Investigation on the workability, mechanical properties and carbon emission performance of fiber-reinforced geopolymer recycled concrete (FRGRC)

Abstract

Geopolymer concrete represents an environmentally friendly alternative to traditional cement, offering potential for reducing carbon emissions and recycling industrial waste. Fiber-reinforced geopolymer concrete (FRGRC) has emerged as a promising material, though challenges persist regarding workability control and achieving adequate strength and ductility. To accelerate the adoption of FRGRC in practical engineering applications and fully capitalize on its low-carbon benefits, this study investigates the influence of various controlling factors on the workability and mechanical properties of FRGRC through a series of experiments. The factors under scrutiny include water-to-binder ratio (w/b, 0.4–0.5), alkali activator concentration (c, 0.2–0.4), blast furnace slag content (BFS/b, 0–1), and polyethylene (PE) fiber content (FC, 0 %-2 %). Findings indicate that while a higher w/b ratio improves workability, it compromises strength; conversely, increasing BFS/b ratio enhances strength but detracts from workability. Higher concentrations of alkali activator improve both workability and strength but delay setting times. PE fibers significantly boost bridging strength and ductility by up to 45 % and one-third respectively when FC is increased by 0.5 %, although excessive FC can diminish workability. An optimal mix design was identified: 0.5 w/b, 0.4c, 50 % BFS/b, and 1.5 % FC, which ensures satisfactory workability and high strength. A predictive formula for compressive strength based on different mix designs was developed. Additionally, incorporating carbon emission data, a formula relating mix ratios to carbon emissions and strength was proposed to guide preliminary FRGRC design, and avoided the situation when pursuing low carbon emissions results in excessively low strength. Through comparison, it is shown that the low-carbon performance and strength of FRGRC are both superior to those of ordinary concrete. This research provides valuable insights for optimizing FRGRC design and assessing carbon emissions in practical applications.