Influence of different fibers on properties of thermal insulation composites based on geopolymer blended with glazed hollow bead

•Thermal insulation composites based on fibers reinforced geopolymer blended with GHB.•The optimal strength is obtained with 15% GHBs, 0.75% PP fiber and liquid-solid ratio of 1.1.•The improving effect follows the sequence: PP fiber, alkali resistant glass fiber and lignin fiber.•Fibers prevent the separation of GHB and geopolymer matrix, inhibit the expansion of cracks. In this work, fly ash and slag were used as aluminosilicate raw materials to prepare geopolymer paste, and different fibers and glazed hollow beads (GHB) were incorporated into the paste to produce various series of fiber reinforced geopolymer composites. The preparation process of geopolymer composites was explored and the optimum preparation conditions was obtained. Compressive strength, flexural strength, water absorption, porosity, thermal conductivity, linear shrinkage rate, microstructure and morphology have been characterized and assessed. Polypropylene fiber, alkali resistant glass fiber and lignin fibers were added to improve the cracking resistance and to enhance the strength. The results show that the optimal strength of fiber reinforced GHB blended geopolymer is obtained with 15% GHB addition, 0.75% fiber addition and liquid-solid ratio of 1.1. The improving effect of fibers on enhancing and anti-shrinkage follows the following sequence: PP fiber, alkali resistant glass fiber and lignin fiber. It is also observed that the fiber not only prevents the separation of the GHB and geopolymer matrix, but also inhibits the generation and expansion of the cracks, and finally improves the strength regardless of hybrid fibers or single fiber.