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Estimation of shrinkage of high-strength concrete including autogenous shrinkage

高强混凝土收缩（包括自收缩）的估算

基本信息

批准号：
09650513
负责人：
MIYAZAWA Shingo
金额：
$ 1.47万
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：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09650513/
关键词：
Concrete Hieh-streneih concrete Drying shrinkage Autogenous shrinkage Shrinkage Relative humidity Size effect Prediction

项目摘要

(1) As autogenous shrinkage of concrete occurs in cement paste phase, it is less than that of cement paste itself because of the presence of aggregate particles. It is assumed that concrete can be expressed by a two-phase model, where aggregate particles are dispersing in cement paste matrix as inclusions. It has been proved that influence of aggregate on autogenous shrink-age can be estimated with an existing two phase model, such as Hobbs' model, for mortar and concrete with different volume concentration of aggregate(2) The total strain including autogenous shrinkage and drying shrinkage decreases with increasing duration of sealed curing for specimen with 0.2 and 0.3 water-cement ratio. But the difference decreases with increasing age, although data for a very long time has not been obtained. For specimen with 0.4, 0.5, and 0.6 water-cement ratios, the duration of sealed curing dose not have significant effect on the total strain at later ages.(3) For the specimens with 0.4, 0.5 an … More d 0.6 water-cement ratios, shrinkage is observed at any atmospheric condition with relative humidity ranging form 40% to 90%, and shrinkage increases with decreasing relative humidity. For specimen with 0.2 w/c, on the other hand, slight expansion is observed at 80% and 90% of relative humidity. For specimen with 0.3 water-cement ratio, volume change is hardly observed at 90 % relative humidity.(4) It can be seen that autogenous shrinkage at early ages increases with specimen size, which is explained by temperature effect and that ultimate value is not considerably influenced by specimen size.(5) Shrinkage of high-strength concrete cannot be precisely estimated form existing models such as JSCE model and RILEM French Chapter model, so prediction model for shrinkage of high-strength concrete has to be established.(6) Shrinkage decreases with increasing ambient relative humidity and expansion can be recorded when ambient relative humidity is more than a certain value that is dependent on water-cement ratio. The value of the specific ambient relative humidity (ρo) at which neither drying shrinkage nor expansion is not recorded, can be determined as a function of water-cement ratio, and coincides with the intemal relative humidity of the concrete Less

(1)由于混凝土的自收缩发生在水泥浆阶段，由于骨料颗粒的存在，混凝土的自收缩小于水泥浆本身的自收缩。假设混凝土可以用两相模型来表示，其中骨料颗粒以包裹体的形式分散在水泥浆体基体中。实验证明，对于骨料体积浓度不同的砂浆和混凝土，骨料对自收缩龄期的影响可以用现有的两相模型（如Hobbs模型）来估计。(2)水灰比为0.2和0.3的试件，包括自收缩和干缩在内的总应变随密封养护时间的延长而减小。但这种差异随着年龄的增长而减小，尽管很长一段时间的数据还没有得到。对于水灰比为0.4、0.5和0.6的试件，密封养护时间对后期总应变影响不显著。(3)在相对湿度为40% ~ 90%的大气条件下，水灰比为0.4、0.5和0.6以上的试件均有收缩现象，且收缩随相对湿度的减小而增大。另一方面，对于0.2 w/c的试样，在80%和90%的相对湿度下观察到轻微的膨胀。对于水灰比为0.3的试样，在90%的相对湿度下几乎观察不到体积变化。(4)早期自收缩率随试样尺寸的增大而增大，这可以用温度效应来解释，试样尺寸对自收缩率的影响不大。(5)现有的JSCE模型、RILEM French Chapter模型等模型无法准确估计高强混凝土的收缩率，需要建立高强混凝土的收缩率预测模型。(6)收缩率随环境相对湿度的增大而减小，当环境相对湿度大于一定值时可记录到膨胀，该值与水灰比有关。不记录干燥收缩和膨胀的特定环境相对湿度（ρo）的值可以确定为水灰比的函数，并与混凝土内部相对湿度相吻合