受冻融混凝土耐久性及荷载耦合下钢筋混凝土粘结性能研究

发布时间：2018-03-04 20:50

本文选题：混凝土　切入点：耐久性　出处：《西安建筑科技大学》2013年博士论文　论文类型：学位论文

【摘要】：寒冷地区经常与水接触的建筑物或构筑物、使用除冰盐的桥面和路面混凝土常发生冻融破坏。混凝土一旦发生冻害，治理将相当困难，同时与其它耐久性因素如碳化和氯盐侵蚀产生复合叠加作用，严重威胁工程结构的使用寿命。渗透型防水涂料对基材具有良好防护效果而又不影响基材的透气性，受到广泛的关注。但是渗透型防水涂料应用于受冻融混凝土耐久性防护并不多见。除了受到环境因素的影响之外，这些结构或构件还要承受机械荷载的作用。国内外尚没有荷载和冻融耦合作用对钢筋混凝土粘结性能影响的报道。因此本文主要开展如下几个方面的研究工作：（1）基于原材料对混凝土抗冻性影响分析的基础上，制作了三种水灰比非引气混凝土和一种水灰比引气混凝土，重点研究四种冻融方式情况下混凝土相对动弹性模量和抗压强度的劣化规律，对混凝土冻融破坏机理进行深入探讨。结果表明，冻融方式对混凝土冻融损伤程度的影响顺序为：饱水冻融＞水冻-气冻循环＞饱水气冻＞非饱水气冻。通过混凝土冻结和融解过程分析，认为内部毛细孔水冻结时产生的结冰压是冻融破坏主要驱动力，降低混凝土内部饱水度可以提高混凝土的抗冻性能。（2）从毛细吸收理论入手，系统研究混凝土干燥程度、环境温度、水浸没试块的深度以及环境的相对湿度对混凝土毛细吸收的影响，从宏观和微观角度研究经受冻融循环后混凝土的吸水性和微观孔结构变化；定量研究受冻融混凝土采用渗透型涂料表面处理后的吸水特性，表面磨损对吸水性能的影响，分析了受冻融混凝土表面处理后的水分侵入机理。结果表明，同一配比混凝土，非引气混凝土毛细吸收系数随着经受循环次数增加而成倍数增大，且增加的趋势对水灰比越大的混凝土愈明显。受冻融混凝土经表面处理后，吸水能力大幅度降低。如果混凝土出现磨损，势必会消减表层混凝土的憎水层厚度，，对其防水效果产生一定的影响。对冻融损伤严重的混凝土，憎水层会变得疏松，使得外部液态水从“水汽传输”逐步过渡到与内部非憎水区的凝结水形成“水路传输”，是冻融损伤混凝土表面防水过早失效的根本原因。（3）开展实验室条件下受冻融混凝土氯离子侵入性能试验研究。结果表明，混凝土冻融损伤对氯离子扩散性能的影响是显著的。混凝土氯离子扩散系数与冻融损伤符合指数函数关系：D F D0ek 。基于Fick第二定律，推导出考虑冻融损伤和冻融剥落影响的氯离子传输模型。通过北京旧西直门立交桥和青岛胶州湾海底隧道验证和应用表明，该模型能够满足工程简单实用要求。（4）研究受冻融混凝土表面防水处理后，室外暴露环境下抗碳化和氯离子侵入性能，以及快冻环境下单面盐冻剥落性能；分析了表面处理后混凝土的盐冻破坏机理。混凝土遭受冻融循环次数不同，硅烷防护对室外暴露混凝土的碳化性能有不同程度的影响。表面处理对未经受冻融循环作用混凝土提高碳化寿命34%，对经受冻融循环作用混凝土的抗碳化能力有所降低。无论混凝土是否经受冻融，对抗氯离子侵蚀和混凝土抗盐冻剥落能力均有良好的防护效果。考虑冻融损伤影响系数、渗透型材料影响系数修正了碳化深度预测模型，给出冻融损伤混凝土抗氯离子侵入所需要的最低硅烷凝胶用量。（5）设计非引气混凝土和引气混凝土两种直拉粘结试件36个，通过自行设计的持载装置，实现了钢筋持载与冻融循环的耦合，并通过中心拉拔试验研究钢筋混凝土粘结性能的退化规律；理论计算证明钢筋与混凝土温度线膨胀系数差异导致界面脱胶的破坏本质；揭示钢筋持载状态下钢筋混凝土粘结性能加剧退化的机理。结果表明，混凝土冻融损伤较小时，钢筋持载对粘结性能影响较小；当混凝土经受多次的冻融循环，冻融损伤度达到0.5时，较小的钢筋持载水平就能够加速钢筋与混凝土粘结性能退化。对引气混凝土粘结试件，持载和冻融复合叠加作用对钢筋混凝土粘结性能影响不明显。（6）研究修复层材料、修复层横向配筋以及冻融对钢筋混凝土粘结性能的影响，并根据试验结果提出具有借鉴性的建议。结果表明，由于SHCC基体具有良好的抗冻能力，材料本身具有良好的耐久性和多缝开裂特性，与老混凝土良好的粘结性能，能够提高钢筋粘结强度、延性和耐环境作用能力，并减小冻融循环作用对钢筋粘结性能的影响，对延长结构的剩余使用寿命非常有利。
[Abstract]:Cold regions often come into contact with water in buildings or structures, the use of deicing salt bridge deck pavement concrete and concrete freeze-thaw damage often occurs. Once the occurrence of frost damage, governance will be difficult, and other factors such as durability, carbonation and chloride corrosion to produce a composite additive effect, a serious threat to the service life of engineering structure of permeable. The waterproof coating has good protective effect on the substrate and does not affect the permeability of the material, has been widely concerned. But the permeation type waterproof coating applied to the freeze-thaw durability of concrete protection is rare. In addition to the influence of environmental factors, the role of these structures to withstand mechanical loads. There is no load and the effects of freezing and thawing the coupling effect on the bond performance of reinforced concrete reports at home and abroad. This paper mainly carried out several aspects of the research work are as follows:
(1) based on the analysis of raw materials on the frost resistance of concrete, making three kinds of non air entraining concrete water cement and a water cement ratio of air entraining concrete, focuses on four kinds of frozen thawing deterioration of concrete way under the condition of relative dynamic elastic modulus and compressive strength of concrete, freeze-thaw damage mechanism are discussed. The results show that freeze-thaw of concrete freezing thawing damage degree of influence order is: saturated freezing thawing of frozen water, gas water freezing, freezing cycle > saturated unsaturated water freezing. Through the concrete freezing and thawing process analysis, internal freezing capillary water generated when the ice pressure is frozen destroy the main driving force, reduce the degree of saturation in concrete can improve the frost resistance of concrete.
