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Article

Preparation and Performance of Alkali-Activated Coal Gasification Slag-Based Backfill Materials

by
Qiang Guo
,
Longyan Tan
,
Meng Li
*,
Zhangjie Yin
,
Zhihui Sun
and
Yuyang Xia
State Key Laboratory for Fine Exploration and Intelligent Development of Coal Resources, China University of Mining and Technology, Xuzhou 221116, China
*
Author to whom correspondence should be addressed.
Appl. Sci. 2025, 15(16), 8995; https://doi.org/10.3390/app15168995
Submission received: 15 July 2025 / Revised: 9 August 2025 / Accepted: 13 August 2025 / Published: 14 August 2025
(This article belongs to the Section Civil Engineering)
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Versions Notes

Abstract

When coal gasification slag is used as a substitute for cement, the prepared cementitious materials may exhibit inadequate properties due to the slag’s limited hydration reactivity, which limits its effectiveness in applications of backfill materials. In this study, alkali activation was used to improve the hydration activity of coal gasification slag. The effect of alkali equivalent on the setting time, rheological properties, and uniaxial compressive strength of the alkali-activated coal gasification slag-based backfill material (ACBM) sample was systematically investigated, and the optimal alkali equivalent was identified. The mineral composition, pore structure, and micromorphology of ACBM samples were characterized using the X-ray diffractometer (XRD), nitrogen adsorption–desorption analyzer (BET), and scanning electron microscope–energy dispersion spectrum (SEM-EDS). The results show that when the alkali equivalent is 4%, the comprehensive performance of ACBM samples is optimal. At this time, the initial setting time and final setting time of ACBM samples are 125 min and 172 min, and the rheological properties are in accordance with the Herschel–Bulkley model. The yield stress, plastic viscosity, and hysteresis loop area are 9.22 Pa, 0.74 Pa·s, and 1014 Pa/s, respectively, and the compressive strength of the ACBM sample at the curing age of 28 days is 2.18 MPa. When the alkali equivalent is further increased to 6%, the initial hydration reaction becomes more intense due to the excessive alkali level, leading to a rapid decline in flowability; the sample cracked at 28 days and its strength decreased considerably. This study provides theoretical guidance for the application of coal gasification slag in the field of backfill mining.

