Influence of the Proportion of Recycled Gravel on Shrinkage and Cracking Risk: Early Age and Long-Term Behavior

Abstract

This paper presents the results of experimental research on recycled concrete at early age and long term. It consists in studying the effect of the proportion of recycled gravel (RG) on shrinkage and cracking risk. Three mixtures were investigated to study the effect of substitution of natural gravel (NG) by the recycled gravel (0% RG, 30% RG and 100% RG). A stress/strength approach was used to quantify the risk of cracking at early age. It is based on experimentally assessed parameters. At long term ring tests were performed to assess the cracking sensitivity induced by drying shrinkage. At early age the results indicate RG affected the properties of the recycled concrete and increase the potential risk of cracking. At long term, the effect of substitution of the recycled gravel on drying shrinkage was not significant. However, the three concrete showed different cracking sensitivity, thus shrinkage-induced cracking was influenced by the evolution of stiffness and relaxation. Finally, compared to the conventional concrete recycled concrete showed higher cracking sensitivity at early age and long term, but the effect was not proportional to the proportion of recycled gravel. 30% RG actually showed higher cracking sensitivity than 100% RG.