Exploring synergistic effects and hydration mechanisms in metakaolin-blended cement system with varying metakaolin and wollastonite content

The quest for sustainable construction practices has led to a growing interest in reducing cement consumption, with supplementary cementitious materials emerging as a promising solution. While reactive admixtures have been extensively studied, there is a noticeable research gap regarding inert admixtures, a critical component of cementitious systems. This paper introduces a novel metakaolin-blended cement system, optimizing the metakaolin, wollastonite, and ground quartz ratios to enhance microstructure and performance. Within this complex quaternary system, we conduct a comprehensive investigation, including assessments of compressive strength, setting times, heat release during hydration, R3 test. Furthermore, we explore hydration products and microstructure through thermogravimetric analysis, X-ray diffraction, backscattered electron imaging, and mercury intrusion porosimetry. The results indicate the influence of wollastonite on clinker reactions and hydration. Although wollastonite slightly increases meso-scale pores, its fibrous shape enhances the overall microstructure. Substituting 50% of metakaolin with wollastonite not only enhances the pozzolanic reactivity but also leads to improved long-term strength. Moreover, the synergistic effect of wollastonite and metakaolin allows for precise tailoring setting times and modulate hydration kinetics, thereby enhancing the overall performance of the cementitious system.