Effect of hydraulic binders on engineering properties of coal ash for utilization in pavement layers.

Utilizing waste materials in road construction has become a compelling alternative owing to the availability of high-quality natural aggregates and the challenges associated with disposing of industrial waste. This study delves into the potential of class F fly ash from coal combustion, which is not self-cementing, requiring additional activators for stabilization. Activators such as lime, ground granulated blast furnace slag (GGBS), and bottom ash were incorporated in diverse proportions. The experimental analysis included tests like modified Proctor compaction, unconfined compressive strength (UCS), California bearing ratio (CBR), and repeated load triaxial tests. Results revealed that the introduction of 1–3% lime, 3–21% ground granulated blast furnace slag, and 10–30% bottom ash, combined with extended curing durations, augmented both compressive strength and California bearing ratio values. The resilient modulus of these mixtures showed an improvement of roughly 70% compared to traditional Wet Mix Macadam. Advanced microscopic studies using X-Ray diffraction (XRD), field emission scanning electron microscopy (FESEM) equipped with energy dispersive spectroscopy (EDS), and thermogravimetric analysis (TGA) identified the formation of calcium silicate hydrates and ettringite as contributing factors to the increased strength. The optimally formulated mixtures met the requirements outlined by the Indian Roads Congress, suggesting their suitability for inclusion in base, subbase courses of flexible pavements, and the dry lean concrete layer of rigid pavements. [ABSTRACT FROM AUTHOR]