Reinforcement using an interlayer system has been demonstrated for more than four decades as a multi-purpose solution to improve performance, to extend service life and thus to reduce maintenance costs of road pavements. Among a large number of existing interlayer systems, glass fibre grids have shown effective use in pavement reinforcement with a hot mix asphalt overlay. Recently they have received increasing attention from the pavement community. However, as for other types of interlayer systems, the mechanisms underlying the effectiveness and proper installation of this type of reinforcement system are still not fully understood, and the choice of the most appropriate grid (e.g. mesh size, tensile strength) and its optimal location in the pavement system are mainly based on experience. This article presents firstly a literature review on the use of glass fibre grids in pavement reinforcement. Then some results of recent full-scale tests on the accelerated pavement testing facility of the IFSTTAR are presented. They confirm that glass fibre grid properly installed near the bottom of the asphalt layer improves significantly the fatigue life of the reinforced pavement. They also demonstrate the efficiency of glass grid use under only a thin asphalt overlay. Finally, first results obtained using an original instrumentation of glass grid strands by means of strain gages, to understand better the mechanical behaviour of the glass fibre reinforcement in a new pavement structure are described.

This paper focuses on the influence of the cyclic loading amplitudes on the behaviour of bitumen and bituminous mixtures. The present work considers only rather small strain amplitude (lower than 100 µm/m for mixtures and 10% for bitumen). Complex modulus tests on mixtures were conducted at four levels of strain amplitude for a large range of temperatures and frequencies. Tension–compression tests at the temperatures lower than 20°C and shear tests at temperatures higher than 20°C were performed to measure the complex modulus of bitumen which is used to produce the mixtures. Moreover, individual strain tests, strain sweep tests and fatigue tests at 10, 30 and 50°C were carried out to study the influence of the strain amplitude and cyclic effects on the complex modulus of bitumen. The obtained results indicated that the nonlinearity (effect of strain amplitude) on both bitumen and bituminous mixtures respects the Time Temperature Superposition Principle (TTSP). However, the temperature–frequency has inverse effects on the nonlinear behaviour of bitumen and bituminous mixtures. The cyclic effect was shown to be not negligible when analysing the nonlinearity phenomenon.

This paper presents an Acoustic Emission characterisation of the damage behaviour of asphalt concrete subjected to bending fatigue loading. An experimental campaign is carried out on an old asphalt concrete extracted from an in-service highway pavement, built-in 2001. Tests were performed in strain-controlled mode with an amplitude of 175 µstrain, a frequency of 25 Hz, and at 10°C. Failure criteria based on modulus decrease are analysed to determine the fatigue lifespan. Acoustic emission measurements are used to investigate the damage and failure processes. A network of eight piezoelectric sensors was used to acquire the acoustic signals. Therefore, different fatigue stages are identified based on the temporal evolution of acoustic activity. Hence, the event’s spatial location is presented to show the crack path propagation. The results show that sensors located at the bottom of the sample register more acoustic activity. The locations of acoustic events were in good agreement with the mechanical background calculations.

Treatment with hydraulic binder is one of the techniques for recycling of reclaimed asphalt pavement (RAP) recovered from road deconstruction. The combined presence of hydraulic binder and bituminous binder (from the RAP) in the mix makes it a composite material, on which the feedback from real road networks is still limited today and which has not yet been considered in the French rational pavement design method (RPDM). The addition of steel fibres in the composite mix allows minimising crack width, solution adopted by the steel fibre-reinforced roller-compacted concrete (FRCC™) technique. FRCC™ mixes with different fibres and RAP contents are compared with another RAP-based material treated with hydraulic binder, ERTALH®. The study discussed in this paper is part of the French National Research Agency project “Recyroute” which aims to evaluate the use of these composite materials in the base layer of heavy traffic roads. Mechanical properties of these composites were investigated by an extensive laboratory test programme. Performance of full-scale pavements was also evaluated throughout an accelerated pavement test (APT). This paper presents the main features and results of the laboratory test programme and the APT experiment as well, leading to propose design parameters of these innovative pavement structures, according to the French RPDM.