Comparison study on the sulfate attack resistivity of cement-based materials modified with nanoSiO2 and conventional SCMs: Mechanical strength and volume stability

Abstract

Abstract Durability of cement-based materials served in sulfate environments is a big concern because of the devastating effects of sulfate attack. By taking the advantages of nanoSiO2 (NS) on the physiochemical properties of cement-based materials, especially at early age, small dosages (1 and 3 wt%) of NS were added into cementitious materials, and the effects of the sulfate attack on the strength development and volume stability were studied. Comparison studies were made with conventional supplementary cementitious materials (SCMs), i.e., silica fume (SF), fly ash (FA) and ground granulated blast-furnace slag (GGBS) at their conventional dosages. Samples were initially standard-cured for 7- and 28-day before curing in 5 wt% Na2SO4 solution for 6 months. It was found that NS effectively improved the early age properties of cement paste/mortar, thus leading to the enhanced mechanical property of samples undergoing sulfate attack and all of which outstood samples containing SF, FA and GGBS. Moreover, after 28-day initially curing, a comparable compressive strength was found in the NS-added sample when compared to FA/GGBS-added sample at 180 days’ sulfate attack. At the same time, the volume expansion of cement paste/mortar, as well as the cracking, in the NS-added sample was greatly reduced and the effect was more pronounced in the 28-day initially cured mortar samples. Work in this study shows NS’s potential of improving the sulfate attack resistivity of cement-based materials.