【作者】 时方稳；

【导师】 杜应吉；

【作者基本信息】 西北农林科技大学 ， 水工结构工程， 2012， 硕士

【摘要】 混凝土耐久性是混凝土最重要的性质，随着粉煤灰混凝土的推广，人们针对粉煤灰混凝土的研究也越来越多，其中粉煤灰混凝土的抗冻性能的研究是非常重要的组成部分，积累了许多宝贵的研究成果和实践经验。为丰富粉煤灰混凝土抗冻性理论研究的资料及工程设计、施工的实际需求，建立粉煤灰混凝土抗冻性预测软件是十分必要的。本文从粉煤灰混凝土冻融循环作用后的相对动弹性模量入手，探索了抗冻性能优劣的评价方法，通过数学建模的方法建立了粉煤灰混凝土抗冻性预测模型，进而开发出粉煤灰混凝土抗冻性预测软件。本文主要内容如下：（1）介绍了粉煤灰混凝土抗冻性的研究现状，分析了各种冻融破坏机理的优缺点，并以冻融损伤的观点看待冻融循环破坏现象。（2）结合前期的粉煤灰混凝土抗冻性试验研究成果，通过分析单因素条件下不同冻融循环次数后的动弹性模量和相对动弹性模量的变化趋势，得知含气量，水胶比和粉煤灰掺量对粉煤灰混凝土抗冻性能均有很大影响。随着水胶比的增大，混凝土动弹性模量减小，相对动弹性模量的下降速度加快；随着引气剂掺量的增加，即含气量的增大，混凝土动弹性模量与相对动弹性模量的下降速度变缓；随着粉煤灰掺量的增大，相对动弹性模量的下降速度加快，动弹性模量呈先减小，后增大，又减小的趋势，即针对确定的水胶比与含气量，存在最优粉煤灰掺量。即含气量的增加延缓了粉煤灰混凝土抗冻性能的劣化速度，而水胶比与粉煤灰掺量的增加加快了粉煤灰混凝土抗冻性能的劣化速度。（3）现行的评价混凝土抗冻性能优劣的标准是抗冻等级，这些抗冻等级都是一些离散点，对于同一个抗冻等级的两组混凝土，无法比较其抗冻性能的优劣，且离散点不利于预测模型的建立。本文从粉煤灰混凝土冻融循环作用后的相对动弹性模量入手，运用宏观唯象损伤力学确定了损伤度D的定义表达式，利用损伤度的连续性将粉煤灰混凝土抗冻耐久性指数DF与冻融循环次数N有机地结合起来，又参照其他经验模型，确立了抗冻耐久性指数与影响混凝土抗冻性的主要因素之间的数学关系表达式的基本结构。通过1stopt软件进行多元非线性回归分析，得出粉煤灰混凝土抗冻性预测数学模型。（4）利用Visual Basic6.0语言编写程序，开发出粉煤灰混凝土抗冻性预测软件，并用工程实例验证，事实说明该软件操作简便，具有较强的适应性和可靠性，能够满足工程实际的需要。更多还原

【Abstract】 Durability of concrete is concrete is the most important properties for fly ash concrete is also moreand more, with the promotion of fly ash concrete, which fly ash concrete frost resistance is a veryimportant part of, and accumulated a lot of valuable research results and practical experience. Informationfor the rich fly ash concrete frost resistance of theoretical research and engineering design, constructionrequirements, fly ash concrete frost forecasting software is essential. From the relative dynamic elasticmodulus of fly ash concrete freeze-thaw cycle after starting to explore the pros and cons of the evaluationof frost resistance of fly ash concrete frost forecasting model by the method of mathematical modeling,led to the development the fly ash concrete frost resistance prediction software. The main content of thispaper is as follows:(1) fly ash concrete frost resistance Research, analyze the advantages and disadvantages of the variousfreeze-thaw damage mechanism, look at the freeze-thaw cycle to the point of view of freeze-thaw damageand failure phenomena.(2) combined with the pre fly ash concrete frost resistance test research, by analyzing the single factorunder the conditions of the dynamic elastic modulus after the freeze-thaw cycles and relative dynamicmodulus of elasticity trends, that the gas content, water binder ratio and fly ash fly ash concrete frostresistance have a significant impact. With the increase of water-cement ratio, concrete, dynamic elasticmodulus decreases, the relative dynamic elastic modulus decreased faster; gas content increases with theincrease of air entraining agent dosage, ie, concrete, dynamic elastic modulus and trend of declineaccelerated relative dynamic modulus of elasticity of the rate of decline slows; with the fly ash contentincreases, the relative dynamic elastic modulus, dynamic modulus of elasticity was first decreases, thenincreases, and also reduces determine the water-cement ratio and air content, the optimum content of flyash. Increase in gas content to slow down the degradation rate of fly ash concrete frost resistance,water-cement ratio and the increase in fly ash accelerated the deterioration speed of the fly ash concretefrost resistance.(3) The current evaluation of concrete frost resistance merits of the standard is the antifreeze level, theseantifreeze levels are discrete points, with a freezing level of two sets of concrete, can not compare themerits of its frost resistance, and the discrete points is not conducive to the prediction model. Relative dynamic elastic modulus of fly ash concrete freeze-thaw cycle after starting the use of phenomenologicaldamage mechanics to determine the damage degree D defined expression, the use of the continuity of thedamage degree of frost durability of fly ash concrete The index DF and freeze-thaw cycles organicallycombine the reference to other empirical models, to establish the basic structure of the mathematicalrelationship between the expression of frost durability index of concrete frost resistance. By1stoptsoftware for multivariate nonlinear regression analysis, fly ash concrete frost resistance predictivemathematical model.(4) the use of Visual Basic6.0language programming, the development of the fly ash concrete frostforecasting software, and engineering example, the fact that the software is simple, strong adaptability andreliability to meet the practical engineering needs.更多还原