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

Abstract

A particle-based C 3 S 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.

Hydration kinetics of oil well cement in the temperature range between 5 and 30°C

“…The scale factor model is primarily developed for practical engineering application purposes, particularly to predict the heat release and transient temperature change of cement-based materials (Pang et al, 2020). It should be noted that the scale factor model has limited use in explaining the physical and chemical mechanisms of cement hydration, which is highly complex and has been the subject of considerable debate (Scherer et al, 2012;Karakosta et al, 2015;Pang and Meyer, 2016a;Pang and Meyer, 2016b;Ma and Kawashima, 2019;Pichler and Lackner, 2020). Nevertheless, the model can provide a fairly accurate simulation of the influence of temperature on cumulative heat evolution under a variety of curing conditions when applied in a numerical way (Pang et al, 2020;Pang et al, 2021).…”

“…Here, the rate constant could be parameters obtained by various cement hydration kinetics models or simply the peak hydration rate (Scherer et al, 2012;Pang and Meyer, 2016b;Pichler and Lackner, 2020;Pang et al, 2021). Previous studies found that the effect of certain accelerators and retarders (CaCl 2 , NaCl, KCl, and sucrose) on the cement hydration rate is similar to that of temperature and pressure, especially at relatively low concentrations (Pang et al, 2015;Sun et al, 2021b).…”

Engineering hydration model for ordinary Portland cement based on heat flow calorimetry data

“…More refined, multiphase, kinetics models, considering the binder composition, e.g., the four clinker phases and gypsum in Portland cement, see, e.g., [3,24,25,27], have been proposed. These models, however, rely heavily on verified material parameters (e.g., rate constants in the scopes of modeling with the Avrami law, which may change with water/cement ratio and grinding fineness) for all clinker phases (and reprocessed product phases, e.g., ettringite and portlandite) and/or separable reactions (e.g., tricalcium aluminate reaction is a multistage reaction in the presence of gypsum).…”

Effects of Traffic Vibrations on the Flexural Properties of Newly Placed PVA-ECC Bridge Repairs

“…If TRVs occur during the setting period, this will probably damage or obstruct the connection of the solid skeleton [13] in the PVA-ECCs, as well as the bond of C-S-H particles or even that of C-S-H gels. After the final set, the hydration of cement is mainly restricted by the diffusion of capillary water in the matrix [14,15], any TRVs that occurred during this period would probably result in the accelerated transportation of free water from the capillary pores toward the interface of the anhydrous cement grains, which would be convenient for the consumption of anhydrous cement grains [16] and further increase the degree of hydration of the matrix, thereby affecting the flexural properties of the PVA-ECCs as a consequence.…”