Practical applications of nano-SiO₂ obtained by different synthesis routs in construction materials domain

Nowadays, there are various nanomaterials embedded in construction materials to improve their mechanical performances, durability, heating resistance as well as some specific properties such as self-cleaning and healing abilities. In this context, investigations regarding the effect of SiO₂ nano-particles embedded in a cement matrix on mechanical properties and microstructure were performed. For this purpose nano-SiO₂ powders were obtained by sol-gel method using different molar ratios of TEOS/ethanol/water. The SiO₂ particles formation was confirmed by X-ray fluorescence analyses (XRF) and their nanometric sizes by scanning electron microscopy (SEM) technique. The cement based materials admixtures were obtained by using the water/binder ratio (w/b) of 0.5 and nano-SiO₂ in the proportions of 0.5%, respectively 0.7 %. The distribution of nano-SiO₂ particles within the cement matrix plays an essential role and governs the performance of these products. Therefore, to facilitate the nano-SiO₂ particles distribution the mixtures were good homogenized in dry state. The mechanical test results showed that after 28 days of hydration the cement based materials with 0.7% nano-SiO₂ content recorded better compressive strengths compared with those of the etalon (E=62MPa vs. M-NS1=72MPa). The microstructure of cement based materials highlighted the presence of Ca(OH)₂, ettringite and calcium silicate hydrates as well as nano-SiO₂ particles distributed into the cement matrix.