大掺量矿渣水泥基材料孔隙结构与透气性研究

发布时间：2019-03-27 18:59

【摘要】：大掺量矿渣水泥基材料已经在土木工程中得到了广泛运用，其耐久性问题越来越受到重视。孔隙结构是决定材料耐久性的重要因素，而渗透性是表征其耐久性的重要指标，研究大掺量矿渣水泥基材料孔隙结构及其渗透性对准确预测结构全寿命周期的耐久性、降低结构使用成本具有重要意义。论文选用水胶比分别为0.3、0.4以及0.5的掺加70%矿渣的净浆及砂浆材料为研究对象，选用相同配合比但不掺矿渣材料作为对照组，，通过MIP孔隙结构测试方法研究不同因素对水泥基材料孔隙结构的影响，并联系工程实际情况，研究了在不同养护条件下水泥基材料孔隙结构的变化；同时采用基于CEMBUREAU气体渗透测试方法的改进方法，选用水胶比为0.28，掺加30%矿渣以及水胶比为0.4，掺加70%矿渣的砂浆及混凝土材料进行气体渗透性研究，并选择绝干、20%、40%、60%以及80%等五个饱水度状态测试了不同饱水度对水泥基材料气体渗透性的影响。研究结果表明掺加70%矿渣会使材料10nm以上孔隙体积减少而10nm以下孔隙体积大幅增加，材料孔隙率、比表面积上升，平均孔径降低，并且水胶比越低，小于10nm孔隙占总孔隙比例越高；养护过程中水分不足会导致材料水化过程中出现自干燥现象，在100~1000nm孔径范围出现大量孔隙，同时削弱1000nm以下孔隙数量，材料孔隙率升高，孔隙曲折度增大；不掺矿渣材料比表面积增大，而掺加矿渣比表面积降低。材料气体渗透性受材料组成影响很大，试验中发现模具过高或者振捣过度会导致材料出现分层，从而导致同一试件上下部分气体渗透测试结果相差较大；砂浆试件孔隙率φ和平均孔径D的乘积φD2与本征渗透系数成线性关系，但是孔隙率降低到一定程度时气体渗透系数就会降至0，混凝土试件孔隙结构与气体渗透系数之间的关系则不明显；渗透系数与饱水度之间的关系大致符合Kr=(1-Sw)η(1-Sw1/m)2m的关系，不同材料渗透系数随饱水度变化的规律不同，所得到的拟合参数也会有所不同。论文最后提出了一种专用于高整体容器混凝土材料气体渗透测试的试件预处理方法。
[Abstract]:Large amount of slag cement-based materials have been widely used in civil engineering, and its durability has been paid more and more attention. Pore structure is an important factor to determine the durability of materials, and permeability is an important index to characterize its durability. The study on pore structure and permeability of cement-based materials with large amount of slag can accurately predict the durability of the whole life cycle of the structure. It is of great significance to reduce the cost of structural use. In this paper, the water-binder ratio is 0.3, 0.4 and 0.5 respectively with 70% slag and mortar materials as the research object, and the same mix ratio but no slag material as the control group. The influence of different factors on the pore structure of cement-based materials was studied by means of MIP pore structure test method, and the change of pore structure of cement-based materials under different curing conditions was studied. At the same time, the modified method based on CEMBUREAU gas permeability test method is adopted. The gas permeability of mortar and concrete with 30% slag, 0.4% slag and 70% slag is studied. The ratio of water to binder is 0.28, the ratio of water to binder is 0.4, and the ratio of slag to cement is 0.4, and 70% slag, respectively. The effects of different saturation degrees on the gas permeability of cement-based materials were tested in five saturation states: absolute dry, 20%, 40%, 60% and 80%. The results show that when 70% slag is added, the pore volume above 10nm decreases and the pore volume below 10nm increases greatly. The porosity, specific surface area and average pore size decrease, and the lower the ratio of water to binder is, the higher the pore volume is, and the lower the pore volume is below 10nm. The ratio of pores smaller than 10nm to total pores is higher; The lack of moisture in the curing process will lead to self-drying phenomenon in the hydration process of the material, a large number of pores appear in the 100~1000nm pore size range, and at the same time weaken the number of pores below 1000nm, the porosity of the material increases, the porosity of the material increases and the porosity curvature increases. The specific surface area of slag-free material increases, while the specific surface area of slag-free material decreases. The gas permeability of the material is greatly affected by the composition of the material. It is found in the experiment that too high mold or excessive vibration will lead to the delamination of the material, which leads to a great difference in the gas permeability test results between the upper and lower parts of the same test piece. The product of porosity 蠁 and average pore diameter D of mortar specimens 蠁 D2 has a linear relationship with intrinsic permeability coefficient, but the gas permeability coefficient will decrease to 0 when porosity decreases to a certain extent. The relationship between pore structure and gas permeability coefficient of concrete specimens is not obvious. The relationship between permeability coefficient and saturation is in accordance with the relation of Kr= (1-Sw) 畏 (1-Sw1/m) 2m. The variation of permeability coefficient with saturation degree is different, and the fitting parameters are also different. At the end of the paper, a pre-treatment method for testing gas permeability of high integral container concrete materials is presented.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU528

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