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.

This study assesses the impact of alkaline treatments and volume fractions on biocomposites composed of a high-density polyethylene (HDPE) matrix reinforced with date palm tree fibers (FPDS). Tensile tests were conducted on both untreated and NaOH-treated biocomposites. Additionally, fiber analysis was performed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results reveal higher strength and stiffness compared to HDPE, albeit with limited plasticity making the material brittle. The NaOH treatment enhances certain mechanical properties. Further assessments encompassed hardness, density, melt index, and Izod impact tests. Two volume fractions, 20% and 25%, of FPDS were tested. The study establishes a correlation between empirical predictions and artificial neural network (ANN) models. Notably, an ANN architecture consisting of two input factors, 10 hidden nodes, and one output provides the analysis of mechanical properties. This investigation highlights the potential of FPDS-reinforced HDPE biocomposites, emphasizing their mechanical performance under various treatments and fiber levels.

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.