(2) from the capillary absorption theory of system of concrete drying degree, environmental temperature, relative humidity and water immersion test block depth and environmental influence on concrete capillary absorption, from the perspective of macro and micro research under freeze-thaw cycles water absorption of concrete and micro pore structure change; quantitative study on characteristics of freezing and thawing of concrete the water permeable coating after surface treatment by surface wear effects on water absorption properties, analysis of freezing and thawing of concrete surface treatment after the water invasion mechanism. The results show that the same ratio of concrete, air entraining concrete capillary absorption coefficient with the number of cycles subjected to multiple increases, and the increase of water cement ratio the greater the more obvious. The concrete freezing and thawing of concrete after surface treatment, greatly reduce the water absorption capacity. If the concrete wear, will cut the surface layer of concrete The thickness of the hydrophobic layer has a certain influence on the waterproof effect of freeze-thaw damage of concrete is serious, the hydrophobic layer will become loose, so that the external liquid water from the water vapor transmission "and gradually transition to the internal condensation of water repellent region to form a" water transfer ", is the fundamental reason of freeze thaw damage of concrete surface waterproof premature failure.
(3) to carry out the experimental research on the chloride ion penetration of freeze-thaw concrete under laboratory conditions. The results show that the influence of concrete freezing thawing damage on chloride diffusion is remarkable. The chloride diffusion coefficient of concrete is in accordance with exponential function relation with freeze thaw damage: D F D0ek.
Based on the second law of Fick, a chloride transport model considering the effects of freeze-thaw damage and freeze-thaw spalling is derived. Through the validation and application of Beijing old Xizhimen flyover and Qingdao Jiaozhou Bay Subsea Tunnel, it is shown that the model can meet the simple and practical engineering requirements.
(4) study on the freeze-thaw treatment of concrete surface waterproof, anti carbonation and chloride ion penetration performance of outdoor environment, and fast freezing environment of single side salt scaling properties; analysis of surface treatment of concrete salt freezing damage mechanism of concrete subjected to freeze-thaw cycles. Different silane protection have different effects on the outdoor exposed concrete carbonation. The surface treatment of the action of freezing thawing of concrete carbonation life improve 34%, to withstand freezing and thawing of concrete carbonation resistance decreased. No matter whether the concrete subjected to freeze-thaw resistance, chloride ion erosion and concrete salt freezing stripping ability has a good protective effect. Considering the freeze-thaw damage effect influence of permeability coefficient, material modified prediction model of carbonation depth, minimum silane gel gives the freeze-thaw damage of concrete anti chloride ion needed for The amount of.
(5) the design of the air entraining concrete and air entraining concrete two straight pull adhesive specimen 36, through a self-designed loading device, the steel loading and freezing thawing cycle coupling, and the degradation of pull-out tests of reinforced concrete bonding properties; theoretical calculations show that the temperature of steel and concrete the expansion coefficient difference leads to the destruction of nature of interfacial debonding; steel reinforced concrete bond to reveal the performance of load increasing degradation mechanism. The results show that the damage is small freezing and thawing of concrete, reinforced loading has little effect on the bonding performance; when the concrete subjected to freeze-thaw cycle times, freeze-thaw damage degree is 0.5, smaller bar the load level can accelerate the degradation of bonding properties between reinforcement and concrete. The air entraining concrete specimen, loading and freeze-thaw effect on adhesive properties of composite reinforced concrete impact is unknown Explicit.
(6) study of repair layer materials, repair layer of transverse reinforcement and freeze-thaw effect on bonding property of reinforced concrete, and put forward many valuable suggestions according to the test results. The results show that because the SHCC matrix has good frost resistance, the material itself has good durability and multiple cracking properties and bonding properties of the old concrete good, can improve the steel bond strength, ductility and resistance to environmental capacity, and reduce the effect of freeze-thaw cycle on bond performance, is very beneficial to extend the remaining life of the structure.

【学位授予单位】：西安建筑科技大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU528

【参考文献】