Hydration kinetics of cement paste containing concrete admixture

✍ Scribed by M.R. Ismail; S.A.S. El-Hemaly

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 390 KB
• Volume: 21
• Category: Article
• ISSN: 0008-8846
• DOI: 10.1016/0008-8846(91)90163-c

✦ Synopsis

The influence of the presence of concrete admixtures on the hydration reaction of cement pastes has been investigated. Two admixtures acting as (1) an accelerator and (2) a retarder, have been added to the cement pastes in various dosages and then cured at different ages between 1 and 28 days in 100% R.H. The kinetics of hydration were determined by the estimation of free Ca(OH) 2 liberated during the hydration as well as the chemically combined water contents of the hydration products by using DTA and TG techniques. The mineralogical composition of the hydration products was investigated by X-ray diffraction method. The results indicate that the presence of such admixtures affect the measured physico-chemical properties of the products. The addition of the accelerator increases the rate of hydration reaction whereas the retarder delays the reaction rate as a result of the surface coating of the reacting grains. The intensity of X-ray peaks characterizing the phases formed during the hydration reaction is generally increased with the accelerator and reduced with the presence of the retarder.