Glass and carbon geogrid reinforcement of asphalt mixtures

Application of geogrids for asphalt layers in road and airport pavements has been studied since early 1980s. This type of geosynthetics is feasible to mitigate reflective cracking and to prolong fatigue life, that is, to reinforce asphalt layers within pavement structure. Up to now, many laboratory and field studies demonstrated significant benefits of using geogrids but still several aspects of their working mechanism within adjacent asphalt layers remain not fully understood and need to be further explored. This paper presents an initial part of the long-term study initiated in Poland in order to fully assess the benefits of using geogrids within asphalt layers. The first part of this paper presents the state-of-the-art review on geogrid applications in asphalt layers. The next part demonstrates and discusses the results obtained on the geogrid-reinforced beams under monotonic and cyclic loading conditions. Three types of large beams were prepared in the laboratory conditions. One group comprises reference beams without any reinforcement and the other two were reinforced, respectively, with glass and carbon geogrids. Specimens were evaluated in a custom-made 3PB/4PB fixture at 13°C in order to observe their behaviour under force-controlled fatigue test and displacement-controlled fracture test. Results demonstrated a beneficial impact of fibre reinforcement on the development of beam deflections in the fatigue tests and significantly higher fracture energy in the post-peak softening region. These results will be used to prepare a new experimental campaign to closely investigate the reinforcement mechanism of geogrids within asphalt layers. The paper concludes with short- and long-term plans necessary to develop an official design procedure for the pavements with geogrid-reinforced asphalt layers in Poland.