Effects of fly ash and crystalline additive on mechanical properties of two-graded roller compacted concrete in a high RCC arch dam

Two-graded roller compacted concrete (RCC) containing high volumes of fly ash has been widely used in anti-seepage structures of RCC dams in China. The crystalline additive as a self-healing addition is added to the grout enriched two-graded RCC to increase crack resistance. The effects of fly ash and crystalline additive on mechanical properties of two-graded RCC were investigated in this research. Tests were performed to measure plastic and hardened RCC properties. The results indicate that the vibrating compacted values and air contents of plastic RCC containing fly ash of up to 58% conform to the engineering requirements. As the fly ash content in RCC increases, the air content increases and the unit weight decreases. Adding crystalline additive to the concrete mixture has no apparent effect on the slumps of grout enriched two-graded RCC, but may increase the air content and reduce the unit weight. The cube compressive strength, splitting tensile strength, axial tensile strength, ultimate tensile strain, modulus of elasticity, and axial compressive strength of two-graded RCC all decrease with increasing amounts of fly ash content. At 90 days, the relations between these properties and two variables, fly ash to cementitious material ratio (F/CF) and water to cementitious material ratio (W/CF), between splitting tensile and cube compressive strengths, between axial tensile and cube compressive strengths, and between axial and splitting tensile strengths were analyzed. The values for these properties of two-graded RCC were lower than those of grout enriched two-graded RCC at the same age, F/CF and W/CF, and adding crystalline additive to the grout enriched two-graded RCC may produce higher values for these properties than that without crystalline additive in most cases. The results confirm the feasibility of using crystalline additive in two-graded RCC of high RCC arch dams.