Comparative study on mechanical properties and microstructure development of ultra-high performance concrete incorporating phosphorous slag under different curing regimes

In this study, the mechanical property and microstructure development of UHPC (ultra-high performance concrete) incorporating different PS (phosphorous slag) content is studied under five curing regimes. The microstructure of UHPC is also discussed by TG, XRD, MIP, the SEM-EDS and 29Si NMR. The result indicated that the high strength of UHPC containing PS is obtained by heat curing in a short time (e.g. The compressive strength of PS60 is 135.5 MPa and 134.4 MPa under curing conditions of 90 °C (48 h) and 1 MPa (6 h), respectively). The cement is completely hydrated, and the hydrated product of calcium hydroxide is completely consumed in UHPC that contains a lot of PS under the heating curing (90 °C, 1 MPa-180 °C and 2 MPa-250 °C) by the result of TG combined with XRD. In addition, the hydration products are tobermorite and xonotlite under high temperature and high pressure curing conditions.