Pozzolanic activity experimental dataset of calcined coal gangue

The coal gangue in this dataset was subjected to a series of processes, including drying, crushing, and milling. Subsequently, the coal gangue powder was subjected to high-temperature calcination in a muffle furnace, with a heating rate of 4 ℃/min. The pozzolanic activity of coal gangue powder was investigated at various calcination temperatures (600 ℃, 700 ℃, 800 ℃, 900 ℃) and different holding times (1h, 2h). Cement mortar specimens containing calcined coal gangue powder were prepared, and their compressive and flexural strengths were tested to evaluate the reactivity of the calcined coal gangue. In addition, the Rapid, Relevant and Reliable (R3) activity test was conducted to test the reactivity. The thermogravimetric analyzer was employed to determine the TG-DTG curves of coal gangue powder. X-ray diffractometer, Fourier infrared spectrometer and scanning electron microscope were utilized to investigate the microstructure of activated coal gangue powder at different temperature ranges. These data can be used for determining the optimal calcination scheme of coal gangue to maximize its potential as a partial cement clinker replacement in cement production, thereby contributing to cost reduction and carbon emission mitigation.


a b s t r a c t
The coal gangue in this dataset was subjected to a series of processes, including drying, crushing, and milling.Subsequently, the coal gangue powder was subjected to hightemperature calcination in a muffle furnace, with a heating rate of 4 • C/min.The pozzolanic activity of coal gangue powder was investigated at various calcination temperatures (60 0 • C, 70 0 • C, 80 0 • C, 90 0 • C) and different holding times (1h, 2h).Cement mortar specimens containing calcined coal gangue powder were prepared, and their compressive and flexural strengths were tested to evaluate the reactivity of the calcined coal gangue.In addition, the Rapid, Relevant and Reliable (R3) activity test was conducted to test the reactivity.The thermogravimetric analyzer was employed to determine the TG-DTG curves of coal gangue powder.X-ray diffractometer, Fourier infrared spectrometer and scanning electron microscope were utilized to investigate the microstructure of activated coal gangue powder at different temperature ranges.These data can be used for determining the optimal calcination scheme of coal gangue to maximize its potential as a partial cement clinker replacement in cement production, thereby contributing to cost reduction and carbon emission mitigation.

Value of the Data
• These data will contribute to the widespread application of coal gangue calcination systems in research, stimulating the pozzolanic activity of coal gangue to maximize its utilization as a partial replacement for clinker in cement production processes, thereby reducing costs and carbon emissions; • These data provide information on the microstructure and phase composition of coal gangue powder before and after calcination; • These data will be beneficial for other scholars to extensively apply the calcination schemes to produce high-activity coal gangue powder, aiming to promote the resource utilization and value enhancement of this solid waste material [2] ; • The experimental data are valuable for engineers and manufacturers.They can refer to the coal gangue calcination regimes obtained in this study to seek more suitable regimes for implementation in manufacturing processes.Furthermore, these findings can also be applicable to similar solid waste materials, aiding in the exploration of sustainable alternatives for cement.

Data Description
The dataset encompasses the reactivity of raw coal gangue under various calcination schemes.The coal gangue is subjected to a process of drying, crushing, and grinding, followed by high-temperature calcination using a muffle furnace with a heating rate of 4 • C/min.The effects of calcination temperature (600 • C, 700 • C, 800 • C, 900 • C) and holding time (1h, 2h) on the pozzolanic activity of coal gangue powder are investigated, and the reactivity indices are determined using the strength comparison method and R3 reactivity test method.Microscopic characterizations including thermogravimetric testing, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) are conducted on the calcined coal gangue powder to obtain data on the microstructure and phase composition of activated coal gangue powder.
Table 1 shows the flexural and compressive strength of specimens containing coal gangue powder from different tem perature after curing for 3, 7, and 28 days.Fig. 1 illustrates the

Experimental design
The raw coal gangue was dried using a blast drying machine (100 • C, 2h), then crushed and ground using a tungsten carbide jaw crusher and a tungsten carbide disc mill (with an 80 μm square sieve and less than 10 % residual).The coal gangue powder was subjected to hightemperature calcination using a muffle furnace with a heating rate of 4 • C/min.Obtaining the pozzolanic activity of coal gangue powder at different calcination temperatures (600 • C, 700 • C, 80 0 • C, 90 0 • C) and holding times (1h, 2h) .The coal gangue powder from each temperature of calcination was substituted for cement clinker at a proportion of 30 %, and the compressive and flexural strengths were tested according to the strength comparison method [3] .The pozzolanic activity of calcined coal gangue was also evaluated using the R3 reactivity test method [4] .The microstructure and phase composition data of the raw coal gangue and the coal gangue calcined at different temperatures were derived.

