Compressive-Strength Evaluation of Recycled Aggregate Self-compacting Concrete Through Hammer Rebound Index

Hammer rebound index is an indirect measure that has traditionally been used to estimate the compressive strength of concrete through the use of statistical models. It is especially useful in the quality control performed during the construction of a concrete structure, as well as in rehabilitation works. The high content of fine aggregate and aggregate powder of Self-Compacting Concrete (SCC) reduces its surface hardness and causes that the models traditionally used to estimate the compressive strength through this indirect measure in conventional concrete are not valid. On the other hand, Recycled Concrete Aggregate (RCA) has a lower surface hardness than Natural Aggregate (NA) due to the presence of adhered mortar, which causes that its addition prevents of using the currently existing models. Therefore, this paper aims to prove the validity of this indirect measure for the in-situ estimation of compressive strength of recycled aggregate SCC. Furthermore, it is also analyzed how the relationship between this indirect measure and the compressive strength of SCC is affected by the modification of the fine RCA content or the nature of the aggregate powder, two aspects that remarkably condition the design and behavior of SCC. The final objective is to provide a useful tool/model that promotes the use of SCC with RCA in real structures.