Mineralogical analysis done on Spanish Portland cement Type I pastes, blended with nanosilica was carried out by conventional and high-resolution thermogravimetric analysis (TG-HRTG) and X-ray diffraction (XRD) in order to determine the quantity of the different mineralogical phases obtained during the hydration process. Simultaneously, mortars with the same materials and replacement ratio were made in order to assess their compressive strength for up to 28 days of curing time. In this paper, the rate and quantity of each one of the main constituent phases of the cement during its hydration process (C-S-H, ettringite, portlandite, stratlingite, etc.) were determined. A correlation between the quantity of C-S-H and the development of compressive strength was established. Additionally, the pozzolanic activity of nanosilica was evaluated by quantifying the fixation of calcium hydroxide and its impact on the development of the compressive strength.

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In this paper the effects of nanosilica (NS) on porosity, capillary suction (UNE 8398:2008), compressive strength (ASTM C 349), and sulfate resistance (ASTM C 1012) were evaluated for mortars made with Portland cement (control) and partially replaced with a commercial NS suspension, in percentages by weight of 0, 1, 3, 5, and 10 %. Mortars with a water/binder (w/b) ratio of 0.55 and addition of superplasticizer, for flow correction, were prepared. NS showed that, it has an important role in pore refining, decreasing the total volume of pores and their diameters.Samples containing NS showed an important positive effect on the capillary suction and sulfate resistance. In the case of expansion due to sulfate attack, mortars with 5 and 10 % of NS decreased expansion by 90 and 95 % respectively after two years of immersion.

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