Magnesium-silicate-hydrate cement pastes: Rheological behavior and strength development

In contrast to Portland cement (PC), magnesium-silicate-hydrate (MgO-SiO 2 ) cement mixes offer a significant advantage due to their lower calcination temperature requirement during production, reduced carbon footprint and energy consumption linked with the manufacturing process. This study presents a detailed investigation of the rheological characteristics and strength development of magnesium-silicate-hydrate cement mixes, along with a series of microstructural analyses to examine the hydration process and phase compositions of the prepared mixes. Results indicated that an increase in the water-to-binder (w/b) ratio decelerated the growth rate of both storage and loss moduli over time. Samples with magnesia-to-silica (m/s) ratios of 4:6 exhibited not only the highest modulus during the initial stages of hydration, but also the most rapid increase. The reaction of MgO and dissolution of SiO 2 were limited in the fresh state, initially resulting in low brucite and M-S-H contents. Although samples with m/s ratios of 5:5 exhibited the highest 28-day compressive strength (38.5 MPa), those with m/s ratios of 4:6 had the highest M-S-H content at 28 days. These findings contributed to existing knowledge by revealing the relationship between rheological characteristics, reaction mechanisms and strength development within MgO-SiO 2 system and highlighted the impact of key factors such as w/b and m/s ratios on both the fresh and hardened properties.