Steel slag and zeolite as sustainable pozzolans for UHPC: an experimental study of binary and ternary pozzolan mixtures under various curing conditions

The production and storage of steel slag, a by-product of the steel industry, pose environmental challenges in various nations. This study investigates the properties of Ultra-High-Performance Concrete (UHPC) with three distinct pozzolans (silica fume, steel slag, and zeolite) in binary pozzolan (BP) and ternary pozzolan (TP) formulations. Silica fume was consistently present as a fixed pozzolan in all mixtures, while steel slag and zeolite were utilized in varying amounts. Moreover, to investigate the effect of humidity on the performance of the pozzolans, UHPC mixtures were cured under standard and ambient air curing conditions. The tests conducted include compressive strength, flexural strength, electrical resistivity, chloride ion migration, abrasion resistance, and pull-off. The results indicated that BP mixtures performed better than TP mixtures. The compressive and flexural strength increased by 3.94% and 2.98%, respectively, with 10% steel slag and by 12.83% and 16.84%, respectively, with 10% zeolite. Steel slag and zeolite also enhanced the durability characteristics of UHPC mixtures significantly. Abrasion loss was reduced by 9.18%–22.02% with steel slag and by 12.85%–19.27% with zeolite. Pull-off test results demonstrated the positive effect of both pozzolans on enhancing resistance, but zeolite yielded better outcomes than steel slag.