Study of ultra-high-performance concrete containing multivariate supplementary cementitious materials: experiments and modeling

In this paper, the effects of partial replacement of cement by metakaolin (MK) and different supplementary cementitious materials (SCMs) were investigated on the compressive strength and elasticity modulus of ultra-high-performance concrete (UHPC) at different ages, and the laws of the effects of MK alone, MK and conventional SCMs on the mechanical properties of UHPC were quantitatively analyzed at the macroscopic level. The results showed that the compressive strength of UHPC reached the maximum value when the MK doping amount reached 10%, and its compressive strength at 7, 28 and 90 days increased by 21%, 28% and 18.2%, respectively. Furthermore, the elasticity modulus of UHPC also showed a similar trend. When MK and Blast furnace slag or Fly ash were compounded, the mechanical properties (compressive strength and elasticity modulus) of UHPC were significantly enhanced in the later stage, showing sound synergistic effects. Based on the experimental test data, a model for predicting the elasticity modulus of UHPC based on the change of time and SCMs was proposed with good reliability.