Xueyu Pang

Modeling the Effect of Curing Temperature and Pressure on Cement Hydration Kinetics

This study shows that chemical shrinkage tests can be used to evaluate the hydration kinetics of cement cured under different temperatures and pressures. Test results suggest that the effect of curing condition on cement hydration is represented by a scale factor on hydration rate as a function of degree of hydration. Therefore, the hydration kinetic curves of cement at any curing condition can be predicted from those of a reference condition by simple coordinate transformations (that is, scaling the x- and/or y-axis using the scale factor). The dependence of the scale factor on curing temperature and curing pressure is related to the activation energy and the activation volume of the cement, respectively. Test results of five different types of oil well cements in this study give an apparent activation energy ranging from 42.5 to 52.6 kJ/mol and an apparent activation volume ranging from –22.3 to –29.5 cm3/mol.

Modeling cement hydration by connecting a nucleation and growth mechanism with a diffusion mechanism. Part II: Portland cement paste hydration

Abstract A particle-based C3S hydration model with only three rate constants developed in Part I of this study is further developed and applied to Portland cement paste hydration. Experimental data are obtained with chemical shrinkage tests of cement pastes prepared with different water to cement (w/c) ratios (0.3–0.5), and cured at different temperatures (24°C–63°C) and pressures (0.69–51.7 MPa). The proposed model produces exceptionally good fits to test data. The fitted results indicate that the entire process of cement hydration can be modeled by connecting a nucleation and growth mechanism with a diffusion mechanism. Furthermore, the results reveal that the deceleration period of cement hydration may be due to the gradual transition of the rate-controlling mechanisms of different particles. The fitted rate constants generally follow basic chemical kinetics laws in terms of their dependencies on curing temperature and pressure, and appear to be largely independent of w/c ratio.

Modeling cement hydration by connecting a nucleation and growth mechanism with a diffusion mechanism. Part I: C3S hydration in dilute suspensions

Abstract A particle-based C3S hydration model, which mathematically connects a nucleation and growth controlled mechanism with a diffusion controlled mechanism, is developed in this study. The model is first formulated and fitted with C3S hydration in stirred dilute suspensions in Part I where interactions between different particles can be ignored, and further developed and fitted with Portland cement paste hydration in Part II to account for inter-particle interactions. Excellent agreement was observed between experimental and modeled results. Three critical rate-controlling parameters, including a parallel growth rate constant, a perpendicular growth rate constant and a diffusion constant, were identified from the proposed model. The dependencies of these parameters on particle size and initial quantity of nuclei are investigated in Part I while their dependencies on cement composition, water-cement ratio, and curing condition are studied in Part II.