Stone Interlayer Pavement Design

Abstract

A project was initiated to evaluate the pavement performance of an alternative pavement design, referred to here as stone interlayer or inverted pavement. The test section consisted of a 4-in. (102-mm) layer of stone base on top of 6 in. (152 mm) of in-place cement stabilized base. The control section consisted of 8.5 in. (216 mm) of cement-stabilized base layer on top of prepared subgrade (standard design). A 3.5-in. (99-mm) layer of flexible pavement was placed over both sections. The objective of the study was to evaluate reflective cracking reduction through the asphaltic pavement as well as overall pavement performance. The project took place in Acadia Parish, Route LA-97, near Jennings, Louisiana. LA-97 is considered a low-volume rural highway, with average daily traffic of 2,000 vehicles. The pavement was monitored for 7 years after construction. During the evaluation period, annual crack survey, ride, and deflection measurements were collected. Additionally, as part of the Louisiana Transportation Research Center accelerated pavement testing research program, the same pavement design was tested to failure using the Accelerated Loading Facility device. Results of the investigation showed that the stone interlayer had significantly reduced the amount of reflective cracking. The ride characteristics and structural capacity of both sections were similar during the evaluation period. Accelerated testing results also verified the superior performance of the stone interlayer pavement system. The cost analysis showed initial construction costs for the stone interlayer system may be as high as 20 percent more than standard design. However, the life of the stone interlayer pavement system is increased to almost five times that of the standard soil cement pavement as tested under accelerated loading.