Effect of Chemical Admixtures on Apparent Activation Energy of Cementitious Systems

The Arrhenius equation is often used to characterize the progress of portland cement hydration for predicting in-place concrete temperature, strength, and other properties. To apply the Arrhenius equation, an activation energy (E-a) value representing the temperature sensitivity of the hydration reactions must be determined. The effects of concrete mixture variables on activation energy, including the effects of chemical admixtures, have not been well researched. This paper examines the effects of set-accelerating, water-reducing/set-retarding, and air-entraining admixtures on apparent (i.e., experimentally determined) activation energy for mixtures with and without supplementary cementitious materials. It was found that a glucose-based water-reducing retarder and two high-range water-reducing admixtures slightly lowered E-a, a lignosulfonate-based water-reducing retarder and a calcium nitrate-based set-accelerating admixture significantly lowered E-a, and a vinsol resin air-entraining agent had no effect. DOI: 10.1061/(ASCE)MT.1943-5533.0000345. (C) 2011 American Society of Civil Engineers.