Abstract:

To address the problems of low strength， poor durability， and brittleness at low temperatures of ordinary polyurethane （PU）， a low⁃density， high⁃strength， fast⁃hardening thermoplastic PU （TPU）/graphene⁃modified PU grouting material was prepared by using TPU and graphene as composite modified together with the addition of small amounts of fly ash， bottom slag， and alkaline activator. The density， expansion ratio， compressive strength， flame retardancy， permeability coefficient， and microscopic morphology of the resultant grouting materials were characterized by using density tester， universal material testing machine， permeability coefficient tester， and fluorescence microscope. The effects of the type and dosage of graphene and TPU on the basic physical properties， mechanical properties， and microstructure of the grouting material were investigated. The results indicated that the prepared grouting material had a density of 0.24~1.25 g/cm³， its expansion ratio reached up to 38 times， and its compressive strength was 15.0~43.8 MPa. The compressive strength of the grouting material was almost doubled compared to the unmodified grouting material. The alcohol lamp combustion experimental results indicated that the flameless combustion time was less than 20 s. Both graphene and TPU can improve the strength， durability， and microscopic morphology of PU. The resulting grouting material exhibits good strength， durability， and elasticity to meet the requirement of various applications as a grouting material.

Key words: polyurethane grouting material, graphene, thermoplastic polyurethane, fly ash, microscopic morphology