C80高性能混凝土微结构高温损伤演化研究

发布时间：2018-01-16 21:19

本文关键词：C80高性能混凝土微结构高温损伤演化研究　出处：《太原理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：高强高性能混凝土因其强度高、承载能力大、性能好的优点,在现代工程中应用广泛。但高强高性能混凝土结构密实,高温下极易发生爆裂,在高强高性能混凝土中添加聚丙烯纤维是较常用的抑制其爆裂的方法。研究高强高性能混凝土内部微结构高温损伤演化的规律,对高强高性能混凝土爆裂机制和聚丙烯纤维抗爆裂机理的研究有重要意义。本文依托国家自然科学基金(批准号:51278325),主要利用X射线CT技术(CT)对高温下C80高性能混凝土(以下简称HPC)和C80掺聚丙烯纤维高性能混凝土(以下简称PPHPC)进行细观损伤演化研究;使用压汞测试方法(MIP)对C80 HPC和C80 PPHPC进行高温后微观损伤演化研究;使用扫描电镜(SEM)研究高温后C80 PPHPC的微观形貌。主要内容如下:1.CT图像的定性分析通过试验得到HPC、PPHPC在不同温度下的CT图像,对CT图像中混凝土内部各组分进行识别和分析,描述孔隙、裂缝等随温度升高的变化情况。观察发现:HPC、PPHPC中的孔径随着温度的升高而扩大。HPC中一般从400℃时开始出现温度裂缝,裂缝数量较少。PPHPC自300℃开始出现温度裂缝,400℃作用下裂缝数量急剧增多,裂缝数量多于HPC。2.CT图像定量分析对HPC、PPHPC的CT图像进行灰度分析,使用Matlab软件得到HPC、PPHPC CT图像的灰度直方图,并进行像素数量统计。HPC、PPHPC的灰度直方图形状随温度的升高出现峰值左移或者小灰度像素数量增多,像素统计结果发现HPC、PPHPC内部缺陷随温度的升高而逐渐劣化。使用软件对HPC、PPHPC CT图像中的裂缝进行提取,计算裂缝的长度、宽度、面积和周长,追踪裂缝在温升过程中的发展情况,结果显示:单条裂缝的长度、宽度、面积和周长会随着温度的升高而增长。裂缝总数量、总长度、宽度、总面积和总周长都随温度的升高而增大,PPHPC裂缝的总参数大于HPC。3.孔结构分析利用压汞测试技术对不同温度作用后的HPC、PPHPC试件进行孔结构测定。结果显示除300℃外,HPC、PPHPC孔隙率变化趋势相似,HPC、PPHPC平均孔径随温度升高而降低、孔比表面随温度的升高而增加。孔隙分布显示HPC、PPHPC在400℃作用后劣化严重,在500℃后产生新一轮劣化,600℃、700℃作用后损伤严重。300℃作用后PPHPC劣化开始,HPC劣化已较严重,HPC孔隙形成“蒸养条件”使得孔隙率低于PPHPC,400℃作用后HPC多害孔占比多于PPHPC,掺入聚丙烯纤维改善高强高性能混凝土高温性能。根据分形几何学知识和压汞试验结果,使用两种数学模型计算孔结构的分形维数。研究表明:不同数学模型计算出的分形维数有所不同,HPC、PPHPC的分形维数在不同温度段、不同孔径范围内差别较大,随温度变化显示出不同的分形特征。4.扫描电镜分析使用扫描电镜技术对常温、300℃、500℃作用后PPHPC微观形貌进行观察。常温时,浆体中的C-S-H、Ca(OH)_2、钙矾石都能显示出其相应的形貌;钙矾石在300℃时已完全分解,C-S-H逐渐变疏松;500℃作用后,Ca(OH)_2已分解,C-S-H极其松散。微观层次上物相的变化直接导致了高强高性能混凝土高温后性能的劣化。
[Abstract]:High strength and high performance concrete with high strength, large bearing capacity, has the advantages of good performance, widely used in modern engineering. But the high strength and high performance concrete dense structure, high temperature easily burst, adding polypropylene fiber in high strength and high performance concrete is more commonly used in the burst suppression. The research of high strength and high performance the concrete internal structure of high temperature damage evolution, it has important significance to study the performance of the Gao Qianggao mechanism and the polypropylene fiber concrete burst spalling mechanism. Based on the National Natural Science Fund (No. 51278325), the main use of X ray CT (CT) of C80 high performance concrete under high temperature (hereinafter referred to as HPC) and C80 polypropylene fiber reinforced high performance concrete (hereinafter referred to as PPHPC) of meso damage evolution research; using test method of mercury (MIP) on C80 HPC and C80 PPHPC after high temperature micro damage evolution Study; using scanning electron microscopy (SEM) morphology of C80 on PPHPC after high temperature. The main contents are as follows: the qualitative analysis of the 1.CT images obtained by HPC test, PPHPC CT images at different temperatures, the concrete CT image components were identified and analyzed, describing the pore, crack changes with temperature rise the observation showed that HPC, PPHPC in diameter with the temperature increasing and expanding.HPC generally from 400 degrees occurred when the temperature cracks, cracks began to appear a small number of.PPHPC temperature cracks from 300 DEG, 400 DEG C under the effect of a sharp increase in the number of cracks cracks, more than the number of HPC.2.CT image quantitative analysis of HPC CT image PPHPC gray scale analysis using Matlab software HPC, PPHPC histogram of CT image, and the number of pixels statistics.HPC, PPHPC histogram shape with the increase of temperature at the peak of the left or small The increase in the number of pixels, the pixel statistical results found that HPC, the internal defects of PPHPC with temperature increasing deterioration. The use of HPC software, PPHPC CT crack in the image extraction, calculation of crack length, width, area and perimeter track, cracks in the temperature rise in the process of development, the results show that the single crack the length, width, area and perimeter will increase with the increase of temperature. The total number of cracks, total length, width, total area and total perimeter are increased with the increase of temperature, the total crack parameter PPHPC is greater than HPC.3. the analysis of pore structure by different temperature on HPC after mercury testing technology, PPHPC test hole determination of structure. The results showed that in addition to 300 DEG C, HPC, PPHPC, HPC, porosity change tendency is similar, the average pore size of PPHPC decreases with the increase of temperature, pore specific surface increases with the increase of temperature. The pore distribution of HPC, PPHPC in 400 The deterioration of the temperature effect, produce a new round of deterioration in 500 DEG C 600 C, 700 C C.300 serious injury effect after PPHPC degradation, HPC degradation is more serious, HPC pore forming "steam curing condition makes the porosity is lower than 400 DEG PPHPC, after HPC and hole accounted for more than PPHPC, polypropylene fiber to improve the high temperature performance of high strength and high performance concrete. According to the fractal geometry knowledge and MIP test results, calculate the fractal dimension of pore structure using two kinds of mathematical models. The study shows that the fractal dimension of different mathematical model to calculate the different, HPC, PPHPC of the fractal dimension in different temperature range. The scope of different pore diameter vary greatly, with the change of temperature shows the fractal characteristics of.4. scanning electron microscope analysis of different temperature, using scanning electron microscopy in 300 DEG, 500 DEG C after PPHPC morphology were observed. At room temperature, slurry in C-S-H, Ca (OH) _2, the ettringite can show the corresponding morphology; ettringite has been completely decomposed at 300 DEG C, C-S-H gradually become loose; 500 DEG C after the action of Ca (OH) _2 decomposition, C-S-H is extremely loose. The micro level changes phase directly leads to the deterioration of high strength and high performance concrete after high temperature performance.

【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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