Volume 8, Issue 7 (July 2011)
Full Depth Reclamation of Asphalt Pavements Using Coal Combustion Byproducts
The objective of this study was to demonstrate the use of Class F coal fly ash in combination with lime or lime kiln dust (LKD) in full depth reclamation (FDR) of failing asphalt pavements. Full-scale test sections (about 4 miles in length) of two structurally deficient asphalt pavements were reclaimed using Class F fly ash in combination with lime and LKD. In addition, control sections were constructed using cement, cement and emulsion, LKD and emulsion, and simple recompaction. The service performance and structural behavior of the reclaimed pavement test sections were monitored to determine how the fly ash sections compared with other admixtures. Service performance and structural behavior were determined through a program of falling weight deflectometer (FWD) tests and embedded sensors installed at the time of construction. Monitoring results of the FWD tests conducted up to 3 yr after reclamation show that the cement, fly ash and LKD, and fly ash and lime sections exhibited resilient modulus values comparable to soil cement. The cement treatment resulted in a significant increase in resilient modulus within three weeks of the end of construction but beyond this curing time stiffness increase was slow. Tests on fly ash and LKD and fly ash and lime test sections indicated a slower short-term increase in stiffness, but the two fly ash stabilized sections 3 yr after construction exhibit average resilient modulus values of 400–1,300 ksi.