Mechanism Analysis of Polyether Shrinkage Reducing Admixture(SRA) Delaying Cement Hydration

Shrinkage reducing admixture is widely used to restrain the shrinkage of concrete, but it will hinder the hydration process of cement. It is of practical significance to explore the source of this negative effect. Polyether type shrinkage reducing admixture is the most widely used shrinkage reducing admixture at present. Taking this kind of shrinkage reducing admixture as the research object. By testing the hydration heat and hydration degree of cement, the surface tension of liquid, the compressive strength and setting time of mortar, the ion concentration in paste pore solution, the maximum solubility and dissolution rate of sulfate, the interaction mechanism between shrinkage reducing admixture and cement was discussed. The results show that the addition of shrinkage reducing admixture can significantly reduce the mechanical properties of mortar and the hydration degree of cement, but the negative effect will gradually decrease with the increase of age, and the setting time of mortar and the hydration heat of cement will also be reduced by adding shrinkage reducing admixture. The decrease of hydroxyl radical concentration, maximum solubility and dissolution rate of sulfate in pore solution is the reason for this phenomenon. There is a bilinear relationship between the surface tension of pore solution and deionized aqueous solution containing shrinkage reducing admixture and the concentration of shrinkage reducing admixture. After the inflection point, the increase of the concentration of shrinkage reducing admixture has no obvious effect on the surface tension, and the delayed addition of shrinkage reducing admixture alleviates its adverse effect on cement hydration and reduces the decrease of mortar strength. © 2024 Cailiao Daobaoshe/ Materials Review. All rights reserved.