A Thermo-Kinetic Approach to Enhance the Use of Clays in Concrete

为了应对基础设施建设对可持续混凝土不断增长的需求，过去的研究确定了可用于部分取代混凝土中水泥的具有碳效率的材料(如飞灰、矿渣)。然而，只有当它们在混凝土环境中表现出更强的反应性时，大量使用这些材料才是有益的。由于这些材料的基本组成-反应性关系没有很好地建立，它们的选择是基于反复试验的方法，这是不可靠的，而且往往导致性能低下。此类材料的质量低和可获得性有限，进一步边缘化了它们作为建筑材料的使用。因此，要产生重大的全球影响，需要确定和调整大量、廉价、碳效率高和高活性的材料，以用于混凝土。粘土在所有地质环境中都很丰富，符合所有这些标准。这项研究旨在通过用粘土和其他容易获得的无机材料取代高达70%的水泥来配制混凝土粘结剂。基于反应性、热力学相互作用和微观结构发展的准确表征，采用整体方法来开发成本和能源高效的策略，以提高粘土的反应性，包括广泛使用的低等级粘土，从而促进其作为混凝土的水泥替代材料的使用。总体而言，这项工作的结果将确定混凝土中大量粘土的比例而不降低性能的方法的新范例，从而为广泛采用真正可持续的混凝土开辟一条道路。知识传播活动，包括培训代表性不足的学生，以及向专业人员和普通受众宣传设计富含粘土的可持续混凝土的经济和社会影响的外联活动，将扩大这项研究的影响。这项研究使用协调的实验和计算任务来阐明可持续粘结剂系统中的基本composition-reactivity-microstructure-property相关性。先进的结构表征和新颖的基于微量热计的反应性评估技术被串联使用，将粘土的组成与其反应性联系起来。这些知识被用来开发高能效的活化程序，最大限度地提高粘土的反应性，包括缺乏高岭石的粘土。结合实验的热力学模型被用来通过控制添加与水泥和粘土协同作用的无机外加剂来支持粘结剂S的反应活性，以最大限度地形成空间填充反应产物。采用了一系列微结构和性能表征技术，包括基于微结构的三维晶格Boltzmann方法，将微结构的演变与工程性能的发展联系起来。紧随其后的是对以富含粘土的可持续粘结剂制成的混凝土的基于规范的工程性能的严格评估。从这些研究中获得的知识被巩固起来，以制定指导方针，以便能够选择和调节粘土的物理/化学性质，以设计具有更高性能的可持续混凝土。

In response to the incessantly increasing demand for sustainable concretes for the construction of infrastructure, past studies have identified carbon-efficient materials (e.g., fly ash, slag) for partial replacement of cement in concrete. High-volume use of these materials, however, is only beneficial when they exhibit enhanced reactivity in concrete environments. As fundamental composition-reactivity relationships for these materials are not well established, their selection is based on trial-and-error based approaches, which are unreliable and often lead to impoverished performance. Low quality and limited availability of such materials further marginalizes their adoption as construction materials. Therefore, to have a significant global impact, abundant, inexpensive, carbon-efficient, and highly reactive materials need to be identified and adapted for use in concrete. Clays, which are abundant in all geological settings, meet all of these criteria. This research aims to formulate binders for concrete by replacing up to 70% of cement with clays and other readily available inorganic materials. A holistic approach, based on accurate characterizations of reactivity, thermodynamic interactions and microstructural development, is employed to develop cost- and energy-efficient strategies to achieve enhanced reactivity of clays, including widely available low-grade clays, thus promoting their use as cement replacement materials for concrete. Overall, outcomes of this work will define a new paradigm in methods of proportioning high volumes of clay in concretes without conceding performance, thereby charting a path for widespread adoption of truly sustainable concretes. Knowledge dissemination activities, including training of underrepresented students and outreach activities to inform professionals and general audience of the economic and societal impacts of designing clay-rich sustainable concretes, will extend the impact of this research. This study employs harmonized experimental and computational tasks to elucidate fundamental composition-reactivity-microstructure-property correlations in sustainable binder systems. Advanced structure characterization and novel microcalorimetry-based reactivity-assessment techniques are used in tandem to link composition of clays to their reactivity. This knowledge is used to develop energy-efficient activation procedures that maximize the reactivity of clays, including kaolinite-deficient clays. A thermodynamic model in conjunction with experiments is used to bolster the binder?s reactivity through controlled additions of inorganic additives that synergistically interact with cement and clay to maximize the formation of space-filling reaction products. A suite of microstructure and performance characterization techniques, including a microstructure-based 3D lattice Boltzmann method, are employed to relate the microstructural evolution to the development of engineering properties. This is followed by rigorous evaluations of specification-based engineering properties of concrete made with clay-rich sustainable binders. Knowledge gained from these studies are consolidated to develop guidelines that enable selection and regulation of physical/chemical properties of clays to design sustainable concretes with enhanced properties.