The influence of fine-grained zeolite, a postindustrial waste from volcanic tuff processing, on the alkaline reactivity of sands used in concrete structures

The possibility of using zeolite as a fine sand substitute to reduce alkali reactivity to safe levels contributes to environmental protection on many levels. Increasing the base of raw materials by using sands previously classified as alkali reactive saves natural resources and lessens CO 2 emissions related to long-distance aggregate transportation. Moreover, managing fine-grained zeolite – an unused by-product, aligns with a circular economy model. Zeolite used in concrete can improve its in-service performance, contributing to the extension of the concrete structure lifespan. This paper discusses an experimental study focused on mitigating the alkali reactivity of sands using zeolite dust (clinoptilolite dust), a by-product of grinding volcanic tuff sourced from the Sokyrnytsya deposit in Ukraine. The novelty of this research lies in the application of zeolite dust as a replacement for the aggregate fraction (0.125–0.250 mm), rather than as a mineral additive replacing cement, as seen in previous studies. Comprehensive petrographic examinations with strong focus on identification of the mineral components susceptible to alkali-silica reaction (ASR) and accelerated mortar-bars ASR tests of sands as well as SEM observations were conducted. These findings helped to determine the main mineral components responsible for ASR-induced expansion, and to understand the sands’ reactivity. The beneficial influence of zeolite aggregates on mitigation of the ASR was proved. However, aging and long-term ASR tests are necessary to fully evaluate the impact of zeolite aggregates on the durability and mechanical performance of concrete. • Fine zeolite performs as a sand substitute to mitigate expansion induced by alkali-silica reaction (ASR) in concrete. • Amount of reactive silica in aggregate does not correlate with ASR-induced expansion magnitude. • Expansion magnitude is influenced by the type of reactive silica in the aggregate. • Zeolite as a sand substitute positively influences the microstructure of mortar-bars. • Mortar-bars with fine-grained zeolite exhibit fewer cracks, localized within grains.