recycled coarse aggregate Physical property NA RCA Sr. No 1 Specific gravity 2.70 2.45 2 Water absorption % 1.37 6.14 3 Impact value % 13.5 25.6 4 Los Angeles abrasion value % 17.3 33.2 3.5 Water Potable tap water which was free of any deleterious materials was used for both mixing and curing of concrete. 4. CONCRETE MIX DESIGN Two concrete mixes were prepared for minimum compressive strength of 20 N/mm2 and 30 N/mm2 for 28 days curing with constant water to cement ratio (w/c) 0.5. The mix design was done according to the IS: 10262- 2009 and numerous trial mixes were conducted to obtain the optimum mix. Once the optimum mix was determined for each grade, it was used to produce concrete with 0%, 25%, 50%, 75% and 100% RCA by weight replacement of natural coarse aggregate. The mix proportions were designed by assuming the aggregates in saturated surface dry condition and 189
  • 5. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME appropriate moisture adjustments were made to cater for the different water absorption properties of the aggregates. The fly ash was used as 25% by weight replacement of cement to achieve proper workability of the mix. Mix Table 5. Mix proportions for different mixes Mix proportion Fly Ash % Constituents (kg/m3) by weight W/C ratio Cement Sand Aggregates M20 1:1.5:3.4 25 400 600 1360 0.5 M30 1:1.25:2.75 25 450 562.5 1237.5 0.5 5. EXPERIMENTAL WORK Concrete cubes of 150 X 150 X 150 mm were cast for compressive strength. All specimens were cast in steel molds and compacted using a vibrating table. After casting, the specimens were cured in air for a period of 24 hrs. The hardened concrete samples were then demoulded after 24 hrs and submerged in a clean water bath for curing until the age of testing i.e. 7 days and 28 days. For each proportion three specimens were tested and the mean value of these measurements was reported for compressive strength. 6. RESULTS AND DISCUSSIONS Table 6 shows the results of the 7 days and 28-days compressive strength of concrete. The test was carried out conforming to IS 516-1959 to obtain compressive strength of concrete at the age of 7 and 28 days. The cubes were tested using Compression Testing Machine of capacity 2000KN. Recycled aggregate (%) 0 25 50 75 100 Table 6. Compressive strength (N/mm2) of concrete mixes M20 % M30 Reduction in Compressive strength Compressive fck strength 7 days 28 days 28 days 7 days 28 days 18.2 25.9 23.5 34.2 17.4 25.8 0.4 20.4 32.1 18.7 26.7 3 % increase 21.9 33.3 12.4 18.6 28.2 17.2 26.7 16.4 21.3 17.8 21.2 29.8 % Reduction in fck 28 days 6.1 2.6 21.9 12.9 From the results, for M 20 grade of concrete, the compressive strength of concrete with 25 % replacement of RCA is in close proximity with 100 % NA concrete and concrete with 50% replacement of RCA has the highest 7-day and 28-day strength which reaches 18.7 MPa and 26.7 MPa respectively, but with increase in the amount of RCA beyond 50 %, there is sharp decrease in the compressive strength. 190
  • 6. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME Compressive strength N/mm2 25 20 15 M20 M30 10 5 0 0 25 50 75 100 Recycled aggregate % Fig 1. Compressive strength of concrete at 7 days Compressive Strength N/ mm2 40 35 30 25 20 M20 M30 15 10 5 0 0 25 50 75 100 Recycled aggregate % Fig 2. Compressive strength of concrete at 28 days Figure 1 and 2 compares the compressive strength of M 20 and M 30 grade of concrete with 0%, 25%, 50%, 75% and 100% replacement of RCA after 7 and 28 days respectively. For M 30 grade of concrete there is 6.5 % decrease in compressive strength with 25 % RCA, as compared to 0.4 % for M 20. Significant decrease in 28 days compressive strength of M 30 grade concrete for all the replacement levels of RCA was found, as compared to M 20 grade. 191
  • 7. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME 7. CONCLUSIONS From the experimental work carried out on Recycled Concrete Aggregates, following conclusions can be drawn: 1. Specific gravity of RCA is lower and Water absorption of RCA is higher than natural aggregate. 2. The compressive strength of M 20 and M 30 grade concrete containing 25% and 50% RCA is in close proximity to that of normal concrete. For M 20 it was seen that compressive strength increased by 3 % with addition of RCA but only up to 50%. 3. When amount of RCA is increased above 50%, it adversely affects the compressive strength of concrete. Reduction in strength for higher percent replacement is due to adhered mortar and higher water absorption capacity of recycled aggregates as compared to conventional aggregates. 4. Compressive strength of M 30 grade of concrete is lower than M 20 grade of concrete for all the replacement levels. 5. The strength of concrete is high during initial stages but gradually reduces during later stages. Thus it can be concluded that RCA up to 50% is satisfactory for structural use and can be used effectively as a full value component for new concrete. Further addition of RCA resulted in decrease of the strength which can be improved by applying more advanced and sophisticated treatment process and casting methods under highly skilled supervision. . REFERENCES [1] [2] M. S. Shetty, “concrete technology”, S. Chand publication company ltd., New Delhi, 2008. Nik. D. Oikonomou, “Recycled concrete aggregates”, Cement & Concrete Composites 27, 315– 318, 2005. [3] M C Limbachiya, A. Koulouris, J J Roberts and A N Fried, “Performance of Recycle Aggregate Concrete”, Kingston University, UK, 2004. [4] Khaldoun R, “Mechanical properties of concrete with recycled coarse aggregate”, Building and Environment journal, volume 42, 2007, 407–415. [5] S. K. Singh and P. C. Sharma, “Use of recycled aggregates in concrete- A Paradigm Shift”, National building materials journal, 2007. [6] Salem Ahmed Abukersh, “High quality recycled aggregate concrete”, Ph. D thesis, School of Engineering and the Built environment, Edinburgh Napier University, UK, 2009. [7] Sami W T and Akmal S A, “Influence of recycled concrete aggregates on strength properties of concrete”, Construction and Building Materials journal, volume 23, 2009, 1163–1167. [8] I. Gull, “Testing of strength of recycled waste concrete and its applicability,” Journal of Construction Engineering and Management, vol. 137, 2011, 1–5. [9] Briton J D and Richardo R,”Recycled aggregate concrete methodology for estimating its long term properties”, Indian journal of engineering and material sciences, volume 17, 2010, 449- 462. [10] IS: 10262-2009 Concrete mix design. [11] P.J.Patel, Mukesh A. Patel and Dr. H.S. Patel, “Effect of Coarse Aggregate Characteristics on Strength Properties of High Performance Concrete using Mineral and Chemical Admixtures”, International Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 2, 2013, pp. 89 - 95, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316. [12] Ghassan Subhi Jameel, “Study the Effect of Addition of Wast Plastic on Compressive and Tensile Strengths of Structural Lightweight Concrete Containing Broken Bricks as Acoarse Aggregate”, International Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 2, 2013, pp. 415 - 432, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316. 192