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.

This paper focuses on the low cement content characteristic of soil slurry materials for mine reclamation, investigating the effects of three types of superplasticizers (polyester-based polycarboxylate (PCE), sodium lignosulfonate (SLS), and naphthalene-based (PNS)) on the flow properties of freshly mixed solidified soil slurry. It proposes a method combining shear rheology and micro-rheology experiments to complete the selection of superplasticizers. The rheological properties of the freshly mixed slurry were compared at different dosages of superplasticizers and various resting times. The results indicate that PCE at 0.4 % dosage exhibits the best dispersion effect in the solidified soil slurry. In-situ ATR FTIR, in-situ low-field NMR, and zeta-potential tests confirmed that PCE can effectively delay the solidification process of the soil slurry to maintain its fluidity. At a PCE dosage of 0.4 %, the spatial hindrance between slurry particles is reduced, increasing the proportion of free water in the solidified soil, with the zeta-potential not being the main factor affecting the rheological properties of the soil slurry. This study provides a theoretical foundation and solutions for regulating the early fluidity of solidified soil slurry materials used in the land reclamation of coal gangue in the Northwest mining areas of China.

To reduce transportation costs for building a lunar base station, it is important to utilise in-situ resources like lunar regolith. Lunar regolith can be used to create a concrete-like material by means of geopolymerization. For application of geopolymerizing mixtures, the rheology of the slurry must be known in advance. This article investigates the rheology of mixtures of lunar dust simulants with water, NaOH (as alkaline agent) and urea (as superplasticizer). The rheology of all the mixtures can be approximated with the Bingham Model. Aging has a dramatic effect on the rheology of the water + simulant mixture and, after 2 days, the yield stress decreases by six times. The presence of NaOH, on the contrary, increases both the apparent viscosity and the yield stress as it promotes geopolymerization. The addition of urea reduces the viscosity by 25%, but it has a limited effect on the yield stress. These findings can enable the design of construction 3D printers on the moon. (C) 2021 COSPAR. Published by Elsevier B.V. All rights reserved.