Performance of nano-modified concrete under freezing and low temperatures

Abstract

In this study four mixtures were prepared at a constant w/b of 0.32 with different combinations of general use cement, Class F fly ash and nano-silica sol, targeting applications in cold weather. All mixtures incorporated calcium nitrate-nitrite solution as an antifreeze admixture. The mixtures were mixed, cast and cured using two different regimes: a constant freezing temperature of-5ºC, and cyclic freezing-low temperatures (-5/5ºC), without heating or insulation during the curing period. The performance of mixtures was assessed by setting time, compressive strength and mercury intrusion porosimetry tests. In addition, scanning electron microscopy was performed to characterize the microstructure of concrete. The incorporation of nanosilica significantly enhanced the overall performance of concrete, even with fly ash, indicating its promising use for cold weather applications in late fall and early spring periods, without the need for conventional heating and insulation practices.