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

冬季混凝土养护对混凝土抗冻融性能的影响

基本信息

批准号：
04650417
负责人：
YAMAMOTO Yasuhiko
金额：
$ 1.34万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04650417/
关键词：
cold weather concreting frost damage water content slow freeze-thaw test freeze-thaw durability curing compressive strength water-cement ratio 若材令コンクリート強度低下回復養生セメントの水和

项目摘要

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.

以下是本研究的主要发现。(1)在混凝土浇筑后立即使混凝土中的水分适度蒸发1 ~ 2天，然后进行充分的潮湿养护，这是一种有效而实用的方法，可以显著提高混凝土的冻融耐久性，而不影响其强度的发展。(2)随着水灰比的降低，养护结束时混凝土所需的抗压强度可能降低。(3)即使在通常的水灰比范围内，例如45%至65%，在寒冷天气下，降低水灰比也可大大缩短混凝土浇筑所需的养护时间。(4)由缓慢的冻融循环作用（如自然气候条件下的冻融循环）引起的内部劣化被认为是孤立的和微小的劣化，如果混凝土中残留有足够量的未水化水泥，则可以通过水泥的水化产物容易地补救。(5)降低水灰比可通过提高混凝土修复内部冻害的能力、提高混凝土养护后强度的抗劣化能力、降低混凝土养护后水泥水化的水饱和度等作用，提高混凝土的抗冻融耐久性。(6)全水饱和混凝土的抗冻融性完全取决于其抗压强度，只有当其抗压强度超过230 kgf/cm ^2时，才能获得满意的抗冻融耐久性。