Concrete and mortar deterioration and fracture: a forensic approach

混凝土和砂浆劣化和断裂：法医方法本研究旨在从微观角度提高对导致劣化因素的复杂组合的理解，并为更耐用的混凝土和砂浆基础设施设计解决方案。这项工作的一个重要重点将是将涉及手工、材料选择和环境暴露的因素与载荷诱导的应力相结合，通过结合微观结构分析、实验和裂缝建模，更好地了解裂缝网络的发展。这种方法不仅需要对混凝土或砂浆中成分的矿物学、化学和分布进行详细的表征，而且还需要对裂缝本身进行详细的表征。该研究计划依赖于非常适合描述裂缝特征的3D和2D成像技术：X射线计算机断层扫描，然后进行薄层切片和光学显微镜检查。这种组合允许在宏观和微观两个层面上绘制详细的裂纹图。同样的样品在扫描电子显微镜下和压痕下进一步询问，允许对胶凝和集料成分进行微到纳米级别的化学和微机械探索。这些技术一起提供了一个全面的评估，允许解释混凝土和砂浆劣化的表现。这种取证方法建立在目前正在进行的研究工作的基础上，包括调查(1)粗集料对混凝土强度的影响，(2)管道混凝土保护层的裂缝发展，以及(3)历史砖石的恢复、修复和保护。这项研究将促进对粘结剂和骨料在荷载诱导的混凝土断裂中所起的作用、混凝土断裂网络与地下环境中侵蚀性溶液的相互作用以及修复砂浆中粘结强度发展的理解。这些成果将为混凝土和砂浆混合设计提供信息并改进实践，并支持建筑业努力应对维护和创造未来混凝土和砖石基础设施的许多挑战。

Concrete and mortar deterioration and fracture: a forensic approach This research aims to improve understanding of the complex combinations of factors that lead to deterioration from a microscopic perspective, and to devise solutions for more durable concrete and mortar based infrastructure. An important focus of this effort will be to unite factors that involve artisanship, choice of materials, and environmental exposure with load-induced stresses, to better understand the development of fracture networks, through a combination of microstructural analysis, experiment, and fracture modeling. This approach requires detailed characterization of not only the mineralogy, chemistry, and distribution of the constituents within the concrete or mortar, but also detailed characterization of the fractures themselves. The research program relies on 3D and 2D imaging techniques well-suited to fracture characterization: x-ray computed tomography followed by thin sectioning and examination by optical microscopy. This combination allows for detailed crack mapping that spans both the macro and micro-level. The same samples are further interrogated under a scanning electron microscope and by indentation, allowing for micro to nano level chemical and micro mechanical exploration of cementitious and aggregate components. Together these techniques provide a thorough assessment that allows for interpretation of manifestations of concrete and mortar deterioration. This forensic approach builds on research efforts currently underway, including investigations of (1) the influence of coarse aggregate on concrete strength, (2) crack development in protective concrete coatings for pipelines, and (3) the restoration, rehabilitation, and preservation of historic masonry. The research will advance understanding of the roles binder and aggregate play under load-induced concrete fracture, the interaction of concrete fracture networks with aggressive solutions in subsurface environments, and bond strength development in restoration mortars. These outcomes will inform and improve practices around concrete and mortar mix design, and support the construction industry's efforts to meet the many challenges of maintaining and creating tomorrow's concrete and masonry based infrastructure.