Bituminous pavements reinforcement with interlayer systems: proposing a routine laboratory fatigue flexural testing procedure

To date a standard method for the laboratory characterization of bituminous pavements reinforcement with synthetic inter layers is not yet recognized. The methods used so far are derived from standardized procedures made for bituminous mixes: fatigue testing according to EN 12697 part 24 in its different procedures, in particular Three Point Bending and Four Point Bending on prismatic specimens. Nevertheless, the presence of inter layers in the double-layered samples demands for particular attention in defining the testing set-up because the asphalt concrete-grid interaction should be tested as close as possible to the in service actual conditions. This paper deals with proposing a flexural testing protocol that, starting from the standard procedure, takes into account the size of the grid mesh and the feasibility of routine testing on laboratory produced and tested samples. For this work a series of 3PB bending tests on double-layered specimens made of plant mixed and site compacted hot mix asphalts was run. Different types of grid-reinforcements were laid to compare the effectiveness of the proposed testing method and protocol in assessing their contribution to the bituminous systems strength. Results have shown the reliability of the proposed method and its capability in providing a relative estimate or indexing of the reinforcement benefits of the tested materials.