Drying of Recycled Aggregate Concrete: Plastic Shrinkage, Cracking Sensitivity, and Durability

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 initial water saturation of recycled concrete gravel (RG). Five mixtures were investigated, one mixture with natural aggregates only (reference concrete) and the second with 100% of RG using four initial water saturations: 30%, 70%, 100% and 120% of saturated surface dried (SSD) state. 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 the effect of initial water saturation on the ultimate drying shrinkage was investigated. The drying shrinkage was correlated with drying depth and the natural carbonation was also studied. At early age the results indicate RG affected the properties of the recycled concrete. However, the concrete with oversaturated RG showed a behavior close to reference concrete in terms of cracking sensitivity. At long term, the drying shrinkage is weakly depending of initial water saturation, but the durability of concrete can be affected by the drying depth. A good correlation between compressive strength at one day and the carbonation depth at 18 months was observed