On utilization and mechanisms of waste aluminium in mitigating alkali-silica reaction (ASR) in concrete

Abstract

Alkali silica reaction (ASR) is one of the most commonly occurring durability issues in concrete structures. In this study, the feasibility of using waste aluminium in bit, powder and dissolved forms as a sustainable alternative to mitigate ASR was investigated. The accelerated mortar bar test was adopted for expansion measurement and mitigation mechanisms were explored with reactive glass dissolution, pore solution and microstructural analyses. Both aluminium bits and aluminum powder at various volume fractions were found to be effective in mitigating ASR, mainly attributable to dissolution control of amorphous silica through integration of [Al(OH)4]- into the silica framework and electrostatic repulsion of OH− at reactive sites. However, the effectiveness of the dissolved aluminum form in controlling ASR was diminished with time due to a ready integration into hydration products. This calls for an investigation into the long-term effectiveness of the proposed mitigation strategies. Also, a higher porosity of concrete due to gas evolution and the resulting adverse effects on mechanical properties would have to be resolved before a possible implementation of the mitigation approach for concrete structures.