钢筋混凝土阻锈剂的发展和研究

钢筋混凝土阻锈剂是解决混凝土中钢筋腐蚀问题的重要方法之一,通过添加阻锈剂,延缓钢筋生锈损坏的时长,大大增加混凝土建筑物的使用寿命。通过简要介绍了钢筋混凝土阻锈剂的技术发展历史背景与其应用以及近年来的研究进展,对钢筋混凝土阻锈剂未来技术方向进行了展望,为研发一种高性能的绿色阻锈剂提供了参考。     

建筑施工现场中焊接技术的质量控制

大部分建筑项目的构筑物以钢筋混凝土结构为主,因此,钢筋焊接是现场施工中的一个重要环节。钢筋的焊接技术种类多样,具体的施工方式也会根据施工环境与工程项目特点的变化而不同。为保证建筑物结构足够稳定、安全,必须对钢筋混凝土结构中的钢筋焊接技术进行质量控制。文章分析了焊接施工各个阶段的质量管控要点,指出各个环节存在的问题,并提出解决方法,希望为焊接施工行业质量管理工作提供参考。     

专家呼吁推广使用环氧树脂涂层钢筋

近日在北京召开的“环氧树脂涂层钢筋应用技术研讨会”上，针对使用一般钢筋混凝土中出现的钢筋腐蚀、严重缩短建筑结构使用寿命问题，有关专家呼吁应推广使用环氧树脂涂层钢筋。     

关于建筑工程钢筋检测的几个问题分析

现代建筑施工过程中会使用到很多钢筋混凝土结构,在施工过程中为了保证施工的质量,提高钢筋混凝土结构的耐久性和使用寿命,对项目工程的钢筋进行检测十分有必要。本文主要结合项目工程实际情况,对钢筋检测过程中常年的几个问题进行分析,希望本次研究对更好的开展钢筋检测有一定的帮助。     

混凝土裂缝产生的原因及应对措施

钢筋混凝土的质量一直建筑工作者需要面对的主要问题,钢筋混凝土的裂缝是建筑施工中最难解决的问题之一,这些裂缝不仅影响建筑物的美观,而且影响建筑物的使用功能,大大降低了建筑物结构的耐久性;破坏其整体性、降低其刚度;引起钢筋腐蚀。因此如何解决这种常见的混凝土裂缝,是设计者和施工者都不应忽视的问题     

久美特涂层对镁水泥混凝土中钢筋保护试验研究

针对镁水泥混凝土自身氯离子对钢筋的腐蚀而降低了镁水泥钢筋混凝土工作寿命的问题,提出利用久美特涂层来缓解氯盐对钢筋的腐蚀作用.试验通过利用电化学工作站对久美特涂层钢筋的镁水泥钢筋混凝土试件在自然环境下和水环境以及氯化镁溶液中的极化曲线进行分析.结果表明:通过对腐蚀电流密度和腐蚀电位的分析得导出久美特涂层可以很好的保护镁水泥钢筋混凝土中的钢筋免受腐蚀,并且混凝土保护层厚度越大钢筋的腐蚀电流密度就越小.在最后腐蚀达到稳定后,久美特涂层钢筋腐蚀电流密度的数量级是钢筋无锈蚀时的100分之一,从而得出久美特涂层对镁水泥钢筋混凝土中的钢筋起到很好的保护作用,使得镁水泥混凝土在盐渍土中依然可以拥有很好的工作性能.     

高流态掺灰混凝土在济钢煤塔加固中的应用

济钢焦炉加煤车更换后 ,荷载比原加煤车增加两倍多 ,通过增加煤塔轨道钢筋混凝土梁截面高度解决强度不足问题。梁底部采用高流态掺灰混凝土进行浇筑。经选材、配合比试验和检测 ,效果良好。本文介绍高流态掺灰混凝土原理、配比和现场施工方法 ,为解决类似工程钢筋密集部位的振捣问题提供参考。     

科尔泰项目钢筋工程施工技术优化

钢筋材料具有很好的延展性，该性能可有效地弥补混凝土结构延展性差的缺陷。钢筋混凝土结构在现代建筑工程中得到了广泛应用。为了进一步发挥钢筋工程的应用价值，文章以科尔泰建筑项目为研究对象，对钢筋工程施工技术的应用要点进行了分析，并提出了一些优化建议。     