1. Introduction

Coal gasification technology, serving as a crucial approach for achieving clean and efficient coal utilization, is the core technology of the modern coal chemical industry [1,2]. By 2024, the conversion of about 350 million tons of standard coal had been achieved, and the gasification products can be used to produce a series of chemical products such as aromatics, coal-based methanol, and synthetic ammonia [3,4]. However, a large amount of coal gasification slag (CGS) is produced during the coal gasification process, with an annual emission of more than 70 million tons [5,6]. Due to the low reaction activity, complex toxic components and high water content of CGS, its comprehensive utilization rate remains limited. At present, the primary disposal methods for coal gasification slag remain predominantly reliant on stockpiling and landfill. The storage volume is increasing at a rate of 4.8–5.29 million tons per year, leading to significant land occupation and serious pollution of water and soil. This situation poses a serious challenge to the green and sustainable development of the coal chemical industry [7,8,9].
The primary approaches for the current utilization and disposal of coal gasification slag involve recycling and blending utilization [10,11], high-value utilization [12], and building material utilization [13]. In recent years, there has been a growing body of theoretical and technical research focusing on these utilization methods—recycling and blending, high-value recovery, and incorporation into building materials. These methods have significantly improved the activation effect of coal gasification slag and developed high-value-added products with excellent performance. However, these technological solutions encounter challenges related to high expenses and a limited scope of implementation [14,15,16]. Backfilling disposal technique has the potential to significantly mitigate the challenges associated with large-scale coal gasification slag disposal. However, most of the current backfill materials are solid wastes such as coal gangue and fly slag, and coal gasification slag has been rarely used as backfill materials [17,18]. Consequently, the coal chemical industry urgently needs to address how to effectively and extensively utilize coal gasification slag on a large scale to promote safe, efficient, environmentally friendly, and low carbon development.
CGS contains a large amount of volcanic slag active substances and can serve as an auxiliary cementitious material to replace cement for backfill mining [19,20,21]. However, studies and practical applications have indicated that when CGS is used as an auxiliary cementitious material to replace cement in backfill materials, its low activity leads to poor mechanical properties of the backfill materials, which significantly weakens the role of the backfill materials in controlling rock formations and reducing surface subsidence [22,23]. Therefore, the premise for making full use of CGS to prepare backfill materials is to stimulate its volcanic slag activity. Alkali-activated materials (AAMs) have attracted significant research attention due to their advantages, including high reactivity, cement replacement potential, and low carbon emissions, making them a promising alternative to traditional cement [24,25]. CGS is rich in Al2O3 and SiO2 and can be used to prepare AAMs. Qin et al. [26] studied the mechanical properties of alkali-activated gangue–slag cementitious materials. The results showed that the cementitious materials exhibited the optimal performance when the alkali activator modulus was 1.3 and the alkali equivalent was 14%; the mechanical properties of the cementitious materials decreased with the decrease in the alkali equivalent. Fang et al. [27] reported that for the sodium silicate activated slag-fly slag system, with the increase in slag and sodium hydroxide concentration, the setting time of the material became shorter, and the compressive strength increased with the increase in slag content and the decrease in activator modulus. In summary, numerous studies have been conducted on alkali-activated gangue and alkali-activated slag; however, research on the preparation of cementitious materials with alkali-activated coal gasification slag is limited. Furthermore, the impact of alkali equivalent on the mechanical properties and flow properties of the alkali-activated coal gasification slag backfill material (ACBM) remains unclarified.
To this end, sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) were taken as alkali activators to prepare the ACBM sample in this study. The main objectives were to enhance the reactivity of coal gasification slag, as well as to improve the flowability and mechanical performance of the prepared ACBM samples. Additionally, the effect of alkali equivalent on the setting time, rheological properties, and mechanical properties of ACBM samples was systematically analyzed, and the mineral composition and micromorphology of ACBM samples were characterized by various testing methods such as the X-ray diffractometer (XRD), nitrogen adsorption–desorption analyzer (BET), and scanning electron microscope and energy dispersive spectrometer (SEM-EDS). This study provides theoretical guidance for the practical application of coal gasification slag in the field of backfill materials.

2. Materials and Methods

2.1. Raw Materials

In this experiment, CGS and coal gauge (CG) were selected as raw materials. The CGS was sourced from Shaanxi Future Energy Chemical Co., Ltd., (Yulin, China) and CG was obtained from the Yangcheng Coal Mine of Shandong Jikuang Luneng Coal and Electricity Co., Ltd., (Jinan, China). The original CGS had a large particle size and limited hydration activity when used as a cementitious component. To enable its use as a complete substitute for cement, CGS was crushed, screened, and ball-milled. After that, the average particle size of CGS was 25.47 μm, measured by a laser particle size analyzer. The coal gangue was crushed and screened to obtain a particle size of 2–5 mm as aggregate. The chemical composition and mineral composition of CGS and CG were analyzed using an X-ray fluorescence spectrometer and an XRD, as shown in Table 1 and Figure 1. The alkaline activator in the experiment was composed of liquid Na2SiO3 and solid NaOH. The Na2SiO3 modulus was 3.3, the mass fraction of SiO2 and Na2O was 26.98% and 8.53%, the density was 1.366 g/mL, and the purity of NaOH was 96%.

2.2. Testing Procedures

As illustrated in Figure 2, the testing procedure consists of three distinct stages.
Stage I: Sample preparation. First, Na2SiO3 and NaOH were mixed to form an alkali-activated solution with a modulus of 1.2. This solution was aged for 24 h for further use. Secondly, CGS and CG were mixed evenly. The prepared alkali-activated solution was mixed with water and stirred for 30 min, poured into the mixed CGS and CG and stirred evenly to obtain ACBM samples. The water–binder ratio of the ACBM sample was set to 0.5, and the alkali equivalents were 0%, 1%, 2%, 4%, and 6%, respectively. Table 2 shows the specific slurry mixing ratios [28].
Stage II: Performance test. The setting time and rheological properties of the fresh slurry were tested using a Vicat instrument and a rheometer, respectively. The slurry was loaded into 70.7 mm cubical mold, demolded after one day of solidification, and placed in a standard curing box for 28 days. The uniaxial compressive strength of the sample after 28 days of curing was tested using a universal testing machine.
Stage III: Microscopic test. After the compressive strength test, the sample was placed in anhydrous ethanol to terminate hydration, and then placed in a drying oven at 60 °C for 24 h for subsequent XRD, BET and SEM tests.

