混凝土硫酸杆菌腐蚀研究进展

对于市政排污管道而言,硫酸杆菌往往是造成其腐蚀的一个主要原因.本文总结了近年来混凝土硫酸杆菌腐蚀的研究进展.归纳认为针对混凝土硫酸杆菌腐蚀的研究大致可以分为两种实验研究方法:细菌模拟测试和现场暴露测试.同时还介绍了混凝土硫酸杆菌的腐蚀机理以及硫酸杆菌侵蚀与化学硫酸侵蚀的区别;总结了在评价混凝土抗硫酸杆菌侵蚀性能时使用的各种参数以及提高混凝土抗侵蚀性能的措施.最后认为虽然对混凝土的硫酸杆菌腐蚀的研究取得了一些进展,但是该领域在国内尚属起步研究阶段,在腐蚀程度的评价、预测模型的建立、细菌与母体的关系以及是否可以利用细菌活动来提高混凝土的抗腐蚀能力等方面的研究还很欠缺,建议尽快加强这些方面的研究     

先进水泥及先进水泥基材料的研究进展

介绍了有关先进水泥和先进水泥基材料的探索和研究进展。消纳工业废渣的低环境负荷水泥技术、高胶凝性高钙水泥熟料体系的研究、高贝利特水泥的研究和应用、地聚合物的深入开发等成果反映了我国在水泥科学领域的突破。水泥基材料的研究进展主要体现在多因素协同作用下水泥基材料性能劣化和寿命预测的研究、大流动度自流平混凝土的研究、改善水泥基材料体积稳定性的研究、高延性纤维增强水泥基复合材料的研究方面。水泥和水泥基材料近期研究重点将主要集中在与节能减排、环保利废有关的新设备、新材料和新技术方面;水泥基材料的抗裂性和耐久性,功能性复合材料的开发也将是研究的重点。     

Influence of chloride ions and hot weather on isolated rusting steel bar in concrete based on NDT and electro-chemical model evaluation

The most prominent durability concern for reinforced concrete (RC) structures is the corrosion of steel reinforcement in concrete. RC buildings exposed to chloride and high temperature environments like sea and deserts suffer from accelerated corrosion of rebars. The chloride attack and increase in the electro-chemical reaction rate of corrosion due to high temperature is a thermodynamic phenomenon influenced by several parameters and some of them are being neglected in the past research works. The purpose of this present paper is therefore, to model and verify by NDT the coupled effects of chloride and temperature on corrosion of reinforcement throughout the life of concrete buildings by incorporating realistic thermodynamic model evaluations and actual field condition NDT. The model evaluation has been accomplished by the use of concrete durability model as a computational platform on which the corrosion based reinforced concrete building performance and quality at early age and throughout the life of concrete structure is examined in both space and time domains under environmental actions of chloride and temperature. On this line, the thermodynamic modeling evaluation of concrete forms the fundamental core of the theoretical approach to achieve both the scientific knowledge and engineering simulations of altering materials. The NDT results for the effect of chloride and temperature on corrosion have been compared with the DuCOM electro-chemical thermodynamic corrosion model evaluation and are found to be in close agreement with each other.     

Experimental and probabilistic analysis of time to corrosion-induced cover cracking for marine reinforced concrete structures

Corrosion-induced concrete cover cracking is an important indication of durability limit state for marine reinforced concrete structures. In this paper, two analytical models predicting the time from corrosion initiation to cover cracking and their main differences were introduced. Based on an accelerated corrosion test, two models’ applicability and variability were compared and discussed with experimental data. Considering the random nature of influencing factors, a probabilistic model was developed by using Monte Carlo simulation technique. The results showed that the cracking time could be modelled by the Weibull distribution. Finally, the probability analytical technology was applied to a marine reinforced concrete pier with four different durability design levels. It is found that both the mean and 90% confidence interval of the cracking time increase when the durability design specifications change from low level to extreme level, which indicates that the accurate prediction of cracking time with a deterministic model will become more difficult accordingly.     

