Shrinkage of recycled aggregate concrete

Abstract

This paper describes the shrinkage of concrete made with recycled aggregates derived from demolition of concrete structures and is based on the 18 500 data matrix generated from 286 studies published in English from 38 countries since 1978. Relative to natural aggregates, the shrinkage of concrete increases at a decreasing rate with coarse recycled concrete aggregate content, giving an average increase of 33% at 100% natural aggregate replacement. This difference between the performance of the two concretes decreases with increasing ambient humidity and concrete strength. Increase in concrete shrinkage with fine and all-in recycled concrete aggregate and other recycled aggregates was found to be too high and variable to make them unsuitable for use in structural concrete. The assessment of the Eurocode 2 (2004), ACI 209·2R (2008) and Bažant-Baweja B3 (2000) models showed that, although the accuracy of the three models is similar, the shrinkage of concrete containing coarse recycled concrete aggregate is generally underestimated. Methods are proposed for determining the shrinkage of concrete made with coarse recycled concrete aggregate together with using Eurocode 2, as well as for minimising its effect on the shrinkage of concrete for a given strength and workability by reducing its cement paste content.