The preparation of cementitious materials by replacing part of the cement with activated coal gangue is of great significance to the cement industry in terms of carbon reduction and coal-based solid waste utilization. For this paper, cementitious material was prepared by firing activated coal gangue under suspension conditions and batching it with limestone powder using Inner Mongolia coal gangue as raw material. The optimal ratio was determined by testing the strength changes of the cementitious material at 3, 7, and 28 days of hydration, and the hydration process and mechanism were explored by combining the pore structure, heat of hydration, chemical composition, phase composition, and microscopic morphological characteristics of the hydration products. The results showed that the active materials formulated from activated gangue and limestone powder can be used to prepare cementitious materials with good performance at the level of 30%–50% replacement of cement. The optimal ratio was 30% replacement of cement, and the mass ratio of calcined gangue to limestone powder was 2:1. The 3 days compressive strength of this ratio was 28.8 MPa, which was only slightly lower than that of cement. However, the 28 days compressive strength of samples reached 67.5 MPa, which was much higher than that of the reference cement. In the hydration of this cementitious material, not only does the activated coal gangue react with the Ca(OH)₂ formed by hydration to form C–S–H gel, but CaCO₃ also participates in the reaction to form a new phase of carbon aluminate, and the two effects together promote the development of the later strength of the samples. This paper can provide a reference for carbon reduction in the cement production process and comprehensive utilization of coal gangue.

Metakaolin-based auxiliary cementitious materials fabricated by coal gangue were achieved. The temperature and time required for the preparation of metakaolin materials from the calcination of coal gangue were optimized based on the analysis of the reaction characteristics and kinetics during the calcination of coal gangue. The phase, microstructures, and activity analysis of the products were performed, and the effect of calcination conditions on the activity of the product was ascertained. The results of thermal analysis-infrared spectra combined experiments indicated that the dehydroxylation of kaolinite was a one-step reaction during the calcination of coal gangue within a temperature range of 379.8 °C–737.3 °C. According to the General Integration, Flynn-Wall-Ozawa and Kissinger methods, the activation energy E of dehydroxylation of kaolinite is 181.62 kJ·mol⁻¹ and pre-index factor A is 10^9.27 s⁻¹ for calculating the calcination time of metakaolin. The experimental results show that high-activity metakaolin products, that with a dissolution rate of 64.79–71.57 wt% of activated alumina and with an effective dissolution rate of 68.82–94.35 wt% of activated silica, are prepared under the condition of calcination for 15 min and the temperature of 700 °C–825 °C. The kinetic model simulation results for the calcination time at different temperatures correspond to the experimental results.

In this paper, a shell structure ceramsite has been prepared and researched in order to attempt a new method of producing lightweight ceramsite. In the experiment, raw material was made into slurry and polypropylene balls were treated with the soak-and-pick process in the slurry to make the green body; later, the green body was dried and fired in the furnace to make the shell structure ceramsite. The result showed that the shell structure ceramsite has an appropriate cylindrical compressive strength (0.87 MPa) with a bulk density at a low level (0.375 × 103 kg/m³), which can be used for lightweight concrete preparation, and with its special structure, it can be used for many other purposes.