Thermally Activated Coal Gangue and Its Application in Phosphogypsum Slag Cement

doi:10.16552/j.cnki.issn1001-1625.2026.0086

Abstract

Abstract:

To address the dual challenges of large-scale phosphogypsum disposal and mineral powder shortage in phosphogypsum slag cement， this study systematically investigated the feasibility of thermally activated coal gangue as a substitute for mineral powder and its influence mechanism on cement performance， while promoting the resource utilization of industrial solid waste. Coal gangue was calcined at 600 ℃ to 800 ℃ for activation and was used to replace mineral powder at various mass fractions （10% to 100%）. The mechanical properties， hydration process， and microstructural evolution of the materials were comprehensively evaluated. The results demonstrate that at early age （7 d）， coal gangue activated at 700 ℃ exhibits optimal enhancement at a 20% replacement rate， with compressive strength increasing by 12.38% compared to the control group. At later age （28 d）， coal gangue activated at 600 ℃ demonstrates superior mechanical performance at a 20% replacement rate， achieving a compressive strength increase of 53.62%. Phase analysis reveals that thermal activation transforms kaolinite in coal gangue into metakaolinite， significantly enhancing the leaching rate of reactive silica and alumina and thereby promoting pozzolanic reactivity， which facilitates increased formation of ettringite （AFt） and C-（A）-S-H gel. Hydration heat analysis confirms that thermally activated materials accelerate the early-stage hydration process and shorten the induction period. This study demonstrates that thermally activated coal gangue can serve as an effective substitute for mineral powder in phosphogypsum slag cement systems， providing crucial technical support for the high-value utilization of bulk solid waste and the development of low-carbon cementitious materials.

Key words: phosphogypsum slag cement, coal gangue, thermal activation, mechanical property, phase analysis, hydration mechanism

CLC Number:

TQ172.1

TANG Pei, LIU Jiaxin, QU Bo, RONG Pengjie, CHEN Wei. Thermally Activated Coal Gangue and Its Application in Phosphogypsum Slag Cement[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2026, 45(8): 2829-2838.

Figures/Tables 12

References 36

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Material	Mass fraction/%
Material	Al₂O₃	SiO₂	Na₂O	MgO	CaO	SO₃	K₂O	P₂O₅	Fe₂O₃	MnO	F	LOI
PG	0.73	7.49	0.11	0.24	33.38	44.87	0.39	0.68	0.50	—	1.15	10.10
GGBS	14.36	29.93	0.35	7.80	43.19	2.51	0.39	0.02	0.28	0.22	—	—
OPC	4.81	19.18	0.21	1.26	63.29	3.84	0.93	0.17	3.24	0.28	—	2.08
CG	21.45	22.30	0.04	0.10	0.80	4.70	0.16	0.03	1.96	—	—	47.44

Material	Mass fraction/%
Material	Al₂O₃	SiO₂	Na₂O	MgO	CaO	SO₃	K₂O	P₂O₅	Fe₂O₃	MnO	F	LOI
PG	0.73	7.49	0.11	0.24	33.38	44.87	0.39	0.68	0.50	—	1.15	10.10
GGBS	14.36	29.93	0.35	7.80	43.19	2.51	0.39	0.02	0.28	0.22	—	—
OPC	4.81	19.18	0.21	1.26	63.29	3.84	0.93	0.17	3.24	0.28	—	2.08
CG	21.45	22.30	0.04	0.10	0.80	4.70	0.16	0.03	1.96	—	—	47.44

Sample	Duration of individual stage/h			Heat release of individual stage/（J·g^-1）
Sample	Stage Ⅰ	Stage Ⅱ	Stage Ⅲ	Stage Ⅰ	Stage Ⅱ	Stage Ⅲ
Ref	2.81	66.78	90.41	9.33	8.53	91.50
CG-600-30%	4.58	66.60	88.82	9.03	9.75	90.73
CG-700-30%	4.35	63.97	96.03	7.64	10.03	93.67
CG-800-30%	3.66	59.62	94.71	7.69	10.55	85.66

Sample	Duration of individual stage/h			Heat release of individual stage/（J·g^-1）
Sample	Stage Ⅰ	Stage Ⅱ	Stage Ⅲ	Stage Ⅰ	Stage Ⅱ	Stage Ⅲ
Ref	2.81	66.78	90.41	9.33	8.53	91.50
CG-600-30%	4.58	66.60	88.82	9.03	9.75	90.73
CG-700-30%	4.35	63.97	96.03	7.64	10.03	93.67
CG-800-30%	3.66	59.62	94.71	7.69	10.55	85.66

Sample	7 d				28 d
	Peak 1		Peak 2		Peak 1		Peak 2
	Temperature/℃	Mass loss/%	Temperature/℃	Mass loss/%	Temperature/℃	Mass loss/%	Temperature/℃	Mass loss/%
Ref	97.74	4.70	138.33	9.52	98.82	5.12	138.44	9.35
CG-600-30%	101.16	6.68	139.38	10.41	106.15	8.59	140.34	10.21
CG-700-30%	95.48	6.62	134.24	8.93	109.59	8.66	141.96	10.41
CG-800-30%	102.39	6.82	140.38	10.53	106.73	7.66	142.38	10.32