Abstract
AbstractUltrafine nanosilica particles have the potential to produce concrete under low temperatures. In this study, nanomodified concrete was cured under freezing temperatures (−10°C and −20°C) using insulation blankets without or with phase change material as conventional and hybrid protection methods, respectively. Six mixtures, incorporating general use and high early strength cements, fly ash (20%), nanosilica (6%), and cold weather admixture system (antifreeze/accelerator), were tested. The mixtures were assessed based on setting times, compressive strength, fluid absorption, and resistance to frost damage in water and salt solution. Moreover, thermogravimetric and mercury intrusion porosimetry were conducted to assess the hydration and microstructural development of concrete under these freezing temperatures. The nanomodified concrete protected by the hybrid system, even with the presence of 20% Class F fly ash, indicated improved hardening, mechanical, and durability performance; thus, such a mix design and protection method might present a viable option for concrete applications in cold conditions down to −20°C.