Performance of ultra-high performance concrete (UHPC) with cement partially replaced by ground granite powder (GGP) under different curing conditions

Properties of ultra-high performance concrete (UHPC) which used ground granite powder (GGP) to replace cement by different ratios (from 0 to 25%) are experimentally investigated. The hydration products and pore structure on the micro scale, and the compressive and flexural strength as well as chloride permeability on the macro scale, were studied. Influence of curing conditions, i.e., standard curing (SC), warm water curing (WWC), and autoclaved curing (AC), was also explored. It was found that though the replacement of cement by GGP did not influence the morphology and chemical compositions of hydration products, however, the pore structure changed significantly over the replacement ratio, i.e., ωGGP. Compared to SC and WWC, AC can significantly improve the hydration degree of cement and promote the polymerization degree of hydration products. WWC and AC also improved the pore structure of UHPC prepared with GGP. Compressive and flexural strength as well as the anti-permeability were found to first increase and then decrease with the growth of ωGGP; the optimal ωGGP were 5%, 10%, and 15% for UHPC specimens cured under SC, WWC, and AC, respectively. It was also found that the compressive and flexural strength are linearly related to the total porosity, while the chloride permeability is linearly related to the contents of harmful and more-harmful pores.