New insights into the effects of calcite coral powder on hydration and strength development of cement pastes

Coral powder (CP) emerges as an eco-friendly alternative to partially replace cement in concrete, addressing environmental concerns associated with cement production while positively impacting local environmental preservation. Understanding its impact on cement-based materials is crucial. This study aims to unravel the mechanisms through which CP impacts the hydration and strength development of cement-based materials. Initially, zeta potential measurements were conducted to delve into CP-ion interactions within cement paste. A range of techniques, including scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), isothermal conduction calorimetry (ICC), and mercury intrusion porosimetry (MIP), were employed to examine the morphology of hydration products, hydration heat, and pore structure. Additionally, compressive strength measurements, crack characterization, and fracture surface observation were utilized to explore the effect of CP on cement paste strength. The findings reveal an interaction between Ca2+ and CP via chemical adsorption, fostering the nucleation and growth of hydration products, thereby promoting cement hydration. CP not only fills pores but also refines the pore structure further through its Ca2+ adsorption mechanism, enhancing the strength of the interface between CP and hydrate. Consequently, cement paste containing CP demonstrates significantly higher compressive strength compared to that containing quartz powder (QP). This study provides theory and technique supports for engineering applications of CP.