Effects of Curing of Winter Concreting on the Freeze-Thaw Resistance of Concrete

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The followings are main findings in this research.(1) The procedure of allowing moderate water-evaporation from concrete for 1 or 2 days immediately after placing of concrete, and, then, providing sufficient moist curing is an effective and practical way of remakably increasing the freeze-thaw durability of concrete without impairing its strength development.(2) The required compressive strength of concrete at the end of curing may be decreased as the water-cement ratio is decreased.(3) Even within the range of usual water-cement ratio, say, 45 to 65 %, the required periods of curing in cold weather concreting can be greatly shortened by lowering the ratio.(4) The inner deteriorations caused by an action of slow freezethaw cycles such as that under the natural weather conditions are considered to be isolated and minute ones, which can be remedied easily by the hydaration products of cement if a sufficient amount of unhydrated cement remains in the concrete.(5) Lowering water-cement ratio enhances the benefit of improving the freeze-thaw durability of concrete through such effects as the increased capability of remedying inner frost damge, increased resistance against deteriorating actions due to atrength increse after curing, decreased degree of water-saturation due to the continued cement hydration after curing.(6) The freeze-thaw resistance of fully saturated concrete with water is dependent entirely on its compressive strength, and satisfactory freeze-thaw durability can be obtainted only when its compressive exceeds about 230 kgf/cm^2.