To improve the service life of pavements, innovative materials have to be used to produce asphalt concrete layers that can better withstand distress phenomena. The rehabilitation of a structural layer on the EN14 (Portuguese national highway 14) using high modulus asphalt concrete (HMAC) has been studied. The project workplan involved the laboratory design of the mixture by undertaking performance tests and constructing trial sections to observe the effectiveness of the mixture. Prismatic specimens were extracted from these trial sections and similar specimens have been produced in the laboratory. Fundamental tests, namely, repetitive four-point bending, were performed on both specimens for several temperatures and loading conditions. This made it possible to determine their mechanical properties, stiffness modulus and phase angle. The values for these parameters enable prediction models to be developed, which can be used to help design high modulus betuminous mixtures.