Prediction of Mechanical Properties of Concrete Made with Recycled Concrete Aggregates Using Statistical Analysis of Data Available in Literature

The concrete design and construction industry has been eagerly adopting sustainability initiatives over the last 20 years to help reduce its carbon footprint, improve economic sustainability, and ensure the important natural resources that support the industry remain available for years to come. Despite these advances, recycled concrete aggregates (RCA) have been significantly underutilized even though they are becoming an increasingly available sustainable resource that can be used to reduce the amount of natural aggregates used in concrete. Use of RCA has been limited, in part, because of a lack of standardized guidance on creating mixture designs and how aggregates may impact concrete properties. Presented in this paper are the results of a statistical analysis of data from over 80 peer reviewed articles that can be used to predict performance in mixtures containing RCA. A large database consisting of 850 compressive strength, 682 elastic modulus, 197 flexural strength, and 462 splitting tensile strength results was created from this literature review with data ranging from 1988 to 2018. Non-linear regression analyses determined that the empirical trends related to compressive strength, elastic modulus, flexural strength, and splitting tensile strength had a linear relationship with the RCA replacement levels depending on absorption capacity, RCA replacement level, effective water-to-cement ratio, maximum aggregate size, and strength of the RCA’s parent concrete. Overall, the RCA replacement ratio and the water-to-cement ratio had significant impacts on concrete mechanical strengths, while other factors such as mix proportioning parameters and aggregate properties had minor effects on the mechanical properties of RCA systems over the large dataset. Additionally, significant reductions in strength were not observed until replacement levels of RCA increased above 20%.