Effect of mineral admixtures on the resistance to sulfate attack of reactive powder concrete

To solve the problem of high carbon emission in RPC production, fly ash (FA) and ground granulated blast furnace slag (GGBS) were used to replace part of cement for the preparation of RPC in this study. The sulfate corrosion resistance of RPC containing mineral admixture was investigated through dry and wet cycle test using a 5% Na2SO4 solution. The influence of different amounts of FA and GGBS replacing cement on the deterioration of the performance of RPC was studied, and the formulas for the mass and compressive strength loss of RPC under dry-wet cycling were developed. The results show that: after the Na2SO4 solution penetrates RPC, it reacts with the cement hydration products to produce erosion products such as gypsum and ettringite (AFt), and due to the expansion effect of erosion products, the gel pores decrease, and the harmful pores gradually increase, causing changes in the strength and quality; the introduction of FA and GGBS serves to fill the pores and diminish the presence of hydrated calcium hydroxide, thus augmenting matrix densification. Strategic substitution optimally harnesses the “superposition effect” of FA and GGBS, resulting in a substantial enhancement of RPC's resistance to sulfate attack. In addition, there is a significant correlation between changes in the microscopic characteristics of RPC and its macroscopic performance.