Performance of generic and proprietary corrosion inhibitors in chloride-contaminated silica fume cement concrete

This paper presents the results of a study conducted to evaluate the improvement in corrosion-resistance of chloride-contaminated silica fume cement concrete due to the use of corrosion inhibitors. Three proprietary and one generic corrosion inhibitors were evaluated for their performance in inhibiting reinforcement corrosion in the silica fume cement concrete specimens contaminated with 0.4%, 1%, and 2% chloride concentration, by weight of cement. Some of the specimens were subjected to wetting and drying cycles and reinforcement corrosion was monitored by measuring corrosion potentials and corrosion current density. Another batch of concrete specimens was partially immersed in the chloride solution and reinforcement corrosion was accelerated by impressing an anodic potential of 2 V. The extent of corrosion increased with increasing chloride contamination in the concrete specimens. Incorporation of inhibitor generally decreased the rate of reinforcement corrosion. The rate of reinforcement corrosion in the concrete specimens incorporating an organic inhibitor that was added to the concrete during mixing was the least followed by that in the concrete specimens on which a penetrating corrosion inhibitor was applied. Further, the accelerated impressed current technique was noted to be suitable for quickly screening the performance of corrosion inhibitors.     

Effectiveness of concrete surface treatmentmaterials in reducing chloride-induced reinforcement corrosion

The effectiveness of concrete surface treatment materials, such as silane, siloxane, acrylic coating, etc., in reducing chloride-induced reinforcement corrosion was investigated. Two sets of reinforced concrete specimens were cast. In the first set, reinforcement corrosion was accelerated by impressing an anodic potential of 2 V and the time to cracking was monitored. The second set of concrete specimens were immersed in the chloride solution and reinforcement corrosion was monitored by measuring corrosion potentials and corrosion current density. Among the surface treatment materials investigated, silane, silane/siloxane with top coat and acrylic coating were effective in reducing the rate of reinforcement corrosion. Furthermore, the data developed in this investigation indicated that the performance of coatings can be quickly evaluated using impressed current technique.     

海洋潮汐区混凝土中氯离子传输过程的试验室模拟方法

Cl-侵蚀是造成混凝土内钢筋锈蚀的主要原因,研究混凝土中氯离子侵蚀过程的试验室模拟方法是进行氯离子侵蚀过程研究的重要条件。本文通过实际海洋工程潮汐区和水下浸泡区氯离子传输过程的对比试验,揭示了干湿循环条件下氯离子在混凝土中的传输速率远大于饱水混凝土内外浓差引起的氯离子扩散速率,从而证明传统的浸泡试验方法无法用来预测干湿循环条件下氯离子传输速率,并在此基础上提出了实际海洋工程潮汐区氯离子传输过程的模拟试验方法,试验证明氯盐溶液喷淋—风干循环加速试验的氯离子传输机理和实际海洋环境潮汐区相同,是模拟海洋潮汐区的氯离子传输过程非常有效的方法。     

Corrosion resistant performance of a chemical quenched rebar in concrete

The corrosion resistance performance of the rebar quenched by a new chemical reagent FM in concrete containing chloride ions was evaluated comparing with bare rebar, water-cooled rebar and air-cooled rebar using electrochemical methods. Two different accelerated corrosion tests (14 cycles of dry/wet alternated corrosion tests and long-term immersion tests) were carried out to accelerate the corrosion process. EIS results of both accelerated corrosion tests showed the corrosion resistance performance of different rebar specimens could be sequenced from high to low as FM-cooled rebar, bare rebar, air-cooled rebar, and water-cooled rebar. It was observed that, after 14 cycles of accelerated corrosion tests, the corrosion degree of FM-cooled rebar is the slightest and most of the initial scale remains undamaged. This result proves that the corrosion resistance of the FM-cooled rebar is much better than the other three kinds of rebar. By using FM-cooling process, the corrosion resistance performance of rebar in concrete has been improved by optimizing the quality of the scale.     

