Air Entrainment of Concrete Against Freeze And Thaw In Cold Areas of Pakistan

Abstract

The study aims to investigate the influence of air entrainment in concrete against freeze-thaw. Standard cylinders with 150 mm diameter and 300mm length of two different mixes were cast and tested after 28 days against freeze-thaw cycles. The controlled specimens and the air-entrained mixes were exposed to 28 freeze and thaw cycles. Besides the freeze and thaw cycles, loss of mass and surface scaling were also measured. It is found that air-entrained specimens offer higher resilience to surface scaling than the control specimen. Similarly, weight loss is dominant in control condition specimens. A nondestructive test, the Schmidt hammer test was conducted for both the mixes before and following freeze and thaw cycles. The results reveal a low reduction in compressive strength of air-entrained mixes in comparison to the control specimen. The results further show that freeze-thaw is dangerous only when the sample is saturated to about 80%; below this freeze-thaw is almost ineffective. The experimental data recommend that air-entraining agents should be used in cold weathering areas like Astore and Skardu, where the average temperature in peak winter is about -13 ºC and the structures are exposed to daily freeze-thaw due to large differences in temperature during day and night.