Sustainable stabilization of sandy soils using steel slag and biopolymer cellulose

Steel slag, a by-product of the steel-making industry, offers potential for soil stabilization but remains underutilized in sandy soils due to slow strength development, low water retention, particle segregation, and bleeding. Cellulose, a plant-based biopolymer, enhances soil water retention and may improve the performance of steel slag-treated sands. This study investigated the stabilization of Masado granite and Toyoura silica sands using steel slag and two forms of unhydrolyzed cellulose: cellulose powder (CP) and carboxymethyl cellulose (CMC). Sands were treated with steel slag at varying contents (0 %, 10 %, 15 %, 30 %, and 50 %) to identify the optimal dosage and the most suitable sand based on unconfined compressive strength (UCS) and pozzolanic reactivity over 3, 7, 14, and 28 days. CP and CMC were added at 0 %, 0.25 %, 0.5 %, 0.75 %, and 1 % to evaluate their effects on the UCS, flowability, compaction, mineralogy, and microstructure. The findings established 30 % steel slag as the optimal dosage, enhancing UCS by 99.05 %. Masado granite sand exhibited the highest UCS (558.85 kPa), outperforming Toyoura silica sand (34 kPa) due to better pozzolanic reactivity. Incorporating 0.5 % cellulose further improved strength, with CMC and CP increasing UCS by 53.29 % and 49.23 %, respectively, through gel thread and fibrous network formation as evidenced by microstructural analysis. This novel cellulose-enhanced steel slag stabilization approach offers a sustainable alternative to cement, reducing carbon emissions by 2.5 % per kilometer of highway embankment. These findings contribute to international geotechnical research by demonstrating an innovative, low-carbon stabilization method with potential applications in global infrastructure development. • The study investigated the interaction of sand, steel slag, and cellulose. • Fine granite sand is more effective for steel slag-treatment. • Pozzolanic reactions in sand-steel slag mixes improved strength. • Cellulose enhanced strength via fiber and gel-thread formation. • Cellulose did not affect the mineralogy of steel-slag-treated sand.