Bora Kutuk

Date of Graduation


Document Type



This report presents the results of an investigation on the effectiveness of glass fiber grids as a reinforcement of the asphalt base layer in a flexible pavement. The study involved both laboratory experimental work and computer analysis of pavement sections. As part of the experimental work, twenty flexible pavement sections (with and without glass fiber grids) were constructed and tested in the laboratory. The laboratory-scale pavement sections were instrumented with pressure cells, displacement gages, and strain gages. Test sections were subjected to 1,000,000 load applications at a frequency of 1.2 Hz. Static loading tests were conducted at intervals of 100,000 load applications. In thirteen experiments, the glass fiber grid was used in the asphalt base layer. In five experiments, with and without reinforcement, a crack was simulated in the hot mix asphalt (thickness of 3-inch (76 mm)) base layer. A series of computer analyses was performed to analyze flexible pavement sections using the KENLAYER (Huang (1993)) computer program and the Finite Element Method (FEM). The laboratory data were compared with results from the computer analysis. Observations on doubly reinforced cases indicate that the vertical stresses in the subgrade is lower in pavement sections with stronger glass grids. In terms of cumulative displacement, results indicate that a 6-inch (152 mm) thick non-reinforced hot-mix asphalt base layer does not improve the performance of the pavement system in comparison to a 3-inch (76 mm) thick reinforced asphalt section. Observations on thinner pavement sections indicate that the increase in vertical subgrade stress caused by a simulated crack is offset by the decrease in vertical subgrade stress due to the reinforcement of the pavement section. The results show that the glass fiber grid used in this study improved the pavement performance. It was also observed that the inclusion of glass fiber grid in the HMA layer provided resistance to crack propagation. Overall, the flexible pavement sections reinforced with glass fiber geogrids (in the asphalt base layer) showed better performance under laboratory test conditions.