Influence of Granite and Iron Ore Waste Incorporation on the Mechanical Behavior of Ultra-High-Strength Concrete

Granite waste (GW) and iron ore waste (IOW) represent significant environmental challenges in Egypt. This study uniquely explores their combined use as partial replacements for conventional aggregates in ultra-high-strength green concrete (UHSGC). Both GW and IOW are industrial byproducts with stable mineral compositions, angular particle shapes, and particle size distributions comparable to those of traditional fine and coarse aggregates. In this investigation, 50% of natural dolomite was replaced with GW, and 40% of natural sand was substituted with IOW. To enhance mechanical performance, steel fibers and silica fume were incorporated into concrete mixtures. A comprehensive experimental program assessed mechanical properties through tests of compressive strength, splitting tensile strength, and flexural strength. Microstructural analyses, including Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD), were also conducted. Results showed that replacing natural dolomite with GW significantly improved the mechanical performance of UHSGC, while the combined use of GW and IOW enhanced early-age compressive strength at 3 days. Furthermore, the approach offers notable environmental and economic benefits. Microstructural analysis confirmed that GW contributes to a more homogeneous matrix, attributed to its filler effect and enhanced pozzolanic activity.