混凝土中钢筋加速锈蚀试验适用性研究

钢筋锈蚀导致其屈服强度降低、力学行为改变,影响钢筋与混凝土之间的粘结性能,钢筋锈蚀量影响钢筋混凝土的失效模式。为研究锈蚀钢筋混凝土结构的相关性能,需要在较短时间内得到所需的锈蚀构件。通过对4种不同工况下混凝土中钢筋电化学加速锈蚀方法进行对比试验,得到了锈蚀后钢筋表面形态特征,分析了模拟自然环境条件下钢筋锈蚀的适用性。试验表明：全浸泡外加电流加速锈蚀方法使钢筋纵向、径向表面形成均匀锈蚀,而自然环境锈蚀钢筋表面锈蚀相对不均匀,坑蚀更明显,两者差异显著;利用全浸泡外加电流加速锈蚀方法进行锈蚀钢筋与混凝土粘结-滑移本构关系和锈蚀钢筋混凝土构件承载能力等研究不合适;半浸泡和贴面外加电流加速锈蚀方法能较好模拟自然环境锈蚀;加速锈蚀试验方法的理论锈蚀质量高于试验锈蚀质量。图12表1参7     

氯离子环境下钢筋混凝土棱柱体抗压力学性能试验研究

针对近海地区混凝土结构在氯离子侵蚀作用下其力学性能不断降低的问题,采用试验研究和理论分析的方法,先对12组RC棱柱体试件在盐雾腐蚀实验室进行了氯离子腐蚀试验,然后对其进行轴心抗压试验。以混凝土强度和锈胀裂缝宽度为变化参数,研究试件在轴心抗压试验下的受压应力-应变曲线,分析试件强度、刚度、延性等的变化规律。结果表明:随着混凝土强度的增大,试件的承载力和延性不断提高;随着箍筋锈蚀裂缝宽度的增大,试件的峰值荷载减小,强度降低,延性变差。     

Investigation on the corrosion resistance of bagasse-rice husk-wood ash blended cement concrete by impressed voltage

In this study, the compressive strength, the durability to chloride penetration and the corrosion of concrete containing bagasse-rice husk-wood ash (BRWA) were tested. Normal strength concrete with water to binder ratio (w/b) of 0.45 and 0.60 were used. The Portland cement was partially replaced with BRWA at the dosage of 10% and 20% by weight of binder. For concrete with w/b of 0.60, the replacement level of 40% was also tested. The chloride penetration resistance of the concretes was evaluated using the measurement of non-steady state chloride diffusion coefficient by accelerated salt ponding. The accelerated corrosion test by impressed voltage (ACTIV) was also performed to verify the findings and to investigate the characteristics of corrosion in terms of the initial current, the time of initial crack, and the weight loss of embedded steel.From the experiment, it was found that the concrete with 20% BRWA had the highest gain of compressive strength at the ages ranging from 7 to 180 days. The results of the experiments of accelerated salt ponding were in good agreement and conformed with ACTIV. The increase of the incorporation of the BRWA reduced the chloride penetration. The diffusion coefficient was reduced by 30–40% and 65–70% for concrete containing 10% BRWA and 20% BRWA compared to control concrete. The results of ACTIV also indicated that the initial current and the weight loss of embedded steel reduced and the time of initial crack increased with the increase in the replacement level of BRWA.     

Chloride ingress and macro-cell corrosion of steel in concrete made with recycled brick aggregate

An investigation on chloride ingress and macro-cell corrosion of steel bars in concrete made with recycled brick aggregate (RBA) was carried out. As control cases, virgin brick aggregate (BA) and stone aggregate (SA) were also investigated. Both cylindrical and cracked prism specimens were studied for 16 different cases. The prism specimens were made with a segmented steel bar providing electrical connection from outside of the specimens to measure macro-cell corrosion current continuously under seawater splash exposure for a period of 30 d using a data logger. Cylindrical specimens were submerged in 3% NaCl solution at a temperature of 40°C to investigate chloride ingress in concrete made with RBA, BA, and SA after 120 and 180 d. Half-cell potential, corrosion area, and depths of corrosion were also investigated. The chloride ingress as well as corrosion of steel bars in concrete made with the different types of aggregate is ordered as RBA > BA > SA.     

氯盐环境下钢筋锈蚀损伤混凝土应力-应变本构模型

采用加速腐蚀试验,对氯盐环境下钢筋锈蚀损伤混凝土棱柱体试件的破坏形态、应力-应变全曲线、峰值应力、峰值应变、极限应变及弹性模量进行了试验研究.结果 表明:钢筋锈蚀损伤混凝土试件的破坏多为微柱失稳破坏,大致平行于受力方向的锈胀裂缝是主要的破裂面;钢筋锈蚀损伤混凝土实测应力-应变全曲线与未锈蚀损伤混凝土相似,但是随着钢筋锈...     

