Development of Sustainable Geopolymer Cellular Concrete Containing Basic Oxygen Furnace Slag Aggregate, Off-ASTM Fly Ash, Ground Granulated Blast Furnace Slag, and Different Fibers

Abstract

This research develops a sustainable, lightweight cellular geopolymer concrete made from industrial by-products and a foaming agent, reinforced with fibers to balance thermal insulation and mechanical performance. The materials used in this study include Off-ASTM fly ash and ground granulated blast furnace slag (GGBFS) as binders, river sand and stockpiled basic oxygen furnace slag (S-BOFS) as aggregates, basalt fiber, polyvinyl alcohol (PVA) fiber, and polypropylene (PP) fiber as reinforcing materials. A total of 16 geopolymer mixtures were designed with no fiber, a single fiber, dual, and triple fiber combinations at both fixed binder ratio (50/50 of FA/GGBFS) and aggregate ratio (75/25 of sand/S-BOFS). The test method to evaluate the performance of mixtures includes fresh property tests (flowability, density, and air content), hardened property tests (density, compressive strength, modulus of elasticity, and tensile strength), and thermal, electrical, and durability tests (electrical resistivity, thermal conductivity, drying shrinkage, and expansion test). The obtained test results show that PVA fiber composites exhibited the highest strength and durability due to strong adhesion and crack bridging, despite increased drying shrinkage. PP fiber composites enhanced the highest workability and electrical resistivity, but exhibit poor thermal insulation. Basalt fiber mixtures showed the lowest results due to the poor dispersion and overall incompatibility with the cellular structure, leading to brittle failure and lower strength. However, basalt fiber composites showed the best thermal insulation and shrinkage control. The cellular structure improved interactions between the fiber and geopolymer matrix, with PVA stabilizing, basalt disrupting, and PP maintaining the pore walls. As a result, PVA fiber composite is recommended for structural applications, PP fiber mixture for workability and electrical insulation, while basalt fiber composite is recommended for more dense structures with the addition of dispersing agents to realize its potential in reducing shrinkage and improving thermal insulation. This work confirms that industrial by-products can be utilized as sustainable, insulating concrete for Kazakhstani weather conditions, with fiber selection being a critical factor for achieving desirable results.