Assessment of fly ash geopolymer concrete with fine and coarse recycled aggregates

Geopolymer concrete (GC) is emerging as a sustainable alternative to conventional concrete; its environmental benefits are further enhanced by incorporating recycled aggregates (RA), which reduce carbon emissions and support construction waste reuse. This study investigates the strength and durability properties of Class-F fly ash (FA)-based GC, incorporating both coarse and fine RA. Different GC mixes were developed with varying proportions of coarse RA (0%, 50%, and 100%), fine RA (0%, 50%, and 100%), or combinations of both. Compression strength was assessed as the primary strength parameter, while durability was evaluated through initial surface absorption, capillary suction tests, and acid attack tests. In addition, electrical resistivity was measured for all GC mixes. The findings suggest that introducing 50% coarse and fine RA, independently or in combination, has a minimal impact on compression strength. However, including fine RA negatively affects GC’s surface absorption and capillary suction more than coarse RA. The electrical resistivity values indicate a moderate risk of corrosion for all GC mixes. The results recommend that RA can be utilised in GC, which can overcome the scarcity of natural aggregates and help to achieve a sustainable environment.