Design and Application of Composite Solidified Agent for Stabilizing Iron Tailings Sand

doi:10.16552/j.cnki.issn1001-1625.2026.0186

Abstract

Abstract:

To address the problems of low strength， insufficient strength growth rate， and large shrinkage of iron tailings sand stabilized materials， a composite solidified agent was prepared from ordinary Portland cement clinker， ground granulated blast-furnace slag powder， and gypsum， and the effects of its composition and dosage of the solidified agent on the mechanical properties， volumetric stability， and durability of iron tailings sand base mixtures were investigated. The results show that the mechanical properties of iron tailings sand stabilized with the solidified agent improve significantly with increasing clinker content. Gypsum exhibits an optimum content， and when the gypsum content is 15% （mass fraction）， the 7 d unconfined compressive strength of iron tailings sand stabilized with the solidified agent reaches 3.43 MPa. Moreover， the drying shrinkage of iron tailings sand stabilized with the solidified agent is markedly reduced with increasing gypsum content. The optimum proportion of the solidified agent is identified as m（clinker）∶m（slag）∶m（gypsum）=15∶70∶15. Compared with cement-stabilized iron tailings sand base mixtures at the same binder dosage， iron tailings sand stabilized with the solidified agent exhibits up to a 46.26% increase in the 180 d strength growth rate and up to a 41.47% reduction in drying shrinkage strain， while water stability and freeze-thaw resistance are also improved. Microstructural analysis shows that a large amount of C-S-H gel forms at later ages in iron tailings sand stabilized with the solidified agent， which significantly enhances later-age strength development rate. Meanwhile， gypsum promotes the early formation of abundant needle- and rod-like ettringite crystals and induces slight expansion， which effectively compensates for the drying shrinkage of iron tailings sand base mixtures and significantly reduces the risk of cracking.

Key words: iron tailings sand, pavement base material, composite solidified agent, unconfined compressive strength, drying shrinkage, durability

CLC Number:

U414

DONG Yonggang, JIA Hongjun, PAN Yating, MA Xikai, JIANG Hui, ZHOU Qiang, CHEN Xiao. Design and Application of Composite Solidified Agent for Stabilizing Iron Tailings Sand[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2026, 45(9): 3317-3329.

Figures/Tables 20

Table 1 Main chemical composition of iron tailings sand

Chemical composition	SiO₂	CaO	Fe₂O₃	Al₂O₃	Na₂O	SO₃	MgO
Mass fraction/%	36.60	25.90	22.93	8.59	1.63	0.53	0.86

Table 2 Physical properties of iron tailings sand

Raw material	Apparent density/（g·cm^-3）	Moisture mass fraction/%	Mud mass fraction/%
Iron tailings sand	3.1	4.0	14.1

Fig.1 Gradation curve of iron tailings sand

Table 3 Main chemical composition of cementitious materials

Material	Mass fraction/%
Material	SiO₂	CaO	Fe₂O₃	Al₂O₃	SO₃	MgO
Cement	17.59	60.62	5.33	4.58	2.65	2.67
Slag	31.50	38.25	3.60	15.80	1.25	6.80
Clinker	21.35	64.52	3.82	5.68	1.25	2.13
Gypsum	0.43	41.62	0.08	0.08	55.53	0.03

Table 4 Physical properties of cement

Physical property

Apparent density/

（g∙cm^-3）

Specific surface

area/（m²∙kg^-1）

Setting time/min

Compressive

strength/MPa

Flexural

strength/MPa

Table 5 Physical properties of other cementitious materials

Material	Apparent density/（g∙cm^-3）	Specific surface area/（m²∙kg^-1）	Moisture mass fraction/%	28 d activity index/%
Slag	2.89	475	0.4	97.3
Clinker	3.15	376	—	—
Gypsum	2.32	915	1.5	—

Table 6 Mix proportion of solidified agent

Sample No.	Mass fraction/%			Optimum moisture content/%	Maximum dry density/（g∙cm^-3）
Sample No.	Clinker	Slag	Gypsum	Optimum moisture content/%	Maximum dry density/（g∙cm^-3）
SL-7.5	7.5	77.5	15	8.52	1.968
SL-15	15	70	15	8.58	1.971
SL-20	20	65	15	8.54	1.967
SL-35	35	50	15	8.52	1.970
SL-50	50	35	15	8.57	1.966
SG-8	15	77	8	8.59	1.962
SG-10	15	75	10	8.55	1.970
SG-15	15	70	15	8.58	1.971
SG-20	15	65	20	8.54	1.965
SG-30	15	55	30	8.56	1.969
SG-40	15	45	40	8.56	1.967

Table 7 Mix proportion of iron tailings sand base mixtures with different binder types and content

Sample No.	Mass fraction/%			Optimum moisture content/%	Maximum dry density/（g∙cm^-3）
Sample No.	Cement	Solidified agent	Iron tailings sand	Optimum moisture content/%	Maximum dry density/（g∙cm^-3）
G-8	0	8	92	8.25	1.920
G-10	0	10	90	8.58	1.971
G-12	0	12	88	8.91	2.052
P-8	8	0	92	8.23	1.916
P-10	10	0	90	8.52	1.964
P-12	12	0	88	8.87	2.045

Fig.2 Effect of clinker content on mechanical properties of solidified agent

Fig.3 Effect of clinker content on 7 d unconfined compressive strength of iron tailings sand stabilized with solidified agent （solidified agent content： 10%）

Fig.4 Effect of gypsum content on mechanical properties of solidified agent

Fig.5 Effect of gypsum content on 7 d unconfined compressive strength of iron tailings sand stabilized with solidified agent （solidified agent content： 10%）

Fig.6 Effect of gypsum content on volume stability of solidified agent and iron tailings sand stabilized with solidified agent （solidified agent content： 10%）

Fig.7 Effects of different binder types and content on unconfined compressive strength of iron tailings sand base mixtures

Fig.8 Effects of different binder types and content on 90 d mechanical properties of iron tailings sand base mixtures

Fig.9 Effects of different binder types and content on volume stability of iron tailings sand base mixtures

Fig.10 Effects of different binder types and content on water stability of iron tailings sand base mixtures

Fig.11 Effects of different binder types and content on freeze-thaw resistance of iron tailings sand base mixtures

Fig.12 XRD patterns of cement and solidified agent

Fig.13 SEM images of cement and solidified agent

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