LAUSR

Abstract In this paper, the optimum alkali activator solution properties in alkali-activated pastes based on ground granulated blast furnace slag (GGBFS) and micro-silica (MS) were investigated. For this purpose, sodium hydroxide (NH) solutions with molarities of 8 M, 12 M, and 16 M were prepared and mixed with sodium silicate (NS) solutions at NS:NH ratios of 1.0, 2.5, and 4.0 to produce the final activator solution. Two sets of pastes were manufactured: (1) pastes based on GGBFS, and (2) pastes in which 10% by weight of GGBFS was replaced with MS. The fresh density increased with increasing NH molarity and NS:NH ratio; whereas, the final setting time reduced with an increase in the aforementioned properties. With regard to the hardened paste, the tests of compression strength, porosity, and electrical resistivity were performed. According to the results, pastes activated with a 12 M NH solution and NS:NH ratio of 2.5 showed the highest compressive strength and electrical resistivity and the lowest porosity. Furthermore, the use of MS increased the compressive strength and electrical resistivity of the optimum paste by 27% and 64%, respectively, over those of the same paste with 100% GGBFS. In the final part, linear regression models were developed to predict the properties of GGBFS and GGBFS/MS pastes. Based on the findings of this study, it is possible to produce a zero-cement paste based on GGBFS and MS, with final setting time of 25–35 min and 1-day compressive strength of 60–70 MPa by using the optimal alkali activator solution, which can be used for repair purposes due its proper setting and strength properties.