Abstract
The formation and development of fatigue cracks in asphalt concrete beams have been extensively studied. Among these studies, however, very few have focused on the effects of geogrids in enhancing the resistance of asphalt concrete to fatigue failure. In addition, findings and conclusions of those studies cannot be effectively applied to most situations in Taiwan. It is therefore necessary to study the formation and development of fatigue cracks in overlaid dense-graded asphalt concrete. Among geogrids used in this laboratory study, two were made of glass fiber with strength of 100 kN/m and 200 kN/m, respectively, and one was made of high-density polyethylene (HDPE) with a strength of 25 kN/m. A series of tests for a beam reinforced with glass geogrids of 100-kN/m strength showed a fatigue life 3 to 5 times that of an unreinforced beam; and for a beam reinforced with 200-kN/m glass geogrids, the fatigue life was 5 to 9 times as long. Beams reinforced with the HDPE geogrids showed a fatigue life equivalent to those reinforced with 100-kN/m glass geogrids. Based on the findings of the laboratory study, an on-site performance study was carried out at a section of the Taiwan Second Freeway (already open for operation) from 80 km 837.5 m to 81 km 262. 5 m. A 10-month rutting-depth measurement was obtained, which confirmed that the improvement from these geogrids over the fatigue life of the pavement overlay so far was obvious and significant.
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