Corrosion of steel reinforcement in structural concrete with carbon material addition

Different types of carbonaceous materials have been added to concrete mixes and their effect on the corrosion of embedded steel has been studied. Using a constant water/cement ratio of 0.42 and different amounts of carbonaceous materials and different curing periods the evolution of the corrosion process in the embedded reinforced bars has been determined. The addition of small quantities of carbonaceous materials to the mixture produces a reduction of the concrete permeability. Tests demonstrate that a decrease of the corrosion level occurs when the content ratio of carbon material addition is increased.     

应力-化学介质-冻融循环协同作用下水泥基材料失效机理及寿命预测的研究

针对水泥基材料在应力-化学介质-冻融循环协同作用下的耐久性进行了研究,并开发了多种材料失效试验方法和装置。砂浆试件应力-化学腐蚀协同作用试验装置的特点是加载稳定,克服了应力松弛;协同作用耐久性试验装置可以用于监测协同作用下钢筋混凝土试件性能的衰减过程。研究发现：矿物掺合料改善抗渗性的能力依次是矿渣粉、活化煤矸石粉、粉煤灰;随应力比加大和冻融循环次数增加,水泥基材料中钢筋锈蚀加速、化学介质的渗透速度和深度增大,协同作用加速了水泥基材料的失效;可以用一元二次函数来近似预测氯盐-冻融循环-弯曲荷载协同耦合作用下的寿命。     

Ternary mixes with high mineral additions contents and corrosion related properties

The choice of blended cements and materials with cementitious properties in concrete is currently seen as a choice that increases the environmental sustainability of the construction industry. The developments with non‐traditional binders (such as the simultaneous incorporation of several types of supplementary cementitious materials) have highlighted new challenges to be researched. In the present paper ternary binders were prepared by mixing ordinary Portland cement (OPC) plus two blended components: low calcium fly ash, blast furnace slag, and/or limestone filler. Several physical and mechanical properties of ternary blend systems have been analyzed in mortar form at several curing ages: 2, 7, 28, and 90 days. Additionally preliminary tests of corrosion performance of reinforcement in these types of mixes have been considered. The results indicate that the use of appropriate content components in ternary blends will allow binders to fulfill the specified mechanical requirements. The best results are obtained when two additions with antagonist properties are mixed, as fly ashes and slags or slags and filler limestone. Besides, certain influence of the effect on durability performance is detected, in particular associated with the stability of the passive state and corrosion of reinforcements in presence of chlorides.     

超高韧性水泥基复合材料与锈蚀钢筋粘结性能试验研究

通过电化学加速锈蚀、钢筋和UHTCC直接拉拔试验对不同锈蚀率(0,1%,2%,3%和5%)下钢筋与UHTCC的粘结性能进行了研究,并与同条件下的混凝土试件进行对比。通过直接拉拔实验得到不同锈蚀率时平均粘结应力与滑移量的关系,采用粘结滑移的连续模型进行拟合,模型值与实验值吻合较好。与混凝土试件锈蚀率超过2%后最大平均粘结应力迅速下降现象不同,UHTCC能充分发挥其对钢筋的约束作用,在锈蚀率小于3%范围内,最大平均粘结应力随锈蚀率增大线性增加,锈蚀率超过3%直到5%基本维持不变,保持较好的粘结性能。     

Gerissener Stahlbeton: Wie korrosionsgefährdet ist die Bewehrung?

Cracked reinforced concrete: What about corrosion risk? The formation of cracks within the tension zone of the concrete is part of the design principle of reinforced concrete structures. The width of these cracks can be limited by means of crack limiting reinforcement. Already by the end of the fifties first examinations have been carried out to determine the influence of cracks and their width on the corrosion risk. Compared to uncracked concrete CO₂ and chlorides as corrosion promoting substances are able to move faster towards the reinforcement within a crack, leading to an earlier depassivation of the reinforcement within the cracks. Before Schießl published his results, from experiments and literature research, it had been assumed that the corrosion rate of reinforcement within cracks increases with increasing crack width. Hence a differentiated maximum crack width linked to exposure classes had to be complied according to the DIN 1045 until the version of 1988. For the first time the DIN 1045 version 1988 did not enclose this differentiation, for durability reasons a maximum crack width of 0.25 mm has been fixed for reinforced concrete. In the version of 2001 the calculated crack width has been raised from 0.25 mm to 0.30 mm. Therewith the findings of Schießl (published in book no. 370 by the Deutscher Ausschuss für Stahlbeton) have been implemented by now. The main contributing factors influencing the corrosion rate of cracked concrete are the concrete quality and the concrete cover and not the crack width, whereas horizontal structural parts exposed to chlorides have to protected generally by additional measures.     

