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STUDY ON PREVENTION METHOD FOR THERMAL CRACK OF CONCRETE PLACED IN HOT WEATHER AMBIENCE

高温环境下混凝土热裂缝防治方法研究

基本信息

批准号：
06650636
负责人：
KOYAMA Tomoyuki
金额：
$ 1.28万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06650636/
关键词：
CONCRETE HOT WEATHER AMBIENCE THERMAL CRACK TEMPERATURE WATER VAPORIZATION COEFFICIENT OF THERMAL EXPANSION TENCILE CAPACITY AUTOGENOUS SHRINKAGE 温度分布脱水量若材令

项目摘要

In this study, prevention method for early age crack at surface layr of concrete slab placed in hot weather ambience was discussed by experiment and numerical analysis on properties of temperature and water vaporization.At first, as basic experiment of thermal crack, time-dependent change of temperature distribution and water vaporization at mortar specimens were measured from immediately after placing toward twenty four hours, and effect of outer conditions (ambient temperature, ambient humidity, wind, solar radiation) and inner conditons (materials, mix proportion) were quantitatively discussed.Next, flow chart for prevent thermal crack was shown. Further, analysis method of thermal strain used in flow chart, estimation method of water vaporizing rate used in analysis were shown, coefficient of thermal expansion of specimens at young age to calculate thermal strain at surface layr from temperature distribution, and tensile capacity as border line of crack occurence were measurd.Using these results, tensile strain at surface layr of slab specimens due to temperature distribution was analyzed, and it was clarified that tensile strain bacame maximum at the same time when tensile capasity became minimum. So it was obvious that crack due to temperature difference between outermost and central layrs was most liable to occur at above mentioned period. And effect of outer conditons and inner conditions were quantitatively clarified.At the end, effect of curing as prevention of thermal crack was discussed. Immediately after starting of curing, tensile strain at surface layr bacame smaller. In the other words, it was cirtificated that curing was very effective to prevent thermal crack. And it was clarified that starting time of curing was important, and it must be started before the period when tensile capasity became minimum.

在这项研究中，通过实验和温度和水汽化特性的数值分析，讨论了在炎热天气环境下放置的混凝土板表层早期裂缝的预防方法。首先，作为热裂纹的基础实验，测量了砂浆试件从放置后到二十四小时内温度分布和水汽化随时间的变化，以及外部条件（环境温度、环境湿度、风、太阳辐射）的影响。并对内部条件（材料、配合比）进行了定量讨论。接下来给出了防止热裂纹的流程图。此外，还显示了流程图中使用的热应变分析方法、分析中使用的水蒸发率的估算方法、根据温度分布计算表层热应变的年轻时试样的热膨胀系数以及作为裂纹发生边界线的拉伸能力。利用这些结果，分析了由于温度分布引起的板坯试样表层的拉伸应变，并表明拉伸应变在同一时间达到最大。拉伸能力达到最小的时间。可见，在上述时期最容易发生因最外层和中间层温差而产生的裂纹。并定量阐明了外部条件和内部条件的影响。最后讨论了固化对防止热裂纹的作用。固化开始后，表层的拉伸应变立即变小。换句话说，已证实固化对于防止热裂纹非常有效。并明确了固化的开始时间很重要，必须在拉伸能力达到最小的时期之前开始。