Accelerated carbonation of alkali-activated vibro-compacted pervious concrete paving blocks

This study explores the use of an accelerated carbonation curing method to enhance the performance of non-structural precast alkali-activated fly ash pervious concrete paving blocks. Using a predefined production process, pervious paving blocks measuring 200 mm × 100 mm × 60 mm were manufactured and subjected to a 3-stage curing process. The blocks were produced with a dry consistence to allow for vibrocompaction, closely mirroring the manufacturing techniques used in the precast industry and enabling immediate demoulding. Initially, all blocks underwent thermal curing at 70 °C for 24 hours, followed by storage in a climatic chamber (20 ± 3 °C, 65 ± 10 % relative humidity) for 7–14 days. Finally, they were exposed to a carbonation chamber with 5 % CO 2 at 23 ± 2 °C, and 60 ± 10 % RH for up to 7 days. Blocks cured without carbonation served as control specimens. All blocks were tested following the European standard EN 1338, which governs the conformity of conventional concrete pavement blocks. Additional properties such as water permeability and water stability were also assessed. The results demonstrated that the accelerated carbonation curing significantly improved the performance of the blocks. Increases of 30 % and 60 % in compressive and splitting tensile strengths, respectively, were reported for the 7-day CO 2 -cured blocks when compared to their control counterparts. The 7-day carbon-cured blocks showed significantly improved abrasion resistance, with mass loss due to abrasion decreasing from 8.2 % to 5.6 % with 7 days of CO 2 exposure. Additionally, microstructural enhancements were observed for the carbonated specimens, positively impacting their overall performance and making them compliant with the standard for practical paving block applications. However, further research is recommended to explore automation in the production process to ensure consistent results and facilitate future standardisation and certification of these blocks. • Fly ash fully replacing Portland cement as precursor for pervious paving block production. • Accelerated carbonation significantly enhanced the performance of concrete. • Increased densification and reduced specimen mass loss in abrasion. • Increased carbonation increased percolation times due to decreased permeability. • Strength improved due to the enhanced polymerization of the aluminosilicate network.