Control of cracking caused by autogenous shrinkage in mass concrete

大体积混凝土自收缩裂缝的控制

基本信息

批准号：
07650531
负责人：
MIYAZAWA Shingo
金额：
$ 1.34万
依托单位：
ASHIKAGA INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07650531/
关键词：
Concrete High- strength concrete Mass concrete Autogenous shrinkage Crack Thermal stress 収縮

项目摘要

Influences of cement type, mix proportion, temperature and specimen size on autogenous shrinkage of concrete were investigated. Influence of autogenous shrinkage on cracking of mass concrete was also investigated with restraining tests where temperature and stress histories of specimens were controlled. Main results of this research are as follows.(1) Influence of cement type on autogenous shrinkage can be setimated with mineral compositon and degree of hydration. Autogenous shrinkage increases by using blast furnace slag with 6000-8000 cm^2/g Blaine Fineness.(2) Predicting model for autogenous shrinkage strain of concrete was proposed. It is function of cement and admixture type, water-binder ratio and effective age. The proposed model is effective for concretes with ordinary Portland cement and with water-binder ratio between 0.2 and 0.56.(3) The rate of autogenous shrinkage increases with temperature of concrete within the range from 20 to 60 ﾟC.It is proved that this effect can be estimated with maturity concept. Autogenous shrinkage during the first 24 hours is lager for a specimen with lager dimensions.(4) Contribution of autogenous shrinkage to restrained stress is increased with decrease in water-cement ratio. For silica fume concrete with water-cement ratio of 0.20, tensile stress generates even when temperature is still increasing. This is because autogenous shrinkage overcomes expansion due to temperature rise.

研究了水泥类型，混合比例，温度和样品大小对混凝土自体收缩的影响。还通过控制标本的温度和应力病史的限制测试研究了自体收缩对质量混凝土破裂的影响。这项研究的主要结果如下。（1）水泥类型对自体收缩的影响可以通过矿物质复合物和水合度来解决。通过使用6000-8000 cm^2/g Blaine细度的喷气炉炉渣，自体收缩量增加。（2）提出了预测混凝土自体收缩株的模型。它是水泥和混合类型，水磨比和有效年龄的功能。提出的模型对于具有普通的波特兰水泥的凸孔，水的比率在0.2至0.56之间。在最初24小时内的自体收缩量是具有啤酒尺寸的样品的啤酒。（4）自源收缩对约束应力的贡献随水泥浆比的降低而增加。对于水泥浆比为0.20的硅烟粉混凝土，即使温度仍在升高，也会产生拉伸应力。是因为自动收缩率由于温度升高而克服了膨胀。