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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. [ABSTRACT FROM AUTHOR]