Effect of curing, fibre content and exposures on compressive strength and elasticity of UHPC

The paper presents an experimental study on the evaluation of the compressive strength and modulus of elasticity of ultra-high performance concrete (UHPC) prepared with varying steel fibre contents, cured in water and exposed in air, and subjected to three exposure conditions (after 28 d of curing): laboratory environment, alternate heating-cooling cycles (heating at 608°C for 2 d and then cooling at room temperature for 2 d), and alternate wet-dry cycles (wetting for 2 d in aggressive salt solution and then drying at 308°C for 2 d). The test results indicate that: (a) although water-curing is better than exposure in air in improving the strength, the difference is not significant, particularly at a higher fibre content, (b) an increase in the fibre content can improve the strength and modulus of elasticity up to a certain extent, but beyond that an increase in the fibre content is not proportionally beneficial and (c) the effect of 6-month exposure to wet-dry and heating-cooling cycles on the strength and modulus of elasticity is negligible; indeed, the heating-cooling cycled specimens have strength and modulus of elasticity higher than the specimens not subjected to the cyclic exposures.