Effect of cement and admixture on the utilization of recycled aggregates in concrete

In this paper, results of an investigation on the effect of type of cement and admixture on fresh and hardened properties of concrete with coarse and fine recycled aggregates (RA) are presented. Natural sand (NS) and natural gravel (NG) were replaced respectively by (15, 30, 70, and 100%) of recycled concrete sand (RS) and recycled concrete gravel (RG). Two types of cement/admixture were used. The fresh (slump, air content and density) and hardened (compressive strength and elastic modulus) properties of recycled aggregates concrete (RAC) are analyzed and compared with those of natural aggregates concrete (NAC). The results indicate that the workability of RAC depends on the combination of cement-admixture and precisely the nature of the admixture and the amount of C3A. RAC can be used with up to 30% of RS and more than 30% of RG.