Tri-axial compressive properties of high-performance fiber-reinforced cementitious composites after exposure to high temperatures

Abstract This study experimentally investigates tri-axial compressive properties of high-performance fiber-reinforced cementitious composites after exposure to high temperatures up to 800 °C. First, 16 mixtures were designed and tested to evaluate the effect of mixture proportioning variables on the tri-axial compressive properties. The investigated mixture proportioning variables included the water-to-binder ratio (0.24–0.36), sand-to-binder ratio (0.36–0.66), fly ash content (60–75%), fiber content (1.5–2.2%), and superplasticizer content (0.10–0.25%). Based on the test results, an optimum mixture was presented and tested at five confining pressure levels up to 25 MPa and three loading rates up to 60 μe/s before and after exposure to high temperature. The cylinders were exposed to the targeted temperatures and then loaded under combined constant lateral confining pressure and an increasing longitudinal compressive load until failure. The tri-axial compressive strength degraded as the heating temperature increased from 200 °C to 800 °C; the strain limit increased with the heating temperature from 600 °C to 800 °C. As the confining pressure increased from 5 MPa to 25 MPa, the tri-axial compressive strength increased by about 50% at 25 °C and 80% at 800 °C.