钢筋形态参数评价方法的适用性分析
Summary
本文采用不同的方法测量钢筋的几何形状和腐蚀量: 质量损失、卡钳、排水测量、三维扫描和 x 射线显微计算机断层扫描 (xct)。
Abstract
腐蚀钢筋长度的不规则和不均匀残余截面极大地改变了其机械性能, 极大地主导了现有混凝土结构的安全性和性能。因此, 正确测量结构中钢筋的几何形状和腐蚀量, 以评估结构的剩余承载力和使用寿命, 是非常重要的。本文介绍并比较了五种不同的测量钢筋的几何形状和腐蚀量的方法。在本协议中, 单根500毫米长、直径14毫米的钢筋是受到加速腐蚀的试样。在质量损失测量、vernier 卡钳、排水测量、三维扫描和 x 射线微计算机断层扫描 (xct) 之前和之后, 对其形态和腐蚀量进行了仔细测量。然后对这些不同方法的适用性和适用性进行了评价。结果表明, vernier 卡钳是测量无腐蚀棒形态的最佳选择, 而三维扫描是最适合于定量测量腐蚀棒的形态的最佳选择。
Introduction
钢筋腐蚀是混凝土结构恶化的主要原因之一, 是混凝土碳化和氯部侵入造成的。在混凝土碳化中, 腐蚀倾向于广义;而在氯化物入侵, 它变得更加本地化1,2。不管是什么原因, 腐蚀会使腐蚀产品的径向膨胀导致混凝土盖发生腐蚀, 使钢筋与其周围混凝土之间的粘结变差, 穿透钢筋表面, 并减少钢筋的横截面面积相当3,4。
由于结构混凝土的非均匀性和使用环境的变化, 钢筋的腐蚀在其表面和长度上随机发生, 具有很大的不确定性。与混凝土碳化引起的广义均匀腐蚀相反, 氯离子入侵引起的点蚀引起了攻击的渗透。此外, 它还会导致腐蚀杆的残余部分在棒材表面和长度之间有很大的差异。因此, 棒材强度和杆延性降低。已经进行了广泛的研究, 以研究腐蚀对钢筋的机械性能的影响 5,6,7, 8,9,10 11,12,13,14,15。然而, 对钢筋形态参数和腐蚀特性的测量方法关注较少。
一些研究人员用质量损失来评估钢筋5、10、11、14 的腐蚀程度。但是, 此方法只能用于确定残段的平均值, 不能测量截面沿长度的分布。朱和佛朗哥改进了这种方法, 将一根钢筋切割成一系列短段, 并称重每个段, 以确定剩余截面沿其长度13,14的区域的变化。然而, 这种方法在切割过程中造成了钢材料的额外损失, 不能准确地接触到腐蚀钢筋的最小残余部分, 这决定了其承载能力。游标卡尺还用于测量 14,15钢筋的几何参数。然而, 腐蚀杆的残余截面是非常不规则的, 并且在被测量的和实际的截面尺寸之间总是有明显的偏差被腐蚀的酒吧。根据阿基米德原理, 克拉克等人采用排水法测量腐蚀杆沿长度的残余部分, 但在这种情况下, 在没有明显精度的情况下, 对钢筋的位移进行了人工控制, 但没有明显的精度11。通过使用电动机自动控制钢筋的位移, 更准确地测量结果, 改进了这种排水方法.最后, 在过去几年中, 随着三维扫描技术的发展, 该方法被用来测量钢筋的几何尺寸 17,18,19, 20.通过三维扫描, 可以精确地获得钢筋的直径、残余面积、质心、偏心、转动惯量和腐蚀渗透。尽管研究人员在不同的实验环境中使用了这些方法, 但在精度、适用性和适用性方面对这些方法没有进行比较和评价。
腐蚀, 特别是点蚀, 与广义腐蚀相比, 不仅改变了腐蚀钢筋的力学性能, 而且降低了混凝土结构的剩余承载力和使用寿命。为了更合理地评估钢筋的力学性能, 必须更准确地测量腐蚀钢筋的形态参数, 以确定钢筋长度腐蚀的空间变异性。这将有助于更准确地评估受腐蚀损坏的钢筋混凝土 (rc) 结构的安全性和可靠性21、22、23、24、25、26 ,27,28,29。
该协议比较了五种讨论的测量钢筋几何形状和腐蚀量的方法。一个单, 500 毫米长, 14 毫米直径, 平圆棒被用作样品, 并在实验室中受到加速腐蚀。在使用每种方法之前和之后, 仔细测量其形态和腐蚀程度, 包括质量损失、vernier 卡钳、排水测量、三维扫描和 x 射线微型计算机断层扫描 (xct)。最后, 对两者的适用性和适用性进行了评价。
需要注意的是, 嵌入混凝土中的带肋钢筋, 而不是暴露在空气中的普通钢筋, 通常用于混凝土结构, 并受到腐蚀。对于带肋的酒吧, vernier 卡钳可能不那么容易应用。由于这些钢筋在混凝土中腐蚀, 与暴露在空气中的钢筋相比, 它们的表面渗透更加不规则。然而, 该协议是为了在同一柱上对不同测量方法的分析的适用性而设计的;因此, 它采用赤裸的平条作为样品, 以消除肋和混凝土非均匀性对形态参数测量的影响。今后还可以进一步研究用其他方法测量腐蚀的肋钢筋。
