Analysis of geometric characteristics of GGBS particles and their influences on cement properties

Abstract

This paper presents an investigation into the geometric characteristics of different ground granulated blast furnace slag (GGBS), including particle size distribution (PSD), shape and their influences on cement properties. Samples of GGBS with different PSDs are prepared using in three processing approaches, a ball mill, an airflow mill and a vibromill. The morphology of GGBS and the PSD is studied, respectively, with scanning electron microscope (SEM) and laser particle analyzer (LPA). The results indicate that the PSD of GGBS processed by an airflow mill is concentrated on a narrow range, whereas the size of GGBS made by a ball mill are distributed in a large range. The morphology of GGBS processed by a vibromill is mostly spherical and its surface is very smooth. The results also show that when GGBS has a similar surface area, the strengths of cement mortar, in which 50% cement is replaced by GGBS, are related to PSD of the GGBS. The early strength of sample containing GGBS processed by a ball mill is higher than that by an airflow mill, whereas the long-term strength of this mix is lower. When 0.05% ZS grinding assistant agent is added into the ball mill, the output of the ball mill increases by 18%, the fluidity of mortar containing GGBS is greatly improved and the fluidity ratio reaches to 106. Strengths of the mortars, consisting of 50% cement and 50% GGBS with and without grinding assistant agent, are similar.