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Quantification of Recycled Concrete Aggregate (RCA) Properties for Usage in Bridges and Pavements: An Ontario Case Study


Given the impending shortage of readily available high-quality aggregate and increasing transportation costs, there is continued pressure to use recycled materials in the construction industry as these materials can provide cost effective and environmentally friendly alternatives to natural or virgin aggregates. This study focused on characterizing two Ontario recycled concrete aggregate (RCA) sources and producing new concrete utilizing RCA as coarse aggregate (RCA concrete). Three aggregate types were investigated, one control virgin aggregate source and two RCAs produced from the crushing of hardened concrete. Each aggregate type was classified according to its size, shape and surface texture. Numerous aggregate tests were performed, including density, absorption, abrasion resistance, adhered mortar content, and crushing value. Control concrete mixtures utilizing the virgin coarse aggregate source were developed with target strengths of 30 and 50 MPa and target slumps between 75 and 100 mm. The virgin coarse aggregate was then replaced with RCA (by volume) to investigate the effect a particular RCA source had on compressive strength and workability. In both RCA concretes the workability decreased when the virgin aggregate source was replaced with RCA. At higher strength levels (i.e., 50 MPa), the RCA concretes performed similarly to the control mixtures. However, at lower strength levels (i.e., 30 MPa), RCA concretes produced compressive strengths that were 7 to 22% higher than the control mixtures. The findings and recommendations derived from this research will assist aggregate suppliers, contractors, and engineers in properly assessing whether a particular RCA source is suitable for use in concrete pavement and bridge structures.

Conference Paper Details

Session title:
L. Butler
J.S. West
S.L. Tighe