Performance evaluation of nano-silica and silica fume on enhancing acid resistance of cement-based composites for underground structures

Abstract

This study aims to evaluate the performance of silica fume (SF) and nano-silica (NS) on enhancing the sulfuric acid resistance of mortar mixtures. The NS and SF were added as substitutions for cement at various dosages. The cured samples were immersed in the sulfuric acid solution with a pH of 2 for 75 d. A compressive strength test and absorption and voids tests were conducted before sulfuric acid immersion. It was found that the addition of SF and NS reduced the volume of permeable voids and increased compressive strength. A thermo-gravimetric analysis was carried out to investigate the hydration of mixtures. The mixtures with SF showed a higher level of pozzolanic reaction compared with mixtures with NS. After the 75 d of immersion, the mixtures with 5% SF and 1% NS showed the best resistance against sulfuric acid because they showed the lowest mass change and length change.