Effects of using recycled concrete aggregates on the shrinkage of high performance concrete

Over the past twenty years the use of Recycled Concrete Aggregate (RCA) has been mostly limited to normal-strength concretes. However, satisfactory properties have been found in previous studies dealing with the use of RCA sourced from medium to high strength concrete in the production of High Performance Concrete (HPC). In this study the effects of RCA were investigated in the plastic, autogenous and drying shrinkage of HPC. The quality of the RCA (sourced from concretes of 100, 60 and 40 MPa) and the replacement ratio (20, 50 and 100%) were assessed. The results revealed that the plastic and drying shrinkage became higher as the quality of the RCA decreased and the replacement ratio increased. However, a reduction in the autogenous shrinkage was proved to be possible by the employment of a higher content of lower quality RCA, as this, in fact, acted as internal curing agent. The effects of the internal curing explained the similar or higher compressive strength results of concretes containing RCA when compared to those obtained from the reference concrete.