混凝土中钢筋锈蚀研究现状与热点问题分析

在恶劣环境条件下,混凝土结构中钢筋的锈蚀问题已成为腐蚀领域和土木工程材料领域共同关注的话题。引起混凝土中钢筋钝化膜破坏进而诱发锈蚀的机理尚未明确,且影响钢筋锈蚀发展的因素复杂多变,最终导致了钢筋混凝土结构过早失效,严重影响了钢筋混凝土结构的服役寿命。首先,评述了导致钢筋锈蚀的3大原因(氯离子侵蚀、碳化作用与杂散电流);其次,阐述了影响钢筋锈蚀发展的重要因素(相对湿度、氧气扩散与温度等);最后,依据研究现状着重分析了钢筋锈蚀研究中出现的氯离子临界值,钢筋–混凝土界面区,开裂–锈蚀交互作用等热点问题。对今后钢筋锈蚀的研究重点进行了展望。     

钢筋混凝土管架栓焊混合连接节点的稳定性试验

针对现有装配式建筑梁柱连接节点稳定性低的问题，以混凝土、钢筋、钢板试件材料为原材料，设计一种新型钢筋混凝土管架梁柱连接节点，并从强度、延性、刚度退化3个方面进行试验。结果表明，所设计钢筋混凝土管架梁柱连接节点通过在梁端设置狗骨而构造塑性铰，可有效增大试件破坏时的极限位移，正向和负向负载下的屈服位移介于27～34 mm，刚度退化较为平稳，满足钢筋混凝土管架稳定性要求，具有较强的连接稳定性。     

光圆钢筋与混凝土界面粘结滑移本构模型研究

对配置光圆钢筋的既有混凝土结构进行承载性能评估时,钢筋与混凝土界面粘结性能优劣是评价该类混凝土结构的重要内容.为此,制作了4组光圆钢筋的中心拉拔试件和2组变形钢筋对比试件,选取粘结长度、钢筋表面形式为主要变量对粘结性能进行试验研究,并通过4组铝合金拉拔试件对比分析光圆筋与混凝土界面的粘结机理.研究结果表明:光圆钢筋的粘结强度显著小于变形钢筋的粘结强度,平均约为变形钢筋粘结强度的18.3%;光圆钢筋的粘结强度主要由化学粘着力和界面摩擦力构成,而铝合金的粘结强度则由化学粘着力构成,平均约为光圆钢筋粘结强度的10%;增加粘结长度后,光圆钢筋的粘结强度随之增大,但铝合金筋的粘结强度无明显变化.进一步基于试验结果及理论分析,建立了光圆钢筋与混凝土界面的粘结-滑移本构模型,并通过已有试验数据对建议模型进行了验证,吻合较好.     

基于不同胶凝材料钢筋混凝土耐腐蚀性试验研究

针对混凝土结构中钢筋的锈蚀问题,以普通硅酸盐水泥和镁水泥作为胶凝材料,制作了钢筋裸露和涂有环氧树脂涂层的4种钢筋混凝土试件,将其浸泡在氯盐、硫酸盐及镁盐的耦合溶液中,利用电化学方法得到极化曲线和交流阻抗谱,通过塔菲尔外推法进行非线性最小二乘法拟合计算得到腐蚀电流密度、腐蚀电位、腐蚀速率等相关评价指标来衡量混凝土中钢筋锈蚀情况.结果表明:长期浸泡在耦合盐溶液中,普通硅酸盐水泥和镁水泥钢筋混凝土试件都发生了较严重的腐蚀,普通硅酸盐水泥的抗腐蚀性优于镁水泥;在钢筋表面涂有GHT涂层可极大地降低钢筋的腐蚀速率;镁水泥GHT涂层混凝土试件的抗腐蚀性能劣于硅酸盐GHT涂层混凝土试件但优于硅酸盐裸露钢筋混凝土.     

Effect of carbon fibres on the mechanical properties and corrosion levels of reinforced portland cement mortars

The changes in mechanical properties of portland cement mortars due to the addition of carbon fibres (CF) to the mix have been studied. Compression and flexural strengths have been determined in relation to the amount of fibres added to the mix, water/binder ratio, curing time and porosity. Additionally, the corrosion level of reinforcing steel bars embedded in portland cement mortars containing CF and silica fume (SF) have also been investigated and reinforcing steel corrosion rates have been determined. As a consequence of the large concentration of oxygen groups in CF surface, a good interaction between the CF and the water of the mortar paste is to be expected. A CF content of 0.5% of cement weight implies an optimum increase in flexural strength and an increase in embedded steel corrosion.     