Effect of corrosion on bond strength of steel and non‐metallic reinforcement

Research attempts on the effect of environmental corrosion on bond between steel bars and concrete, report considerable losses of bond strength. Alternative solutions to the corrosion problem include the use of non‐metallic reinforcement. In this paper the effects of environmental corrosion (through accelerated carbonation) on the bond properties of fiber reinforced polymer (FRP) bars with the surrounding concrete are investigated. The work presented is part of an extensive project addressing the durability of FRP in concrete 1 . It was found out that, in contrast to what is generally believed, concrete alkalinity does not have a major impact on the durability of FRP bar and its bond strength. The expected bond deterioration due to carbonation is more than compensated by the increase in compressive strength due to time and carbonation, contrary to the case when steel reinforcement is used.     

DFG‐research‐group: Modelling reinforcement corrosion – overview of the project

A strong interest for the durability of reinforced concrete structures currently exists in industry and research [1]. Against the background of immense costs for maintaining reinforced concrete structures and repairing damage caused by corroding reinforcement steel, this interest lead to a German joint research project. The aim of this network‐based (www.bam.de/dfg537.htm) research group is, to deliver the basic knowledge of the corrosion propagation and to make a probabilistic tool available for engineers so that a complete design for durability, concerning reinforcement corrosion, will be possible.     

钢筋阻锈剂的阻锈机理及性能评价的研究进展

钢筋腐蚀是引起钢筋混凝土构筑物提前失效的主要因素,应用钢筋阻锈剂是主要的防腐蚀措施之一。重点介绍了海洋环境中,氯盐的侵蚀机理和阻锈剂的作用机理;讨论了阻锈剂的性能评价方法和应用现状;指出高效且环境友好复合型阻锈剂的合成是今后研究的主要方向,这对于提高我国钢筋混凝土结构耐久性具有重要意义。     

Local detailed inspection methods to determine concrete properties on structures

During assessment of reinforced concrete structures, information about concrete properties can give a clearer insight into the prevailing reasons for premature degradation of structures. In this paper an overview is given of methods for local detailed inspection of concrete properties in corroding reinforced concrete structures. Recommended non‐destructive, semi‐destructive and destructive testing methods for determining mechanical and durability properties of concrete are given, together with some practical information about performing the method and analysing obtained results. Recommended criteria for evaluating concrete quality and potential risk of corrosion due to poor concrete performance are also given.     

Electrochemical realkalisation for rehabilitation of reinforced concrete structures

In steel reinforced and prestressed concrete structures depassivation of the reinforcing steel can take place due to carbonation of the concrete cover. Depending on humidity and oxygen availability subsequent corrosion reactions will be initiated. Such conditions require measures to exclude corrosion induced damages during the designed lifetime of the structure. In the last few years an electrochemical realkalisation treatment has been proposed as adequate rehabilitation technique for carbonated concrete. This temporary treatment should increase the pH-value of the concrete pore water solution due to penetration of alkaline electrolyte from the concrete surface as well as repassivate the reinforcement due to electro chemical reactions at the steel surface. In order to clarify the different mechanisms taking place during electrochemical realkalisation laboratory tests have been carried out using carbonated reinforced mortar specimens. The investigations were aimed at checking the influence of various parameters, e.g. treatment time and current density, as well as the efficiency and long-term durability of this rehabilitation method.     

