Performance of concrete made with commercially produced coarse recycled concrete aggregate

Performance tests have been carried out for fresh and hardened properties of concrete made with commercially produced coarse recycled concrete aggregate and natural fine sand. Test results indicate that the difference between the characteristics of fresh and hardened recycled aggregate concrete and natural aggregate concrete is perhaps relatively narrower than reported for laboratory-crushed recycled aggregate concrete mixtures. For concrete without blast furnace slag having similar volumetric mixture proportions and workability there was no difference at the 5% significance level in concrete compressive and tensile strengths of recycled concrete and control normal concrete made from natural basalt aggregate and fine sand. Water absorption rates and carbonation of recycled concrete and reference concrete were comparable for most applications. However, the abrasion loss of recycled aggregate concrete made with ordinary portland cement increased by about 12% compared to normal concrete, while the corresponding drying shrinkage was about 25% higher at 1 year. The ratio of splitting tensile strength to compressive strength was found to be in good agreement with established values derived for equivalent grade concretes made with normal-weight natural aggregates. One-year test results indicate that incremental improvements in durability characteristics can further be achieved with the use of blast furnace slag cement. Enhanced fresh and hardened concrete properties of the investigated recycled concrete aggregate as compared to aggregate derived from laboratory-crushed concrete arise primarily from improved aggregate grading and quality achievable in plant crushing operations. (C) 2001 Elsevier Science Ltd. All rights reserved.