Bulk utilization of steel slag–fly ash composite: a sustainable alternative for use as road construction materials

Abstract

This study explores the utilization of steel slag and fly ash in road construction to address the increasing demand for pavement materials and the scarcity of natural aggregates. For this purpose, steel slag–fly ash composite is stabilized with lime and ground granulated blast furnace slag (GGBS) to assess their utility as a subbase and base material in flexible pavements. Laboratory tests, including compaction and unconfined compressive strength, are conducted on the trial mixes to determine the optimal combinations. Subsequently, durability and resilient modulus tests are performed on the optimum mixes to evaluate their suitability as subbase and base materials. The study identifies the mixes 56% Steel slag + 40% Fly ash + 1% Lime + 3% GGBS and 86% Steel slag + 10% Fly ash + 1% Lime + 3% GGBS as the optimum choices for the subbase layer, while the mixes 76% Steel slag + 20% Fly ash + 1% Lime + 3% GGBS and 70% Steel slag + 20% Fly ash + 1% Lime + 9% GGBS is selected as the optimum mixes for the base layer of flexible pavement and Dry Lean concrete layer for rigid pavement, respectively. After 28 days of curing, the resilient moduli of the optimal subbase and base mixes are 86% and 122% higher than those of conventional granular subbase (GSB) and wet mix macadam (WMM), respectively. Plaxis-3D software demonstrates that the pavement constructed with optimal mixtures in the subbase and base layers has a longer service life than pavement constructed with a conventional granular subbase and wet mix macadam layers. These findings highlight the potential of utilizing bulk quantities of industrial by-products in road construction, offering an environmentally-friendly solution while enhancing pavement performance and longevity.