Structural Evaluation of Flexible Pavement Constructed with Steel Slag-Fly Ash-Lime Mix in the Base Layer

The concept of utilizing industrial wastes for road construction can be materialized only by evaluating the field performance of roads constructed with these wastes. The present study encompasses the laboratory investigation of steel slag-fly ash-lime (SFL) mix substantiated by field evaluation of flexible pavement test sections constructed with SFL mix in the base layer. Based on grain size analysis and unconfined compressive strength (UCS) test, 75% steel slag+19% fly ash+6% lime mix was chosen as a potential replacement for wet mix macadam (WMM) in the base layer of flexible pavement. The UCS test results were supported by the shear strength parameters and resilient moduli of optimum SFL mix. The superior stiffness characteristics of the SFL mix obtained in laboratory investigation were validated with a detailed structural evaluation of flexible pavement test sections constructed with 150 and 250 mm thick SFL base. Stiffness-based quality control approach was adopted during the construction of test sections through light weight deflectometer (LWD). SFL base layers exhibited higher in situ stiffness when compared to that of WMM. From the structural evaluation of test sections with falling weight deflectometer (FWD), sections with SFL base layer exhibited lower peak deflections than that of conventional WMM. The back-calculated elastic modulus computed from FWD test for SFL base layers was more than five times that of WMM. Furthermore, test sections with SFL base layer showed a service life ratio up to 2.6 and a notable cost saving up to 15% compared to conventional WMM layer.