【作者】 陶琦；

【导师】 巴恒静；

【作者基本信息】 哈尔滨工业大学 ， 结构工程， 2010， 博士

【摘要】 混凝土的寿命预测在近些年是一个研究热点,多数学者都是以Fick第二定律为基础,研究氯离子渗透进入混凝土后的分布情况,预测混凝土结构的寿命,然而Fick第二定律的边界条件不符合混凝土的实际情况,并且由于混凝土自身组成特点和化学结合能力等的影响,通过Fick第二定律预测混凝土的寿命不准确。本文主要通过变电压的加速氯离子渗透试验来预测混凝土的寿命,根据不同电压下混凝土中氯离子含量的变化规律,找到加速电压与达到氯离子临界浓度的时间之间的关系,最终预测海水中混凝土自然渗透情况下的寿命。本文中以混凝土中钢筋锈蚀的临界氯离子浓度为寿命预测的边界条件,认为混凝土中氯离子浓度达到临界浓度时,混凝土的寿命终止。在混凝土中预埋钢筋和参比电极,进行20V、12V、6V和3V直流电压下的钢筋快速锈蚀试验,对试验结果分析后得到了C30空白混凝土、复掺掺合料和引气剂C30混凝土、C60空白混凝土、复掺掺合料和引气剂C60混凝土的临界氯离子浓度。对以上四个不同配合比的混凝土进行变电压的加速氯离子渗透试验,加速电压分别为20V、12V、6V和3V,研究发现3d后混凝土中氯离子含量随时间呈线性增加,通过建立加速电压与达到临界氯离子浓度的时间之间的关系,得到了寿命预测的方程,并预测混凝土在海水中自然渗透情况下的寿命。预测已使用14年的青岛某处防波堤混凝土的剩余寿命,对现场取样混凝土进行变电压的氯离子渗透试验,预测其剩余寿命为18.72年,按照该混凝土的配合比在试验室条件下还原出全新的混凝土,预测其寿命为35.01年,两个寿命之差为16.29年,与混凝土已经使用的年限相差2.29年,因此通过变电压的快速氯离子渗透试验可以较准确的预测混凝土的剩余寿命。对C30空白混凝土、复掺掺合料和引气剂C30混凝土、C60空白混凝土、复掺掺合料和引气剂C60混凝土进行了100次和150次的盐冻试验,研究发现C30空白混凝土无法抵抗100次盐冻循环,盐冻后完全破坏,对盐冻后的复掺掺合料和引气剂C30混凝土、C60空白混凝土、复掺掺合料和引气剂C60混凝土进行剩余寿命预测,C30复掺掺合料和引气剂混凝土盐冻100次后寿命为29.62年,盐冻150次后为24.9年,C60空白混凝土盐冻100次和150次后寿命为35.51年和32.17年,C60复掺掺合料和引气剂的混凝土盐冻100次和150次后寿命为50.85年和45.66年。引入盐冻损伤系数k_yd,得到了k_yd与盐冻次数之间的关系,建立了盐冻前后混凝土的寿命预测方程。对混凝土施加20%和40%极限荷载的压应力,重复加荷200次后预测混凝土的剩余寿命。试验结果表明C30空白混凝土加载20%和40%压应力后寿命为21.61年和16.66年。C30复掺掺合料和引气剂的混凝土加载20%和40%压应力后寿命为33.3年和32.97年。C60空白混凝土加载20%和40%压应力后寿命为38.24年和34.82年。C60复掺掺合料和引气剂的混凝土加载20%和40%压应力后寿命为49.8年和44.84年。引入重复压应力损伤系数k_yl,得到了k_yl与加载程度之间的关系,建立了重复压应力前后混凝土的寿命预测方程。更多还原

【Abstract】 Service life prediction of concrete has been a hot topic in recent years. Based on Fick’s second law, most of the researchers studied chloride ion distribution in concrete and predicted service life of concrete structures. But the boundary conditions of Fick’s second law were not coincident with the field conditions. In addition, the predicted service life of concrete structures was not accurate because of the influence of concrete compositions and chemical binding effect.In this thesis, the service life of concrete structure was predicted through accelerated chlorid ion penetration test under various voltages. According to change rule of chloride ion content in concrete under various voltages, the relationship between critical concentration time and voltage was obtained. Based on the obtained results, the service life of concrete structures in natural marine environment was predicted.In this study, the critical chloride ion concentration leading to steel corrosion was considered as boundary condition of service life prediction. That meaned service life of concrete structures terminated when chloride ion concentation reached critical value. With steel bar and reference electrode casted in concrete specimens, the rapid steel corrosion test was done under 20V, 12V, 6V and 3V voltage. Through the analysis of the experimental results, the critical chloride ion concentrations of C30 control specimen, C30 specimen with mineral admixture and air-inducing agent, C60 control specimen and C60 specimen with mineral admixture and air-inducing agent were obtained.For the concrete specimens mentioned above, the accelerated chloride ion penetation test was done under 20V, 12V, 6V and 3V voltage. The research results indicated that chloride ion content increased linearly with time after 3 days. Through the establishment of relationship between critical concentration time and voltage, the service life prediction equation was obtained. Based on the obtained results, the service life of concrete structures in natural marine environment was predicted.For the breakwater concrete structure with service time of 14 years in Qingdao, the specimens were distrilled and the residual life was predicted through chloride ion penetration test under various voltages. The predicted result was 18.72 years. For the new concrete specimens with the same mixing proportions, the predicted service life was 35.01 years. The difference between the two predicted results mentioned above was 16.29 years, which was 2.29 years shorter than the actual service life. So through the rapid chloride ion penetration test, the residual service life of concrete structures could be prediced precisely.For C30 control specimen, C30 specimen with mineral admixture and air-inducing agent, C60 control specimen and C60 specimen with mineral admixture and air-inducing agent, salt frost test were done with 100 and 150 freezing and thawing cycles. The results showed that C30 control specimen can not resist the 100-cycle salt frost damage and was fully destroyed. After salt forst test, the residual service life of C30 specimen with mineral admixture and air-inducing agent, C60 control specimen and C60 specimen with mineral admixture and air-inducing agent were predicted. For C30 specimen with mineral admixture and air-inducing agent, the predicted residual life were 29.62 years and 24.9 years afer 100 and 150 cycles. For C60 control specimen, the predicted residual life were 35.51 years and 32.17 years afer 100 and 150 cycles. For C60 specimen with mineral admixture and air-inducing agent, the predicted residual life were 50.85 years and 45.66 years afer 100 and 150 cycles. Through the introduction of salt frost damage coefficient k_yd, the relationship between k_yd and freezing-thawing cycles was obtained and service life prediction model before and after salt frost test were established.Compressive pressure with value of 20% and 40% ultimate load was applied to concrete specimens. After 200-cycle repeated-load test, the residual service life of specimens mentioned above was predicted. The experimental results showed that the predicted results were 21.61 and 16.66 years after repeated-load test with pressure of 20% and 40% ultimate load for C30 control specimen. For C30 specimen with mineral admixture and air-inducing agent, the predicted results were 33.3 and 32.97 years after repeated-load test with pressure of 20% and 40% ultimate load. For C60 control specimen, the predicted results were 38.24 and 34.82 years after repeated-load test with pressure of 20% and 40% ultimate load. For C60 specimen with mineral admixture and air-inducing agent, the predicted results were 49.8 and 44.84 years after repeated-load test with pressure of 20% and 40% ultimate load. Through the introduction of repeated-load damage coefficient k_yl, the relationship between k_yl and peak load value was obtained and service life prediction model before and after repeated-load test were established.更多还原