Effects of the use of recycled concrete aggregates on the drying shrinkage of normal and high strength concrete

The main difference of the Recycled Concrete Aggregate (RCA), compared to the natural ones, is their greater porosity and, consequently, higher water absorption. Many researches have been carried out to investigate the influence of the use of RCA on the mechanical properties of concrete, but studies on the effects of RCA on the main concrete deformations is still very limited. The drying shrinkage is an important property, because it produces internal tensions and mass loss and, consequently, reduction in the concrete volume. This process can cause multiple cracking, damaging the durability of the material.
In this context, this study presents the results of an experimental campaign to evaluate the influence of RCAs on the drying shrinkage and the mechanical properties of different Recycled Aggregate Concrete (RAC) mixtures. RCAs from laboratory-produced waste were used in two size fractions (i.e., 4.8 mm to 9.5 mm and 9.5 mm to 19 mm). Normal and high strength concrete (35 and 60 MPa) with 100% of RCA in each size fraction were produced. The results showed that the smaller the modulus of elasticity, the greater the drying shrinkage. In addition, the drying shrinkage of the RACs was slightly higher than the strain of the reference mixtures.