Stabilization of fly ash and lime sludge composites: Assessment of its performance as base course material

In the present study, two potential industrial waste materials, such as, fly ash (FA) and lime sludge (LS) that are generated in bulk quantities and poses environmental hazards were mixed and stabilized using lime (CL) and gypsum (G) in order to make them suitable for use in Civil Engineering construction applications. Different mix proportion of FA and LS stabilized with different % of CL and G were studied and tested for unconfined compressive strength (UCS), split tensile strength test (STS) and California bearing ratio (CBR) to check the suitability of prepared composite for construction industries. It is noted that the optimal composition consisted of FA and LS in 1:1 ratio, 12% CL and 1% G content. The composite was also found to be durable with no leaching of heavy metals. Further, the selected composite was further studied for the microstructural development through scanning electron microscopy (SEM) and X-ray diffraction (XRD) to understand the phenomenon of chemical process or reaction and reason for strength gain. The developed composite (50FA + 50LS + 12CL + 1G) is suggested for application as base course layer material in flexible pavements due to its good requisite strength and durability. It is further highlighted that issues of uncertainty in strength and stiffness characteristics of pavement layer materials and its implications on analysis and design of flexible pavements can be studied through reliability based approach in combination with numerical analysis and Monte Carlo simulations.