Factors influencing the micro-mechanical properties of MgO-SiO2 pastes

MgO-based cements represent a promising, low-CO 2 alternative to traditional Portland cement. In magnesium silicate cements, M-S-H is the main phase. Although the thermodynamic properties and hydration mechanisms of this phase have been investigated, studies on its mechanical behaviour remain limited. This study aimed to determine the factors influencing the micro-mechanical properties of the MgO-SiO 2 pastes. Detailed chemical (X-ray diffraction, Thermogravimetric analysis, Energy-dispersive spectrometry analysis), microstructural (water porosity), and mechanical (indentation) analyses were conducted. The source of raw materials and the production protocol (mortar mixer, ball mill, pressing) influence the mineralogy of pastes and silicon distribution. Additives have a moderate impact on the mineralogy of pastes. Samples with the lowest porosity exhibit the highest elastic properties. Once the effect of porosity is accounted for, a higher brucite content correlates with increased elastic properties. • The production protocol is the main factor influencing the pastes' mineralogy, microstructure and mechanical properties. • Additives have moderate impacts on the mineralogy of pastes. • Additives do not affect the microstructure directly. • Once the effect of porosity is accounted for, a higher brucite content correlates with increased elastic properties.