Self healing of early age cracks in cementitious materials

混凝土是世界上使用最多的建筑材料，很容易出现裂缝，这往往会损害其结构完整性和耐久性。传统的混凝土修复在一定程度上未能缓解这一问题，因为在大多数情况下，只有在混凝土已经恶化之后才能发现损坏。由于已建成的基础设施恶化，加拿大每年花费约100亿美元的公共资金进行维修或更换，其影响在经济、社会和经济上都是灾难性的。美国土木工程师协会估计，在5年内修复和翻新基础设施需要2.2万亿美元。因此，需要开发一种新的混凝土，既不裂缝，又能在裂缝发生时自我修复。因此，通过模仿大自然久经考验的策略，自修复混凝土已成为一种替代和可持续的解决方案。因此，本研究旨在开发一种能在裂缝发生时自密封的水泥砂浆。长期目标是开发用于设计和打印自主自愈合胶凝材料的规范和工具。这种自我修复砂浆使用的是非混凝土固有的封装式愈合剂。当裂缝穿过胶囊并反应并将破裂的面部粘合在一起时，治愈剂就会释放出来。自主自愈砂浆的效率取决于胶囊在混合过程中的存活率、胶囊与砂浆的机械兼容性、胶囊粘结强度、治愈剂流动特性以及胶囊的分布。因此，开发了实验和分析程序，以1)量化三维裂纹在胶凝材料中交叉胶囊和自愈的可能性，2)分析随着砂浆硬化和收缩裂缝的发展，胶囊和砂浆之间的力学相互作用，3)通过实验确定在搅拌和放置砂浆期间生存所需的胶囊的性能，以及4)实验研究随着砂浆硬化和收缩裂缝的发展胶囊的有效性和耐久性。这项研究在许多方面都是新颖的。它提供了一个整体的方法来研究自愈合砂浆的力学和化学方面，包括胶凝材料、聚合物胶囊和治愈剂，以及它们之间的相互作用。这项研究针对缺乏定量知识和措施的自修复砂浆的主要领域，将为评估自修复砂浆的性能和耐久性提供分析模型和测试方法，并为可靠和有效地设计自修复砂浆提供量化工具。从长远来看，转化和调动产生的知识将显著提高我们对混凝土性能和耐久性的了解，并确保可持续的加拿大混凝土基础设施将持续数代人，并为加拿大带来经济增长。

Concrete, the world's most used construction material, is susceptible to cracking that tends to compromise its structural integrity and durability. Traditional concrete repairs have failed in part to mitigate the problem because, in most cases, damage is only detected after concrete deterioration has already progressed. The implications have been economically, socially, and economically disastrous owing to a deteriorated built infrastructure that is costing Canada about $10 billion annually of public funds to repair or replace. The American Society of Civil Engineers estimated $2.2 trillion are needed to repair and retrofit the infrastructure over 5 years. As a result, a need exists to develop a new concrete that is either crack free or can heal itself in the event of cracking. Hence, self-healing concrete has emerged as an alternative and sustainable solution by emulating nature's time-tested strategy. Accordingly, this study aims to develop a cementitious mortar that can self-seal when cracking occurs. The long-term objective is to develop specifications and tools for designing and printing autonomic self-healing cementitious material. The self-healing mortar utilizes encapsulated healing agents that are not intrinsic to concrete. The healing agents are released when cracks cross the capsules and react and bind the cracked faces together. The efficiency of the autonomic self-healing mortar depends on the survivability of the capsules during mixing, mechanical compatibility of capsules and mortar, capsules bond strength, healing agents flow properties, and distribution of the capsules. Accordingly, experimental and analytical programs were developed to 1) quantify the likelihood of a 3-D crack intersecting capsules and self-healing in cementitious material, 2) investigate analytically the mechanical interaction between capsules and mortar as the mortar hardens and shrinkage cracks develop, 3) determine experimentally the capsules' properties necessary to survive during mixing and placing of mortar, and 4) study experimentally the efficacy and durability of capsules as mortar hardens and shrinkage cracks develop. This research is novel in many ways. It provides a holistic approach to study the mechanical and chemical aspects of self-healing mortar which includes cementitious material, polymeric capsules and healing agents, and their interactions. This research which addresses major areas of self-healing mortar that lack quantitative knowledge and measures, will yield analytical models and test methods for evaluating the performance and durability of self-healing mortar, and quantification tools for reliably and effectively designing self-healing mortar. In the long-term, translating and mobilizing the generated knowledge will significantly improve our understanding of the performance and durability of concrete, and ensure sustainable Canadian concrete infrastructure that will endure for many generations and provide economic growth to Canada.