Experimental study on autogenous shrinkage behaviors of different Portland blast furnace slag cements

Abstract

In this study, the differences in autogenous shrinkage behaviors among the Portland blast furnace slag (BFS) cements were investigated experimentally. Portland BFS cements that contain 40–45% BFS were collected from eight different plants in Japan and their autogenous shrinkage at early ages were measured with mortar specimens. After the proper thermal dilation correction of the experimental results, it is indicated that several Portland BFS cements could exhibit significantly different autogenous shrinkage behaviors, even if they are in the same class for the products. The laser diffraction test was conducted to compare fineness of cement particles, but the fineness property of Portland BFS cements was inconsistent with the measured autogenous shrinkages. Subsequently, the chemical composition of each powder and the reaction progress of cement paste specimens were measured by thermal gravimetric analysis and X-ray diffraction Rietveld analysis (XRD). It was realized that the crystallized slag mineral contents through the heat treatment process are consistent with the autogenous shrinkage measurement results and well correlated with hydration level of slag. The crystallized slag mineral contents through the heating process can be an indicator to assess the degree of autogenous shrinkage. The differences in the composition of BFS can be identified through the heat treatment process and this can result in different reaction progresses and autogenous shrinkage behaviors among Portland BFS cements.