IDR: Optical Imaging of High pH Dependent Degradation in Infrastructure Materials

这个跨学科研究（IDR）项目的目标是研究使用先进的化学传感方法来测量新鲜和老化混凝土的pH值。这项工作将通过空间和时间分辨率的测量来更好地理解混凝土结构中的酸/碱依赖降解现象。该项目的方法是专门用于研究混凝土中的碱骨料反应，这是混凝土结构过早退化的主要原因。这种高度依赖于pH值的降解反应发生在水化波特兰水泥的高pH介质和周围的骨料之间，产生膨胀的副产物，导致混凝土的显著开裂。所提出的方法将利用由合成卟啉传感器分子制成的化学传感器，当与混凝土中的碱接触时，其光谱显示ph特异性变化。传感器分子将混合到新混凝土中或应用于断裂的混凝土表面，以实现pH值的测量。该研究项目将结合合成化学家的专业知识来设计和合成合适的ph感应发色团，以及土木工程师的专业知识来应用这些发色团来研究碱-硅对混凝土材料的反应。如果成功，通过这笔资助创造的知识将使研究人员能够更好地了解碱离子的动力学和混凝土结构中由此产生的压力。这种理解最终将提高我们在混凝土结构的测试、缓解、修复、监测、早期检测和使用寿命预测方面的能力。

The objective of this Interdisciplinary Research (IDR) project is to study the use of advanced chemical sensing methods to measure the pH values in fresh and aging concrete. This work will be carried out for better understanding the acid/alkali dependent degradation phenomena in concrete structures by measurements with spatial and temporal resolution. The project's approach is specifically designed to study alkali-aggregate reactions in concrete, a major contributor to the premature deterioration of concrete structures. This strongly pH-dependent degradation reaction that takes place between the high pH media of hydrated Portland cement and the surrounding aggregate, produces expansive byproducts that result in the significant cracking of concrete. The proposed method will utilize a chemosensor made from a synthetic porphyrin-based sensor molecule that shows pH-specific changes in its optical spectrum when in contact with the alkali in concrete. The sensor molecule will be mixed into fresh concrete or applied onto fractured concrete surfaces to enable the measurement of pH levels. This research project will combine the expertise of a synthetic chemist for the design and synthesis of suitable pH-sensing chromophores, and the expertise of civil engineers to apply these chromophores in the study of alkali-silica reaction to concrete materials.If successful, the knowledge created through this grant will enable researchers to better understand the kinetics of alkali ions and the resulting distress in concrete structures. This understanding will ultimately enhance our capabilities in testing, mitigation, remediation, monitoring, early detection and service life prediction of concrete structures.