This investigation aimed to develop structural blended cement pastes with high mechanical properties for building envelope purposes. The effect of nano silicate (NS) replacement on the properties of blended white cement pastes as compared with the control paste have been studied through the measurements of indirect tensile strength (ITS). NS was thermally activated at 850 A degrees C for 2 h and used to partially replace Portland white cement (PWC) at different ratios. The activation effect of NS on the ITS have also been studied. The cement pastes were prepared using water of consistency. The pastes were removed from the mold after 24 h and then immersed in a water bath for hydration. The 7-day aged pastes were tested after drying for 24 h at 105 A degrees C. Different physical properties such as thermal resistivity, solar reflectivity, water absorption and apparent porosity were measured. It was found that, activation of NS decreases the porosity allowing the blended cement paste to be denser, consequently increasing the ITS. Increasing the replacement content of unactivated NS upto 2%, improved the ITS by about 40% compared with the control paste. Also, the thermal activation of the NS has a very good influence in enhancing the ITS to about 50% with respect to the 2% unactivated blended paste. The results also showed that increasing the replacement content generally increases the water absorption and the porosity of blended white cement pastes, while, slightly improving the thermal resistivity. Activation of NS reduced the solar reflectivity of blended pastes as compared with unactivated blended pastes. An optimum replacement of around 2% can be concluded from the current work.