Effect of steel fibers, polypropylene fibers, and silica fume on the properties of ultra-high-performance geopolymer concrete

Abstract

This study investigates the properties of ultra-high-performance geopolymer concrete (UHPGC) incorporating polypropylene fiber (PPF) or steel fiber (St.F) along with silica fume (SF). Various volume fractions of PPF and St.F (0%, 0.5%, 1%, 1.5%, and 2%) were utilized in UHPGC production. To evaluate fresh properties, 20% SF and 30% by weight of the binder were added. Slump flow and mechanical properties were examined through compressive strength (CS), splitting tensile strength (STS), flexural strength (FS), modulus of elasticity (ME), and drying shrinkage (DS). Transport properties were analyzed based on water permeability (WP), chloride permeability (CP), and water sorptivity (WS). The effect of elevated temperatures (200 °C, 400 °C, 600 °C, and 800 °C) on CS was also explored. The results indicated that the mixtures containing 30% SF showed greater strength compared to 20% SF. In addition, the inclusion of fibers enhanced the mechanical properties in a direct relationship with the increase in fiber content. At 28 days, the mixture containing 2% St.F achieved CS, FS, and STS values of 172.8 MPa, 19.9 MPa, and 29.4 MPa, respectively. The mixtures containing 30% SF and without fibers showed the best transport properties, with WP, CP, and WS results of 1.3 × 10⁻¹¹ cm/s, 210 Coulombs, and 5.7 × 10⁻⁴ mm/s^0.5, respectively. The incorporation of fibers contributed to the reduction of drying shrinkage and damage caused by elevated temperatures.