Behavior of fresh and hardened concretes with antifreeze admixtures in deep-freeze low temperatures and exterior winter conditions

• Effects of antifreeze admixtures on the exterior winter condition were investigated.
• Workability of concrete was improved.
• Calcium nitrate protects concrete against freezing even in the plastic state.
• Urea provides protection up to −10 °C without any extra protection precaution.
• Best results have been obtained with the combination of calcium nitrate and urea.

This research investigates properties of concrete prepared with urea and calcium nitrate anti-freeze admixtures and cured in different low deep-freeze temperatures and exterior winter conditions in Erzurum, Turkey. Four different mixtures were prepared and they are control, 9% calcium nitrate, 9% urea and combination of 4.5% urea + 4.5% calcium nitrate. Antifreeze admixtures were used by weight of cement dosage. After casting, one group of samples from each batch were immediately cured in four different low deep-freeze temperatures (−5, −10, −15 and −20 °C) for 7, 28, 90 and 365 days (90 days deepfreeze curing + 275 days laboratory condition). Another group of samples was cured in water (23 ± 2) °C for 7, 28, 90 and 365 (90 days water curing + 275 days laboratory condition) days, according to ASTM C 192. The others were exposed to exterior winter conditions of Erzurum, Turkey, for 90 and 365 days. Ultrasonic pulse velocity (UPV) and compressive strength were evaluated for 7, 28, 90 and 365 days. Both compressive strength and UPV were very low for −15 and −20 °C at 7 and 28 days of curing durations, especially for control and samples containing 9% urea. However, with the increase of curing period, both compressive strength and UPV values of samples with the combination of 4.5% urea + 4.5% calcium nitrate increased. Adding 4.5% calcium nitrate and 4.5% urea caused an increment in the compressive strength of about 108% and 82% for 90 and 365 days in exterior winter conditions, respectively, when compared to the compressive strength of control sample that was exposed to the same conditions.