2.3. Test Methods

2.3.1. Setting Time Test

The initial and final setting times of the fresh slurry were assessed in accordance with the Chinese National Standard GB/T1346-2024. To determine the initial setting time, the elapsed period until the Vicat needle penetrated to a depth of 4 ± 1 mm above the base plate was recorded; measurements were conducted at 5 min intervals. The final setting time was defined as the point when the needle no longer produced a visible indentation on the specimen surface, with observations performed every 15 min.

2.3.2. Rheological Properties Tests

A rheometer (Anton Paar 92, Graz, Austria) was used to perform rheological tests on ACBM. The rheological test scheme was based on reference [29].

2.3.3. Mechanical Properties Tests

Uniaxial compressive strength testing of the specimens was performed using a WAW-1000D servo-hydraulic universal testing machine, following the procedures outlined in Chinese Standard GB/T 17671-2021. Specimens were evaluated at curing ages of 3, 7, and 28 days. Triplicate measurements were conducted for each sample, and the mean value was reported as the representative result.

2.3.4. XRD Tests

Specimens were immersed in anhydrous ethanol for 24 h, with solvent replacement occurring every 12 h. Following immersion, samples underwent vacuum drying at 45 °C for 24 h until constant mass was achieved. The dehydrated material was subsequently ground to pass through a 200-mesh screen. Phase composition analysis employed a Bruker D2 Phaser diffractometer, with XRD patterns collected across a 2θ angular range of 5° to 70° using a scanning speed of 5°/min.

2.3.5. BET Tests

The specific surface area and pore structure of the samples were characterized using a Micromeritics ASAP 2460 analyzer (USA) via nitrogen physisorption at 77 K. Measurements were performed across a relative pressure (P/P0) range spanning from 0.05 to 0.995.

2.3.6. SEM Tests

Sample morphology was examined using a Gemini SEM 300 field emission environmental scanning electron microscope (ZEISS, Oberkochen, Germany). The analysis was conducted at an accelerating voltage of 20 kV, with specimens prepared by gold sputter coating prior to imaging.

3. Experimental Results and Discussion

3.1. Effect of Alkali Equivalent on the ACBM Performance

3.1.1. Setting Time

The initial setting and final setting time significantly affect the transportation performance, construction quality, and durability of ACBM samples. The appropriate setting time can not only ensure the stability of the backfill material during transportation, but also allows for timely solidification and hardening after backfilling, thereby providing a safety guarantee for subsequent operations [30,31]. Figure 3 shows the initial and final setting times of ACBM samples, and the error bars represent the standard deviation of three measurements. It can be found that with the increase in alkali equivalent, the initial and final setting times of ACBM samples both decrease. When the alkali equivalent increases from 2% to 4%, the setting time changes sharply, with the initial setting decreasing from 236 min to 125 min, and the final setting decreasing from 357 min to 172 min. This is because when the alkalinity of the solution reaches the threshold, the high concentration of hydroxide ion breaks the bonds of Si-O and Al-O, changing from local erosion to overall depolymerization. The dissolution rate of coal gasification slag and slag is accelerated, instantly releasing a large number of active ions (Ca2+, [SiO4]4−, and [AlO4]5−). The nucleation sites in the system increase, generating a large number of hydration products, which sharply shortens the setting time of the system [32]. When the alkali equivalent reaches 6%, the initial setting time and final setting time are 54 min and 21 min, respectively. At this time, the ACBM sample does not meet the transportation criteria required for backfilling slurry [33].

