The Use of Nano Silica for Improving Mechanical Properties of Hardened Cement Paste

The influence of adding Nano particles of silicon dioxide (SiO₂) on cement pastes was studied for both water and vacuum curing methods. Specimens made up of different percentage of Nano Silica were tested at different ages ranging from 3-56 days. The effect of (5-20 nm) Nano-Silica on the strength development of Nano-cement was determined using Material Tests System (MTS). The purpose of the study was to investigate the effect of Nano-Silica addition on the compressive strength and on the signature phase of calcium silicate hydrate during the hydration process of a cement paste. Percentage of 5 and 10% Nano-Silica by volume of cement were used in this study and compared with 0% Nano-Silica representing control paste. The ratio of water to cementations material (w/c) for all mixtures was kept constant at 0.40. The experimental results show that the compressive strengths of the hardened cement paste with 5% Nano-Silica particles were all higher than those of controlled paste for both water and vacuum cured specimens. This increase in strength may be attributed to the reaction between Nano-Silica and Calcium Hydroxide (CH) to develop more calcium silicate hydrate(C-S-H) resulting in higher strength. On the contrary, the addition of 10% Nano-Silica yields lower compressive strength than the reference paste. The result also show that the vacuum cured specimens yield higher strength than the water cured specimens for up to 28 days. Nevertheless, the final strength for water cured specimens was higher than for vacuum cured specimens.