高频电磁波在媒质中的反射波特征分析

地质雷达探测方法是通过识别高频电磁波在媒质中的反射渡(即回波信号)特征来推断目标体的类型及空间赋存状态.文章以金属板、混凝土钢筋、地下含水层、破碎岩体、断层带及岩溶洞穴等目标体为例,分别对其反射信号的图像特征进行振幅特征、相位特征及时频特征分析,总结不同媒质对高频电磁波的反射特征,提高地质雷达探测方面对异常的判断能力和...     

基于形态学及边缘检测的雷达图像特征提取

介绍了雷达技术在混凝土结构无损检测中的应用原理,制作了模拟空洞、裂缝、不密实缺陷的混凝土试件,得到了缺陷的雷达图像典型特征.将数字图像处理技术应用于雷达图像的后处理中,形态学腐蚀、膨胀处理后图像的主要特征得到体现,次要因素得以忽略,为雷达图像的判读、解释起到良好的区分作用.边缘检测结合腐蚀、膨胀能快速而准确地得到图像的...     

氯盐环境下再生混凝土框架边节点抗震性能试验研究

为研究氯盐环境下再生混凝土框架边节点的抗震性能,以再生粗骨料取代率和钢筋锈蚀率为变量,设计8个钢筋混凝土框架边节点,采用覆盖海绵和不锈钢网,按1∶1比例干湿循环的方法通电加速锈蚀,达到预期锈蚀率后观测锈胀裂缝,之后进行拟静力试验,以研究模拟地震动下节点试件的破坏过程和滞回特性。结果表明:在未锈蚀的情况下,再生粗骨料取代率为50%和70%的试件在承载力、刚度、延性和耗能等方面低于普通混凝土试件,而取代率为100%的试件则与普通混凝土试件相差不大;采用干湿循环的通电锈蚀方法可较好地模拟实际氯盐环境,使钢筋产生红棕色铁锈并发生坑蚀;对再生粗骨料取代率为100%的试件,其承载力和刚度在锈蚀率小于2. 18%(最大锈胀裂缝宽度为1. 20 mm)时变化不大,不小于2. 18%时显著下降,其延性和耗能能力在锈蚀率小于4. 17%(最大锈胀裂缝宽度为3. 08 mm)时略高于未锈蚀试件,不小于4. 17%时(节点箍筋锈断)迅速降低。     

长期暴露混凝土结构中的氯离子侵入研究

根据混凝土中氯离子浓度曲线评价暴露在海洋或道路除冰盐环境下的混凝土结构钢筋腐蚀风险,是一个可靠而有效的方法。对暴露26a的码头和暴露21a的挡浪坝钻取了一批直径100mm的混凝土芯样,同时在实验室制作了三组配合比的混凝土试件进行对比试验。对暴露混凝土的原始资料和环境条件进行了分析,在实验室测定了芯样和试件中的氯离子分布,根据氯离子分布曲线对氯离子扩散系数进行了评价,分析了材料因素和环境因素对氯离子分布的影响。结果表明：实际暴露混凝土中氯离子扩散系数随暴露时间衰减明显;混凝土所处的局部环境造成表层氯离子分布形态有差异;但受混凝土暴露整体环境的影响,混凝土内部氯离子分布则比较一致;混凝土质量差异对氯离子侵入的影响需经过长时间暴露后才能得以反映。图8表8参14     

基于PZT波传播法的混凝土内部钢筋锈蚀监测方法

为有效监测钢筋混凝土结构内部钢筋的锈蚀,提出了基于压电陶瓷(PZT)波传播法的钢筋锈蚀监测方法.首先,基于PZT波传播法对变形钢筋进行了试验研究及数值模拟,找出了应力波在无锈蚀钢筋中的传播衰减规律;然后,设计制作了18个钢筋混凝土试件,在埋入每个试件中的钢筋表面相同位置粘贴PZT激励器/传感器;最后,对试件进行电化学快速锈蚀,并在试件锈蚀过程中,对其进行PZT测试,来追踪锈蚀对应力波传播特性的影响.结果表明:钢筋锈蚀严重影响应力波的传播衰减规律,传感器接收到的信号幅值与钢筋锈蚀率之间呈二次函数的关系.     

