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Evaluation of Accumulated Damage in Reinforced Concrete at Early Age

钢筋混凝土早期累积损伤的评估

基本信息

批准号：
01850107
负责人：
OZAWA Kazumasa
金额：
$ 4.35万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B).
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

The objective of this study is to evaluate the accumulated damage and micro fracture in concrete caused by hardening and drying shrinkage, heat and water transfer and external stress at early age, and to develop the new system for evaluating the time-dependent performance for durability of concrete structures.1. Time-dependent and path-dependent hydration of cementThe evaluation method for activation energy of cement in concrete was developed. The model for path-dependent hydration of cement at any temperature and any any age was proposed.2. Activation energy and mix proportionIt was clarified that the activation energy representing temperature dependency of cement is controlled by the dispersion of cement in concrete. General relationship between mix proportion and activation energy was successively proposed.3. Evaluation of accumulated damageEvaluation method of accumulated damage caused by hardening and drying shrinkage and segregation in cover concrete around reinforcing bars was proposed with use of tension-stiffness of concrete. Resistance to the damage was also successively evaluated by average tensile strength, average tensile plastic deformation and bond deterioration.4. Water movement and drying shrinkage in concreteModel for predicting water movement in concrete at fresh state and after being hardened was proposed, which affects the damage and micro fracture in concrete. Relationship between water movement by drying and shrinkage in concrete was clarified based on the micro-structure of concrete.

本研究的目的是评估混凝土早期硬化与干燥收缩、热传导与水传导以及外部应力引起的累积损伤和微断裂，并开发新的混凝土结构耐久性时变性能评估体系.水泥水化的时间依赖性和路径依赖性建立了混凝土中水泥水化活化能的估算方法。提出了任意温度、任意龄期下水泥水化的路径依赖模型.活化能和配合比表明水泥的温度依赖性活化能受水泥在混凝土中的分散度控制。提出了配合比与活化能的一般关系式.累积损伤的评价提出了用混凝土的抗拉刚度来评价钢筋周围保护层混凝土硬化、干燥收缩和离析引起的累积损伤的方法。通过平均拉伸强度、平均拉伸塑性变形和粘结劣化等指标对复合材料的抗损伤性能进行了评价.混凝土中的水分运动与干缩提出了新拌混凝土和硬化后混凝土中水分运动的预测模型，该模型对混凝土的损伤和微断裂有重要影响。从混凝土的微观结构出发，阐明了混凝土干燥水分运动与收缩的关系。