Modeling Hydration Kinetics of the Portland-Cement-Based Cementitious Systems with Mortar Blends by Non-Assumptive Projection Pursuit Regression

Qin, Can; Gong, Jingwei; Xie, Gangchuan

doi:10.1016/j.tca.2021.179035

Cited by 10 publications

(1 citation statement)

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“…Cement is a commonly used material in hydraulic buildings [ 1 , 2 , 3 , 4 , 5 ]; however, the phenomenon of cracking concrete due to temperature stress occurs from time to time. The temperature around the environment of a hydraulic building can seriously affect cement hydration [ 6 , 7 ], and reducing the hydration rate of cement to avoid concentrated exotherm is one way to deal with this problem [ 8 ]. However, most scholars have mainly focused on reducing the hydration rate of cement under ambient temperature conditions by adding traditional mineral admixtures such as fly ash [ 9 ], silica fume [ 10 ], and slag [ 11 ], etc.…”

Section: Introductionmentioning

confidence: 99%

Effect of Different Temperatures on the Hydration Kinetics of Urea-Doped Cement Pastes

Luan

et al. 2022

Materials

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Urea can solve the problem of concrete cracking due to temperature stress. However, its effect is affected by temperature. The influencing mechanism of temperature on urea-doped cement pastes is still unclear. This paper explores the effect of different temperatures on the hydration kinetics of urea-doped cement pastes. The isothermal calorimeter (TAM Air) was used to test hydration at three constant temperatures (20 °C, 40 °C, and 60 °C). The effects of the urea admixture and temperature on the hydration process and hydration kinetics parameters were investigated. The hydration mechanism was analyzed, and the changes in macroscopic mechanical compressive strength and porosity were tested. The results show that, as the urea content (UC) increases, the rate of hydration gradually decreases, and the increase in temperature promotes the inhibitory effect of urea. At 60 °C, UC of 8% can be reduced by 23.5% compared with the pure cement (PC) group’s hydration rate. As the temperature increases from 20 °C to 60 °C, the Krstulovic–Dabic model changes from the NG-I-D process to the NG-D process. The effect of urea on the compressive strength of the cement is mainly shown in the early stage, and its effect on later strength is not obvious. In addition, urea will increase its early porosity. The porosity will gradually decrease in the later stage. The results of the study clarify the effect of temperature on urea-doped cement pastes. The optimal content of urea in cement is about 8%, which will provide theoretical guidance for solving the cracking problem of large-volume concrete due to temperature stress.

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