【作者】 刘志强；

【导师】 赵铁军； F.H.Wittmann；

【作者基本信息】 青岛理工大学 ， 结构工程， 2012， 硕士

【摘要】 近年来，伴随着经济的持续增长，我国在基础设施建设方面取得了举世瞩目的成就，然而由于种种原因的影响下，我国的每年发生的火灾次数以及火灾造成的经济损失也在逐年攀升，考虑到混凝土结构在火灾等高温作用下往往进行加固维修后继续使用，因此有必要对混凝土结构在高温作用后的性能损伤开展研究。关于在混凝土高温下以及高温作用后的性能方面已开展了大量的相关研究，但是这些研究大多集中在混凝土的力学性能方面，关于混凝土在高温作用后的长期性能以及耐久性的损伤却较少涉及，此外，混凝土结构在受到火灾作用并进行消防灭火的过程中，往往可能受到喷水冷却，而以往的研究中却较少考虑。针对以上问题，本课题主要开展了以下试验研究：（1）对高温后通过不同冷却方式冷却的混凝土试块的剩余抗压强度开展研究，并通过数值拟合分析其随高温最高作用温度的演化规律；（2）对高温后的混凝土试块进行超声波检测，以分析混凝土在不同高温温度作用的超声检测参数和动弹性模量的变化；（3）对高温作用后通过不同冷却方式冷却的混凝土试件的断裂能进行测定，分析高温作用后混凝土断裂能的变化，以研究高温后混凝土结构的抗开裂性能的变化；（4）对高温后通过不同冷却方式冷却的混凝土试块进行毛细吸水试验及氯离子侵蚀试验，并分析高温作用以及冷却方式对混凝土抗毛细吸水性能以及抗氯离子侵蚀能的损伤；（5）对高温后通过不同冷却方式冷却的混凝土进行再养护，研究再养护措施对混凝土试块的性能的愈合效果。结果表明：（1）高温作用对混凝土的抗压强度造成严重劣化，而且冷却方式对混凝土高温后的剩余强度影响显著，对于A配比混凝土，在300℃高温作用后，自然冷却的混凝土抗压强度降低约3.5%，而喷水冷却的混凝土试块强度降低高达20%，此外，通过数值拟合得出了混凝土相对剩余抗压强度随温度的函数关系；（2）通过超声检测以及公式计算得出混凝土的剩余动弹性模量随着最大作用温度的升高而逐渐降低，但冷却方式对混凝土剩余动弹性模量的影响不明显；高温后混凝土试块的超声检测参数与混凝土最高作用温度服从一定的函数关系，并通过函数迭代得出混凝土高温后相对剩余强度与超声检测参数的函数关系；（3）混凝土的高温后的剩余断裂能随最高作用温度的增大而减小，500℃高温作用后，自然冷却混凝土的断裂能降低达44%，而喷水冷却的混凝土其剩余断裂能低于自然冷却的混凝土；（4）高温后混凝土的抗毛细吸水性能及抗氯离子侵蚀性能均出现严重劣化，并且喷水冷却的混凝土遭到的劣化更为严重；（5）通过再养护后混凝土的抗毛细吸收性能及抗氯离子侵蚀性能得到一定的提升。更多还原

【Abstract】 In recent years, with the development of the economy, our country had greatachievement in the construction of the infrastructure. However, for some reasons, theamount of fire disasters and the economic loss caused were increasing year by year.Considering that，the concrete structures usually continue to be used after the exposureto fire, it’s necessary to study the performance of concrete after the effect of theelevated temperature.By now, a great deal of research have been carried out on the residualperformance of concrete after the effect of elevated temperature, but most of themwere focused on the mechanical performance, but littlie on the damage of thedurability and long-term performance. Besides that, in the process of fireextinguishment, a great deal of water will be used, which will be absorbed by the dryconcrete. Such points mentioned above were little concerned in the past researches.For questions above, in this dissertation the main experimental research were asfollows:(1) Study the residual compressive strength after the effect of elevatedtemperature, and find out the rules that the residual strength follows by numericalfitting;(2) Test the concrete specimens by ultra sonic measurement to find out thechanging rules of ultra sonic parameter and elastic modulus;(3) Test the fractureenergy of the concrete specimens after the effect of elevated temperature and cooled bydifferent regime, and analyze the Anti cracking performance of concrete after heating.(4) In order to analyze the damage of heating and cooling regime on the permeabilityof concrete, water capillary absorption and chloride penetration were carried out.(5)After heated and cooled by different regime, recure the specimens to study the effect ofthe rehydration.The experiment results indicated that (1) The compressive strength of specimenswill deteriorate badly after heating, and the cooling regime can influence the residualstrength observably, by numerical fitting, the function relationship was built up whichdescribe the changing rule of residual strength.(2) The elastic modulus measured by ultra sonic method decreased with the temperature increasing, and the cooling regimedidn’t influence the elastic modulus obviously, besides that, by analyzing the ultrasonic parameters, the function relationships were built up which describe the changingrules of such parameters.(3)With the temperature increasing, the residual fractureenergy got decreased, and the fracture energy of specimens cooled by water was lessthan that cooled in the air.(4) The ability of anti-capillary absorption and chloridepenetration were deteriorated badly, and the specimens cooled by water were damagedmore badly;(5)After recurring, the permeability and chloride resistance got developed.更多还原