**Abstract**

Several studies on the behavior of concrete at high temperatures are the subject of recent concerns, following the latest fires in various European tunnels. In these extreme conditions, significant degradations of concrete structures can be observed (peeling, cracking, breaking of the structure). A priori prediction of concrete behavior during this type of stress is therefore essential and is not possible without a good understanding of the different mechanisms of concrete damage at high temperatures. These mechanisms are often considered as the main causes of cracking and peeling of concrete subjected to high temperatures. Therefore, a fire can strongly modify the behavior of concrete and jeopardize the stability of concrete. In case of fires, it is necessary to know the instantaneous and residual behavior of concrete subjected to temperatures up to 1000°C. In this work we present a study of the mechanical performance of high-temperature high-performance concrete (HPC) exposed to four maximum temperatures, 200, 400, 600, and 900°C. The results obtained show that the mechanical strength at 28 days increases with the degree of temperature compared with that measured at 20°C. On the contrary, a clear decrease is observed between 600 and 900°C.

**Keywords:** HPC, high temperatures, mechanical strength, porosity, mineral additions
