【作者】 杜鹏；

【导师】 姚燕； 王玲；

【作者基本信息】 中国建筑材料科学研究总院 ， 材料学， 2014， 博士

【摘要】 实际服役混凝土结构通常处于复杂的环境因素作用下，其劣化过程是物理、化学和力学等因素耦合作用的过程，这些因素耦合作用造成的混凝土损伤远大于各因素单独作用的叠加。为指导实际工程中混凝土的配合比设计，混凝土耐久性及寿命预测体系的研究趋势和热点已由单一因素向多因素耦合作用发展。然而，以冻融为主因素的多因素耦合作用下的混凝土耐久性研究还显得不足，存在以下问题：多因素耦合作用下的混凝土耐久性评价还采用以往用于单因素作用下的评价指标，即评价方法相对落后于实际的耐久性研究；现有混凝土损伤模型和寿命预测体系多是基于单因素作用下的；对已经取得的成果还缺乏归纳总结。为解决上述问题，本文首先开发了混凝土冻融耐久性数据库系统，对以往学者的试验数据与参考模型进行归纳总结，以此作为建模的前提基础之一；然后，用应变表征了多因素耦合作用下混凝土的耐久性能，以此作为建模的另外一个前提基础；最终，建立了两个多因素耦合作用下的混凝土损伤模型并结合寿命预测方法对实际工程进行了寿命评估和预测，为有抗冻要求的服役混凝土耐久性设计和寿命预测研究提供了新思路。本文主要试验工作及结果如下：1）开发了混凝土冻融耐久性数据库系统。借助于RILEM TC246-TDC技术委员会平台，收集到来自15个国家和地区的34位著名学者关于多因素耦合作用下混凝土耐久性研究成果以及冻融损伤与寿命预测模型；经过严格的筛选得到入库试验数据和模型，并与计算机技术相结合，打造了数据管理的集成化平台，具有跨平台性和可扩展性等优点以及查询和搜索功能。2）用应变表征了多因素耦合作用下混凝土的耐久性能。无损监测的应变具有实时性、连续性，冻融（简称FTC）单因素作用下，混凝土残余应变的产生证明了混凝土基体的损伤是一个不断累积的不可逆的劣化过程，它与基体内部裂纹的不断萌生与扩展直接相关；冻融和盐溶液侵蚀（简称FTC-Cl）双因素作用下，同一配合比混凝土在3.5wt.%的NaCl溶液中冻融产生的残余应变比水冻大，说明盐溶液加速了混凝土的冻融损伤；冻融、盐溶液侵蚀和弯曲应力（简称FTC-Cl-BS）三因素耦合作用下，施加恒定的弯曲应力比越大，混凝土试件拉应力区的应变与残余应变均越大，说明应力的施加加速了混凝土的损伤劣化。3）建立了混凝土的残余应变冻融损伤演化方程。在FTC单因素、FTC-Cl双因素和FTC-Cl-BS三因素耦合作用下，混凝土的残余应变变化规律均符合单段或双段变化模式，单段变化模式一般适用于抗冻性较强的混凝土，双段变化模式一般适用于抗冻性较差的混凝土；结合混凝土冻融耐久性数据库系统中其他学者的残余应变数据，对演化方程进行验证，结果显示计算值和实测值之间具有较高的吻合度。4）建立了基于残余应变的FTC-Cl双因素耦合作用下混凝土冻融损伤数值模型（M-FTC+Cl）。该损伤数值模型适用于FTC单因素和FTC-Cl双因素作用，对混凝土损伤程度变量曲线的拟合相关系数在0.95以上；该模型还可以预测特定条件下混凝土的最终快速冻融循环次数，再结合寿命预测方法可以预测特定环境下服役混凝土的安全使用寿命。5）将冻融损伤、盐溶液侵蚀等环境因素进行了力学统一等效转化，建立了基于应变的FTC-Cl-BS三因素耦合作用下混凝土损伤力学模型（M-FTC+Cl+BS）。该损伤力学模型适用于FTC-BS双因素和FTC-Cl-BS三因素作用，模型建立了应变与快速冻融循环次数之间的关系；利用该模型计算的混凝土最终快速冻融循环次数与实际测量值非常接近；该模型结合寿命预测方法可以预测特定环境下服役混凝土的安全使用寿命。6）将冻融损伤模型与实际工程的寿命预测相关联，对实际工程进行了寿命预测。通过计算，长白山飞行区跑道、停机坪混凝土的使用寿命预测值分别为43年和52年，符合最低设计年限为30年的要求；青岛海湾大桥承台、箱梁混凝土的使用寿命预测值分别为144年、110～123年，也符合设计使用寿命100年的使用要求。更多还原

