Mechanisms of action of shrinkage reducing admixtures and recommendations for targeted application

摘要

In order to widen the knowledge of the mechanisms of action of shrinkage reducing admixtures, the effect of three commercially available shrinkage-reducing agents (SRA) and two active substances (W) contained in these reducers on the autogenous and drying shrinkage of hardened cement paste has been evaluated for various relative humidities. For this purpose, cement paste samples were taken from a total of four different cement types (two Portland cements, one blast furnace cement, and one Portland-limestone cement with water/cement ratios between 0.25 and 0.50), and subsequently put in storage for a period of up to one year. The effects of the shrinkage reducing admixtures on the composition and surface tension of the pore solution and on the hydration, porosity, relative humidity and compressive strength of the cement paste were analyzed.