INTERNATIONAL JOURNAL OF CIVIL AND STRUCTURAL ENGINEERING Volume 6, No 2, 2015

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1 INTERNATIONAL JOURNAL OF CIVIL AND STRUCTURAL ENGINEERING Volume 6, No 2, 2015 Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0 Research article ISSN Effect of replacement of natural by recycled derived from field demolished concrete on the workability and characteristics of concrete Manjunath M 1, Prakash K B 2 1- Research scholar, Walchand College of Engineering, Department of Civil Engineering, Sangli , Maharastra State, India 2- Principal, Government Engineering College, Haveri , Karnataka, India manjunathm162@gmail.com doi: /ijcser.6010 ABSTRACT This paper presents an experimental investigation on the effect of replacing natural coarse aggregate by recycled aggregate obtained by processing field demolished concrete on the properties of recycled aggregate concrete. The natural coarse aggregate (NA) in concrete was replaced by recycled coarse aggregate (RA) at different percentages. Workability tests and tests such as compressive test, tensile test, flexural test and impact test are conducted to study the effect of replacing NA by RA. Test results show that for different percentage replacements of natural coarse by recycled there is a reduction in of concrete with the increase in the percentage of replacement. For replacement of natural by recycled up to 20%, the reduction in was marginal. Keyword: Recycled aggregate, compressive, tensile, flexural, impact. 1. Introduction Cement concrete remains the main construction material used in the construction industry. For its suitability and adaptability with respect to the changing environment, concrete must be such that it can conserve resources, protect the environment, economize and lead to proper utilization of energy. To achieve this, major emphasis must be laid on the use of wastes and by-products in cement and concrete used for new constructions. The utilization of recycled concrete is particularly very promising as percent of concrete is made of (Mehta P.K 2006). Along with increased consumption of natural resources, on the other hand there is also a manifold increase in the amount of waste that the concrete industry has to deal with. Waste concrete is produced mainly by demolition activities and also by natural disasters like earthquake, avalanches, etc., and human causes like war, structural failures, etc. The waste arising from demolitions is estimated to be close to 100 million tonnes every year in the developed countries. A similar estimate for India would reveal a staggering figure (Amjad Masood 1998). Both issues have come under intense scrutiny and criticism of environmental conservation. While recycled are commonly employed as secondary in road construction, to promote recycled concrete in wider applications, it has to meet the requirements for its intended use. In this regard there are two main aspects, which require close attention before considering recycled in structural concrete: (i) inferior physical properties, for example lower density and higher absorption as compared to natural and (ii) likelihood of problems inherited from the parent concrete (Satish B.D Received on July 2015 Published on November

2 2006). In general, the effects of using recycled-concrete aggregate instead of natural aggregate are (a) reduced compressive (b) reduced modulus of elasticity (c) increased drying shrinkage and creep and (d) increased damping capacity. The reduction in ranges between 12 to 25 percent, while, the reduction in modulus of elasticity varies from 10 to 33 percent. Creep of recycled aggregate concrete was found to be 30 to 60 percent greater and drying shrinkage 20 to 50 percent greater than concrete made with natural (ACI Committee). In this study experiments are conducted to study the effect of replacing natural coarse by recycled on the properties of concrete. The recycled coarse aggregate is obtained from field demolished concrete. Workability and characteristics are investigated by replacing natural coarse by recycled. The different percentage replacements of natural coarse by recycled considered are 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100%.The properties investigated on hardened concrete include compressive, tensile, flexural and impact. 2. Research significance Recycled are seldom utilized in structural applications; instead they have been used as fillers in road construction and in low-level applications due to material defects such as large water absorption capacity and their elongated and angular shape. The experimental results give an encouraging trend towards utilization of recycled from field demolished concrete by blending with natural in making recycled aggregate concrete for structural applications. 3. Experimental program 3.1 Materials Ordinary Portland cement confirming to 43 grade as per IS: with specific gravity 3.15 was used. The fine aggregate used was locally available natural sand conforming to zone-ii grading requirements of IS with specific gravity 2.62 and fineness modulus 2.53, and the natural coarse used are 20 mm down size. The recycled coarse used in the experimental study are obtained from field demolished reinforced cement concrete slab, beam and columns. The original concrete can be characterized as nominal mix concrete of M15 grade, 12 to 15 years old and exposed to Mild environmental conditions. The conversion of waste concrete into was carried out in plants meant for production of crushed aggregate from natural rock. The crushed product was screened and sizes below 4.75mm were rejected. The recycled coarse used in the experimental study were 20 mm down size. The recycled coarse aggregate was standardized to satisfy the grading requirements as per Indian standard I.S The physical properties of natural coarse and recycled coarse are given in table Mix proportion The experimental investigation was based on a reference concrete mix of grade M20 using natural. On the basis of the material properties, the proportioning of concrete mix International Journal of Civil and Structural Engineering 120

