Performance of polypropylene fiber reinforced GGBFS-based alkali activated composites under sulfate and freeze–thaw conditions

Currently, alkali activated materials are being actively explored as an alternative to conventional Portland cement composites in the construction industry. The approach of incorporating fibers in quasi-brittle materials is to overcome the shortfall due to high brittleness, lower toughness/deformation capabilities, and improve crack/shrinkage resistance. The study intends to assess the impact of different parametric variances on the mechanical and durability properties of 100% ground granulated blast furnace slag (GGBFS) based alkali activated composite (AAC) incorporated with polypropylene fibers. A total of 20 AAC mixes were produced with a polypropylene fiber contents of 0, 0.15, and 0.3% vol. fraction; polypropylene fiber length of 12 mm (short) and 20 mm (long); alkaline activating solution monomer ratio of 2.5 and 3.0, and curing regimes as ambient and heat-based. Besides the evaluation of compressive and flexural strengths under normal conditions, the specimens were subjected to the sulfate attack with exposure to 3, 5, and 7% concentrated solution of sodium and magnesium sulfate/seawater and the freeze–thaw effect of 90 cycles. The residual compressive strength and weight change results were examined before and after the exposure to these harsh environmental conditions to assess its durability. The results showed considerable improvement in flexural strength in all samples and increased compressive strength in samples with 0.15% short polypropylene fibers (12 mm), while a slight reduction in compressive strength due to reinforcement of 0.3% long fiber (20 mm). Furthermore, incorporation of 0.15% short polypropylene fibers in composites with an alkaline activating solution monomer ratio of 2.5 showed considerable improvement in sulfate and freeze–thaw resistance.