Mechanical properties and durability of high-performance concrete internally cured using lightweight aggregates

Abstract

An experimental investigation was conducted to determine the effect of internal curing of natural lightweight aggregates (LWAs) on the shrinkage, mechanical properties, and durability of high-performance concrete (HPC). Conventional aggregates were partially substituted with prewetted coarse and fine LWA at dosages of 5, 10, and 20% by volume. The early age autogenous shrinkage and drying shrinkage of the HPC mixtures were monitored for up to 180 days. The investigated properties of the HPC mixtures included compressive strength, modulus of elasticity, and splitting tensile strength at 28 days, as well as rapid chloride permeability and water absorption. The results revealed that, at a replacement level of 20% for both coarse and fine aggregates, the reduction in autogenous shrinkage of the HPC mixtures was approximately 118% at 28 days and 65% at 18 days. Furthermore, the test results indicated that the autogenous shrinkage measured between 15 h and 7 days after casting was reduced by approximately 75%. Fine LWAs were more effective in reducing autogenous shrinkage than coarse LWAs. This was attributed to the small particles, which allowed a good distribution of the water-filled internal curing within the cement matrix. It was also found that using up to 20% LWA could modify the 28-day autogenous shrinkage of HPC by reducing the cube compressive strength up to 70 MPa as compared to 86 MPa for the control mixture. In addition, the obtained strength values of the concrete mixes were found to be within the acceptable range specified by the ACI standard to be categorized as HPC. The findings of the study revealed that the utilization of LWA is feasible as an internal curing method for decreasing the volume changes, particularly at the early ages, and for avoiding the formation of cracks in HPC.