Effectiveness of geogrids in roadway construction by large scale laboratory tests

Geogrids have been widely used in the roadway construction as reinforcement in pavement foundations. Geogrids have been effective in practice for reducing rutting damage, distributing traffic loads within the pavement foundation layers, increasing the resilient modulus of base course, improving drainage, reducing differential freeze/thaw problems, and stabilization effects on the subgrade layer. How to accurately evaluate structural benefits of geogrids in pavement foundation is a difficult issue because many factors can affect structural benefits, such as geogrid stiffness, geogrid aperture and rib shape, aperture and rib sizes, the geogrid location/depth, hot mix asphalt thicknesses, base aggregate quality, stiffness thicknesses, and subgrade stiffness. In this research, we used an Integrated Mobile Accelerated Test System (IMAS) to evaluate reinforcement effects of geogrids. The IMAS system mainly consists of a 5 ft wide and 3 ft deep rigid box and automatic loading frame. A total of eight test configurations were constructed by varying geogrid types (i.e., light-duty biaxial, heavy-duty biaxial, light-duty triaxial, and heavy-duty triaxial geogrids), geogrid locations in pavement (i.e., at the interface between base and subgrade or in the base course), and base aggregate thicknesses. The IMAS can perform cyclic load tests of pavement foundation sections to a large number of load cycles, which simulates vehicle-loading conditions expected during the service life of a pavement system to evaluate the long-term performance of the pavement structure. Testing results include resilient modulus, and permanent deformation of the pavement foundation for evaluating structural benefits of geogrids as a function of geogrid types, geogrid locations, and base aggregate thicknesses. The results of this research will help better design geogrids in roadways to improve pavement quality, extend pavement service life, and reduce life-cycle costs