Use of Recycled Concrete Aggregates in Precast/Prestressed Concrete

Abstract

This paper describes a preliminary investigation on factors related to the use of recycled concrete aggregates (RCA) in precast/prestressed concrete applications. In particular, the effects of RCA are experimentally investigated for: 1) the bond between seven-wire prestressing steel strand and concrete; 2) the compression strength gain of concrete with time; and (3) the compression stiffness gain of concrete with time. The test specimens were made by replacing the natural course aggregates in the concrete mixtures with RCA from: 1) discarded/rejected precast concrete; and 2) returned ready-mix concrete. The data to-date show that the introduction of RCA results in an effect (decrease or increase) in the strand bond strength that is consistent with the effect of RCA on the compression strength of concrete. For the materials tested, RCA from precast concrete performed better than RCA from returned ready-mix concrete. The use of RCA did not have a significant effect on the rate of concrete compression strength gain with time. The results for the stiffness gain of concrete with time were somewhat more varied than the results for the strength gain.