3.1.2. Rheological Properties

The rheological properties of the slurry exhibit shear-rate dependence. Figure 4 presents the flow curves depicting apparent viscosity versus shear rate and shear stress versus shear rate for ACBM specimens. As illustrated in Figure 4a, apparent viscosity undergoes rapid reduction followed by stabilization with an increasing shear rate across samples of varying alkali equivalents. This behavior arises from dynamic restructuring of the slurry’s internal flocculated network under applied shear. Specifically, shear-induced disruption of the microstructure competes with particle-interaction-driven reformation. This competition establishes a dynamic equilibrium wherein structural breakdown and reconstruction processes balance, ultimately resulting in viscosity plateauing [34]. Under the same shear rate, the apparent viscosity of ACBM samples gradually decreases as the alkali equivalent increases from 0% to 4%. This is because an appropriate increase in the alkali equivalent enables the high concentration of Na+ ions in the alkaline solution to compress the double electric layer on the surface of the gel particles; consequently, the electrostatic repulsion between the particles is reduced, leading to improved particle dispersion [35]. When the alkali equivalent is further increased to 6%, the apparent viscosity increases sharply. This is mainly because the high concentration of hydroxide ion increases the dissolution rate of CGS and CG, accelerates the hydration reaction, and leads to the formation of the gel network and an increase in the apparent viscosity of ACBM samples [36].
Figure 4b demonstrates that shear stress evolution mirrors the apparent viscosity trend at equivalent shear rates. To quantify key rheological parameters—yield stress and plastic viscosity—the experimental flow behavior of ACBM specimens was modeled using the Herschel–Bulkley (H-B) constitutive equation [29]. The rheological parameters of ACBM fitted by H-B are shown in Table 3, with R2 greater than 0.99, indicating a high degree of fitting.
Figure 5 shows the evolution of yield stress and plastic viscosity of ACBM samples changing with the alkali equivalent. As the alkali equivalent increases, both the yield stress and plastic viscosity initially decrease and subsequently increase. When the alkali equivalent is 4%, the yield stress and plastic viscosity of ACBM samples are the lowest, at 9.22 Pa and 0.74 Pa·s, respectively. When the alkali equivalent is further increased, the yield stress and plastic viscosity increase sharply. This can be attributed to two reasons: firstly, the increase in alkali equivalent intensifies the hydration reaction rate, consumes free water, and reduces the thickness of the lubricating water film between particles; secondly, sodium silicate itself has a certain viscosity, and the viscosity increases with the increase in alkali equivalent [37].
Shear stress application generates non-overlapping ascending and descending flow curves, forming a hysteresis loop in the slurry’s rheological profile. This enclosed area quantifies the slurry’s thixotropic character [37]. The magnitude of thixotropy correlates directly with the population of reversible flocculated structures imposing resistance to flow, representing a critical metric for rheological assessment. Figure 6 shows the hysteresis loop area. As the alkali equivalent increases, the hysteresis loop area of ACBM samples also increases gradually. When the alkali equivalent increases from 4% to 6%, the hysteresis loop area increases significantly, from 1014 Pa/s to 1897 Pa/s, increasing by 87%. This is because when the alkali equivalent is 6%, the alkalinity of the slurry increases, the polycondensation reaction rate and the dissolved ion concentration in the slurry reach the critical point, so that a large amount of gel network is formed in the slurry, which increases the thixotropic properties of the slurry [38].

3.2. Effect of Alkali Equivalent on Mechanical Properties of ACBM Samples

The mechanical strength of the backfill material affects the effect of controlling the rock formation. Figure 7 shows the compressive strength of ACBM samples under different alkali equivalents, and the error bars represent the standard deviation of three measurements. As shown in Figure 7, the compressive strength of ACBM samples at the curing age of 3 days and 7 days gradually increases as the alkali equivalent increases from 0% to 6%. It is worth noting that when the alkali equivalent increases to 6%, the compressive strength of the ACBM6 samples at the curing age of 28 days drops sharply, which is 49% lower than that at the curing age of 7 days and significantly lower than that of the ACBM4 samples. This phenomenon can be attributed to the imbalance of reaction kinetics caused by excessive alkali equivalent. The initial hydration reaction proceeds vigorously, leading to a significant shrinkage of the rapidly formed gel network [39]. As the curing age increases, microcracks are induced on the surface of the sample, with the maximum width of the crack reaching 5.2 mm, accounting for 7% of the specimen width, resulting in a decrease in strength. The actual image of the ACBM6 samples presented in Figure 7 further validates this finding.
According to the working performance test results in Section 3.1, a 4% alkali equivalent is determined to be the optimal proportion for ACBM samples. At this time, the ACBM sample demonstrates improved flowability and enhanced 28 d compressive strength, ensuring long-term structural stability and fulfilling the application requirements for backfilling mining [40].

