Asserting the Applicability of Copper Slag and Fly Ash as Cemented Base Materials in Flexible Pavement from a Full-Scale Field Study

Abstract

This research made innovative use of copper slag and fly ash in the construction of a cemented base course of flexible pavement. A full-scale field study evaluated the structural and functional performance of flexible pavement test sections constructed using various combinations of copper slag and fly ash (Class F or Class C) with and without lime. Various performance parameters, namely deflection basin parameters, dissipated energy, back-calculated elastic modulus, service life ratio, and roughness index, were evaluated for flexible pavement test sections constructed with 250-mm-thick conventional granular base [wet-mix macadam (WMM)], 150-mm- and 250-mm-thick copper slag–Class F fly ash–lime (CFL) (70% copper slag +23% Class F fly ash +7% lime) and copper slag–Class C fly ash (CCF) (40% copper slag +60% Class C fly ash) base layers. Falling weight deflectometer tests and bump integrator tests were performed in situ; laboratory tests, namely unconfined compression and resilient modulus tests, were performed on core samples. The average elastic moduli, back-calculated from six FWD tests conducted over 15 months after construction, for CCF and CFL base were 430 and 602 MPa, which are more than 3 times that of WMM. Significant waste utilization up to 1,348 tons of copper slag and 945 tons of fly ash per kilometer length of road can be achieved by using CCF and CFL mixes in base layers of flexible pavement with a service life ratio as high as 1.78 and cost efficiency of 17.4%.