Freeze-thaw resistance of Ultra-High performance concrete: Dependence on concrete composition

•The effects of compositions on freeze–thaw resistance of UHPC were studied.•The SEM and MIP tests were conducted to reveal the freeze–thaw mechanism of UHPC.•The grey correlation entropy was used to evaluate the influence extent of factors on the freeze–thaw resistance of UHPC. The concrete compositions have a crucial influence on the freeze–thaw resistance of ultra-high performance concrete (UHPC). The UHPCs with different concrete compositions were designed and prepared. Based on weight measurement and compressive strength test, the mass loss rate and compressive strength loss rate were used to evaluate the influence of different factors (water binder ratio, steel fiber, superplasticizer, silica fume and fly ash) on the freeze–thaw resistance of UHPC. The scanning electron microscope (SEM) test and mercury intrusion porosimetry (MIP) test were carried out to reveal the freeze–thaw mechanism of UHPC. Furthermore, the grey correlation entropy method was employed to evaluate the influence extent of different factors on the freeze–thaw resistance of UHPC. The results show that the freeze–thaw resistance of UHPC can be improved with the reduction of water binder ratio, which indicates the lower average pore size and cumulative pore volume of UHPC with lower water binder ratio. The steel fiber, silica fume and fly ash can improve the freeze–thaw resistance of UHPC at a proper content. Among these factors, the most significant influencing factor is the water binder ratio, followed by the silica fume, steel fiber, superplasticizer, and the fly ash shows the least effect on the freeze–thaw resistance of UHPC.