Comparative laboratory investigation into pavement materials for road tunnels

This article concerns road safety in tunnels and focuses specifically on the behaviour of pavements during accidental fires. Their role is investigated through a comparative laboratory investigation of materials used worldwide: hot mix asphalts (HMAs) and Portland cement concrete (PCC). In addition, the investigation also considers a relatively new material made of an open-grade bituminous mixture filled with cement mortar, in literature known as grouted macadam (GM). The comparison is carried out by developing an experimental plan with four main goals: assessment of the effect of fire exposure, evaluation of the effect of exposure to high temperatures, measurement of the decay of mechanical characteristics as a result of fire and exposure to high temperatures, and assessment of the types and concentration of smoke emitted during fire exposure. Results from the investigation led to the conclusion that HMA is the least suitable material for tunnel applications as it showed the worst performance in all four test categories. PCC shows the best performance in the tunnel-fire scenario and GM may also be considered suitable for tunnel-pavement application as it showed a similar or even better performance compared to PCC.