Mechanical strength and durability of GBFS geopolymer modified with metakaolin and functionalized beta-silicon carbide whiskers

Abstract

Durability is crucial for materials development in construction and transportation industries. This paper investigates the mechanical strength and durability of alkali-activated granulated blast-furnace slag (GBFS) and modified geopolymer with varying contents of metakaolin (MK) and functionalized beta-silicon carbide whiskers (β-SiCw). Functionalized β-SiCw were prepared utilizing successful chemical methods. Macroscopic experiments tested mechanical strength, bulk density loss rate after exposure to severe conditions, and durability through sulfate wet-dry and freeze-thaw cycles. Microscopic experiments, including SEM-EDS, XRD, TG-DSC, and BET, revealed the microstructure mechanisms. Results showed that MK and functionalized β-SiCw improved mechanical strength by creating a more reactive phase and denser pore structures. Reduced bulk density loss rates and enhanced durability were observed, with a 71.9 % mass loss and 63.4 % compressive strength loss reduction after 50 freeze-thaw cycles, and a 12.2 % decrease in compressive strength loss after 56 days of sulfate wet-dry cycles, compared to control groups. The modified geopolymer had higher tortuosity and finer porosity due to more gel formation and nucleation sites, and functionalized β-SiCw effectively bridged micro-cracks and micro-pores.