碳化过程中水泥基材料微结构演变的比较研究

发布时间：2018-05-24 07:24

本文选题：碳化 + 净浆　；参考：《东南大学》2015年硕士论文

【摘要】：混凝土结构内部碱性物质的碳化反应是影响混凝土耐久性的重要原因。现有关于碳化的定量预测模型中含有微结构参数的很少。为了深入地对混凝土使用寿命进行预测,有必要对水泥基材料碳化后不同碳化区微观结构差异进行研究。本文以水灰比、掺合料、加载和碳化浓度等不同条件下,对水泥净浆和砂浆进行了分区研究。采用。TG-DSC、MIP等测试方法,对其物相组成及孔结构变化等微结构演变进行了表征,为基于微结构的碳化模型的建立提供依据。试验结果表明,不管是净浆还是砂浆,水灰比越大,其完全碳化区尺寸、部分碳化区尺寸越大。相同水灰比条件下,净浆试件的完全碳化区尺寸、部分碳化区尺寸均大于砂浆试件。水泥净浆的部分碳化区尺寸随碳化龄期的延长而增大。水灰比越大,其pH值变化区越长,且pH值变化区尺寸与完全碳化区尺寸间比值越大。热重法测得的部分碳化区的长度大于pH值变化区长度。不管是砂浆还是净浆,试件总孔隙率、最可几孔径随着碳化方向的深度的加深而变大,即碳化程度越大,总孔隙率、最可几孔径越小。孔饱和度随着深度的增加而减小,即随着碳化程度的加深,孔饱和度增加。水泥净浆的部分碳化区(5-10mm)的总孔隙率、及孔饱和度均大于同水灰比的砂浆。不同CO_2浓度碳化试验表明：CO_2浓度越高,净浆试件部分碳化区尺寸越长,测得pH值变化区尺寸越大。CO_2浓度越低,碳化越充分,即碳化生成的碳酸钙含量越多,且碳化后部分碳化区、完全碳化区的孔隙率越小、饱和度越大；在碳化后试件的完全碳化区(0-5mm)与部分碳化区(5-10mm),总孔隙率及最可几孔径均随着浓度的增加而增大。即CO_2浓度越小,其部分碳化区孔径细化越明显。加掺合料试验表明：在本文试验条件下,与纯水泥净浆试件相比,掺合料(30%粉煤灰或50%矿粉)对0.35水胶比的水泥基材料碳化深度的影响并不明显,没有出现明显的部分碳化区,但碳化后大孔(孔径434nm的孔)占总孔的比例变大。加载碳化耦合试验表明：0.35水灰比砂浆试件碳化14天,其受拉区的部分碳化区尺寸大于受压区。相同水灰比,受拉区的碳化程度大于受压区。
[Abstract]:The carbonation reaction of alkaline substance in concrete structure is an important reason to affect the durability of concrete. Few of the existing quantitative prediction models for carbonation contain microstructural parameters. In order to predict the service life of concrete, it is necessary to study the microstructure difference of different carbonization areas after carbonization of cement based materials. In this paper, the partition study of cement mortar and mortar was carried out under different conditions, such as water-cement ratio, admixture, loading and carbonation concentration. The microstructure evolution such as phase composition and pore structure changes were characterized by means of .TG-DSC-MIP, which provided the basis for the establishment of carbonation model based on microstructure. The experimental results show that the larger the water-cement ratio is, the larger the size of the complete carbonization zone and the partial carbonization zone is. Under the same water-cement ratio, the size of the complete carbonation zone and the partial carbonization zone of the pure slurry specimen are all larger than that of the mortar specimen. The size of partial carbonation zone of cement paste increases with the increase of carbonation age. The larger the water-cement ratio, the longer the pH region and the larger the ratio between the size of the pH region and the size of the complete carbonization zone. The length of partial carbonation zone measured by thermogravimetric method is longer than that of pH value. Whether mortar or mortar, the total porosity of the specimen increases with the depth of carbonation direction, that is, the greater the carbonation degree, the smaller the total porosity and the most probable pore size. The pore saturation decreases with the increase of depth, that is, with the deepening of carbonization degree, the pore saturation increases. The total porosity and pore saturation of the cement paste are higher than those of the mortar with the same water / cement ratio. The carbonization test of different CO_2 concentration shows that the higher the concentration of CO_2 is, the longer the carbonation zone of the sample is, and the larger the size of the measured pH value is, the lower the concentration of CO _ 2 is, and the more adequate carbonation is, that is, the more calcium carbonate is produced by carbonation, the longer the size of the carbonation zone is. In the partial carbonation zone, the porosity of the complete carbonation zone is smaller and the saturation is larger, and the total porosity and the most probable pore size increase with the increase of the concentration of the carbonized specimen. The total porosity and the most probable pore size increase with the increase of the concentration. That is, the smaller the concentration of CO_2, the more obvious the pore size of the carbonized zone is. The experiment of adding admixture shows that, compared with the pure cement paste specimen, the effect of 30% fly ash or 50% mineral powder on the carbonation depth of cement based material with 0.35 water-binder ratio is not obvious, and there is no obvious partial carbonization zone. However, after carbonization, the proportion of large pore (pore size 434nm pore) to total pore becomes larger. The results of carbonization coupling test show that the size of the carbonization zone in the tensile zone is larger than that in the compression zone after 14 days of carbonization. At the same water / cement ratio, the carbonization degree of the tensile zone is greater than that of the compressive zone.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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