Numerical Modeling of the Long-Term Behavior of Passive Fire Protection Mortars Applied on Concrete Tunnels

Abstract

Experiences show that the design of overlay mortars is a complicated matter as far as long-term durability and dimensional stability are concerned. In many cases, applied mortars crack or delaminate a few years after application. The same is true for passive fire protection mortars (PFP mortars). The mortar must remain crack free and must not delaminate during the planned service life, that means the fire protection requirements must be combined with the durability requirements. In this paper, an approach based on a numerical model is used to forecast the long-term behavior of PFP mortars. By means of this model, the time-dependent humidity, temperature, stress, and strain distributions, as well as the crack formation can be calculated in a realistic way. The minimal adhesive strength between overlay and substrate which is necessary to prevent delamination during the planned service life has been calculated. Material properties and climatic boundary conditions have been taken into account. The results allow the tailored optimization of PFP mortars.