Environmental problems caused by large amounts of CO₂ generated by coal–electricity integration bases have raised concerns. To solve these problems, this study develops a CO₂ foam concrete (CFC) material with both heat insulation and carbon fixation characteristics to realize CO₂ in situ storage and utilization. In this study, a Portland-cement-based CO₂ foam concrete (PC-CFC) with good thermal insulation performance and carbon fixation ability is prepared using carbonation pretreatment cement and a physical foaming method. The effects of CO₂ on the compressive strength, thermal insulation, and carbon fixation properties of PC-CFC are studied. The internal relationship between the compressive strength, thermal insulation, and carbon fixation performance of PC-CFC is analyzed, and the feasibility of PC-CFC as a filling material to realize the in situ mineralization and storage of CO₂ in the coal–electricity integration base is discussed. The experimental results show that the compressive strength of PC-CFC is significantly improved by CO₂ curing. However, CO₂ in the PC-CFC pores may weaken the strength of the pore structure, and the compressive strength decreases by 3.62% for each 1% increase in PC-CFC porosity. Using CO₂ as a foaming gas and the physical foaming method to prepare CFC can achieve improved thermal insulation performance. The thermal conductivity of PC-CFC is 0.0512–0.0905 W/(m·K). In addition, the compressive strength of PC-CFC increases by 19.08% when the thermal conductivity of PC-CFC increases by 1%. On the premise of meeting the thermal insulation requirements, PC-CFC can achieve improved compressive strength. The carbon sequestration rate of the PC-CFC skeleton is 6.1–8.57%, and the carbon storage capacity of PC-CFC pores is 1.36–2.60 kg/ton, which has obvious carbon sequestration potential; however, the preparation process and parameters of PC-CFC still require further improvement. The research results show that PC-CFC has great potential for engineering applications and is of great significance for realizing carbon reduction at the coal–electricity integration base.

The aim of this paper is to study the particle size effect of fly ash (FLA) on pore structure and strength of Fly Ash Foamed Geopolymer (FAFG). Information on the macro-pores such as macro-pore size and distribution of FAFG is captured through binarization processing. Porosity and compressive strength of FAFG are respectively tested by Archimedes density test method and uniaxial compressive strength test method. It can be concluded that the FLA particle size has an effect on the pore structure and strength of FAFG. More specifically, the effect of FLA particle size shows itself macroscopically on the quantity of middle and large macro-pores and the uniformity of macro-pores distribution, and microscopically on the quantity of micro-holes and cracks and calcium silicate (C-S-H) quantity at the early stage of FAFG mixture. All of the properties of FAFG follow some kind of changing rule except at the turning point when FLA particle is of 0.125~0.25 mm in size. To explain clearly the root cause of FLA particle size effect on FAFG, SEM, and XRD are employed to explore the microstructure of FAFG and the component of FLA. It turns out to be the amorphous phase SiO₂ content in FLA of different particle sizes which could determine the reaction extent of FAFG mixture.

An evaluation of the failures of coal under variable conditions in relation to the stability of coal pillars is an important issue for coal mining. This paper presents the results of an experimental investigation of the mechanical behavior of brittle coal under plane-strain biaxial stress state (PSBSS) compression. The synthetic specimens were meant to test the ductile properties. Modified surface instability detection apparatus was setup to carry out the tests. The results show that the stress-strain curves of coal and synthetic specimens under the PSBSS can be divided into four typical stages, namely original microcrack closure, elastic deformation, sudden stress drop, and residual behavior. The stress-strain curve of coal under PSBSS compression showed periodic stress drops during the post-peak phase, while the curve of the synthetic specimen presented a moderate decrease during the post-peak stage. The remarkable residual strengths of the coal and composites can be observed using these curves, which is vital to the stability of specimens after the failure strength is exceeded. Strain rates have a significant effect on the strength of coal samples under PSBSS compression. Specifically, a higher strain rate indicates a greater peak strength. The failure modes for coal and synthetic specimens are different. During PSBSS compressive tests, coal showed a split failure under different strain rates. For flexible composites, the failure pattern is conjugate shear failure. The study indicated that the Modified Lade and Modified Wiebols-Cook criteria are competent for estimating the defined strength coefficient, which is a ratio proposed to estimate the PSBSS peak strength.

Determining the physical and mechanical behavior of sedimentary rocks is one of the most common challenges in deep rock mass engineering. Experiments were con-ducted to study the physical and mechanical properties of coal measure mudstone with SEM, XRD, and uniaxial compression testing. The results show that temperature has a significant effect on the physical and mechanical properties of coal measure mudstone. The presence of clay minerals in the evaluated mudstone contributes to the unique characteristics seen at high temperature. The mudstone experiences obvious color changes on the surface as temperature rises. This is mostly attributed to the iron-bearing clay minerals. Internal color change is caused by thermal de-composition of kerogen associated with the clay minerals. As the major clay mineral in mudstone, kaolinite undergoes significant phase changes at high temperatures, which leads to changes in mechanical properties. From 25?C to 200?C, due to the evaporation of absorbed water from the clay minerals, the strength of the mudstone increases significantly. As the temperature continues to rise beyond this, water evaporation continues and the rock strength increases gradually from 200?C to 400?C. When the temperature reaches 400?C, this mudstone was strengthened as a result of decomposition of the kaolinite and thermal expansion of crystalline minerals. Above 600?C, dehydration of the clay minerals ends while thermal cracking initiates gradually, which results in decreasing strength