Abstract: In order to reduce the amount of river sand in ultra-high performance concrete (UHPC) and improve its compressive fracture characteristics, the effects of manufactured sand, rubber particles, water-binder ratio and steel fiber on the fluidity and compressive strength of UHPC at different levels were analyzed through the design of four-factor and four-level orthogonal tests, and the optimal group with the best comprehensive performance was obtained. The energy evolution characteristics of compressive failure of rubber-manufactured sand UHPC were investigated. The results show that: 1) among the factors, the greatest influence on the fluidity and compressive strength of UHPC mix are water-binder ratio and steel fiber respectively. The fluidity of UHPC increases significantly with the increase of water-binder ratio, while the compressive strength has a positive effect on steel fiber content. 2) When rubber content and manufactured sand replaces river sand by 10% and 40% respectively (rubber replaces river sand with equal volume, and manufactured sand replaces river sand with equal quality, which is equivalent to saving 50% of river sand), the compressive strength of UHPC reaches 118.5 MPa. 3) From the view of failure morphology and energy evolution, the UHPC shows brittle-elongation transformation mechanical characteristics after mixing steel fiber and rubber particles. UHPC in the optimal group maintained better integrity than those in the control group when the stress peak was reached.

Key words: manufactured sand, UHPC, hard and brittle, compressive failure, energy evolution, orthogonal test