Morphological, Physico-Chemical, and Thermal Characterization of Non-Reactive Protective Materials for Steel Structures

This study addresses the critical issue of fire safety in densely populated urban areas and focuses on the resilience of new and existing buildings, with an emphasis on passive fire protection materials for steel structures. Conventional fire codes are considered potentially restrictive, which has led to research in the field of performance-based fire safety engineering (FSE). This research focuses specifically on non-reactive passive fire protection materials, which are known to protect steel elements from high fire temperatures. Two kinds of materials, calcium silicate-based cement (CSC) and gypsum (GP), are investigated using morphological, physicochemical, and thermal analyses in more realistic fire scenarios. Unlike standard fire curves, such as ISO 834, lower heating rates (up to 100°C/min) allowed for a more realistic assessment of the material effectiveness in protecting steel structures from fire. CSC releases only free water molecules within 150°C, resulting in a lower weight loss up to 1000°C, with endothermic transformations totaling 270 J/g. GP releases both free and bound water molecules at different temperatures and triggers several endothermic reactions (with a higher total amount of heat removed from the fire 670 J/g), which increases fire resistance. This mechanism uses the external heat generated by the fire to vaporise water, which increases the fire resistance of the material. This study links the chemical and thermal properties of passive fire protection materials to their fire performance, showing that materials with similar compositions can behave differently. This highlights the need for a new classification system based on material-specific properties.