Assessment, optimization, and modeling of concrete repairs for enhanced performance and durability

可见的基础设施衰退已经成为加拿大主要担忧的一个原因。加拿大人的安全不仅受到突如其来的不可预见的失败的影响，而且我们社会有效运作的能力也受到当前在社区内运送货物和人员的挑战的威胁。修复老化的基础设施被认为是国家的关键需求，目前市级和省级预算的一半以上用于修复和恢复。然而，正如过去的失败所证明的那样，设计出结构有效、坚固、耐用和可持续的修复仍然是困难的。修复效果和性能退化受到密切相关的机械、物理和化学现象的影响，其中一些现象目前在修复设计中没有得到适当的考虑，主要是因为它们的性质和影响没有得到充分的了解。此外，人们越来越关注普通波特兰水泥(OPC)混凝土的环境可持续性。OPC生产每生产一吨水泥就会释放大约一吨二氧化碳，可耗尽的自然资源被开采出来，为OPC生产提供原材料。虽然用更环保的外加剂部分取代OPC是常见的做法，但应该寻求更可持续的解决方案。 该项目的主要目标是调查维修中那些仍不清楚的方面，并提供工具，以便将其纳入结构和非结构维修的设计、评估和优化。研究成果将对基础设施的安全性和耐用性产生积极影响，减少所需的进一步维修和维护作业，从而最大限度地减少长期成本和碳足迹。通过不同应力条件下的力学测试，对基材修复结合韧性和粘结力进行了实验研究。比较了不同材料和外加剂的性能，并建立了维修优化、结构和耐久性分析的模型。对修复电化学不兼容性和流体传输特性进行评估、建模和优化；这些是影响修复易受有害化学和物理过程的影响的关键特性，包括腐蚀、冻融、化学侵蚀和收缩。此外，还对碱激发低钙飞灰、偏高岭土以及偏高岭土与矿渣的组合制备的替代低碳足迹粘结剂用于混凝土修补的可行性进行了评估，并确定了其应用领域。最后，将不同研究的结果应用于一个钢筋混凝土柱修复的示范项目中，以评估和论证所开发的材料和解决方案的有效性以及预测模型的准确性。

Visible declining infrastructure has become a reason for major concern in Canada. Not only is the safety of Canadians compromised by sudden non-predicted failures, but also the ability of our society to function effectively is jeopardized by the current challenges to moving goods and people within communities. Repairing aging infrastructure is considered a critical national need, with more than half of the municipal and provincial budgets now directed at repair and rehabilitation. Nonetheless, designing repairs that are structurally effective, robust, durable, and sustainable remains difficult as it was proven by past failures. Repair effectiveness and degradation are affected by strongly interrelated mechanical, physical and chemical phenomena, some of which are currently not properly considered in repair design, mainly because their nature and effects are not fully understood. Furthermore, there is increasing concern by the environmental sustainability of the Ordinary Portland Cement (OPC) concretes commonly employed. OPC manufacturing releases about a ton of CO2 for each ton of cement produced and exhaustible natural resources are exploited to supply raw materials for OPC production. Although it is common practice to partially replace OPC with more environmentally friendly admixtures, more sustainable solutions should be pursued. The main goal of this project is to investigate those aspects of repairs that remain unclear and provide tools for their inclusion in design, assessment, and optimization of structural and non-structural repairs. Research outcomes will positively impact infrastructure safety and durability, lead to a reduction of further repair and maintenance operations required and, thus, minimize long-term costs and carbon footprint. Substrate-repair bond toughness and cohesiveness are experimentally investigated through mechanical tests under different stress conditions. The performance of various materials and admixtures are compared and models are developed for repair optimization and for structural and durability analysis. Repair electrochemical incompatibility and fluid-transport properties are assessed, modeled, and optimized; these are critical properties affecting repair vulnerability to harmful chemical and physical processes, including corrosion, freeze-thaw, chemical attack, and shrinkage. Furthermore, the feasibility of concrete repairs made with alternative low-carbon-footprint binders obtained with alkali-activated low-calcium fly ash, metakaolin, and combination of metakaolin and slag is assessed and fields of applications are identified. Finally, the outcomes of the different studies are applied in a demonstration project regarding the rehabilitation of a reinforced concrete column, to evaluate and demonstrate the effectiveness of materials and solutions developed and the accuracy of the predictive models.