3 was carried out in accordance to IS and as per the guidelines of IS 10262:2009. The mix proportion of reference mix was 1(cement): 2.02(sand): 3.66 (coarse aggregate) with water cement ratio of 0.55 for M20 grade of concrete. Table 1: Physical properties of natural coarse and recycled coarse Properties Natural coarse Recycled coarse Fineness modulus Specific gravity Water absorption (percentage) Bulk density in loose state (kg/m 3 ) Bulk density in compacted state (kg/m 3 ) Impact value (percentage) Crushing value (percentage) Los Angles abrasion value (percentage) Preparation of specimens The recycled aggregate concrete (RAC), was obtained by replacing natural aggregate in the reference mix. The natural coarse were replaced by recycled in the proportion of 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100%, on the basis of absolute volume method of replacement. The were maintained in saturated surface dry (SSD) state. The recycled were subjected to pre-wetting. To measure the workability, slump test and compaction factor test were carried out for each replacement level of natural coarse by recycled. To determine the characteristics, specimens for each variation for the various tests were cast and cured for 28 days. 3.4 Testing of concrete Concrete cubes of size 150x150x150 mm were tested for compressive as per IS: To get the tensile, cylindrical specimens of size 150mm diameter and 300 mm length were tested as per IS: For flexural, beam specimens of size 100x100x500mm were tested. Two point loading was adopted on an effective span of 400 mm to get pure bending, while testing the beam specimens as per IS: For impact, cylindrical specimens of 150mm diameter and 60mm height were prepared and tested on Schruder s impact testing machine. A hammer of weight 45.4 N was dropped from a height of 0.457m. Number of blows required to cause first crack and final failure were noted down to calculate impact. 4. Results and discussion 4.1 Workability results Table 2 gives the workability test results as measured from slump test and compaction factor test carried out with different percentage replacement of natural coarse by recycled. From the slump and compaction factor results, it was observed that as the percentage replacement of natural coarse by recycled is increased there is International Journal of Civil and Structural Engineering 121

4 marginal decrease in workability. As compared to concrete with natural (0% replacement), the slump values for recycled aggregate concrete (100% replacement) shows a decrease of about 14.90%. Similarly, the compaction factor values for recycled aggregate concrete shows a decrease of about 5.50% as compared to concrete with natural. Table 2: Workability test results with different percentage replacement of natural coarse by recycled. replacement of natural by recycled Workability through Slump (mm) Compaction factor Compressive test results Table 3 gives the overall results of compressive of concrete with different percentage replacement of natural coarse by recycled. Table also gives the percentage decrease of compressive with respect to the reference mix. Variation of compressive at different percentage replacement of natural coarse by recycled can be depicted in the form of graph as shown in figure 1. Table 3: Overall results of compressive replacement of natural by recycled Compressive (MPa) decrease of compressive with respect to reference mix 0 (Ref.mix) International Journal of Civil and Structural Engineering 122

5 Figure 1 : Variation of compressive of concrete produced by replacing natural coarse by recycled The results of the compressive obtained for different percentage replacements of natural coarse by recycled indicated that there is a reduction in compressive with increase in the percentage of replacement. The concrete produced by replacing 100% natural coarse by recycled shows 27.80% decrease of compressive as compared to reference concrete with 0% replacement. This is in conformity with other researchers. Ravindrarajaiah (Sri.Ravindrarajah R 1985) has reported 24% decrease of compressive, Rammurthy has reported 15% to 20% decrease of compressive, Etxeberria has reported 20% to 25 % decrease and Topcu & Sengel have reported 23.5 % to 33%, decrease of compressive respectively. 4.3 Tensile test results Table 4 gives the overall results of tensile of concrete with different percentage replacement of natural coarse by recycled. Variation of tensile at different percentage replacement of natural coarse by recycled can be depicted in the form of graph as shown in figure 2. Table 4: Overall results of tensile replacement of decrease of Tensile natural tensile by with (MPa) recycled respect to reference mix (Ref. mix) International Journal of Civil and Structural Engineering 123

6 Figure 2: Variation of tensile of concrete produced by replacing natural coarse by recycled The results of the tensile obtained for different percentage replacements of natural coarse by recycled indicated that there was a reduction in tensile with increase in the percentage of replacement. The concrete produced by replacing 100% natural coarse by recycled shows about 24.68% decrease of tensile as compared to reference concrete with 0% replacement. 4.4 Flexural test results Table 5 gives the overall results of flexural of concrete with different percentage replacement of natural coarse by recycled. Variation of flexural at different percentage replacement of natural coarse by recycled can be depicted in the form of graph as shown in figure 3. Table 5: Overall results of flexural decrease of replacement flexural Flexural of natural with (MPa) by recycled respect to reference mix 0 (Ref.mix) International Journal of Civil and Structural Engineering 124

