Effect of Nano-Silica (SiO2) on the Hydration Kinetics of Cement

This study investigated the influence of addingnano silica (SiO2) on the cement hydrationprocess, particularly on the formation of calciumsilicate hydrate (C-S-H) at different stages ofhydration. The study investigated the effect ofadding nano-silica on the mechanical propertiesof the hardened cement corresponding to theformation of C-S-H during the hydration processof a cement paste. Specimens made up of fourdifferent percentage of nano silica (0%, 1%, 3%and 5%) were tested at different stages ofhydration ranging from 3 to 56 days. The effect ofnano-silica on the compressive strength, stressstrain,and elastic modulus of nano-cement wasexamined using MTS and Forney testingmachines. The signature phase and formation ofC-S-H and calcium hydroxide (CH) weremonitored using Fourier Transform InfraredSpectroscopy (FTIR) and Scanning ElectronMicroscopy (SEM). The study also investigated theeffect of curing method (vacuum and water curing)on the strength development. The experimentalresults show that the formation of calcium silicatehydrate (C-S-H) increases significantly during theearly stages of hydration which correspond to thedrastic increase in compressive strength. Theformation of C-S-H continues to increasethroughout the 56 days but at a moderate rate. Theresults reveal that 1% of nano silica by volume ofcement is the optimum ratio that yields themaximum strength. The results also indicated thatthe strength of the traditional water curedspecimens were higher than that of vacuum curedspecimens.