Influence of initial curing conditions and exposure environments on chloride migration in concrete using electrochemical method

To investigate the influence of initial curing conditions and exposure environments on chloride ions’ migration in concrete, the specimens that were cured in different conditions and placed in several marine environments were studied. The amount of chloride ions passing through the specimen’s section was monitored in the accelerated chloride migration test. The effective chloride diffusion coefficients (D_e) were calculated from the steady-state on the basis of Nernst-Planck’s equation. The results indicated that the initial curing conditions and the wet-dry interval of external environments have coupling influence on effective diffusion coefficient of chloride ion significantly. D_e reflected the density and pore connectivity of concrete. The co-effects of the initial curing condition and following exposure environment should be taken into account in durability design for concrete structure located in marine environment.     

钢筋锈蚀对钢筋混凝土结构固有频率和阻尼比影响的试验研究

针对钢筋锈蚀使钢筋混凝土结构的抗震性能和耐久性能退化,并且对结构动力特性产生影响的现象,采用电化学加速锈蚀方法,通过法拉第定律控制锈蚀程度,将钢筋的理论锈蚀率分为5%,10%,15%三个锈蚀阶段,在实验室中模拟了钢筋混凝土梁中钢筋的锈蚀过程。根据悬臂梁的自由振动衰减特性,采用自由衰减法采集了钢筋混凝土梁的固有频率和阻尼比,研究了钢筋锈蚀对钢筋混凝土梁固有频率和阻尼比的影响。结果表明:钢筋锈蚀对钢筋混凝土梁的固有频率和阻尼比有显著影响,钢筋混凝土梁的固有频率随着钢筋锈蚀程度的加深而呈减小趋势,阻尼比随着钢筋锈蚀程度的加深而呈增大趋势,因此阻尼比可以作为损伤指标用于混凝土结构腐蚀损伤检测。     

锈蚀工字形型钢与混凝土黏结滑移特性及损伤本构模型研究

由于海底隧道服役环境中氯离子含量高,初期支护中的工字钢将不可避免产生锈蚀,导致工字钢与混凝土黏结性能下降,严重影响海底隧道支护体系的耐久性.该研究主要目的是研究锈蚀对工字钢与混凝土界面间黏结滑移行为的影响.首先对工字形型钢混凝土试件进行加速锈蚀试验和推出试验,得到试件破坏形态及黏结滑移曲线,在此基础上分析试件的黏结滑移...     

钢筋与再生及普通混凝土黏结性能退化的对比研究

为了研究锈蚀钢筋与再生及普通混凝土的黏结性能退化的差异,通过电化学方法,得到了6种不同钢筋锈蚀率的再生及普通混凝土试件;采用拔出试验方法,对比分析了锈蚀对2种混凝土试件黏结性能退化规律的差别。结果表明:再生混凝土的相对极限黏结强度和黏结刚度均较普通混凝土低;随着钢筋锈蚀率增加,两种试件的极限滑移量的差别逐渐增大;再生混凝土试件开裂时刻较普通混凝土试件早,且一旦保护层开裂后,再生混凝土的裂缝宽度较普通混凝土稍大。     

Influence of initial curing conditions and exposure environments on chloride migration in concrete using electrochemical method

To investigate the influence of initial curing conditions and exposure environments on chloride ions’ migration in concrete, the specimens that were cured in different conditions and placed in several marine environments were studied. The amount of chloride ions passing through the specimen’s section was monitored in the accelerated chloride migration test. The effective chloride diffusion coefficients (D _e) were calculated from the steady-state on the basis of Nernst-Planck’s equation. The results indicated that the initial curing conditions and the wet-dry interval of external environments have coupling influence on effective diffusion coefficient of chloride ion significantly. D _e reflected the density and pore connectivity of concrete. The co-effects of the initial curing condition and following exposure environment should be taken into account in durability design for concrete structure located in marine environment.     

地质雷达信号分析的双正交小波预测反褶积法

为了降低电磁波衰减、噪声干扰等因素对地质雷达检测效果的影响,提出一种双正交小波预测反褶积法(PDBW法)。在PDBW法中,针对地质雷达检测信号选取具有最小重构误差的双正交小波基,运用该小波基将地质雷达检测信号分解成不同频段的时域子信号,对各频段的时域子信号进行预测反褶积等滤波处理,再对处理后的子信号进行重构变换,得到PDBW法的处理结果。将PDBW法用于实验检测信号处理,并将处理结果与预测反褶积法的处理结果进行比较,结果表明:PDBW法能有效压制多次回波干扰,准确识别深部信号,显著提高深部信号信噪比,从而进一步改善地质雷达探测分辨率和图像分析的准确性。