Recent trends and forecasts on the availability of fly ash, slag, and lithium admixtures for use in concrete suggest a need to seek reliable alternatives for the mitigation of alkali–silica reaction (ASR). One such option may be aluminum-based admixtures. Past studies have shown that supplementary cementitious materials that contain alumina (Al2O3) are more effective at mitigating ASR than are supplementary cementitious materials purely rich in silica (SiO2). To establish the effectiveness and mechanisms of ASR mitigation by alumina, this research used pure hydrated alumina, Al(OH)3, as a cement replacement. The objectives of the study were to determine if Al(OH)3 can successfully mitigate ASR and to investigate five hypothesized mechanisms by which Al(OH)3 may mitigate ASR. The hypothesized mechanisms are ( a) reducing pH and alkalis in concrete pore solution, ( b) consuming and reducing portlandite and dissolved calcium in the pore solution, ( c) reducing silica dissolution and damage to aggregates at high pH, ( d) altering the composition of ASR gel and creating innocuous gels, and ( e) reducing water and ion transport by reducing the porosity and pore size of cement paste. The results show that Al(OH)3 can effectively mitigate ASR through mechanisms ( a), ( b), and primarily ( c).

No abstract