Early-age and microstructural properties of glass powder blended cement paste : improvement by seawater

Abstract

The incorporation of conventional supplementary cementitious materials (e.g. fly ash) in concrete generally induces a longer setting time and inferior early-age strength. This study aims to evaluate the effectiveness of using seawater (SW) as mixing water in improving the early-age properties of cement pastes/mortars prepared with waste glass powder (WGP) which has a low reactivity. By means of measurements of rheological behaviors, macro/micro mechanical properties, hydration kinetics of the WGP blended cement with SW, and other microstructural analytical techniques, the early-age performances were investigated. The results showed that the incorporation of WGP increased yield stress and plastic viscosity of the cement paste due to its fine particle size, negative surface charge and hydrolysis effect. The use of SW further changed the rheological properties by accelerating the hydration of cement. The dissolved ions from the WGP and the presence of SW in the cement paste were beneficial to shortening the prolonged setting time induced by the replacement of cement by the WGP. The combined use of SW was effective in overcoming the inferior early-age strength caused by the dilution effect of WGP inclusion at the very early age. The enhanced precipitation of hydration products, increased degree of hydration, refined pore structure were responsible for the increase of the early-age strength of the WGP blended cement prepared with SW.