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Fundamental Study on Freeze-Thaw Resistance of Early-Age Concrete and Its Evaluation Methods

早龄混凝土抗冻融性能基础研究及其评价方法

基本信息

批准号：
02650331
负责人：
YAMAMOTO Yasuhiko
金额：
$ 1.22万
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：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

The followings are main findings in this research.1. The freeze-thaw resistance of concrete at early ages can not be adequately evaluated by means of conventional method, because the dynamic modulus of elasticity of concrete specimens increases to a great extent during the test even when they are subjected to rapid freeze-thaw cycles in water.2. The modified relative dynamic modulus of elasticity(REi)defined as below can be utilized for a valid evaluation of freeze-thaw resistance of concrete at early ages.REi(%)= 100 Emi/Eciwhere, Emi : measured dynamic modulus of elasticity after i-cycles of freeze-thawEci : dynamic modulus of elasticity In an Ideal state with no inner defect at the time of measuring Emi, which can be determined from a good hyperbolic correlation between the maturity and dynamic modulus of elasticity of specimens subjecting no freeze-thaw cycles.3. In the region where the residual strain of concrete after thawing exceed 100xlO^<-6>, there exists a straight-line relation between the number of freeze thaw cycles In a normal scale and the residual strain In a logarithmic scale. The quantity(A), which is calculated by the following equation using the value of gradient(a)of the linear relation can be a convenient index for adequately evaluating the freeze-thaw resistance of concrete.A = 10^a - 14. The compressive strength of concrete required to be free from the internal damage by freeze-thaw action at its Initial stages differs greatly, in general, depending on its water-cement ratio.

本研究的主要研究结果如下： 1．由于混凝土试件在水中快速冻融循环，其动态弹性模量在试验过程中仍大幅增加，因此常规方法无法充分评价混凝土早期的抗冻融性能。 2．修正后的相对动态弹性模量(REi)定义如下，可用于有效评价混凝土早期抗冻融性能。REi(%)= 100 Emi/Eci 其中，Emi ：冻融i次后测得的动态弹性模量Eci ：动态弹性模量在测量Emi时无内部缺陷的理想状态下，由未经历冻融循环的标本的成熟度与动态弹性模量之间良好的双曲相关性可以确定。 3．在混凝土解冻后残余应变超过100×10^-6的区域，正常标度的冻融循环次数与对数标度的残余应变之间存在直线关系。使用线性关系的梯度(a)值通过以下方程计算出的量(A)可以是充分评价混凝土抗冻融性能的一个方便的指标。A = 10^a - 14。混凝土在其初始阶段免受冻融作用造成内部损坏所需的抗压强度通常根据其水灰比的不同而有很大差异。