Effect of C-S-H Nucleating Agent on Cement Hydration

Abstract

This work aims to study the effect of a nucleating agent on cement hydration. Firstly, the C-S-H crystal nucleation early strength agent (CNA) is prepared. Then, the effects of CNA on cement hydration mechanism, early strength enhancement effect, C-S-H content, 28-days hydration degree and 28-days fractal dimension of hydration products are studied by hydration kinetics calculation, resistivity test, BET specific surface area test and quantitative analysis of backscattered electron (BSE) images, respectively. The results show that CNA significantly improves the hydration degree of cement mixture, which is better than triethanolamine (TEA). CNA shortens the beginning time of the induction period by 49.3 min and the end time of the cement hydration acceleration period by 105.1 min than the blank sample. CNA increases the fractal dimension of hydration products, while TEA decreases the fractal dimension. CNA significantly improves the early strength of cement mortars; the 1-day and 3-days strength of cement mortars with CNA are more than the 3-days and 7-days strength of the blank sample. These results will provide a reference for the practical application of the C-S-H nucleating agent.

Microstructure of CEM II/B-S Pastes Modified with Set Accelerating Admixtures

“…Modern setting and hardening accelerating admixtures mainly have a physical effect by introducing additional micro- or nanoparticles into the batch water, which play the role of heterogeneous nucleation seeds (C-S-H seeds, crystallization seeds) [ 40 ]. Such particles are synthetic C-S-H phase—the main product of hydration of the cement that is dispersed in cement paste [ 41 , 42 ]. As a result, hydration products are formed not only on the surface of cement grains, but also in the spaces between them [ 42 , 43 , 44 ].…”

“…Such particles are synthetic C-S-H phase—the main product of hydration of the cement that is dispersed in cement paste [ 41 , 42 ]. As a result, hydration products are formed not only on the surface of cement grains, but also in the spaces between them [ 42 , 43 , 44 ]. This effect is visible also in the term of refinement of porosity pattern [ 43 , 45 ].…”