Use of Construction and Demolition Waste as Fine Aggregate in Manufacturing Concrete Paving Blocks A.A.T. Darshika 1 and K.M.L.A. Udamulla 2 1 Department of Civil and Environmental Engineering Faculty of Science and Engineering University of Wolverhampton Wolverhampton WV1 1LY UNITED KINGDOM 2 Department of Civil Engineering Faculty of Engineering Technology The Open University of Sri Lanka Nawala SRI LANKA E-mail: tharunidarshika12@gmail.com Abstract: Disposal of construction and demolition waste that are released in huge quantities is a massive problem worldwide. Several attempts exist to augment its beneficial use. An attempt has been made to utilize this material for manufacturing concrete paving blocks. This study presents an experimental investigation carried out on the potential for using recycled construction and demolition waste as a partial substitute material for fine aggregate (sand) in manufacturing of concrete paving blocks for road paving. The paving blocks were cast by keeping aggregate-cement ratio at 3.5, watercement ratio 0.5 and by replacing river sand with recycled construction and demolition waste fine aggregate in percentages of 0%, 25%, 50%, 75% and 100%. The physical and mechanical properties (compressive strength, water absorption and unpolished slip resistance value) of paving blocks were evaluated. The test results demonstrate that the concrete paving blocks with 25% of RCDW fine aggregate replacement by the mass of sand reached the standard values of properties as prescribed in the Sri Lankan Standard 1425 : part1 : 2011, specification for concrete paving blocks : part 1- requirements. The findings from this research suggest that the recycled construction and demolition waste can be used as a partial substitute for fine aggregate in concrete paving block production. Therefore, the study will help reducing the usage of depleting resources by reducing the use of sand and minimizing environmental hazards through waste disposal by making use of recycled construction and demolition waste. Keywords: Concrete paving blocks (CPB), Recycled Construction and Demolition Waste (RCDW), fine aggregate, compressive strength, water absorption, unpolished slip resistance 1. INTRODUCTION Huge amounts of waste materials are being produced daily from many constructions, industries and human activities with fast industrialization and population growth. A large amount of these waste materials are generated from the construction regions, a bigger part of which is obtained from demolished buildings. These waste materials are directly dumped to the environment and this causes environmental pollution. There is an urgent need to find ways to handle such waste owing to growing environmental concerns. Therefore there is a growing need to reuse and recycle the waste for different construction purposes so that this will reduce the pressure on natural resources as well. Block paving is a common and very popular method of landscaping suitable for various applications including driveways, paths, patios, public utility areas, road and parking lots. As the country Sri Lanka continues to develop and urbanize at a rapid rate, the need for cement paving blocks becomes an essential part of town and city development and expansion. As the construction of CPB is increasing, experts in the construction industry have understood the requirement of alternative materials for construction of CPBs as natural aggregates are getting scarce and rapid extraction of sand from river beds result in many harmful problems (Nadeesha et al 2013). The use of waste material in producing concrete paving blocks could be a viable solution for the recovery and recycling of waste materials. 221
Therefore, recycled construction and demolition waste sand in manufacturing of concrete paving blocks can be considered as an alternative to safeguard depleting natural sand. Baskaran and Gopinath, (2011) reports that compressive strengths of sample blocks obtained from local concrete paving block manufacturers have met the criteria meant for Sri Lankan Standards for Concrete Paving Blocks in strength classes 2, 3, 4 roads and none of them were compatible with the compressive strength criterion meant for strength class 1 roads. Accordingly to introduce an alternative material to natural sand bottom ash is considered a worthwhile substitute. In this situation, the study was aimed at finding the feasibility of using recycled construction and demolition waste as a partial substitute to fine aggregate in manufacturing concrete paving blocks (CPB) for Sri Lankan roads and its effects on the physical and mechanical properties of concrete paving blocks so produced. The results are compared with standard specification of Sri Lankan Standards (SLS) specification for concrete paving blocks Part 1: Requirements. 2. METHODOLOGY 2.1 Materials 2.1.1. Cement As the binding material Ordinary Portland cement was used. This belongs to a strength class of 42.5 N and in compliance with SLS 107: Specification for Ordinary Portland Cement. 2.1.2. Aggregates Two types of aggregates were used in the manufacturing of concrete paving blocks; coarse and fine. Nominal size of 20 mm coarse aggregate with specific gravity of 2.73 was used. Fine aggregates were river sand which was sieved through a 10 mm BS 410 with specific gravity of 2.74 and recycled fine aggregate with 2.3 was taken from COWAM (Construction and Waste Management- Sri Lanka) center in Galle, Sri Lanka. The Figure 1 shows the particle size distribution test results for the collected samples of river sand and RCDW fine aggregate performed according to BS 812-103.1: 1985 and they are located within the standard BS 882:1992 limits. 2.2 Methods Figure 1 Particle size distribution curve 2.2.1. Mixture Composition and Fabrication of Paving Blocks A series of mixtures were prepared with an aggregate to cement (A/C) ratio of 3.5 and water to cement ratio of 0.5. A total of 5 mixtures were prepared with RCDW sand content of 0%, 25%, 50%, 222
