A Comprehensive Analysis of Recycled Concrete Aggregate (RCA) Characteristics and Effective Use of RCA Characteristics in Concrete Mixture Design

Concrete waste contributes to the majority of 230-530 million tons of Construction and Demolition wastes produced in the US each year, yet only a small proportion of which is recycled. Recycling waste concrete and producing recycled concrete aggregate (RCA) is one of the crucial topics in civil engineering as it promotes sustainability through reducing the demand for the natural resources and consumption of landfill space, and lowering the production costs. Major obstacles that hinder the use of RCA in concrete construction are the lack of specifications and procedures for qualifying an RCA source and the unclear impact of RCA on concrete performance. A more comprehensive study focused on RCA characterization and its use in concrete mixture design is needed. Most of the current practices and standard specifications use only gradation, specific gravity, and absorption to characterize and classify RCA, as they are easily accessible and generally considered to be related to the strength and residual mortar content of RCA. However, it is unclear if these parameters can sufficiently characterize RCA for concrete applications. The proposed study considers and evaluates various parameters that can be used to describe the physical, mechanical, and durability characteristics of RCA. Besides, with the more effective characterization, a more rational mixture design of concrete that is incorporating RCA has been developed. There is a misconception that the properties of concrete are definitely compromised with the incorporation of RCA. However, the study showed that with an effective characterization of the geometrical and physical properties of RCA, and particle packing-based mixture design approach, concrete with workability and mechanical properties comparable to normal concrete could be achieved. This study provides a concrete mixture design method that incorporates key RCA characteristics, focusing on pavement concrete. Finally, the effect of RCA mechanical properties on mechanical properties and cracking behavior of concrete was studied, which will provide insights into the role of RCA in the mechanical properties of concrete