Corrosion of Carbon Steel and Corrosion-Resistant Rebars in Concrete Structures Under Chloride Ion Attack

Corrosion of reinforced concrete is the most challenging durability problem that threatens reinforced concrete structures, especially structures that are subject to severe environmental conditions (i.e., highway bridges, marine structures, etc.). Corrosion of reinforcing steel leads to cracking and spalling of the concrete cover and billions of dollars are spent every year on repairing such damaged structures. New types of reinforcements have been developed to avoid these high-cost repairs. Thus, it is important to study the corrosion behavior of these new types of reinforcements and compare them to the traditional carbon steel reinforcements. This study aimed at characterizing the corrosion behavior of three competing reinforcing steels; conventional carbon steel, micro-composite steel (MMFX-2) and 316LN stainless steel, through experiments in carbonated and non-carbonated concrete exposed to chloride-laden environments. Synthetic pore water solutions have been used to simulate both cases of sound and carbonated concrete under chloride ions attack. A three-electrode corrosion cell is used for determining the corrosion characteristics and rates. Multiple electrochemical techniques were applied using a Gamry PC4? potentiostat manufactured by Gamry Instruments (Warminster, PA). DC corrosion measurements were applied on samples subjected to fixed chloride concentration in the solution.     

粉煤灰与混凝土结构的耐久性

化学侵蚀、碳化腐蚀，钢筋锈蚀，冻融循环，碱集料腐蚀等是影响混凝土耐久性的常见破坏因素，讨论了掺加粉煤灰改善混凝土结构耐久性的作用机理和作用效果。     

三峡地区材料33年土壤腐蚀行为研究

综合分析钢铁、水泥制品、塑料等四类材料在三峡地区埋设33年的土壤腐蚀数据、总结了材料在三峡土壤中的腐蚀规律,讨论了三峡地区土壤的腐蚀性,提出了选材与防护建议     

电化学频率调制技术在混凝土钢筋锈蚀中的应用

为获取更为真实的钢筋锈蚀动力学参数,运用电化学频率调制技术对混凝土中锈蚀钢筋进行了测试;通过与单向极化三点法测试结果对比,明确了电化学频率调制技术的测试参数;结果表明,混凝土中锈蚀钢筋B_a范围在65~250 mV/dec,大于溶液中的30~120 mV/dec;对EFM测试得到的极化电阻R_P和腐蚀电流I_corr进行曲线拟合分析,得到两者之间经验关系,修正了线性极化法B值。     

Durability properties of concrete with blended cements

The study of chloride‐induced corrosion started more than three decades ago, after extensive cases of damage were observed on reinforced concrete structures in coastal regions and on infrastructural objects exposed to salt action. Nowadays, the basis for sustainable concrete industry lies in these three aspects: reducing CO₂ emissions by using by‐products of other industries (slag, fly ash, silica fume) for cement production, conservation of natural resources by replacing part of the aggregate with recycled construction waste, as well as use of recycled water in concrete production, and finally, construction of durable concrete structures. Durability design procedures for reinforced concrete structures in aggressive environments are still to a large extent empirical, especially in the case of using blended cements. The type of cement has a considerable effect on the properties of concrete, especially concrete resistance to the penetration of chloride ions. The paper presents results of testing durability and deformational properties of concrete produced with quaternary‐blended cement. A clearer insight into these properties is a necessary starting point for the performance‐based design of concrete prepared with blended cements, leading to more durable and corrosion‐free concrete structures in aggressive environments.     

Korrosionverhalten von schlaffer und vorgespannter Bewehrung in Betonbauteilen

Corrosion behaviour of stressed and prestressed reinforcement in concrete structural elements In steel reinforced or prestressed concrete structures corrosion protection of the reinforcement is resulting from the high alkalinity of the concrete environment which guarantees passivity of the steel surface. The long time efficiency of the corrosion protection is a function of the design of the structure and influence from the properties of the used concrete materials as well as the environmental conditions of the structure. Essential factors preventing corrosion are given by a good quality and thickness of the concrete covering, a proper curing of the concrete and position of the reinforcement which avoids cracks and defects in the concrete covering. Passivity of the reinforcement can be destroyed by carbonisation of the concrete or a sufficiently high amount of chlorides in the concrete. Under such conditions in prestressing steels hydrogen induced stress corrosion occurs while in normal steel reinforcement the corrosion products due to their increasing volume lead to cracking and spalling of the concrete and a decreasing cross section of the reinforcement. In this report typical failures are demonstrated and discussed.