Laboratory and field investigations of alkali-silica reaction prevention by supplementary cementitious materials: Influence of the free alkali loading

Performance tests are often used to evaluate the effect of supplementary cementitious materials (SCMs) on alkali-silica reaction (ASR). However, these tests may be quite demanding, thus other approaches may be more efficient to identify the materials that are worthwhile testing further. This paper presents ASR expansion data obtained from outdoor exposure (2.5 years) and three accelerated laboratory tests: ASTM C1567, TI-B 51, and RILEM AAR-10. A reactive sand containing porous flint, which caused damage in structures after only a few years, was tested with Portland cement and a wide range of SCMs: fly ash, two biomass ashes, two calcined clays, sewage sludge ash, crushed brick, and glass beads. Expansion data were compared with free alkali loadings determined on companion paste samples. It was observed that no expansion occurred below around 2.4 kg/m³ free Na₂O_eq in AAR-10 and outdoors (so far). Conversely, no clear trend was found with ASMT C1567 and TI-B 51 results, probably because the outcomes of these immersion tests depend on the transport properties of the specimens and interactions with the surrounding solutions. Since expansions in AAR-10 and outdoors correlate, the free alkali loading seems a promising parameter for screening how SCMs influence the risk of deleterious ASR.