3.3. Microstructure of ACBM Samples

3.3.1. XRD Results

Figure 8 shows the XRD spectra of ACBM samples under different alkali equivalents. As shown in Figure 8, the diffraction peak intensities of quartz, calcite, kaolinite, and muscovite are relatively high, while the diffraction peak intensities of other substances are not obvious. With the increase in alkali equivalent, the diffraction peaks of quartz and calcite decrease. This indicates that the active SiO2 in CGS and CG undergoes a reaction with the alkaline activator to form gel-like substances such as C-S-H, C-A-S-H, and N-A-S-H [41]. However, ACBM samples still contain a certain amount of inactive SiO2, which primarily originated from CG and did not engage in the reaction. The peak intensities of kaolinite and muscovite are also weakened. This is because in a strong alkaline environment, the crystal structure is destroyed and dissolved by hydroxide ion, releasing active SiO2 and Al2O3 [42].

3.3.2. BET Results

Figure 9 presents the BET for ACBM specimens at varying alkali equivalent levels. The data reveal a distinct trend: both specific surface area and total pore volume initially decline with increasing alkali content before exhibiting a substantial rise. Minimum values for these parameters (28.25 m2/g specific surface area and 0.0541 cm3/g total pore volume) occur at 4% alkali equivalent. This reduction is attributed to accelerated CGS dissolution under highly alkaline conditions. The resultant substantial formation of hydrated gelation products fills available pores, consequently diminishing both surface area and overall pore volume. When the alkali equivalent reaches 6%, compared to the ACBM4 sample, the specific surface area of the ACBM6 sample increases from 28.25 m2/g to 34.38 m2/g, an increase of 21.73%. The total pore volume of the ACBM6 sample increases from 0.0541 cm3/g to 0.0644 cm3/g, an increase of 19.04%. This can be primarily attributed to the excessive alkali content, which leads to cracking in the later stages and the formation of numerous cracks in the sample. This observation aligns with the experimental results presented in Section 3.2.

3.3.3. Morphology and Microstructure

Figure 10 is the SEM-EDS image of ACBM samples. The ACBM0 exhibits a porous structure with numerous voids, while only a limited quantity of hydration products is present, resulting in an overall loosely packed configuration. When the alkali equivalent is 4%, a large amount of hydration products (mainly N-A-S-H gel and C-S-H gel) are produced in ACBM4. As a result, the connection between particles is significantly improved, leading to reduced pore volume and a denser microstructure. The element distributions of Si and Na in ACBM0 and ACBM4 samples are analyzed through EDS surface scanning. Compared with ACBM0, the distribution density of Si and Na elements in ACBM4 is higher. This increase can be primarily attributed to the addition of the alkali initiator. It also proves that adding alkali initiator introduces a large number of Si and Na sources, provides more nucleation sites, and produces more hydration products such as aluminosilicate gel and hydrated calcium silicate [43].

4. Conclusions

In this study, an alkali-activated coal gasification slag-based backfill material was prepared, and the effects of different alkali equivalents on its flow properties and mechanical properties were studied. The main conclusions are as follows:
(1) With the increase in alkali equivalent, the setting time gradually decreases, the yield stress and plastic viscosity first decrease and then increase, and the thixotropic properties are enhanced, while the 28 d compressive strength first increases and then decreases. By integrating multiple properties, the optima alkali equivalent is determined to be 4%.
(2) At 4% alkali equivalent, ACBM specimens exhibited initial and final setting times of 125 min and 172 min, respectively. Rheological characterization revealed compliance with the Herschel–Bulkley model, yielding three key parameters: yield stress (9.22 Pa), plastic viscosity (0.74 Pa·s), and hysteresis loop area (1014 Pa/s). ACBM specimens subsequently developed a 28-day compressive strength of 2.18 MPa.
(3) Properly increasing the alkali equivalent can promote ACBM samples to form more hydration products, fill the pores of the sample, reduce the specific surface area and total pore volume, and make the microstructure denser. However, when the alkali equivalent exceeds 4%, the early hydration reaction is violent, and poor flow properties and cracks can be induced in the sample, resulting in the decreased compressive strength of the sample at the curing age of 28 days.

Author Contributions

Conceptualization, M.L. and Z.S.; Data curation, Q.G.; Formal analysis, Q.G.; Funding acquisition, M.L.; Investigation, Q.G. and L.T.; Methodology, Q.G.; Resources, M.L.; Supervision, M.L. and Z.Y.; Visualization, Y.X.; Writing—original draft, Q.G.; Writing—review and editing, M.L. and L.T. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the National Key R&D Program of China [2023YFC3904300], the National Natural Science Foundation of China [52474112], and the Natural Science Foundation of Jiangsu Province [BK20231498].