Materials
The coal gangue used in this experiment was sourced from Shandong Huafeng Coal Mine.It predominantly exhibits a blackish-gray appearance with a predominantly sheet-like or block-like shape, displaying variations in size and shape.After drying and grinding the coal gangue, X-ray fluorescence (XRF) testing was conducted, and the results are presented in Table 2 .According to the Chinese National Standard GB/T 35986-2018 [5] , the LOI (loss on ignition) of the coal gangue powder was determined, which was found to be 13.85 %.
The cement clinker used in this study was Type I Portland cement with a grade of 52.5.X-ray fluorescence (XRF) testing was conducted on the cement clinker, and the elemental composition is presented in Table 3 .The physical properties of the cement are provided in Table 4 .The sand used in the study complied with GB/T 17671-2021 [6] .It consists of naturally occurring rounded silica sand with a SiO2 content not less than 98 %, and its particle size ranges from 0.08 to 2mm.

Strength comparison method
According to the strength comparison method, cement mortar specimens were prepared by substituting 30 % of cement clinker with coal gangue powder.A control experiment without coal gangue powder was also conducted.The mortar specimens were prepared following the requirements of GB/T 17671-2021 [6] , with a cement to standard sand ratio of 1:3 and a waterto-cement ratio of 0.50.After mixing in a planetary mixer, the mortar was molded on a vibration table to form standard prismatic test specimens (40 × 40 × 160mm).The specimens were then cured in a standard curing chamber at a temperature of 20 ± 1 • C and a humidity of not less than 90 % for 3 days, 7 days, and 28 days, respectively.The compressive and flexural strengths of the resin sand specimens were then tested using the YAW-300 electro-hydraulic servo pressure testing machine.The pozzolanic activity index of the coal gangue powder was calculated by comparing the strengths of the cement mortar with coal gangue powder to those of the same age control group without coal gangue powder.

R3 activity test method
As shown in Fig. 7 , the coal gangue reactivity was evaluated using the R3 test method according to the proportions specified in Table 5 .The coal gangue from each temperature was used to prepare the paste, which was then sealed and cured in a water bath at 40 °C for 7 days.Subsequently, the cured samples were sliced and dried in an oven at 80 °C until a constant weight was achieved.The dried samples were then heated in a furnace at 350 °C for 2 h, and the loss of  combined water was calculated based on the difference in weight before and after calcination.The weight difference represents the loss of combined water.

Thermogravimetric analysis
The thermalgravimetric analyzer (TGA) manufactured by Mettler in Switzerland was used to study the relationship between the mass of coal gangue powder and the temperature.Approximately 10 mg of powder sample was accurately weighed and placed inside an alumina crucible, which was then positioned on the microbalance of the TGA instrument.An empty alumina crucible was placed on the other side as a reference.After securing the sample, the instrument was started, and the temperature was increased from room temperature to 10 0 0 °C at a heating rate of 10 °C/min.Nitrogen gas was used as the testing atmosphere, and TG-DTG curves were generated.

X-ray diffraction test
The coal gangue powder was subjected to X-ray diffraction (XRD) testing using a SmartLab SE X-ray diffractometer manufactured by Rigaku, Japan.The sample does not contain any magnetic elements, and its phase and crystal structure were observed.A suitable amount of well-prepared powder sample was placed in the grooves of glass slides that were wiped with alcohol and then smoothed.The glass slides were placed on the sample stage of the diffractometer, and a copper target was used for the scan.The scanning range was set between 10 to 80 degrees, with a scanning speed of 5 °/min.The data were processed using JADE 6.5 software.

Fourier-transform infrared test
The coal gangue powder was subjected to Fourier-transform infrared (FTIR) spectroscopy using a Nicolet iS 10 instrument manufactured by Thermo Fisher Scientific, USA.The FTIR analysis involved inferring the phase composition and conducting phase transition analysis based on the molecular structure interruptions.The KBr pellet method was used as the testing technique, with a mass ratio of approximately 100:1 between the spectrally pure potassium bromide (KBr) and the powder sample.The FTIR spectra were obtained with a resolution of 0.4 cm-1 and an average of 128 scans.

Scanning electron microscope test
The microstructure of coal gangue powder was captured using a scanning electron microscope (SEM) model S4800, manufactured by Hitachi, Japan.The samples were directly adhered to conductive adhesive and coated with a thin layer of gold without performing backscattering.The observation included both morphology and energy-dispersive X-ray spectroscopy (EDS) point scanning, with an energy range for EDS analysis spanning from Be4 to U92.The prepared samples were placed inside the sample chamber of the scanning electron microscope, and the lens distance and magnification were adjusted to initiate observation and capture images.The instrument offers a maximum resolution of 1.4 nm, magnification ranging from 20 to 80 0,0 0 0 times, and an accelerating voltage of 0.5 to 30 kV.

Limitations
None.

Ethics Statements
No human subjects, animal experiments and data collected from social media platforms were involved in this work.

Table 1
Strength of pulverized coal gangue mortar.

Table 2
Chemical composition of coal gangue.

Table 3
Chemical composition of cement.