Effects of Water-cement Ratio and Hydration Heat Regulating Materials on Hydration Process of Early-age Cementitious Materials

Abstract

By means of low-field nuclear magnetic resonance (LF-NMR), the transverse relaxation time (T ₂) signals of physically bound water in cement paste were monitored to indicate water content change and characterize the early-age hydration process. With the curves of the T ₂ signals and hydration time obtained, the hydration process could be divided into four typical periods using the null points of the second derivative curve, and the influences of water-cement ratio (w/c) and hydration heat regulating materials (HHRM) on hydration process were analyzed. The experimental results showed that the hydration rate of pure cement paste in accelerated period presented a positive correlation with w/c. Compared to pure cement paste, the addition of HHRM extended all four periods, and led to a much faster hydration rate in initial period as well as a slower rate in accelerated period. Finally, according to the LF-NMR test results, the early-age hydration model of cementitious materials was proposed considering w/c and HHRM content.

Keywords

hydration / water-cement ratio / hydration heat regulating materials / cementitious materials / early age / low-field nuclear magnetic resonance

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