【Abstract】 In fact, concrete in service is usually subject to complex environmental factors.Its deterioration is a process with coupling action including physics, chemistry,mechanics and so on. The damage caused by these coupling factors is far greater thanthat caused by a sum of each action. To guide the durability design of concrete inpractical projects, the research tendency on concrete durability and service lifeprediction system is developing from single factor to multiple factors. But there aresome problems on freeze-thaw durability research of concrete under multi-factorcoupling. Firstly, the durability research of concrete under multi-factor coupling alluses the test parameters under single factor. In other words, the evaluation method islagging behind the actual durability research. Secondly, the present damage modelsand service life prediction system of concrete are mostly established under singlefactor. Finally, lack of summary for the present research results of concrete durabilityunder multiple factors leads to that it is not easy to perfect the research system andrealize the accuracy and continuity of service life prediction system.To solve the problem above, a database system of concrete freeze-thawdurability as one of the premises to establish service life prediction models wasdeveloped to summarize the previous test results and reference models. Then strainwas used to analyze the damage and deterioration in concrete under multi-factorcoupling as another premise to establish service life prediction models. Finally, twofreeze-thaw damage models were established and used to evaluate and predict theservice life of practical engineering combined with freeze-thaw comparing relationbetween inside and outside, providing a new approach to predict the service life andguidance for durability design of concrete which is required for frost resistance. Thefollowing research results were obtained.1) A database system of concrete freeze-thaw durability was developed. With theaid of RILEM TC246-TDC as the platform, the durability research results, thefreeze-thaw damage and service life prediction models of concrete under multi-factorcoupling were collected from34famous scholars who are from15countries. Theexperimental data and models in the database were filtered strictly. These materialsscience results were combined with the computer technology, creating an integrateddata management platform. The database system has the feature of goodacross-platform, powerful expansibility, etc and the function of query and search.2) Strain was used to characterize the concrete durability under multi-factorcoupling. Strain may have certain inherent advantages when compared to other testparameters, such as real-time nondestructive monitor, more accurate and continuouswith little error that is caused by manual intervention, etc. Under single factor offreeze-thaw cycles (FTC), the produced residual strain proves that the damage of concrete matrix is a continued accumulated and irreversible deterioration process.This process is directly related to the continued initiation and propagation of cracks inmatrix. Under freeze-thaw cycles coupled with chloride attack (FTC-Cl), the residualstrain produced in3.5wt.%NaCl solution is larger than in water, showing that theNaCl solution accelerates the freeze-thaw damage of concrete. Under freeze-thawcycles, chloride attack coupled with bending stress (FTC-Cl-BS), the strain andresidual strain of concrete tensile region are both larger with the larger constantbending stress ratio, showing that the applied stress accelerates the damage ofconcrete.3) The residual strain freeze-thaw damage evolution equation was established.Under FTC, FTC-Cl and FTC-Cl-BS, the residual strain variation all conforms to asingle-segment variation mode or a double-segment variation mode. Thesingle-segment variation mode applies to the concrete that has better frost resistance,and the double-segment variation mode applies to the concrete that has poorer frostresistance. Furthermore, the validation of residual strain freeze-thaw damageevolution equation shows that there is good agreement between computed data andmeasured data.4) The freeze-thaw damage numerical model of concrete subject to FTC-Cl wasestablished based on residual strain. This damage numerical model applies to both thesingle factor of FTC and the two factors of FTC-Cl. The correlation coefficients of thedamage degree variable curve of concrete fitted by the model are all greater than0.95.The model can also predict the final number of rapid freeze-thaw cycles of concreteunder certain conditions, and then can predict the safe service life of concrete inservice under certain environmental factors combined with service life predictionmethod.5) Converting the microscopic action mechanism to a macroscopic mechanicaleffect, the damage mechanical model of concrete subject to FTC-Cl-BS wasestablished based on strain. This damage mechanical model applies to both twofactors of FTC-BS and three factors of FTC-Cl-BS, and establishes a relationshipbetween strain and number of rapid freeze-thaw cycles. The model computed data ofthe final number of rapid freeze-thaw cycles is very close to the measured data. Themodel can predict the safe service life of concrete in service under certainenvironmental factors combined with service life prediction method.6) Associating the established damage models with service life prediction ofpractical engineering, the service life of practical engineering was predicted. Bycomputing, the predicted service life of concrete of the airport runway and the tarmacused in Changbaishan airport are43years and52years respectively, meeting therequirement of the designed minimum service life of30years. The predicted servicelife of concrete of the bearing platform and the box girder used in Qingdao BayBridge are144years and110～123years respectively, also meeting the requirement of the designed service life of100years.更多还原