Effect of fly ash on mechanical properties and microstructure of cellulose fiber-reinforced concrete under sulfate dry–wet cycle attack

Abstract In this work, the deterioration characteristics of the mechanical properties of cellulose fiber-reinforced concrete (CFRC) under sulfate dry–wet cycles were studied. The influence of 10%, 20%, and 30% cement replacement with fly ash (FA) on the durability of CFRC was also considered. After 180 dry–wet cycles, the CFRC soaked in sodium sulfate solution with 5% concentration was tested. The mechanical properties were evaluated, including mass loss, the uniaxial stress–strain relationship, and the splitting tensile strength. Results show that FA has a negative effect on the initial mechanical properties of CFRC. The sulfate resistance durability of CFRC is greatly affected by the FA content. Compared with CFRC without FA, low-volume FA can significantly improve the mechanical properties. However, 30% FA has a negative impact on the durability of CFRC. In addition, the pore information parameters obtained by nuclear magnetic resonance indicate that macropores have a negative effect on the sulfate resistance durability of CFRC, whereas micropores and mesopores are favorable. In contrast, 20% FA can refine the pores and improve the strength of the matrix, thus improving the durability of CFRC.