Microwave Evaluation and Modeling of Rapid Chloride Ingress in Mortar

砂浆中氯化物快速侵入的微波评估和建模

• 批准号: 0233243
• 负责人: Reza Zoughi
• 金额: $ 5.72万
• 依托单位: Missouri University of Science and Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-01 至 2003-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0233243&HistoricalAwards=false
• 关键词: Microwave; Evaluation; Modeling; Rapid; Chloride

ABSTRACTSteel corrosion and the resulting deterioration of reinforced concrete structures is one of the primary causes of increasing damage to infrastructure. Corrosion of the reinforcing steel is implicated as a cause of damage to the majority of the 226,000 reinforced concrete bridges described by the Federal Highway Administration (FHWA) as deficient. In 1991, the United States Department of Transportation estimated rehabilitation costs for these damaged bridges at $90.9 billion. Concrete normally provides reinforcing steel with adequate corrosion protection. When steel is encased in concrete, a protective iron oxide film forms at the steel-concrete interface due to the high pH of the concrete. However, the presence of a sufficient concentration of chloride ions can compromise the passive layer. In the presence of moisture, the steel will corrode. Development of a reliable test method for in-situ measurement of the chloride ion penetration depth and concentration in concrete structures would be invaluable to the concrete and construction industry. From an economic standpoint, accurate measurements of the concentration of chlorides and penetration depth in concrete structures, would allow agencies to more effectively allocate funding for repair of those structures with the most critical needs. Thus, the overall objective of the proposed investigation is to gain a more complete understanding of the fundamental implications of microwave measurements of cement-based materials exposed to chloride solutions. A methodical research plan is proposed in order to correlate microwave measurements to the salt content and chloride penetration depth in mortar. Mortar samples will be cyclically ponded with salt solution. After the samples are oven dried, a very accurate and sensitive microwave characterization technique will be used to evaluate their dielectric properties using four independent complex reflection and transmission coefficients. This information is then used in conjunction with a discrete layered electromagnetic model and a dielectric mixing formula to render information about the salt volume content as a function of depth into the samples. This process is repeated for a number of soaking cycles, giving information about salt penetration gradient and total content as a function of depth into the sample, sample make-up and soaking cycle. The anticipated outcome of this proposed investigation constitutes a significant and comprehensive leap forward in the path to evaluating chloride ingress in reinforced concrete structures.

摘要钢筋混凝土结构的腐蚀和劣化是造成基础设施破坏日益严重的主要原因之一。美国联邦公路管理局（FHWA）称，22万6千座钢筋混凝土桥梁中，大部分存在缺陷，其中钢筋腐蚀是造成桥梁损坏的原因。1991年，美国运输部估计这些受损桥梁的修复费用为909亿美元。混凝土通常为钢筋提供足够的防腐保护。当钢被包裹在混凝土中时，由于混凝土的高pH值，在钢-混凝土界面形成一层保护性的氧化铁膜。然而，足够浓度的氯离子的存在会破坏钝化层。在有水分的情况下，钢会腐蚀。开发一种可靠的原位测量氯离子在混凝土结构中的渗透深度和浓度的测试方法对混凝土和建筑行业具有不可估量的价值。从经济角度来看，准确测量氯化物的浓度和混凝土结构的渗透深度将使各机构能够更有效地拨出资金，用于修复那些最急需的结构。因此，拟议调查的总体目标是更全面地了解暴露于氯化物溶液的水泥基材料的微波测量的基本含义。为了将微波测量与砂浆中盐含量和氯化物渗透深度相关联，提出了一种系统的研究方案。砂浆样品将与盐溶液循环浸泡。样品经过烘箱干燥后，将使用一种非常精确和敏感的微波表征技术，利用四个独立的复反射和透射系数来评估其介电性能。然后将该信息与离散分层电磁模型和介电混合公式结合使用，以呈现盐体积含量作为样品深度函数的信息。这一过程重复了许多次浸泡循环，得到盐渗透梯度和总含量的信息，作为进入样品的深度、样品组成和浸泡周期的函数。这项拟议调查的预期结果在评估钢筋混凝土结构中氯化物进入的道路上构成了重大而全面的飞跃。