Use of no-fines concrete as a building material: Strength,durability properties and corrosion protection of embedded steel

Although no-fines concrete has been generally used for paving applications, it could be considered in other non-structural applications, such as reinforced panels, thanks to its acoustic, thermal and permeability properties. In this work, mechanical, durability-related properties and the protection provided by no-fines concrete to embedded steel against carbonation-induced corrosion have been investigated on mixtures with compressive strength in the range 7–30 MPa. Additional protections, such as a mixed-in hydrophobic admixture, the coating of cement paste on the reinforcing bar or the use of galvanized or stainless steel bars, are also considered. Results show that, although no-fines concrete is susceptible to fast carbonation and it cannot provide long-term passivation to embedded steel, it may prevent corrosion in elements exposed to the atmosphere and sheltered by rain. In case of frequent contact with water, additional protections are required, preferably based on the use of corrosion resistant bars.     

High-strength low-alloy,weathering, steel as reinforcement in the presence of chloride ions

The chloride induced corrosion of both conventional reinforcing and high-strength, low-alloy, weathering, steel bars was studied. The bars were inbeded in concrete and the latter was salted with dosages typical for bridge decks. After five years, all samples containing conventional reinforcing were severely cracked. All of the samples containing the high-strength, low-alloy steel were completely free of cracks.     

掺防冻剂混凝土钢筋阻锈机理的研究

阐述了含不同浓度氯盐及亚硝酸盐防冻剂的砂浆,经水化后砂浆孔溶液中各种离子的浓度随着养护时间所发生的变化,并测定埋入钢筋的电极电位、钢筋腐蚀面积率、钢筋腐蚀减量等。实验结果表明:钢筋腐蚀时的电极电位、钢筋腐蚀面积率、钢筋腐蚀减量等性能与砂浆孔溶液中的离子浓度有密切的联系;掺入的NO_2~-浓度越大,硬化砂浆细孔溶液中的NO_2与Cl~-的摩尔比也越大,抑制钢筋腐蚀的效果越明显。     

Effect of corrosion on bond in reinforced concrete under cyclic loading

Cyclic loading can result in severe deterioration in the bond between reinforcing steel bar and the surrounding concrete, especially when the reinforcement is corroded. In this study, tests were carried out for bond stress-slip response of corroded reinforcement with concrete under cyclic loading. Parameters investigated include: corrosion level, confinement, bar type, and loading history. The results revealed that bond behaviour was significantly reduced under cyclic loading. Degradation in bond was significantly less for deformed bars than for smooth bars at the initial loading cycle, but the difference was diminished with loading. The bond reduction was more substantial for unconfined steel bars than for confined bars. The relatively high level of corrosion caused degradation primarily in the initial five cycles, the effect of corrosion being decreased with loading. It was also demonstrated that the cyclic bond stress-slip curves depended on loading history.     

Study of interactions between sodium monofluorophosphate and hardened cement paste and their consequences on concrete transfer properties

Surface applied corrosion inhibitors are one of the methods used to protect embedded reinforcing bars from corrosion. This paper presents a study of interactions that can occur between sodium monofluorophosphate (MFP) and concrete during its transport from the applied surface to the steel. Interactions of MFP with portlandite have clearly been observed with X-ray diffraction diagrams. Tests with solutions have been realised, and show that an amorphous gel appears when MFP is in contact with a saturated calcium hydroxide solution. Percolation tests have highlighted the consequences of these reactions on concrete properties. In the last part of this study, quantitative chemical analysis of the percolate is presented: they show that when the concentration of the MFP solution increases, more MFP is found in the percolate even if a large part is kept in the concrete sample.     

FRP筋混凝土结构的现状与发展

由钢筋腐蚀导致混凝土结构破坏的现象普遍,国内外专家学者一直在寻找解决这一问题的方法.最近人们发现,利用轻质、高强度、耐腐蚀的纤维增强聚合物(FRP)材料取代钢筋是解决这一问题的根本性方法.本文总结了最近国内外关于FRP材料的最新研究成果,对FRP材料未来的发展做出了展望.     

Modeling bond strength of corroded reinforcement without stirrups

Deterioration of bond strength between concrete and reinforcement is of great importance in studying the strength of structural members with corroded reinforcements. A simple analytical model is proposed to demonstrate the effect of corrosion of reinforcing bar on reduction of bond strength. The corrosion pressure due to expansive action of corrosion products before and after corrosion cracking is firstly estimated. Then, reduction of bar confinement caused by cover cracking, change of friction coefficient between the steel and the concrete, and reduction of the friction force on the bearing face as well as deterioration of the ribs of the deformed bars due to steel corrosion are considered in calculating the mechanical interactions between reinforcing bar and concrete. As a result, the bond strength of corroded bars is calculated. The theoretical results are compared with the experimental results and agree with those results well.