Ultra-high-performance concrete (UHPC) is known for its outstanding strength and durability but is often limited by the high cost of traditional materials, like cement, fine aggregates, and silica fume. This review examines the use of industrial by-products—specifically, iron tailings, steel slag, and desulfurization gypsum—as sustainable alternatives in UHPC mix design. These materials serve as supplementary cementitious components and fine aggregates, helping reduce environmental impacts and production costs. This study highlights the synergistic hydration mechanisms between Portland cement and waste-based materials, leading to improved microstructure and long-term strength. The role of steel fibers in enhancing crack resistance is also discussed. Challenges related to workability, cost, and lack of standardization are addressed, along with opportunities for innovative mix designs, low-carbon binders, and 3D printing. Overall, this paper underscores the potential of industrial by-products to advance sustainable, high-performance UHPC solutions.

This study used refining slag (RS), ground granulated blast furnace slag (GGBS), steel slag (SS), and desulfurized gypsum (DG) to prepare a mine-filling cementitious material. The developed cementitious material and tailings sand were mixed to prepare a novel mine backfill material with better performance and a lower cost. The macroscopic properties and hydration mechanism of the cemented solid waste-based backfill were investigated when RS content was 0, 5%, 10%, 15%, 20%, 30% and 40%. The results showed that introducing RS could reduce the bleeding rate and shorten the setting time of backfill slurry while significantly enhancing the 3-day compressive strength of backfill. Compared to JL-0, the bleeding rate decreased by 50.3% as the RS content was raised to 15%, while the setting time was shortened by 36.5%, and the 3-day compressive strength increased by 4.3 times. As the RS content did not exceed 20%, the 28-day compressive strength of the backfill was not lower than that of the cement backfill (4.3 MPa). The results of microanalysis (including XRD, FT-IR, SEM, TG-DSC, and heat of hydration) revealed that the hydration products of the RS-GGBS-SS-DG quaternary material are primarily C-(A)-S-H gels and AFt. The main effect of RS is to improve the content of aluminates, accelerating and increasing the production of AFt, thus leading to faster overall hydration. This research can provide data support for the application of RS in the mine-filling field. Applying quaternary solid waste-based cementitious materials in the mine-filling field has good economic benefits.

This study investigates the use of iron mine tailings (ITs) as a fine aggregate and a clinker-free binder composed of ground granulated blast-furnace slag (GBFS), desulfurization gypsum (DG), and basic oxygen furnace slag (BOFS) to produce low-cost ultra-high-performance concrete (UHPC). The research optimizes the UHPC base by evaluating the impact of key parameters, including the BOFS to GBFS ratio, DG content, BOFS fineness, and binder-to-sand ratio on compressive strength. The study also compares the use of iron mine tailings and silica sand as fine aggregates, demonstrating that tailings are a viable substitute. The results show that the optimal mix, consisting of a 1:1 BOFS to GBFS ratio, 15% DG, and 400 m²/kg BOFS fineness, achieves a compressive strength of 113.7 MPa after 28 days when using iron mine tailings as fine aggregate. Microstructural analysis through X-ray diffraction (XRD), thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) reveal that the primary hydration products—C-S-H gel and AFt—contribute to the dense and strong microstructure of the UHPC. This research offers a sustainable approach to producing cost-effective UHPC by utilizing industrial waste materials, providing a promising solution for reducing both environmental impact and production costs in construction.

Semi-dry desulfurization ash (SDA) is generated in rapidly increasing quantities and remains underutilised, despite its high CaO content, which makes it a promising candidate for CO₂ storage via carbonation curing. However, the carbonation behaviour and consolidation mechanism of standalone SDA compacts are not yet well understood. In this study, SDA compacts were prepared at water-to-solid (w/s) ratios of 1.5:10 and 1.83:10 and subjected to carbonation curing for 0–24 h under controlled CO₂ conditions. Compressive strength, CO₂ uptake, and microstructural evolution were assessed using XRD, TG–DTG, FTIR, and SEM. CO₂ uptake increased with curing time and reached approximately 20% after 24 h, whereas compressive strength exhibited a non-linear response, peaking at 8.67 MPa after 6 h at w/s = 1.5:10 and declining thereafter. Phase and microstructural analyses indicate that strength development is governed by the transformation of Ca(OH)₂ to CaCO₃ polymorphs, with early densification followed by increased porosity as calcite coarsens. Sulphur-bearing phases (e.g., CaSO₃·0.5H₂O) remain largely inert under the tested conditions. These findings demonstrate that carbonation curing can significantly enhance CO₂ fixation in SDA and generate low-strength construction materials while also highlighting the need to optimise mix design and curing parameters to mitigate strength loss at extended curing times.

Concrete production is associated with significant CO2 emissions and natural resource depletion. In this study, a fully solid waste-based ultra-high performance concrete (SW-UHPC) formulation was developed. The binder comprised refining slag, steel slag, blast furnace slag and desulfurisation gypsum, while coarse steel slag was used as the aggregate. The effects of the water-to-binder (w/b) ratio (ranging from 0.18 to 0.22) on the workability, mechanical properties and hydration products of SW-UHPC were systematically investigated. Results indicate that reducing the w/b ratio led to decreased workability but enhanced compressive strength. The maximum compressive strength at 28 days exceeded 113 MPa at a w/b ratio of 0.18, while toughness peaked at a w/b ratio of 0.20. Increasing the w/b ratio promoted the degree of hydration, resulting in greater formation of hydration products, including ettringite and C-(A)-S-H gel, accompanied by gypsum consumption and increased hydration heat. Backscatter electron images demonstrated reduced porosity of the concrete at lower w/b ratios, consistent with observed compressive strength enhancement. The influence of the w/b ratio is governed by two competing mechanisms: hydration continuity and microstructural densification. Overall, the use of these solid waste-derived constituents enabled a reduction of >50% raw-material-related carbon emissions compared with conventional UHPC, while achieving effective and safe valorisation of multiple industrial by-products.