Egyptian volcanic glass powder as a modifier agent for alkali-activated slag cement

Abstract

Egypt is a rich country with natural volcanic glass, which can be utilized to produce possibility volcanic glass powder (VGP). This VGP can then be employed as a pozzolanic material for the Portland cement (PC) system. In this investigation, for the first time, the possibility to employ Egyptian volcanic glass powder (VGP) as a modifier agent for alkali-activated slag (AAS) cement was studied. The volcanic glass (VG) was delivered from a quarry in the form of lumps pieces. After crushing and powdering, it was blended with slag in proportions of up to 30 wt% of slag (as a partial replacement). The slag free from VGP and those containing VGP were activated by an alkaline activator to produce alkali-activated cement. The effect of various ratios of VGP on flowability, setting time, compressive strength, transport properties, environmental conditions measured by wetting/drying cycles, crystalline phases, hydration products, and microstructures of AAS cement were investigated. The results confirmed that VGP is an amorphous material rich in silica and has a suitable ratio of alumina. The incorporation of 10% VGP was the optimal ratio. Higher ratios of VGP than 10% showed an adverse effect on the AAS cement properties.