Concrete tunnels face a phenomenon called "spalling" where intense heat causes moisture inside concrete to turn to steam explosively, ejecting chunks of concrete and exposing rebar.
If you are searching for NFPA 502 Standard for Road Tunnels- Bridges- and Other Limited Access Highways.pdf , ensure you are looking for the latest edition (2023) to access modern requirements for electric vehicle fires, ventilation critical velocity, and bridge fire protection that older versions lack. Concrete tunnels face a phenomenon called "spalling" where
Updated Table 7.2 discussing required systems based on tunnel category, updated wiring requirements for tunnels, introduced categorization of bridges and elevated highways, added a new chapter on water-based fire-fighting systems, and included system commissioning guidelines and periodic testing requirements. In addition, if any element of a structure
In addition, if any element of a structure used for parking garages, bus terminals, or truck terminals is used to allow the travel of road vehicles as a means of access to or egress from that structure, it shall be characterized as a facility and treated as such under this standard. ventilation critical velocity