Deformation properties and direct shear of medium strength concrete prepared with 100% recycled coarse aggregates

The lack of a thorough understanding of the structural behavior of recycled aggregate concrete has become increasingly obvious in recent years. This paper presents the deformation properties and direct shear of medium strength structure concrete prepared with 100% recycled aggregate and Class-F fly ash (RAC) as compared to those of the corresponding natural aggregate concrete (NAC). During this study, five water-binder ratios of 0.50, 0.44, 0.40, 0.36 and 0.32 were used to prepare the concrete with target cube compressive strength ranging from 45 to 70 MPa using natural or recycled coarse aggregates. Fly ash was added of 25% by cement weight in all concrete mixtures. The results show that the 28-day cube and cylinder compressive strength, flexural and the direct shear strength of RAC were on the average of 85% of those NAC with the same mix proportions. Moreover the modulus of elasticity of RAC was on the average of 14% lower than that of NAC. Furthermore, the drying shrinkage and chloride ion penetration of RAC was on the average of 24% and 14% higher than that of NAC. The results showed that the medium strength structural concrete can be produced by using 100% recycled aggregate and Class-F fly ash.