Understanding the Mechanism and Kinetics of Pyrrhotite-induced Damage in Concrete

这项研究将提供必要的基础知识，以快速，可靠地区分混凝土的耐久性和有害骨料。具体而言，它将集中在磁黄铁矿引起的损害，在具体的机制和动力学，这种情况已经摧毁了一些住宅社区在美国北方。由于优质的原生骨料正在枯竭，在确定和采购高质量和耐用的建筑骨料方面的挑战正在增加。 自然资源的可持续管理需要一个深思熟虑的使用剩余供应的哲学。该项目将导致确定最佳的协议，用于检测和量化的磁黄铁矿在混凝土中的反应。通过科学选择骨料，可以降低补救过早恶化和混凝土退化的成本。因此，社会和经济效益很高，并转化为设计可持续建筑环境的新知识和技术。该项目的成果将确保混凝土建筑物和结构的安全性、适用性和持续使用，沿着保护其所有者和居住者的健康和经济生计。（聚集体中丰富的硫化物矿物）在与湿气和大气氧接触时氧化，在混凝土中形成膨胀性的氢氧化铁和硫酸。后者随后导致二次损伤，包括酸侵蚀、硫酸盐侵蚀和钢筋腐蚀。到目前为止，磁黄铁矿的氧化只在酸性矿山排水（低pH值）的情况下进行了分析。本研究的新奇在于对混凝土环境中磁黄铁矿的氧化进行了深入研究。具体而言，pH值，温度，相对湿度和氧气水平对混凝土中的反应和损伤演变的幅度和速率的影响将被量化。将进行铁氧化物相的选择性溶解，并进行地球化学计算，以计算磁黄铁矿反应性引起的体积变化。将建立综合的氧气输送和热力学模型，以便快速可靠地评估和预测损害。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This research will deliver fundamental knowledge necessary to rapidly and reliably distinguish durable from deleterious aggregates for concrete. Specifically, it will focus on mechanisms and kinetics of pyrrhotite-induced damage in concrete, a situation that has devastated some residential communities in the northern United States. Challenges in identifying and procuring high quality and durable construction aggregate are on the rise, as good quality virgin aggregates are being depleted. Sustainable management of natural resources requires a well-thought-out philosophy of using the remaining supplies. This project will lead to identifying optimal protocols for detection and quantification of pyrrhotite reactivity in concrete. By enabling science-driven selection of the aggregates, the costs of remediating premature deterioration and concrete degradation can be reduced. As such, societal and economic benefits are high and translate into new knowledge and technology to design sustainable built environment. The outcomes of this project will ensure safety, serviceability and continued use of concrete buildings and structures, along with protecting health and financial livelihood of their owners and occupants.The pyrrhotite damage in concrete is a result of deleterious expansions taking place when pyrrhotite (an abundant sulfide mineral in aggregates) oxidizes in contact with moisture and atmospheric oxygen, forming expansive iron hydroxides and sulfuric acid inside concrete. The latter subsequently leads to secondary damages, including acid attack, sulfate attack, and rebar corrosion. To date, pyrrhotite oxidation has been analyzed only in the context of acid mine drainage (low pH). The novelty of this research is in thorough investigation of pyrrhotite oxidation in concrete environment. Specifically, the effects of pH, temperature, RH, and oxygen level on the magnitude and rate of reaction and damage evolution in concrete will be quantified. Selective dissolution of Fe-oxide phases will be conducted and geochemical calculations executed to calculate volumetric changes resulting from pyrrhotite reactivity. Integrated oxygen transport and thermodynamic models will be created for rapid and reliable assessment and prediction of damage. While developed for pyrrhotite-related degradation, this transformative approach will be applicable to a wide array of aggregate-induced damages in concrete.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.