Roles of diatomite in hydration, microstructure and strength development of cement paste

Abstract

The production of cement has a significant environmental impact, and the use of mineral admixtures can mitigate this impact by reducing the clinker rate. Diatomite powder (DP) possesses unique properties, such as micronized and sub-micronized porous structures, and a large specific surface area, making it an ideal cement replacement. To gain a better understanding of the mechanisms underlying its performance as a cement replacement, the reference used was quartz powder (QP) in this study, and zeta potential tests were conducted to characterize the surface chemical properties of DP. Subsequently, how it affects the cement paste hydration, microstructure and strength development was investigated. Results revealed that DP, owing to its sub-micronized porous structure and chemical composition, exhibited a higher affinity for Ca2+ ions compared to QP, which significantly affects the formation of C-S-H. This heightened affinity facilitated the nucleation and growth of C-S-H, leading to a shortened hydration induction period. Furthermore, the incorporation of DP into cement paste resulted in a refinement of the pore structure. This enhancement is due to the relatively small particle size of DP, its chemical reactivity, and its surface affinity for uniform distribution of hydration product. Notably, the DP-hydration interface exhibited significantly higher strength compared to the interface between QP and hydration products. As a result of improving pore structure and strengthening the DP-hydrate interface, the cement paste blended with DP demonstrated compressive strength comparable to that of pure cement paste and considerably higher than the cement paste incorporating QP.