Concrete Durability: Linking Material Properties and Field Performance

混凝土是世界上使用最广泛的建筑材料，但人们往往对其认识不足，设计不当，导致在许多恶劣的暴露条件下过早变质。申请人的研究计划旨在对在不同环境中可能发生的劣化过程有一个基本的了解，确定适当的材料特性来抵抗破坏力，量化和预测劣化速度，并用现场性能研究来验证实验观察。正在进行的研究计划的主要重点是继续开发和改进适当的测试方法和预测模型，以评估混凝土对一些更普遍的劣化形式的抗力；这些劣化形式是：(I)氯离子侵入和钢材腐蚀，(Ii)碱-硅酸反应，(Iii)硫酸盐侵蚀，以及(Iv)ASR和冻融相结合。该研究计划的主要目标是：*1.验证现有的氯离子渗透预测模型，包括申请人和不同合作者开发的模型。将通过持续的长期实验室和实地暴露测试以及结构抽样进行验证。将开发一个两阶段模型，以包括碳化作用从表面渗透时的影响。*2.开发改进的碱-硅酸反应(ASR)试验方法，在暴露条件下提供足够的水分，而不允许碱从混凝土中进出。验证和校准将使用申请者和合作者建立的许多长期暴露场所的数据，并通过使用几十年来一直被监测的现有结构的数据来进行。*3.ASR与冻融攻击的协同作用。ASR会导致混凝土膨胀和开裂，这本身可能不会导致结构寿命的终止，但可能会使其更容易受到其他工艺的影响。具有一定ASR损伤级别和不同饱和度的混凝土将暴露在冻融循环中。研究计划的这一部分(ASR-冻结/解冻)将与俄勒冈州立大学(以前与普渡大学合作)的Jason Weiss合作进行。*4.改进的混凝土抗硫酸盐侵蚀试验的发展。这项测试将使用硫酸盐暴露现场的数据进行基准测试。**

Concrete is the most widely-used construction material in the world but is often poorly understood and inadequately designed leading to premature deterioration in many aggressive exposure conditions. The applicant's research program is aimed at developing a fundamental understanding of the deterioration processes that can occur in different environments, determining the appropriate material properties to resist the destructive forces, quantifying and predicting rates of deterioration, and validating experimental observations with field performance studies. The main focus of the ongoing research program is to continue the development and improvement of appropriate test methods and predictive models for evaluating concrete's resistance to some of the more prevalent forms of deterioration; these are: (i) chloride ingress and corrosion of steel, (ii) alkali-silica reaction, (iii) sulfate attack, and (iv) combined ASR and freeze-thaw. The main objectives of the research program are: ***1. Validation of existing models for predicting chloride penetration, including models developed by the applicant and various collaborators. Validation will be conducted through ongoing long-term laboratory and field-exposure testing, and sampling of structures. A two-phase model will be developed to include the impact of carbonation as it penetrates from the surface. ***2. Development of improved test methods for alkali-silica reaction (ASR) with exposure conditions designed to provide sufficient moisture without allowing the ingress or egress of alkalis from the concrete. Validation and calibration will be performed using data from numerous long-term exposure sites that have been established by the applicant and collaborators, and through the use of data from existing structures that have been monitored for decades. ***3. Synergy between ASR and freeze-thaw attack. ASR results in expansion and cracking of concrete which may not in itself result in the end of the life of a structure but which may render it more vulnerable to other processes. Concretes with a range of ASR-damage levels and various degrees of saturation will be exposed to freeze-thaw cycles. This component of the research program (ASR-freeze/thaw) will conducted in collaboration with Jason Weiss of Oregon State University (previously with Purdue University). ***4. Development of an improved test for evaluating sulfate resistance of concrete. The test will be benchmarked using data from a sulfate exposure site. **