Numerical calculations of vapour pressure in concrete exposed to fire Available to Purchase

According to the diffusion equation and the hypothetical relationship between vapour pressure, moisture density and temperature, a differential file method is used to calculate the inner vapour pressure of concrete at high temperatures. When concrete is heated, a distribution field of vapour pressure will be formed. If the temperature changes, the value and the location of the peak pressure in concrete will change. However, the temperature at which the peak pressure is obtained is nearly the same, ranging from 220°C to 240°C. Calculation results show that the vapour pressure reaches peak values at a distance of less than 10 mm from the heating surface when the heating time is not more than 1 h according to the ISO 834 heating regime. The peak pressure values are from 1 MPa to 2 MPa depending on heating time. Some explanations about concrete spalling are given, which indicate that vapour pressure is the main reason for the spalling of concrete.