Effects of supplementary cementitious materials on pore-solution chemistry of blended cements
Rusheng Qian, Yunsheng Zhang, Cheng Liu, Zhiyong Liu, Yu Zhang, Guojian Liu
Abstract
Supplementary cementitious materials (SCMs) are usually employed to replace partial cement and the pore-solution chemistry of blended cements is extremely essential for their cement hydration and durability. In this work, the pore-solutions of cement pastes with various water-to-cement (w/c) ratios and SCMs (fly ash, ground granulated blast-furnace slag and silica fume) are extracted for observing their ions and conductivities. The results illustrate that Na+, K+, OH−, Ca2+ and SO42− are the main and their concentrations are declined by the improving w/c ratios and SCMs dosages and thus decreasing their conductivities. The conductivity evolution shows three typical periods: induction (<5 h), acceleration (5 h-7d) and deceleration (>7d). The pore-solution conductivities of pastes with various w/c ratios are predicted well by the model established (R2 > 0.90) while the SCMs decline the model effectiveness. The OH−, K+ and SO42− provide the conductivities over 90% of the whole with the contributions in decreasing order.