Determination of the Main Parameters of Alkali Silica Reaction Using System Identification Method
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Although concrete is widely considered a very durable material, if conditions are such, it can be vulnerable to deterioration and early distress development. Alkali-silica reaction (ASR) is a major durability problem in concrete structures. The product of this reaction is a gel that is hygroscopic in nature. When the gel absorbs moisture, it swells leading to tensile stresses in concrete. When those stresses coming from the gel swelling exceed the tensile strength of concrete, cracks occur. This paper is part of a broader research study to assist engineers to effectively mitigate ASR in concrete, leading to an increase in the life span of concrete structures. To achieve this objective, a comprehensive study on different types of aggregates of different reactivity was conducted to formulate a robust approach that takes into account the factors affecting ASR, such as temperature, moisture, calcium concentration, and alkalinity. A kinetic model was proposed to determine aggregate ASR characteristics which were calculated using the system identification method. Analysis of the results validates that ASR is a thermally activated process and, therefore, the reactivity of an aggregate can be characterized in terms of its activation energy (Ea) using the Arrhenius equation. 2010 ASCE.