The evaluation of Wood Ash as a potential preventive measure against alkali-silica reaction induced expansion and deterioration

Over the past decades, a wide number of research programs were conducted and demonstrated the efficiency of supplementary cementing materials (SCMs) to mitigate alkali-silica reaction (ASR)-induced expansion and deterioration. However, the anticipated depletion in the coming years of some of the most common SCMs used in concrete makes imperative the finding of new potential SCMs sources. This research aims to study the performance of wood ash (WA), a by-product of biochar combustion, as a preventive measure against ASR. Two highly reactive aggregates (i.e., fine and coarse) and different WA replacement levels (i.e., 10%, 20%, 50% and 60%) were selected for this research and accelerated tests were performed in the laboratory (i.e., accelerated concrete prism test – ACPT and the accelerated mortar bar test – AMBT). AMBT results indicated a potential benefit of using WA to mitigate ASR-development whereas the ACPT yielded completely opposite results, which highlights important inconsistencies of these test procedures to appraise preventive measures against ASR. Furthermore, the microscopic damage features and mechanical properties losses of ASR-affected concrete incorporating WA at distinct replacement levels were studied through the Damage Rating Index and Stiffness Damage Test, showing an agreement with the induced expansion results obtained through the ACPT.