Abstract Manager

Concrete placement under low temperatures has been challenging in cold regions such as Canada, the United States, and Europe. Casting concrete under cold temperatures without the proper precautions negatively affects cement hydration reactions, which regulate the development of mechanical, physical, and microstructural properties of concrete. Accordingly, in cold regions, the construction season is limited to warmer periods to alleviate the rigorous requirements of casting concrete under cold temperatures. The addition of antifreeze agents with/without accelerating admixtures as a cold weather admixture system (CWAS) in concrete has been introduced as a practical solution to mitigate the noxious effects of cold weather on concrete. Also, nanoparticles can potentially speed up the reactivity of cementitious binders cast and cured at low temperatures. In this study, the effect of two types of economical and commercially available antifreeze additives: calcium nitrate-based (CN) and urea, on the performance of concrete with and without nano-silica was evaluated. Four mixtures were mixed, cast, and cured at -5℃, which represents the minimum average temperature in early spring and late fall in many cold regions. All mixtures were covered with a commercial non-R-rated tarp to mitigate surface water loss without any heating.  The different mixtures were assessed in terms of setting time, strength development, durability performance, and hydration development using thermogravimetry analysis. The synoptic results showed that concrete samples containing CNA acquired higher mechanical and durability properties compared to urea. Furthermore, the addition of nano-silica proved to be efficient at enhancing concrete performance in all aspects. Thermal analysis substantiated the efficacy of the used antifreeze and nanomaterials to sustain the continual maturity of the cement paste. This highlights the promising use of nano-modified concrete, incorporating economical antifreeze admixtures, for cold weather applications down to -5 ℃, without heating practices and/or insulation.