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Proposal for Durability Verification Technique of Concrete from the Viewpoing of Deteriorated Depth Under Freezing and Thawing Action

从冻融劣化深度角度提出混凝土耐久性验证技术

基本信息

批准号：
14550467
负责人：
SHOYA Masami
金额：
$ 2.05万
依托单位：
Hachinohe 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：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

The frost resistance verification of concrete in JSCE has been conducted with the relative dynamic modulus of elasticity of specimen. However, the technique of frost resistance verification with the relative dynamic modulus of elasticity is made using the small specimen in limited testing conditions, and it will be not a rational technique on the design of actual concrete structure. Therefore, it may be said that the technique is similar to the conventional method to restrict the water cement ratio of concrete.On the other side, JSCE standard specification for maintenance of concrete structures enacted in 2001, specified that frost damage in concrete structure should be rationally predicted based on the deteriorated depth due to freezing and thawing action.This study aims at the basic proposal for durability verification technique on damage of concrete from deteriorated depth focusing the surface layer of concrete structures under freezing and thawing action. The research results are summarized as follows.1.Evaluation of Frost Damage on Concrete by Using Improved Pull-off MethodFrost damages of various concretes due to freezing and thawing action, were evaluated by improved pull-off method. The assessing method for frost damage of concrete with the deteriorated depth using measured pull-off strength in the cover concrete was investigated in various test conditions. In this study, the tests were conducted changing the water cement ratio, the air content, the freezing and thawing procedure, exposed area, age of concrete and so on.2.Proposal of Durability Verification Technique of Concrete by Improved Pull-off MethodThe fundamental idea for the durability verification technique is base on deteriorated depth due to freezing and thawing action judging from the tensile strength at the distance from the concrete surface by using improved pull-off method. A new verification equation using deteriorated depth of concrete was tentatively proposed.

利用试件的相对动弹性模量对JSCE混凝土的抗冻性进行了验证。然而，利用相对动弹性模量进行抗冻性验证的技术是在有限的试验条件下采用小试件进行的，在实际混凝土结构的设计中并不是一种合理的技术。因此，可以说该技术类似于传统的限制混凝土水灰比的方法。另一方面，2001年颁布的JSCE混凝土结构养护标准规范规定，应根据冻融作用下的恶化深度，合理预测混凝土结构的冻损。以冻融作用下混凝土结构表层为重点，对混凝土劣化深度损伤耐久性验证技术提出了基本建议。研究结果总结如下：1。用改进拉脱法评价混凝土冻损用改进拉脱法评价各种混凝土在冻融作用下的冻损。在不同的试验条件下，研究了利用覆盖层拉脱强度测定老化深度下混凝土冻损的评估方法。本研究通过改变水灰比、空气含量、冻融程序、暴露面积、混凝土龄期等因素进行试验。基于改进拉脱法的混凝土耐久性验证技术的提出基于改进拉脱法从离混凝土表面距离处的抗拉强度判断冻融作用引起的劣化深度来进行耐久性验证技术的基本思想。初步提出了一种新的以混凝土劣化深度为参数的验证方程。