Phase quantification in cementitious materials by dynamic modulus mapping

Understanding mechanism at the microscale level is essential for tailoring cementitious material to achieve better concrete and structure performance. To identify the distinct microstructural features and to provide insight into the mechanism by which the phases in hardened paste possess, this study adopts the technique of quantitative modulus mapping in the form of Scanning Probe Microscopy (SPM) images to characterize non-destructively the hardened ordinary Portland cement (OPC) paste and slag-blended cement paste at the microscale level. It is found that SPM modulus mapping is capable of identifying individual phase based on the local variation of nanomechanical properties. A method is proposed to quantify the size of the identified phase, especially the thickness of the inner C-S-H layer. With the facilitation of SPM mapping image, the indent location can be located to recognize in which phase the nanoindentation has been made. The results indicate the significance of SPM-based modulus mapping technique as a powerful tool for fundamental study of the cementitious materials with more attractive features of higher spatial resolution to quantify the phase size in nanometer scale level under a nondestructive testing condition.