7 Figure 3: Variation of flexural of concrete produced by replacing natural coarse by recycled The results of the flexural obtained for different percentage replacements of natural coarse by recycled indicated that there was a reduction in flexural with increase in the percentage of replacement. The concrete produced by replacing 100% natural coarse by recycled shows 26.26% decrease of flexural as compared to reference concrete with 0% replacement. 4.4 Impact test results Table 6 gives the overall results of impact of concrete with different percentage replacement of natural coarse by recycled. Variation of impact at different percentage replacement of natural coarse by recycled can be depicted in the form of graph as shown in figure 4. replacement of natural by recycled Table 6: Overall results of impact First crack Final failure decrease of Impact Impact impact with (N-m) (N-m) respect to reference mix decrease of impact with respect to reference mix 0 (Ref.mix) International Journal of Civil and Structural Engineering 125

8 Figure 4: Variation of impact of concrete produced by replacing natural coarse by recycled The results of the impact for both the first crack and final failure obtained for different percentage replacements of natural coarse by recycled indicated that there was a reduction in impact with increase in the percentage of replacement. The concrete produced by replacing 100% natural coarse by recycled shows 25.00% and 26.92% decrease of impact for first crack and final failure respectively with 0% replacement. The reduction in the characteristics of concrete with replacements of natural coarse by recycled may be attributed to the following reasons: (i) Compared to density of natural coarse aggregate (1534 kg/m 3 ), the recycled coarse aggregate has lower density (1337 kg/m 3 ); due to the old mortar adhering to the, resulting in reduced concrete density (ii) The mechanical properties of recycled i.e. crushing value (32.50%) and abrasion value (25.79%) are inferior as compared to natural (21.42% and 8.36% respectively). 5. Concluding remarks Following conclusions may be drawn based on the test results, observation and discussion for the grade of concrete (M20) investigated: International Journal of Civil and Structural Engineering 126

9 1. Workability of concrete reduces as the percentage replacement of natural coarse by recycled increases. 2. There is a reduction in compressive, tensile, flexural and impact of concrete with increase in the percentage replacement of natural coarse by recycled. 3. With 100% replacement of natural coarse by recycled the decrease of compressive, tensile, flexural and impact (for formation of final failure) was found to be 27.80, 24.68, and percent respectively. For replacement of natural by recycled upto 20%, the effects are marginal; the reduction in workability in terms of slump was about 1% and the reduction in various properties (compressive, tensile, flexural and impact ) was in the range of 4 to 6%; indicating that recycled aggregate from field demolished concrete can be blended with natural upto 20% without any modification in the mix design for M20 grade concrete applications. 6. References 1. ACI Committee 555 report, (2002), Removal and reuses of hardened concrete ACI Materials Journal, May-June 2002, pp Amjad Masood, Tazyeen Ahmad, Farrukh Ghani and Devendra Singh Rawat, (1998), Variation in of concrete on addition of demolished waste, The Indian Concrete Journal, 74 (1), pp Etxeberria, M. Vazquez, E., Mari, A., and Barra, M. (2007), Influence of amount of recycled coarse and production process on properties of recycled aggregate concrete, Cement and Concrete Research, 37, pp Ilker Bekir Topcu and Selim Sengel, (2004), Properties of concretes produced with waste concrete aggregate, Cement and Concrete Research, 34, pp Mehta P.K., and Monteiro P.J.M., (2006), Concrete - Microstructure, Properties, and Materials, 3 rd edition, TATA McGraw-Hill Education Pvt. Ltd. 6. Ramamurthy, K. and Gumaste, K.S.,(1998), Properties of recycled aggregate concrete, The Indian Concrete Journal, 74(1), pp Satish B.D., and Mukesh C.L.,(2006), Coarse recycled aggregate A sustainable concrete solution, The Indian Concrete Journal, 82(7), pp Sri.Ravindrarajah R., and Tam C.T., (1985), Properties of concrete made with crushed concrete as coarse aggregate, Magazine of Concrete Research, 37(130), pp IS 8112, (1989,) Specification for Ordinary Portland Cement, Bureau of Indian Standards, New Delhi 10. IS383, (1970), Specifications for coarse and fine from natural sources for concrete, Bureau of Indian Standards, New Delhi. International Journal of Civil and Structural Engineering 127

10 11. IS 456, (2000), Plain and Reinforced concrete code of practice, Bureau of Indian Standards, New Delhi. 12. IS 10262, (2009), Recommended guidelines for concrete mix proportioning, Bureau of Indian Standards, New Delhi. International Journal of Civil and Structural Engineering 128