Seeding effects of submicron CaAl-NO3 LDH particles on the hydration and properties of Portland cement and sulfoaluminate cement pastes

Abstract

Layered double hydroxide (LDH) is reported to improve the durability of concretes, primarily due to its ability to exchange anionic species, including chloride, which is implicated in corrosion-driven durability issues. However, there is no comprehensive study investigating the effect of LDH on the properties of different cement systems at both early and mature ages. In this study, the early age and mature age properties of Portland cement (OPC) and calcium sulfoaluminate (CSA) cement pastes seeded with submicron-sized calcium aluminum-NO3 LDH (CaAl-NO3 LDH) were investigated. The effects of the 1–5%mass dosage of LDH on the hydration of both cement systems were characterized by rheology, isothermal calorimetry, porosimetry, compressive strength tests, thermogravimetric analysis, and x-ray diffraction. Time-dependent rheology results indicate that CaAl-NO3 LDH seeding enhanced the buildability of cement pastes, as evidenced by increased plasticity loss, hardening, and yield stress. While LDH seeding accelerated hydration kinetics for both CSA and OPC pastes, interestingly, the OPC exhibited reduced heat release, suggesting potential applications of LDH as heat sink in various areas, including building in hot climates, reducing heat and crack-propensity in mass concrete placements, and 3D-printed OPC-based concretes. Although LDH slightly decreased compressive strengths at both 1d and 28d, its primary role was to expedite the hydration process without enhancing the microstructure or strength of the final product.