Grant: Discovery Grants Program - Individual

The aging of concrete infrastructures is a threat to the Canadian economy and the serviceability of infrastructures. Aggregate reactions are among the causes of infrastructure aging in North America and worldwide. There are two classes of aggregate reactions: alkali-aggregate reactions (AAR) and oxidation of sulphide-bearing aggregates. The AAR has been known since 1940 with well-established research, while cases related to the oxidation of sulphide phases are relatively new in Canada. Despite the 80 years of research on AAR of its two types: alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR), more research is needed to understand the role of cold climate and the application of winter salts on the long-term deterioration of concrete with reactive aggregates. Moreover, the limited supply of traditional preventive measures used to conquer the damaging reaction, such as fly ash, mandates the search for economic preventive and mitigation measures. For the second class of aggregate reactions, the oxidation of sulphide aggregates, research is needed to fully understand the factors that affect the oxidation rate and its subsequent sulphate attack. Knowing such factors and developing reliable test methods will help identify preventive measures and manage structures containing this type of aggregates. The long-term objectives of this proposed research are to contribute to the resiliency of Canadian infrastructures by producing durable concrete with extended service life. The other linked objective is to promote responsible consumption and production - one of the UN Sustainable Development Goals - by enabling the use of available aggregates in the project areas, whether or not they are reactive. The latter objective will reduce the carbon dioxide emission associated with hauling non-reactive aggregates from locations far from the construction sites. Another objective is establishing strategies to repair and manage structures affected by aggregate reactions, particularly sulphide oxidation, which is relatively new. Achieving these objectives requires comprehensive research to investigate the durability of concrete with reactive aggregates under conditions that simulate field exposure, including simultaneous modes of deterioration, and to find locally available materials that provide mitigation in new and aged structures. With the above-mentioned long-term goals in mind, the short-term objectives of his research are (i) evaluate the performance of concrete under combined ASR and freezing/thawing cycles and establish a test method to evaluate the combined mechanisms with and without deicing salts, (ii) findings new and feasible ways to prevent ASR under conditions that mimic field exposure; and (iii) investigate the factors affecting the rate of oxidation in concrete with sulphide-bearing aggregates and develop prevention/mitigation strategies.