Effect of fire exposure on physico-mechanical and microstructural properties of concrete containing high volume slag cement

Abstract

Abstract In this study, the microstructural and mechanical properties of concrete containing high volume slag (ground granulated blast furnace slag) cement activated by Ordinary Portland cement (OPC) were investigated at a range of progressively high temperature. The slag cement was activated by portlandite (CH) formed during the hydration of OPC. During the hydration process of slag and OPC, the amount of CH content increased with the continuous hydration reaction of OPC. This study revealed that the slag cement replacement ratio had significant effects on the microstructural and mechanical properties of concrete after high temperature exposure. The tested concretes were prepared by the slag cement replacement ratio of 0.3, 0.5 and 0.7 while the post-heating temperatures were 200 °C, 400 °C, 600 °C and 800 °C. Compressive strength of the concrete decreased with the increasing of slag content. When the exposure temperature increased from 200 °C to 400 °C, the compressive strength was increased for all concrete group expect for the group casted from 30% OPC and 70% slag cement. The SEM (scanning electron microscope) results for the 7th and 56th days curing the concrete groups casted from 30% slag and 70% OPC, 50% slag and 50% OPC showed a well-structured C S H gel compared to the reference concrete group casted from 70% slag and 30% OPC. In addition, the SEM investigation revealed that the concrete casted from 30% slag and 70% OPC have more structured C S H gels and better fire resistance compared to the other concrete groups.