The effects of waste concrete properties on recycled aggregate concrete properties

The effects of waste concrete (WC) properties (compressive strength of the concrete and its aggregate) on the properties of recycled aggregate concrete (RAC) were investigated in two parts: WC and RAC. WCs, the first part of the study, cover three different strength limestone aggregate types and concrete mixtures with five different water/concrete ratios (0·69, 0·54, 0·42, 0·37, 0·32) in each aggregate type. RACs, the second part of the study, were prepared with three different w/c ratios (0·30, 0·35, 0·40), and 100% coarse recycled aggregates supplied from each WC. Some tests – compressive strength, ultrasonic pulse velocity, Schmidt rebound hammer, specific gravity and water absorption – were performed on the hardened WC and RAC samples. It was found that the compressive strength of RAC was mainly dependent on the strength of limestone aggregate and w/c ratio, while WC strength affected the strength to a lesser extent. The correlation coefficients of RAC for the ultrasonic pulse velocity, Schmidt rebound number, specific gravity and water absorption values against uniaxial compressive strength were found to be significantly lower than those of WC.