Effect of concrete mixing plant sludge powder on properties of ultra-high performance concrete

The output of concrete mixing plant sludge (CMPS) is large and increases year by year, which needs to be disposed urgently. The effect of CMPS powder replacing silica fume (SF) on the properties of ultra-high performance concrete (UHPC) was investigated through testing the fluidity, compressive strengths, shrinkage, pore structure, micromorphology and nanoscale properties. The obtained results indicated that the use of CMPS powder substituting SF improved the fluidity of UHPC; 20% CMPS powder replacing SF increased the compressive strengths of UHPC, but with the further increase of CMPS powder, the strengths of UHPC were reduced, and the compressive strength of UHPC including 60% CMPS powder was less than 100 MPa at 28 days; the incorporation of CMPS powder increased the shrinkage of UHPC, so it is necessary to pay attention to the cracking sensitivity of CMPS powder UHPC; the use of CMPS powder replacing 20% SF produced more calcium silicate hydrate and reduced porosity of UHPC, and had no remarkable effect on the interfacial transition zone of UHPC.