Incorporation of Admixtures in Recycled Aggregate Concrete: A Review

Abstract

The huge amount of annual concrete production poses significant harmful environmental impact. The demand for construction and concrete production consequently results in a huge demand for natural aggregate thereby causing great concerns for aggregate availability. Recycling waste concrete which often times end up in landfill is one of the major solutions to reduce its environmental effects. Waste concrete are crushed to desired sizes and used as replacement for natural aggregate to a certain degree in the production of new concrete. A reduction in strength has been reported after various researches with most recommending an optimum replacement percentage of 30% beyond which are decline in strength properties is evident. Thus, it becomes necessary to improve this performance and increase the amount of concrete waste reduction. To produce highperformance concrete, early researchers altered the watercement ration to achieve the desired results. Thereafter, they employed the use of chemical and mineral admixtures alongside specialised production process. In addition to performance improvement, Mineral admixture will function to substitute or reduce the consumption of Portland cement leading to a low impact, less energy consuming building material. This paper reviews the effect of admixtures on the mechanical properties of recycled aggregate concrete and possible areas for future research were identified and recommended.