Performance Evaluation of Fly Ash–Based Inverted Pavement System

Abstract

The inverted pavement system is an alternate type of pavement system compared to rigid and flexible pavement systems. The base layer of inverted pavements is generally a cement-treated layer with varied cement content, depending on the unconfined compressive strength criteria and durability. In the present study, fly ash was used as a replacement for aggregate in the cemented base layer; in the cemented subbase layer, only fly ash and cement were used. An optimized combination of fly ash (22%), aggregate (78%), and cement (3%) was used for the cemented base layer. For the cemented subbase layer, 7% cement and 93% fly ash were used. Therefore, 22% aggregate in cemented base and 100% aggregate in cemented subbase layer can be saved. For the field investigation, a test track was constructed for 0.5 million standard axles (MSA), and performance was monitored with both nondestructive testing (NDT), that is, falling weight deflectometer (FWD), Benkelman beam deflection (BBD), and ultrasonic pulse velocity (UPV), and destructive testing (actual loading, plate load test and dynamic cone penetration test) on the test track. The NDT testing showed that the cemented layers performed well. However, it was found that the pavement failed prematurely under actual loading. The plate load test showed that crack relief failed because of compaction issues. Last, finite-element modeling of the test section using PLAXIS 3D version 2013 showed the vertical stress distribution in the inverted pavement.