Protocol
Representative Results
Discussion
图 6a和6A显示, 未腐蚀棒材试样的测量直径在其长度上没有显著变化。沿杆长测量的直径之间的最大差异仅为 0.11 mm 左右, 最大偏差为0.7%。这表明, 使用游标卡尺可以很好地评估无腐蚀条形图的几何形状。但是, 在同一截面的不同角度测量的直径之间的差异是一致的, 而且差别很大。对于给定的棒材试样, 最大直径为 14.62 mm 和 14.62 mm, 角度为45°和 135°, 最大偏差为4%…
Disclosures
The authors have nothing to disclose.
Acknowledgements
深圳大学作者非常感谢国家自然科学基金 (51520105012 号和51278303号) 和广东省教育部 (重点) 项目的资助。(编号 2014kzdxm051), 他们还感谢深圳大学土木工程学院广东省海洋土木工程耐久性重点实验室提供的检测设施和设备。
Materials
| Supplies | |||
| Plastic ruler | Deli Group Co.,Ltd. | No.6240 | |
| white paint pen | SINO PATH Enterprises.,Ltd. | SP-110 | |
| Tube with Branch | Customized-made | ||
| Measurement cylinder | Beijing Huake Bomex Glass Co., Ltd. | ||
| 500mL Beaker | Beijing Huake Bomex Glass Co. , Ltd. | CP-201 | |
| sandpaper | Shanghai Noon Decoration Material Co., Ltd. | P04 | |
| white developer | SHANGHAI XINMEIDA FLAW DETECTION MATERIAL CO., LTD. | FA-5 | |
| Reagents | |||
| epoxy resin adhesive | Hunan Baxiongdi New Material Co., Ltd. | DY·E·44 | |
| epoxy hardener | Hunan Baxiongdi New Material Co., Ltd. | DY·EP | |
| HCl | Dongguan Dongjiang Chemical Reagent Co., Ltd. | AR-2500ml | |
| saturated lime water | Xilong Chemical Co., Ltd. | AR-500g | |
| Equipment | |||
| Digital electronic scale | Kaifeng Group Co., Ltd. | Model JCS-0040 | |
| Digital vernier caliper | Shanghai Measuring & Cutting Tool Works Co., Ltd. | Model ST-089-229-090 | |
| Cutting machine | Robert Bosch GmbH | TCO2000 | |
| 3D reconstructed X-ray microscope | XRADIA | Model MICROXCT-400 | |
| 3D scanner | HOLON Three-dimensional Technology(Shenzhen) Co.,Ltd. | Model HL-3DX+ | |
| Electromechanical Universal Testing Machine | MTS SYSTEMS (China) Co., Ltd. | Model C64.305 |
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