Effect of steel fibre and manufactured sand on mechanical properties of alkali-activated slag green cementitious material after high temperature

Abstract

This study investigated the mechanical properties of alkali-activated slag cementitious material (AASCM) after exposure to 20–800 ℃ considering the effect of steel fibre content and aggregate type to promote the use of AASCM in structural engineering. The volume contents of steel fibre were 0%, 0.5%, 1.0% and 1.5%, and the aggregate types were manufactured sand and natural river sand. The residual compressive, tensile strength and mass loss were determined. Besides, the microstructure and phase composition of AASCM before and after high temperature exposure were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the tensile and compressive properties of manufactured sand AASCM were inferior to that of natural river sand after high temperature exposure. Below 600 ℃, steel fibre can improve the mechanical properties of AASCM. Steel fibre oxidation fails and effectively loses its strengthening effect on AASCM with the temperature reaching 800 ℃, resulting in a notable decrease in strength of AASCM. The models for calculating mass loss, compressive strength, and tensile strength of steel fibre reinforced AASCM after high temperature exposure were established.

Keywords

• Alkali-activated slag
• Compressive strength
• High temperature
• Manufactured sand
• Steel fibre
• Tensile strength