多因素协同作用下粉煤灰—矿渣粉混凝土耐久性能的研究

发布时间：2018-07-20 09:46

【摘要】：混凝土的冻融破坏会给处于负温地区的基础设施建设带来损坏。实际服役混凝土通常处于复杂的机械荷载和环境因素作用下，其劣化过程是一个复杂的物理、化学、力学等共同作用的过程，研究多因素条件下的混凝土的耐久性，可以为实际混凝土工程的耐久性评估和寿命预测提供依据，从而指导实际工程中的混凝土耐久性设计。本文以常用的掺有粉煤灰和矿渣粉的混凝土（FA-BFS混凝土）为研究对象，模拟了实际工程中混凝土遭受的多重因素；探索了多因素协同作用下混凝土的性能退化规律和评价方法；采用粘贴式应变计监测了混凝土基体的变形，研究了基体的残余应变和冷冻过程表观冻胀系数的变化；结合与抗冻性传统参数的对比结果和残余应变的演变规律，提出了混凝土冻融破坏的损伤模型。本文取得了以下研究成果： 1）明确了双因素和三因素作用下混凝土劣化的形式以及各因素对混凝土劣化过程的影响。 2）用应变表征了混凝土冻融过程中所产生的内部损伤。冻融过程中混凝土基体产生了不可逆的残余应变，残余应变与冻融条件下基体内部孔隙结构及裂纹的产生与扩展直接相关，可以用来表征基体的损伤程度。 3）提出了混凝土在冻融循环降温过程的表观冻胀系数的概念，并建立了用其表征混凝土冻融损伤的方法。 4）初步建立了基于残余应变的混凝土冻融损伤模型，并提出了将其运用于实际工程的初步思路。用Boltzmann函数分析了混凝土基体残余应变的增长规律，提出了残余应变表征混凝土损伤的初步模型，，将混凝土劣化分为三个阶段。第一阶段由于内部溶液结冰膨胀混凝土基体开始产生膨胀性微裂纹，基体产生较大变形；第二阶段，混凝土内部裂纹开始导通，内部水分的迁移使得混凝土变形持续线性缓慢增长；第三阶段，混凝土内部裂纹密度增加，孔隙连通程度较大，疏松的饱水基体在冻胀力的作用下产生破坏性的大幅变形。 5）通过实验验证了对于单独作用下混凝土耐久性增强的三种措施，即掺加引气剂、表面树脂增强和钢纤维增强，对多因素协同条件下混凝土的耐久性增强依然有效。
[Abstract]:Concrete freeze-thaw damage will bring damage to the infrastructure in the negative temperature area. Concrete in practical service is usually subjected to complex mechanical loads and environmental factors, and its deterioration process is a complex process of physical, chemical and mechanical interaction. The durability of concrete under multi-factor conditions is studied. It can provide basis for durability evaluation and life prediction of practical concrete engineering, and guide concrete durability design in practical engineering. In this paper, the common concrete mixed with fly ash and slag powder (FA-BFS concrete) is used as the research object to simulate the multi-factors of concrete in practical engineering, and to explore the performance degradation law and evaluation method of concrete under multi-factor synergistic action. The deformation of concrete matrix was monitored by a adhesive strain gauge, and the changes of the matrix residual strain and the apparent frost heave coefficient during the freezing process were studied, and the results of comparison with the traditional freezing resistance parameters and the evolution law of the residual strain were combined. The damage model of freeze-thaw failure of concrete is proposed. In this paper, the following research results are obtained: 1) the form of concrete deterioration under the action of two factors and three factors and the influence of each factor on the deterioration process of concrete are clarified. 2) the concrete is characterized by strain. Internal damage caused by freezing and thawing. During freeze-thaw process, the concrete matrix produces irreversible residual strain, which is directly related to the formation and propagation of pore structure and cracks in the matrix under freeze-thaw conditions. It can be used to characterize the damage degree of the matrix. 3) the concept of the apparent frost heave coefficient of concrete during the freezing and thawing cycle cooling process is proposed. The method to characterize the freeze-thaw damage of concrete is established. 4) the freeze-thaw damage model of concrete based on residual strain is preliminarily established, and the preliminary idea of applying it to practical engineering is put forward. The growth law of residual strain in concrete matrix is analyzed by using Boltzmann function. A preliminary model of residual strain to characterize the damage of concrete is proposed. The deterioration of concrete is divided into three stages. In the first stage, the inner solution icing expansion concrete matrix began to produce expansive microcracks, and the matrix produced large deformation. In the second stage, the internal cracks of the concrete began to conduct. In the third stage, the density of internal cracks increases and the degree of pore connectivity increases. Under the action of frost heaving force, loose saturated matrix produces destructive large deformation. 5) through experiments, three measures to enhance the durability of concrete under single action, that is, adding air entraining agent, are verified. Surface resin reinforcement and steel fiber reinforcement are still effective for durability enhancement of concrete under multi-factor synergistic conditions.
【学位授予单位】：中国建筑材料科学研究总院
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU528.2

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