Mechanical Properties of Plant Fibers Reinforced Alkali-Activated Slag Cementitious Material at High Temperature

With the depletion of natural resources and the growing awareness of environmental protection, it is increasingly important to apply more renewable resources in construction material. Considering the low-cost and abundance of plant fibers, this paper proposes a novel cementitious material called plant fibers reinforced alkali-activated slag cementitious material (PF-AASCM). Specifically, the author investigated the types and features of fibers and how they affect the AASCM properties. On this basis, the influencing factors of the mechanical properties and microstructure of PF-AASCM were determined, and the measures to enhance the compressive and flexural strengths of the PF-AASCM were evaluated one by one. Next, the potential of applying plant fibers as internal enhancements of the AASCM was thoroughly explored. The results show that the PF-AASCM is economically and technically viable for many construction applications. The plant fiber reinforcement can enhance the ultimate strength of the AASCM rapidly (70 % growth in 7d and 120 MPa/17,000psi in 28d), resulting in excellent acid resistance and freeze-thaw durability. In addition, the optimal mix ratio is 1:4 wt.% between sodium hydroxide and potassium silicate. Under this ratio, the mechanical properties and microstructural features of the sample will be comparable to those of Portland cement. The compressive strength of single-row-hole sample of wheat straw reinforced AASCM was 10.75MPa at room temperature, equivalent to that of standard concrete sample MU7.5. The compressive strength of such a PF-AASCM decreased linearly with the growth in temperature. After the temperature reached 600 ⁰, the plant fiber still exerted a certain tensile force on the matrix. By contrast, the polypropylene fiber started to melt down after the temperature increased to 200 ~ 400 ⁰, causing brittle failure of the matrix. Under the high temperature of 200 ~ 400 ⁰, the fine steel fiber enhanced the compressive properties of samples, which showed clear plastic deformation. The research results shed new light on reducing pollution and enhancing AASCM ductility