Laboratory and in Situ Damage Evaluation of Geogrid Used in Asphalt Concrete Pavement

We present in this paper, the damage evaluation of 9 different types of geogrids which have been recovered from laboratory asphalt compacted slabs and in situ test sections of asphalt concrete pavements. After pavement construction, the geogrids have been recovered from different locations on the field sections, and their residual mechanical properties have been evaluated in the laboratory. The same tests have been performed for recovered grids from laboratory compacted slabs. Different compaction processes have been applied for a simulated semi-coarse asphalt concrete made with a petroleum oil to the same hot mixed asphalt which has been used in situ. For the compaction, a wheel tracking device which provides a free rolling and mimics the rubber tired rollers or a compaction damaging device being more representative of on site steel rollers has been used. The tensile strength, stiffness modulus and fatigue strength of each yarn of the grids recovered from test sections have been measured. The main results are that, if the tensile strength is decreased by the compaction process, the stiffness modulus remains practically unaffected and we can observe a clear influence of the grid coating on the tensile strength and modulus. Finally, tensile fatigue tests on recovered warp or filling yarns have been carried out, proving that, even if the grid is damaged during the compaction process, its endurance limit, even if it is decreased compared to virgin warp yarns, remains over the asphalt concrete fatigue limit.