Evaluating the Combined Effects of Stress and Exposure on the Deterioration Rate of Concrete

评估应力和暴露对混凝土劣化率的综合影响

• 批准号: 342535-2013
• 负责人: Boyd, Andrew
• 金额: $ 1.89万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2013
• 资助国家: 加拿大
• 起止时间: 2013-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=527640
• 关键词: Evaluating; Combined; Effects; Stress; Exposure

Concrete is inherently a brittle material, exhibiting low tensile strength and strain capacities. From a structural viewpoint, this is overcome by the addition of reinforcing steel to carry applied tensile loads. However, tensile stresses are still present in the concrete and it tends to crack relatively easily in service. The initiation of cracking leads to accelerated deterioration as deleterious agents penetrate more readily into the cracks. At this point, the rate of deterioration increases exponentially as cracks widen or more cracks form. In addition, the majority of durability-related deterioration processes affecting concrete share a similar basic damaging mechanism; internal expansion resulting in tensile stresses that ultimately lead to cracking. Tensile stresses induced by loading and those resulting from durability-related deterioration processes should be additive, thus accelerating the degradation rate of concrete when acting in concert. However, standard durability tests do not include the effects of stress on deterioration, being instead limited to unloaded specimens. This situation results in a gross overestimation of the deterioration resistance of concrete exposed to deleterious environments. The intent of the proposed research project is to evaluate the effect of combining service loads with deleterious exposure conditions in order to more closely simulate real-world concrete deterioration processes in structures. This type of combined approach is truly unique in the area of standardized durability testing. During exposure, specimens will also be monitored on a regular basis using nondestructive techniques in an attempt to develop better evaluation techniques and criteria for the inspection of real-world structures. The primary focus of the proposed research will be to develop a systematic approach to evaluate and quantify the resultant cracking and its effect on mechanical and transport properties, and ultimately service life.

混凝土本质上是一种脆性材料，表现出低拉伸强度和应变能力。从结构的角度来看，这可以通过添加加固钢来承担施加拉伸载荷来克服。但是，混凝土中仍然存在拉伸应力，并且在使用中往往相对容易破裂。随着有害特工更容易渗透到裂缝中，开裂的启动会导致加速恶化。在这一点上，随着裂缝的扩大或更多的裂纹形成，劣化速率呈指数增加。此外，影响混凝土的大多数与耐用性的恶化过程具有相似的基本损害机制。内部膨胀导致拉伸应力最终导致破裂。负载引起的拉伸应力和与耐用性相关的恶化过程产生的应力应具有添加剂，从而加速了在协同作用时混凝土的降解率。但是，标准耐用性测试不包括应力对劣化的影响，而是仅限于卸载标本。这种情况导致对暴露于有害环境的混凝土的恶化抗性的高估。拟议的研究项目的目的是评估将服务负荷与有害暴露条件相结合的效果，以便更紧密地模拟结构中的现实世界混凝土劣化过程。这种组合方法在标准化耐用性测试领域确实是独一无二的。在暴露期间，还将使用非破坏性技术定期监控标本，以试图开发更好的评估技术和检查现实世界结构的标准。拟议研究的主要重点是开发一种系统的方法来评估和量化所得的破裂及其对机械和运输特性的影响，并最终导致使用寿命。