1. Synergistic effects of different ionic surfactants and temperature on rheological behavior and air-void structure of cement mortar.
- Author
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Zhang, Junyi, Gao, Xiaojian, Wang, Jingfeng, and Xia, Yan
- Subjects
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IONIC surfactants , *CATIONIC surfactants , *ANIONIC surfactants , *CEMENT , *HYDRATION kinetics , *PSEUDOPLASTIC fluids , *MORTAR - Abstract
The influence of air entrainment on rheological behavior of fresh cementitious materials has attracted a lot of attention in the past years, but the results are still in controversy. In this research, cement mortars were prepared with equivalent air contents using different air-entraining admixtures (AEAs) to measure their fresh-state performance and hardened air-void system at variable temperature conditions, which aimed to clarify and unveil the coupled effects of different surfactants and temperature for the first time. The adsorption amount of AEA, zeta potential of cement, along with hydration kinetics of mixtures were evaluated to characterize the interaction of air bubbles with cement grains. It was found that for mixture without superplasticizer (SP), the impact of air entrainment on rheological parameters was dependent on the interaction intensity of AEA molecules with cement. For SP-plasticized mixture, air entrainment tended to cause a shear-thinning behavior with decreased plastic viscosity, while its influence on yield stress was in accordance with the situation without SP. The hardened samples with anionic surfactant contained more small voids and lacked big voids, whereas the samples with cationic surfactant showed opposite outcomes. With temperature decreasing, both the average chord length and the spacing factor of air voids increased owing to the reduced yield stress of mixture. The results will provide in-depth illustrations for understanding how air bubbles change the rheological behavior of mixture, and more importantly it will explain the seemingly inconsistent findings reported by previous literatures. • How air bubbles affected rheological behavior of mixtures with various states was clarified. • The coupled influence of surfactant type and temperature on air-void system were explored. • The crucial role of surfactant interaction with cement for fresh-state performance was revealed. • The reasons why temperature decreasing at fresh-state degraded air-void structure were analyzed. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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