Early hydration and setting of oil well cement

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• 作者：Jie Zhang ; Emily A. Weissinger ; Sulapha Peethamparan ; George W. Scherer
• 关键词：A. Hydration ; A. Kinetics ; A. Workability ; C. Shrinkage ; D. Admixture
• 刊名：Cement and Concrete Research
• 出版年：2010
• 出版时间：July 2010
• 年：2010
• 卷：40
• 期：7
• 页码：1023-1033
• 全文大小：1802 K

文摘

A broad experimental study has been performed to characterize the early hydration and setting of cement pastes prepared with Class H oil well cement at water-to-cement ratios (w/c) from 0.25 to 0.40, cured at temperatures from 10 to 60 °C, and mixed with chemical additives. Chemical shrinkage during hydration was measured by a newly developed system, degree of hydration was determined by thermogravimetric analysis, and setting time was tested by Vicat and ultrasonic velocity measurements. A Boundary Nucleation and Growth model provides a good fit to the chemical shrinkage data.

Temperature increase and accelerator additions expedite the rate of cement hydration by causing more rapid nucleation of hydration products, leading to earlier setting; conversely, retarder and viscosity modifying agents delay cement nucleation, causing later setting times. Lower w/c paste needs less hydration product to form a percolating solid network (i.e., to reach the initial setting point). However, for the systems evaluated, at a given w/c, the degree of hydration at setting is a constant, regardless of the effects of ambient temperature or the presence of additives.