The large coal production and consumption has caused environmental problems worldwide as a source of energy production with irreparable effects on soil, water, and the ecosystem. In addition, producing coal waste in coal washing plants and burying it intensifies the issue in nature. Due to the rising generation of coal waste from various sources, this study utilized several forms of coal waste obtained from a coal-washing plant in the production of both structural concrete (with a water-cement ratio of 0.54) and non-structural concrete (with a water-cement ratio of 0.7). The impact of coal waste on compressive strength (CS) was examined at curing ages of 7, 28, and 56 days. Various percentages of coal waste were substituted for both cement and sand. A superplasticizer was incorporated into the concrete mixtures to enhance the workability and achieve the desired slump and strength levels. According to the compressive strength findings, the ideal replacement level of sand with jig coal waste was 30 %. For 56-day-old specimens, the optimal substitution rates for cement with jig coal waste powder, flotation coal waste, and coal waste ash were found to be 10 %, 10 %, and 20 %, respectively. Notably, adding 10 % coal waste powder and coal waste ash increased compressive strength by 22 %, 23 %, and 44 % at 56 days.

Low-plasticity soils, characterized by low plasticity and high sand content, present challenges in engineering projects due to their inadequate strength and stability. This study evaluates the comparative effects of coal waste and silica fume as stabilizers to improve the mechanical properties of silty soils. Key parameters such as liquid limit (LL), plastic limit (PL), plasticity index (PI), maximum dry density (MDD), unconfined compressive strength (UCS), and shear strength were assessed through laboratory experiments with varying stabilizer proportions (3-12%). Results showed that silica fume increased the LL of Tarnol soil by 36% and reduced its PI, while coal waste improved the LL of Chaklala soil by 48%, also reducing its PI. Both stabilizers decreased MDD and increased optimum moisture content (OMC). Notably, UCS increased by 77% in Tarnol soil with 12% silica fume and by 83% in Chaklala soil with 12% coal waste after 28 days of curing. Coal waste improved the cohesion of Chaklala soil by a factor of 1.29 and its internal friction angle by 1.04, while silica fume enhanced Tarnol soil cohesion by 1.35 and its internal friction angle by 1.032. These findings demonstrate the potential of coal waste and silica fume as cost-effective, sustainable stabilizers for improving the geotechnical performance of low-plasticity soils. The study contributes valuable insights into using industrial by-products for soil stabilization, offering practical applications for enhancing soil strength and stability in construction and infrastructure projects.

Coal waste (CW) could be used for soil stabilization due to the pozzolanic elements it contains. There hasn't been much investigation into how different fibers affect the mechanical qualities of stabilized sand, although adding fibers of any kind to soils may improve the soil because of fiber characteristics like rigidity. For this reason, several tests were carried out on sand that contained 6% cement (by dry weight of used sand), 5 wt% CW, 0, 0.25 wt%, and 0.50 wt% fiber, as well as the unconfined compressive strength (UCS) test, indirect tensile strength (ITS) test, unconsolidated undrained triaxial test (UU), scanning electron microscope (SEM) test and ultrasonic pulse velocity (UPV) test. The results showed that in comparison to other fiber reinforced mix designs, the specimen reinforced with 0.5% fibers and the mix design of 0.25 wt% glass and 0.25 wt% polypropylene (PP) fibers exhibited the maximum strength. Examining the impact of fiber type found that glass fibers influence PP strength more favorably than other fiber types. The use of PP fibers is an excellent solution for the problem of large strains in design processes, while adding glass fibers is considered a suitable treatment for issues related to small strains.