The impact of environmental humidity on the mechanical property and microstructure of magnesium silicate hydrate cement

Abstract

Environmental factors have a significant impact on the performance of cement-based materials. As a new type of low-carbon cementitious material, the performance of magnesium silicate hydrate cement (MSHC) under different environmental humidity conditions is crucial for its application. This study aimed to investigate the effects of environmental humidity on the hardening properties of MSHC. Compressive strength tests of MSHC were conducted under four different relative humidity (RH) conditions (RH of 33%, 58%, 75%, and 97%) and water curing (RH-w) condition. Microanalysis techniques were employed to reveal the strength mechanisms of MSHC under different environmental humidity conditions. The results showed that MSHC exhibited the optimal mechanical performance when RH was 75%, reaching 42.29 MPa. When RH was 58%, the compressive strength of MSHC was close to the optimal level, which was 41.02 MPa. However, under other humidity conditions (RH33, RH97, and RH-w), the compressive strength of MSHC was much lower than the optimal level, decreasing by 30.93%, 41.90%, and 63.66%, respectively. Pore structure analysis showed that the volume of detrimental pores (>100 nm) in the sample was the lowest when RH was 75%. Compared with RH75, the volume of detrimental pores in RH33, RH58, RH97, and RH-w increased by 20.47%, 9.83%, 36.77%, and 156.92%, respectively. In addition, the variation of environmental humidity resulted in different polymerization levels in the M-S-H gel, and higher degrees of polymerization were observed when RH was 58% and 75%.