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

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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.