Effect of modified wheat straw fiber on properties of fiber cement-based composites at high temperatures

Abstract

To solve the poor fireproof performance of plant fibers, one of the technical difficulties, and use more straw fibers as construction materials, wheat straw fibers (WSFs) have been subject to flame-retardant modification. Then, tests and analysis over the modified WSFs per the burning behavior and pyrolysis performance have been made. The physical and mechanical, and thermal insulation properties of wheat straw fiber cement-based composites (WSFCC) at high temperatures were characterized. The results are as follows: Ammonium polyphosphate (APP), magnesium hydroxide (MH), and aluminum hydroxide (ATH), three fire retardants, all affect the chemical structure of WSFs. P, Mg, and Al elements of the three retardants are successfully adsorbed onto the fibers' surface subject to modification. Flame-retardant WSFs significantly outperforms the non-flame-retardant ones per thermostability and flame retardancy. The heat release rate (HRR), total heat release (THR), effective heat of combustion (EHC), and mass loss rate (MLR) of most flame-retardant WSFs are obviously lower than those of non-flame-retardant ones. The APP-modified WSFs demonstrate higher total smoke production (TSP), while WSFs modified with composite flame retardants perform better in flame retardancy and smoke suppression. The MLR of WSFCC at high-temperature increases as the temperature goes higher. The compressive and flexural strengths of WSFCC decrease with the increase of temperature and the decrease mitigates after 350 °C. In terms of thermal conductivity, composite-flame-retardant fiber WSFCC are much higher than non-flame-retardant fiber and APP-modified fiber WSFCC. As the temperature rises, the thermal conductivity of composite-flame-retardant fiber WSFCC tends to decrease.