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. XRD patterns of CGS and CG.
Figure 1. XRD patterns of CGS and CG.
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Figure 2. Test flow chart.
Figure 2. Test flow chart.
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Figure 3. Setting time of ACBM samples.
Figure 3. Setting time of ACBM samples.
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Figure 4. Rheological properties of ACBM samples at different alkali equivalents: (a) shear stress, (b) plastic viscosity.
Figure 4. Rheological properties of ACBM samples at different alkali equivalents: (a) shear stress, (b) plastic viscosity.
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Figure 5. Relationship between yield stress and plastic viscosity and alkali equivalent.
Figure 5. Relationship between yield stress and plastic viscosity and alkali equivalent.
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Figure 6. Relationship between hysteresis loop area and alkali equivalent of ACBM samples.
Figure 6. Relationship between hysteresis loop area and alkali equivalent of ACBM samples.
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Figure 7. Changes in compressive strength of ACBM samples with alkali equivalent.
Figure 7. Changes in compressive strength of ACBM samples with alkali equivalent.
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Figure 8. XRD spectrum of ACBM samples under different alkali equivalents.
Figure 8. XRD spectrum of ACBM samples under different alkali equivalents.
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Figure 9. BET of ACBM samples under different base equivalents.
Figure 9. BET of ACBM samples under different base equivalents.
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Figure 10. SEM-EDS images of ACBM samples under different alkali equivalents, (a) ACBM0 and (b) ACBM4.
Figure 10. SEM-EDS images of ACBM samples under different alkali equivalents, (a) ACBM0 and (b) ACBM4.
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Table 1. Chemical composition of CGS and CG.
Table 1. Chemical composition of CGS and CG.
CompositionSiO2Al2O3Fe2O3CaOK2OMgONa2OTiO2SO3
CGS58.4524.364.702.353.120.961.731.950.87
CG52.6119.858.741.495.512.431.021.461.93
Table 2. Mixing ratio of ACBM samples.
Table 2. Mixing ratio of ACBM samples.
SampleCGS/gCG/gWater–Binder RatioAlkali Activator ModulusAlkali Equivalent/%
ACBM070300.51.20
ACBM11
ACBM22
ACBM44
ACBM66
Table 3. Rheological model at varying alkaline activator dosages.
Table 3. Rheological model at varying alkaline activator dosages.
SampleRheological ModelFitting Resultsτ0/Paη/Pa·snR2
ACBM0H-Bτ = 56.14 + 2.53γ0.8056.142.530.800.9995
ACBM1τ = 16.87 + 0.91γ0.6616.870.910.660.9996
ACBM2τ = 9.34 + 0.76γ0.559.340.760.550.9989
ACBM4τ = 9.22 + 0.74γ0.729.220.740.720.9969
ACBM6τ = 36.75 + 1.81γ0.8536.751.810.850.9998
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MDPI and ACS Style

Guo, Q.; Tan, L.; Li, M.; Yin, Z.; Sun, Z.; Xia, Y. Preparation and Performance of Alkali-Activated Coal Gasification Slag-Based Backfill Materials. Appl. Sci. 2025, 15, 8995. https://doi.org/10.3390/app15168995

AMA Style

Guo Q, Tan L, Li M, Yin Z, Sun Z, Xia Y. Preparation and Performance of Alkali-Activated Coal Gasification Slag-Based Backfill Materials. Applied Sciences. 2025; 15(16):8995. https://doi.org/10.3390/app15168995

Chicago/Turabian Style

Guo, Qiang, Longyan Tan, Meng Li, Zhangjie Yin, Zhihui Sun, and Yuyang Xia. 2025. "Preparation and Performance of Alkali-Activated Coal Gasification Slag-Based Backfill Materials" Applied Sciences 15, no. 16: 8995. https://doi.org/10.3390/app15168995

APA Style

Guo, Q., Tan, L., Li, M., Yin, Z., Sun, Z., & Xia, Y. (2025). Preparation and Performance of Alkali-Activated Coal Gasification Slag-Based Backfill Materials. Applied Sciences, 15(16), 8995. https://doi.org/10.3390/app15168995

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