Micromechanical properties of cementitious composites

Abstract

Micromechanical properties of cement matrices in cementitious composites were investigated by means of the microindentation method. The research focused on the correlation between micromechanical properties such as modulus of elasticity and creep, and distance of the indentation from the aggregate-matrix interface. Composites based on ordinary Portland cement (OPC) matrix were examined after exposure to two types of ageing procedures. The sub-micron accuracy of the positioning system of the microindentation apparatus provided means for a meaningful investigation of cement matrix in close vicinity to the aggregate-matrix interface. For the purpose of statistical analyses, the data were divided into two groups with respect to the distance of the indent from the aggregatematrix interface. While the tests performed within a 30 μm distance from the interface were classified as indents within the interfacial transition zone (ITZ), indents outside this distance were considered to describe properties of the ‘bulk matrix’. The results provide quantitative comparison of the microstructural properties of the interfacial transition zone (ITZ) with those of the bulk cement matrix assessed by well understood characteristics such as elastic modulus and creep. It was shown that, for unaged specimens, the elastic modulus measured within the interfacial transition zone was about 25% lower than that of the bulk matrix. Such results have significant consequences for improvement in modelling of cementitious composites.