Performances of Heat-Insulating Concrete Doped with Straw Fibers for Use in Tunnels

Current research efforts aim to develop insulating building materials to cope with hot tunnels by using crop straw fibers. The amount of straw fiber incorporated included different percentages of the gelling material mass: 0% (reference specimen), 2.5%, 5%, 7.5%, and 10%. The study focused on the concrete’s compressive strength, permeability, and thermal coefficient. The thermal coefficient of dry concrete decreased with increasing fiber content. However, the porosity of concrete mixed with more straw fibers increased, thus decreasing compressive strength. Concrete with a fiber content of 7.5% had the best overall performance, and it had a low thermal conductivity (0.158 W/(m·k)). According to COMSOL simulation results, the tunnel wind flow temperature of concrete with 7.5% fiber content was lower than the tunnel wind flow temperature of plain concrete. Thus, the obtained straw fiber heat-insulating concrete is a promising candidate material for tunnel insulation.

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