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Title: Effects of Recycled Aggregates on Concrete Properties
Keywords: Construction and demolition waste, sustainable development, recycled concrete aggregate, recycled aggregate concrete, mechanical properties, shrinkage
Issue Date: 14-Jul-2011
Citation: LIM LOK GUAN JACOB (2011-07-14). Effects of Recycled Aggregates on Concrete Properties. ScholarBank@NUS Repository.
Abstract: Sustainable development is gaining popularity around the globe nowadays. The rapid development in Singapore has resulted in significant amount of waste generation from various sectors. Being a small country with limited natural resources, it is timely to explore the potential of recycling these waste materials into resources for construction related applications. The Building and Construction Authority (BCA) has been working closely with industry partners to promote wider adoption of sustainable materials in our built environment. The idea of reusing aggregates from local demolition waste for structural concrete was one of the strategies used. Recycled aggregates (RA) are comprised of crushed, graded inorganic particles processed from the materials that have been recovered from the constructions and demolition debris. For the conservation of natural resources, reusing and recycling of construction and demolition waste (C&DW) is the most obvious way to achieve sustainability in the construction sector. Currently, recycled concrete aggregate (RCA) is produced from C&DW in modern recycling facilities, under good quality control provisions which could lead to improve merits in performance compared with the earlier days of recycling. A recycled aggregate concrete (RAC) produced with the combination of natural aggregate (NA) and recycled concrete aggregate (RCA) is obviously more sustainable and economical than using conventional natural aggregate concrete (NAC) alone. The aim of this study is to compare the engineering properties as well as durability performance of RAC to the conventional concrete. This particular study shows that the properties of aggregates (i.e. physical, mechanical, and chemical), and hence the quality of RCA is varies from the 4 different major recycling plants. The first step in the investigation involved the characterization of RCA through testing including physical, mechanical and chemical. Aggregates were classified based on the requirements of SS EN 12620:2008 which provided the main guidance for aggregates for concrete. Following the establishment of the aggregates conformity for concrete production, a further in-depth investigation involved the production of designed concrete mixes; Grade 30, Grade 60 and Grade 80 with the natural aggregates being replaced by RCA in various proportions (20%, 50% and 100%). The investigation included assessment of the engineering properties (i.e. compressive strength, flexural strength, tensile splitting strength, modulus of elasticity and drying shrinkage) and the durability properties (i.e. rapid chloride permeability test) of equivalent strength concrete in the fresh state as well as in the hardened state. Based on the findings, it was found that concrete properties of Grade 30 containing different percentages of recycled aggregates did not differ much compared to the control mixes, provided that the effective water/cement ratio was kept constant. However, for concrete properties of Grade 60 and Grade 80 it was generally observed that the higher replacement % of recycled aggregates lowered the strength of recycled aggregates concrete. Besides, effects of two RCA parameters (i.e. particle density and Los Angeles abrasion) have significant effects on the strength. Further research is recommended with higher replacement percentage of RCA for RAC properties. Based on the 6 months monitoring, generally the properties of RCA produced by the 4 plants were not consistent. It can however be improved with more stringent quality control.
Appears in Collections:Master's Theses (Open)

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