75% and 100% by replacement ratio of fine aggregate by weight. Paving blocks were cast in fiber moulds of size 220mm 110mm 80mm by using the concrete mixture and manual compaction. Block specimens were cured at room temperature of 25 C in a water bath until tested. 2.2.2. Test Methods The compressive strength, unpolished slip resistance value (USRV) and water absorption were determined according to Sri Lanka Standard Institution (2011), specification for concrete paving blocks part 02: Test methods. The densities of paving blocks were determined using a water displacement method as per BS 1881 part 114 for hardened concrete (BS, 1881-114, 1983). The compressive strength of specimens was tested under 7, 14 and 28 days curing conditions. The water absorption, dry density and unpolished slip resistance values were tested at 28 days curing conditions. When determining the unpolished slip resistance values, the position of pointer of the friction test equipment on the scale was recorded after the catching of pendulum arm by releasing of pendulum and pointer from the horizontal position. This operation was performed five times by rewetting the specimen each time and mean of the last three readings were recorded. Pendulum value was calculated as the mean of the two recorded mean values measured in opposite directions when the wide slider was used over a swept length of 126 mm. The final results are presented as an average value of two specimens. 2.2.3. Specification Required for Concrete Paving Block According to the Sri Lankan Standard (SLS) 1425 Part 1: 2011 Compressive strength refer table 1 Slip/skid resistance (USRV) 55 Water absorption (%) 6 Strength class Table 1 Minimum strength requirement and block thickness Average compressive strength (N/mm 2 ) Individual compressive strength (N/mm 2 ) Block thickness (mm) 1 50 40 80,100 2 40 32 80,100 3 30 25 80,100 4 15 12 60 3. RESULTS AND DISCUSSION 3.1 Compressive Strength The compressive strength values of concrete paving blocks at the ages of 7, 14, and 28 are presented in figure 2. The compressive strength is found to decrease with increase of RCDW sand replacement on samples of aged 7, 14 and 28 days. It shows that RCDW sand has a significant effect on the strength properties of concrete paving blocks. This may due to weaker bonding of RCDW sand compared to that of river sand. 223
Figure 2 Variation of Compressive Strength with RCDW Sand Replacement 3.2 Water absorption The water absorption test results of concrete paving blocks are presented in figure 2 with Sri Lanka standard requirements. The water absorption is found to increase with the increase of RCDW sand replacement. The blocks fabricated with 25% of RCDW sand satisfies the SLS requirement of water absorption. Adhered harden cement paste which is attached to RCW sand may have led to the increase in water absorption. Figure 3 Variation of water absorption with RCDW sand replacement 3.3 Unpolished Slip Resistance Value The Unpolished slip resistance value results of concrete paving blocks are presented in figure 3 with Sri Lankan standard requirement. Unpolished slip resistance values of all the samples are found to be greater than the SLS requirement. 224
Figure 4 Variation of Unpolished Slip Resistance Values with RCDW Sand Replacement 4. CONCLUSIONS The minimum average compressive strength for strength class 1, 2 and 3 should be 50Mpa, 40Mpa and 30Mpa respectively according to the Sri Lankan standard 1425 Part 1 : 2011 Specification for concrete paving blocks Part 1: Requirements. By considering the compressive strength results of the series, 25%, 50%, 75% and 100% of RCDW sand replacement mixture achieved the SLS requirement for strength class 2 and strength class 3 roads. None of the tested CBPs compatible with the criterion of compressive strength meant for strength class 1 road. The Unpolished Slip Resistance Values of all specimens exceeded value of 55 and fulfilled the SLS requirement. The value of water absorption of the specimen which was fabricated by using 25% of RCDW sand was found to be less than 6% and this satisfied the Sri Lankan Standard. Mixture which is 25% of RCDW fine aggregate replacement has accomplished all the required specifications described in the SLS 1425:2011. This research suggest that RCDW sand can be applied as a partial substitute to fine aggregate in the manufacturing of concrete paving blocks. The results from this research suggest that construction and demolition waste sand can be applied as a partial substitute for fine aggregate in concrete paving block production. Therefore, this study will help in reducing the usage of depleting resources by reducing the use of sand, and minimizing environmental hazards through waste disposal by making use of construction and demolition waste sand. ACKNOWLEDGEMENTS Authors wish to express their sincere gratitude to academic and non-academic staff of the department of Civil Engineering, CINEC campus of Sri Lanka for their guidance and support. The support granted by Research and Development division of Road Development Authority (RDA) and Engineering Soil Laboratory (ESL) by granting permission to carry out laboratory tests is greatly acknowledged. REFERENCES Baskaran, K. & Gopinath, K. 2011, State of the art of concrete paving blocks in Sri Lanka (CPBs), Civil Engineering Research for Industry 2011, Department of civil Engineering University of Moratuwa.pp 13-19. Erandi, N.G.N, Sakunthala, W.C, Udamulla, K.K.L.A, 2013, Properties of concrete paving blocks made by using Bottom Ash as a partial replacement of natural sand, 4 th International conference on 225
Structural Engineering and Construction Management, 13 th, 14 th 15 th December, Earl s Regency Hotel, Kandy, Sri Lanka. Sri Lanka Standard Institution (2011), Specification for concrete paving blocks part 01: Requirements, Sri Lanka standard Institution, Colombo, Sri Lanka. Sri Lanka Standard Institution (2011), Specification for concrete paving blocks part 02: Test methods, Sri Lanka standard Institution, Colombo, Sri Lanka. 226