Rheological and fresh properties of self-compacting concretes containing coarse and fine recycled concrete aggregates

• We studied use of recycled concrete aggregate (RCA) in SCC.
• Fine and coarse RCAs were replaced with natural aggregates at various levels.
• Effect of RCAs on the rheological and fresh properties of SCC was investigated.
• Various models were used to describe the rheological behaviour of SCC with RCA.
• Herschel-Bulkley and modified Bingham models provide better results for SCC.

In this study, the rheological and fresh properties of self-compacting concrete (SCC) using recycled concrete aggregate (RCA) as both coarse and fine aggregates have been investigated. SCC mixtures were prepared containing natural aggregate replacements at the levels of 0, 50 and 100% for coarse recycled concrete aggregates (CRCA) and in each series of mixtures fine recycled concrete aggregate (FRCA) replacements were varied at the levels of 0, 25, 50, 75 and 100%. In all concrete mixtures, 20% of cement content was replaced with fly ash (FA) and water-to-binder ratio (w/b) was used as 0.32. Herschel-Bulkley and modified Bingham models were adopted in this paper instead of traditional Bingham model to describe the rheological behaviour of SCC with RCA indicating a non-linear and shear thickening behaviour due to lower yield stress close to zero. The influence of RCA replacements on the shear thickening behaviour of SCC was explained using the rheological analyses. The slump flow and T500 time, V-funnel time and L-box height ratio tests were carried out to identify the effects of both CRCA and FRCA utilisations on the fresh properties of SCC. The results reveal that Herschel-Bulkley and modified Bingham models provide well defined rheological representations for SCC with RCA. The self-compactibility characteristics of the concretes are remarkably improved by the replacement levels of CRCA and FRCA used in SCC mixtures.