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

Abstract

In contrast to Portland cement (PC), magnesium-silicate-hydrate (MgO-SiO2) 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 SiO2 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-SiO2 system and highlighted the impact of key factors such as w/b and m/s ratios on both the fresh and hardened properties.

Keywords

• Magnesia
• Silica
• Rheological characteristics
• Strength development
• Microstructure