Characterization of the microstructure and strength of cement paste by microhardness testing

Abstract

The structure and properties of cement paste were investigated by means of microhardness testing. The characteristics of the paste were defined by the microhardness value itself and by the parameters obtained from the evaluation of the indentation size effect. The latter effect is due to the dependence of the microhardness value on the indentation load. In cement pastes higher loads resulted in higher microhardness. which is in contrast to the observations in metals. Analysis of this dependence by two parameters was shown to be effective in quantification of microstructural characteristics. Linear relations between strength and microhardness were obtained, but they differed with testing conditions in the microhardness test. These differences could be interpreted in terms of the microstructural characteristics as quantified by the indentation size effect. The influence of age, silica fume and waterlcement ratio was characterized by these means.