Mechanical properties of lightweight concrete after fire exposure

The paper presents an experimental research project that focused on analysing the short‐term residual mechanical properties of lightweight concrete after exposure to temperatures of up to 600 °C and the effects of the short‐term residual mechanical properties on the post‐fire loadbearing capacity of different concrete sections. The experimental programme was conducted on four different concrete mixes by determining the mechanical properties immediately after cooling and up to 96 h after cooling. The following properties were investigated: compressive strength, ultrasonic pulse velocity and stress‐strain curves. The results show that the compressive strength undergoes an additional reduction in comparison to the initial residual strength (0 h property) of up to 20 % in the reference time period. A numerical study is presented at the end of the paper in order to quantify the effects of the short‐term strength reduction on the axial loadbearing capacity of slender and stocky concrete columns.