Recycled Aggregate Concrete for Transportation Infrastructure

Abstract

With rapid urbanization and development in the field of construction the demand for natural aggregates is increasing day by day with a corresponding increase in concrete production. Extraction of natural aggregates from mother earth leads to destruction of environment. Also, in the process of urbanization, the buildings and other structures which no-longer serve the intended purpose are often demolished. However, the disposal of this construction debris is becoming a major concern in the current era. The solution for these concerns are interdependent and inter connected. The use of the construction and demolition waste in concrete as a replacement of the natural aggregates is recognized as a viable way to effectively utilize this waste. These aggregates are known as recycled concrete aggregates. Though the idea of using construction and demolition waste in concrete in infrastructure projects has been in practice for a long time around the world, its use in India is limited till date.This paper reports the results of a laboratory based exploratory study aimed at characterizing the properties of recycled aggregate and recycled aggregate concrete, to verify their utilization in civil infrastructure. Recycled aggregates used in this study were generated by crushing of concrete cubes tested in the laboratory. Five different concrete mixes were produced; three recycled aggregate concrete viz with 50%, 75% and 100% recycled aggregates with fly ash, and two natural aggregate concrete mixes with and without fly ash, respectively. Triple mixing method was adopted for making of recycled aggregate concrete. Compressive strength, split tensile strength, flexural strength, modulus of elasticity, water absorption and resistivity of the concrete were determined. It was observed that there was no significant variation in compressive strength, split tensile strength and flexural strength of concrete, while the modulus of elasticity and resistivity decreased and water absorption increased with increase in percentage of recycled aggregates. The findings from the study show that the recycled concrete aggregate may be useful for construction of transportation infrastructure such as pavements and bridges. However, further research is needed particularly on the long term field performance of the recycled aggregate concrete before it can be used with confidence.