Rheological concerns arising from the use of anti-freezing additives in cement mortar with/without SP and AEA for low-temperature construction

Abstract

This paper aims to provide insights into the coupled influence of typical anti-freezing agents (AFAs) and cold environment on rheological performance of cement mortar with/without different superplasticizer (SP) and air-entraining agent (AEA) components. Fresh mixtures were prepared with chemical admixtures singly or in groups (AFA; AFA/SP; AFA/SP/AEA) for the continuous measurement of their time-dependent rheological behavior at variable temperatures (24 °C; 0 °C; −5 °C; −10 °C). Hydration kinetics, pore solution and air-void system were systematically evaluated to provide evidences supporting for the variations in rheological parameters. It was found that the yield stress of mixture decreased and the plastic viscosity increased with the temperature falling from 24 °C to 0 °C, while both the yield stress and the plastic viscosity increased rapidly with the temperature falling from 0 °C to −10 °C. Temperature could affect the rheological parameters development by changing the interaction of SP with ions. For the SP-plasticized mixtures under low temperature, the dosage of calcium nitrite (CN) as AFA should be carefully restricted. For the air-entrained mixtures, the incorporation of CN enhanced the shear stress in the high shear rate region, while the incorporation of ethylene glycol (EG) showed a converse behavior. The results will provide theoretical supports for the manufacture and the early-age properties control of flowable concrete during winter construction.