Impact of meta-stable chloride hydrate phases on concrete durability at near-freezing temperatures

近冰点温度下亚稳定氯化物水合物相对混凝土耐久性的影响

• 批准号: RGPIN-2014-05027
• 负责人: Peterson, Karl
• 金额: $ 1.46万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=662033
• 关键词: Impact; meta; stable; chloride; hydrate

Winter maintenance practices for concrete pavements have undergone major changes within the last ten years. De-icing/anti-icing strategies based on traditional rock salt (NaCl) have expanded to include alternative chemicals based on magnesium chloride, calcium chloride, and potassium acetate, to name a few. The impact of these new chemicals and new application methodologies on the durability of concrete infrastructure is not fully understood. The goal of the research program is to understand concrete degradation mechanisms attributed to the expansive precipitation of secondary chloride phases that occur at temperatures near 0°C. At temperatures near the freezing point of water the formation of complex calcium oxychloride (Ca-oxy) hydrate phases has been shown to cause expansion and damage in concrete, but the instability of these phases at room temperature and humidity has hampered further study. This research program incorporates both an experimental laboratory approach, and the exploratory real-world sampling of concrete exposed to chloride ion solutions and freeze-thaw (F-T) environments. In the laboratory portion, carefully controlled constant-immersion and evaporative-front exposure experiments will be conducted on a matrix of concrete mixtures, and coupled with periodic sampling to assess the development of secondary minerals and damage through a combination of mass and length change measurements, strength testing, combined scanning electron microscopy energy dispersive x-ray spectrometry (SEM/EDS), x-ray micro-fluorescence (µXRF), x-ray computed tomography (CT), and x-ray diffraction (XRD) techniques. In addition, Ca-oxy hydrate will be synthesized and characterized to determine its crystallographic and thermodynamic properties. To compliment the laboratory study, a series of field sites will be identified and the concrete sampled and recovered in such a manner as to maintain field temperature and humidity conditions for XRD analysis, particularly for the preservation of Ca-oxy hydrate phases. The information collected will be used to help integrate the formation of these secondary phases into existing models for the prediction of chloride penetration and concrete degradation.

过去十年中，混凝土路面的冬季维护实践发生了重大变化，基于传统岩盐 (NaCl) 的除冰/防冰策略已扩展到包括基于氯化镁、氯化钙和醋酸钾的替代化学品。仅举几例。这些新化学品和新应用方法对混凝土基础设施耐久性的影响尚未完全了解。该研究计划的目标是了解由于二次氯化物相膨胀沉淀而导致的混凝土降解机制。温度接近在接近水冰点的温度下，复杂的氯氧化钙（Ca-oxy）水合物相的形成已被证明会导致混凝土膨胀和损坏，但这些相在室温和湿度下的不稳定性进一步阻碍了混凝土的形成。该研究计划结合了实验实验室方法和对暴露于氯离子溶液和冻融（F-T）环境中的混凝土进行探索性现实采样。蒸发前暴露实验将在混凝土混合物基质上进行，并结合定期取样，通过质量和长度变化测量、强度测试、组合扫描电子显微镜能量色散 x- 的组合来评估次生矿物的发育和损害。射线光谱分析 (SEM/EDS)、X 射线微荧光 (μXRF)、X 射线计算机断层扫描 (CT) 和 X 射线衍射 (XRD) 技术。将进行合成和表征，以确定其晶体学和热力学特性，以补充实验室研究，将确定一系列现场地点并对混凝土进行采样和回收，以维持 XRD 分析的现场温度和湿度条件。收集的信息将用于帮助将这些二次相的形成整合到现有模型中，以预测氯化物渗透和混凝土降解。