A REVIEW OF RECYCLED CONCRETE AGGREGATES AS A SUSTAINABLE CONSTRUCTION MATERIAL

: The recent increase in structural developments worldwide, has given rise to the consumption of natural aggregates and energy hence generating a vast amount of construction and demolition waste. Natural aggregates occupy 60-75 percent in volume of the concrete matrix. It is beneficial to recycle construction and demolition waste, for construction activities. One such material retained from construction sites is waste concrete, which can be used to produce recycled concrete aggregates (RCAs). Recycling waste concrete produces a substitute to natural aggregates and preserves the environment by reducing waste disposal at landfills and conserving energy. The use of recycled concrete aggregates has piqued the interest of many researchers by utilization of a full or partial substitution to that of natural aggregates in concrete mixtures. Over the last decade, a significant volume of literature has been published discussing the properties and microstructure of recycled concrete aggregates and its response when used in a new concrete mix. Within this paper a brief history of RCAs is outlined together with statistics on the quantity of concrete waste produced, recycled and its practical applications. A comparison between the RCA and natural aggregate properties are discussed on a microscopic level, such as the density and water absorption capacities. Further to this, a summary of the mechanical and durability parameters are discussed such as compressive, tensile and flexural strengths together with chloride ion penetration. Several pre-treatment methods such as: acid treatment and the use of fine mineral fillers are also discussed. Finally, the conclusions and gaps are stated.