Thermal Performance of Reactive and Non‐Reactive Fire Protective Materials Under Non‐Standard Heating Regimes: An Experimental Parametric Study

In civil engineering, fire passive protection is generally adopted to hinder the mechanical performance decay that high temperature yields on bare steel. The fire resistance of protective materials is affected by several factors (e.g., microstructure, chemical composition, input flux). In modern codes, worldwide, the use of a performance-based approach for assessing the behaviour of structures in fire is enabled. However, it requires a reliable characterisation of the thermo-physical behaviour of all materials involved, including fire protection, at elevated temperatures. In this article the authors present the results of an experimental parametric investigation, in which cone calorimeter tests were used to assess the protective performance of four different fire protection materials, namely (i) gypsum- and (ii) cement-based boards, (iii) lightweight gypsum-based SFRM, and (iv) water-based intumescent coating. The evidence detected through cone calorimeter tests was interpreted on the basis of microscale investigations on the chemo-physical response at high temperature, to result in sound correlations between the effective thermal conductivity, at the macroscale, and the ongoing material evolution at the microscale. This study seems to justify the use of a scenario-independent thermal conductivity for both cement- and gypsum-based boards, as well as intumescent coatings beyond the activation temperature. Differently, this consideration does not fit what has been observed with the spray-applied plaster (SFRM).