Properties of crushed recycled fine aggregate in concrete mixes

Abstract

In many developing countries, the construction activities growth tremendously with sometimes, constituting large amount of waste produce by Construction and Demolition (C&D) works. Since C&D waste had been disposed incorrectly, many researchers and concrete engineers suggested that reused or recycling the waste is more profitable and an appropriate alternative to improve the construction method. The utilization of waste material is able to conserve the raw material but also preserve the environment. This study discusses on several physical and mechanical properties of crushed recycled fine aggregates to replace fine natural aggregate (sand) in the production of new concrete. Recycled Fine Aggregate (RFA) concrete is crushed into the fine aggregate with particles size less than 5mm diameter. The replacement level or RFA is varied, by replacing to 0%, 25%, 50%, 75% and 100%. Sieve analysis, specific gravity and water absorption test have been examined to check on fine recycled aggregates characteristic. In order to achieve the objectives, test for concrete samples were conducted in two categories which is fresh concrete test and hardened test. For fresh concrete test, slump test were conducted to measure the degree of the workability of the fresh concrete. The hardened test such as compressive strength, flexural strength, density of cube and ultrasonic pulse velocity test were investigated. It was obtained that the compressive and flexural strength decrease with increment of replacement. However, after 28 days of curing time, the concrete containing recycled aggregate rates of strength development are almost similar to the natural concrete. It was cleared that at 25% replacement the reduction of concrete strength is at 2% - 3%. Meanwhile, it was found that the water absorption of the fine crushed concrete waste much greater than natural aggregate. Finally, it can be conclude that it is possible to replace the normal fine aggregate with the fine crushed concrete waste aggregate since the properties obtained were similar to the conventional concrete.