【作者】 任鹏；

【导师】 孟庆林；

【作者基本信息】 华南理工大学 ， 建筑技术科学， 2011， 博士

【摘要】 墙体开裂的防治一直是多学科领域和工程应用中长期关注的重要课题。但目前研究墙体开裂多集中于砌块或砌体的干燥收缩的控制,作为墙体干湿交替诱发变形过程中的湿胀问题一直没有给予充分重视。由于缺少专门的实验方法,国内外学者研究湿胀问题时不得不选用干缩测量方法代替,不符合膨胀发展规律,测量精度受到很大影响。因此,急需探索建立测量建筑材料湿胀性能的实验原理和方法,为科研和工程检测提供依据。本文针对吸水膨胀和吸湿膨胀两类湿胀现象,重点研究了膨胀发展规律及其测量方法：1.针对湿胀机理和过程进行了系统阐述。通过机理分析,发现现有干缩实验的原理和方法无法满足吸水膨胀实验要求,为此提出并建立了新的实验方法——动态吸水膨胀实验方法。基于对水中材料试件吸水过程进行的假设,解决了材料吸水量连续测量难题,论证了试件水中固定、膨胀量测量以及标距定位等关键问题。2.根据动态吸水膨胀实验原理和方法,建立了一套吸水量和膨胀量测量、记录的动态湿胀测量装置。实现了吸水膨胀过程的连续、自动、精确的测量,消除了人工测量误差,避免传统实验中由试件频繁出入水中导致的吸水过程不连续,以及在实验初期吸水膨胀过快导致的测量不准确等难题。3.根据试件吸水过程的假设和标距定位原理和方法,推导出湿胀过程的膨胀值和吸水率瞬态计算模型,并应用动态湿胀测量装置对加气混凝土砖、灰砂砖、混凝土砖以及加气混凝土砌块进行了动态吸水膨胀实验,确定了动态吸水膨胀实验结束判据；从微观层面分析了典型砌墙砖的吸水发展过程和膨胀发展过程,并分别拟合双指数衰减吸水率-时间实验模型和膨胀-时间实验模型；分析了材料吸水膨胀规律,获得了吸水膨胀过程的分段函数实验模型,研究表明,加气混凝土砖、灰砂砖和混凝土砖吸水膨胀在0-2h、0-2h和0-15min的首段遵循幂函数增长规律;加气混凝土砖和灰砂砖2h后时段遵循S型曲线增长规律；混凝土砖15min后时段遵循直线增长规律。4.采用动态吸湿膨胀实验方法,对加气混凝土砖、灰砂砖、混凝土砖进行了动态吸湿膨胀实验。讨论并确定了砌墙砖尺寸试件的动态吸湿膨胀实验的结束判据：4d膨胀变化量-0.001mm与吸湿曲线贴近渐近线。从微观层面分析了各区间和总体的吸湿膨胀发展规律,得到了吸湿膨胀实验模型。表明,在恒温环境、相对湿度40%-80%条件下,加气混凝土砖吸湿膨胀遵循指数发展规律,灰砂砖和混凝土砖符合S型曲线发展规律。更多还原

【Abstract】 The crack prevention of walls is an important problem in multidiscipline fields and structure engineering, but it is almost focused on the restraint of drying shrinkage of blocks and masonry structures. Hygric expansion as a important part of dry-wet cycling is not payed attention. Because lack of the definite test method, drying shrinkage test method always is used in the research and test of hygric expansion, which isn’t in conformity with hygric expansion discipline and influnce the measurement precision. Therefore, it’s exigent to build up a test principle and method of wall material hygric expansion in order to provideing the scientific data for research and engineering detection. As to the phenomenon of water expansion and moisture expansion, this thesis is to study the expansion discipline and its measuring method. The main research works are as follows:1. The thesis expound systematically moisture expansion mechanism and process. Through the analysis of the mechanism, it’s found that the existing drying shrinkage test principle and method can’t meet the challenge of water expansion test. So dynamic measuring method of water expansion as a new test method is proposed. Through supposing the water absorption mode, it’s successful solved of dynamic measurement of water aborption in water. And solutions of the fixed method, expansion measurement, standard bar of test piece are proposed.2. On basis of dynamic test principle and method of water absorption and expansion, a dynamic moisture expansion measuring equipment (DMEME) as a measuring function of water absorption and expansion is developed, which achieves the measurement of continuity, automaticity and accuracy; DMEME eliminates manual work error, avoids water absorption process interrupted, and water expansion process is hard to measure in initial period of the test.3. Based on water absorption mode supposition and principle and method of the gauge length positioning system, the thesis deduces caculation model of water absorption and expansion, and chooses a aerated concrete brick, lime-sand brick, concrete brick and aerated concrete block to do a dynamic water expansion test. The test finishing criterion is discussed. From the microcosmic aspect, water absorpton process and expansion process of typical wall brick are analysed, and water absorption-time test models and expansion-time test models with the double exponential decay function are fitted respectively. The water expansion discipline is analysed, and the test models of piecewise function on basis of water absorption properties are fitted respectively:the water expansion test models of the aerated concrete brick, lime-sand brick and concrete brick follow the power function growth law in their frist step; those of the aerated concrete brick and lime-sand brick follows the S-type cruve growth law, and the concrete brick follow a straight line model.4. Using the dynamic moisture expansion test method, the thesis chooses a aerated concrete brick, lime-sand brick and concrete brick to do a dynamic moisture absorption expansion test. The test finishing criterion should be decided commonly by expansion change which over a period of 4 d is less than 0.001mm and the curve values which is close to the asymptotic final value. From the microcosmic aspect, moisture expansion process are all analysed in each and whole section, and moisture expansion test models are fitted:the water expansion test models of the aerated concrete brick follows exponential function growth law, and these of the lime-sand brick and concrete brick follow the S-type cruve growth law in constant temperature and 40%-80% relative humidity conditions.更多还原