Development of Sustainable Fiber-Reinforced Ambient-Cured SCGC with Enhanced Mechanical and Microstructural Properties for Infrastructure Applications

Self-compacting geopolymer concrete (SCGC) has been recognized as a sustainable alternative to conventional cement-based materials. The SCGC includes the convenience of self-compacting concrete (SCC) with the environmental benefits of geopolymers. However, its brittle nature, limited flexural and tensile strength, and the need for temperature curing pose challenges in the application of SCGC in the construction of structures. To address these limitations, this study developed high-strength fiber-reinforced SCGC (HS-FRSCGC) as a novel sustainable material, featuring significantly enhanced ductility, mechanical properties, and microstructure, cured at ambient temperature suitable for on-site application in the construction industry. Three types of stainless steel fibers were used to determine the optimum volume fraction and aspect ratio for the development of HS-FRSCGC: micro fibers (1%, 2%, and 3% by volume), macro fibers (1%, 2%, and 3% by volume), and hybrid fibers (combination of 1% micro and 1% macro fibers by volume). The workability properties of the mixes declined with increased volume fraction and aspect ratio, while the compressive strength improved for up to 2% fiber inclusion. The HS-FRSCGC mix with 2% hybrid fibers achieved a high slump flow of 720 mm and a high compressive strength of 74.5 MPa, along with significant increases in flexural, splitting tensile, direct tensile strengths, and ductility. Microstructural results confirmed that the crack-bridging capabilities of fibers and the strong interfacial transition zone of fibers and paste significantly improved the mechanical properties and microstructure of SCGC.