Quantitative analysis on ground blast furnace slag behavior in hardened cement pastes based on backscattered electron imaging and image analysis technology

•BSE and image analysis technology quantify GBFS content in hardened cement paste.•Quantitative analysis is governed by slag dosage, fineness, W/B and curing age.•A linear correlation between areal fraction of slag and other factors is proposed.

Grounded blast furnace slag is one of common supplementary cementitious materials in Portland cement concrete, and is capable of improving the performance of concrete and reducing the costs. Once hardened, the dosage of slag in concrete matrix is hard to evaluate. Three types of ground blast furnace slag (GBFS) are used to prepare cement-slag pastes with different water binder ratios, and the finenesses and original dosages of GBFS are various. Backscattered electron (BSE) images combining with image analysis method are used to analyze the areal fraction of GBFS in the pastes. The feasibility of this method is analyzed, and it is proved that the method is effective in quantitative analysis on the content of GBFS in hardened cement pastes. The multivariate linear correlations between areal fraction of GBFS, curing age, GBFS fineness, original dosage of GBFS, are created. It is capable of obtaining original dosage of GBFS based on existing parameters.