Durability Aspects of Concrete made with High Volume of Coarse Recycled Concrete Aggregate

摘要

Most applications of conventional concrete do not consider implementing the use of Recycled Concrete Aggregate (RCA) in production due to its physical properties and corresponding drawbacks. In cases where RCA is used, replacement levels of virgin aggregate with RCA typically do not exceed 15%, in order to minimize on the drawbacks. To take another approach, this paper presents results from a study aimed at maximizing the RCA replacement levels, while making only minor adjustments in mix design, to achieve both equivalent strength and durability performance of RCA concrete to their virgin aggregate counterparts. Concrete specimens were tested for compressive strength, drying shrinkage, and effects of released alkalis from RCA on triggering disruptive expansion, if used with sand that marginally meets the expansion limit. Through modifications in mix design, the drawbacks of RCA (reduced strength, increased drying shrinkage, and promoting ASR potential) were successfully mitigated at coarse RCA replacement levels up to 100%. Through the use of higher replacement levels of RCA in the production of concrete, the environmental impacts of virgin aggregate harvesting may be reduced, as well as providing a more economical means of disposing of waste concrete for ready mix producers.