Spatially Resolved Elastic Modulus of Magnesium Silicate Hydrate: A Cementitious Material

Magnesium-based cement such as magnesium silicate hydrate (M–S–H) has drawn interest as a substitute for ordinary Portland cement. The precise determination of M–S–H's elastic modulus is essential in assessing the mechanical performance of M–S–H-based concrete. Atomic force microscopy (AFM) allows for spatially resolved quantification of nanomechanical characteristics of materials, including thin overgrowths on substrates. In this study, elastic modulus maps of M–S–H grown on single crystal mica surfaces were obtained using amplitude modulation–frequency modulation AFM. The effects of the Mg-to-Si molar ratio and morphology on the elastic modulus of M–S–H films were investigated. AFM reveals elastic moduli ranging from 5 to 15 and 40 to 64 GPa, depending on the growth reaction time and morphology. A comparison with calcium silicate hydrate found in traditional cement reveals insights into the influence of silicate polymerization on the material's stiffness. These findings demonstrate the effectiveness of AFM in quantitatively describing the mechanical characteristics of cementitious phases and suggest that M–S–H cement has the potential for use in a variety of construction applications.