Waste liquid-added regeneration activator to enhance the pore structure and compressive strength of geopolymer-foam-fiber: A sustainable strategy of kenaf fiber pretreatment and reuse

Abstract

Developing good pore structure, high-strength inorganic insulation materials derived from fiber-reinforced foaming geopolymer, is desirable for several applications. In this paper, a low-cost, eco-friendly, and high-efficiency method was proposed for processing alkali-treated kenaf fibers (TKF) and metakaolin geopolymer into lightweight yet strong bulk structure geopolymer-foam-fiber (GFF). The composites were produced using H2O2 as foaming agent. The waste liquid of TKF and activator (NaOH and Na2SiO3) were mixed and considered as the regenerating activator. Disordered TKF and regenerating activator with higher viscosity play a crucial role in the mechanical and pore structure of the composites. The results showed that when the foaming agent content increased, the compressive strength of composites decreased. The record-high compressive strength of geopolymer-foam (GF) increased by 1.1–2.1 times and 1.2–2.7 times for ambient temperature and 50 ℃, respectively. GFF with homogeneous pore distribution and high porosity were successfully fabricated by introducing TKF. Therefore, the thermal conductivity and compressive strength were in the ranges of 0.118–0.248 W/(m·k) (comparable to GF) and 1.6–19.9 MPa (1.1–2.6 times increase compared with GF), respectively. This low-cost and no-waste production of geopolymer foam material can enhance the utilization of agricultural waste and the development of inorganic insulation materials.