Advances in Materials Science and Engineering
Volume 2021 (2021), Article ID 5576768, 9 pages
https://doi.org/10.1155/2021/5576768

Research Article

Experimental Study on the Fine Iron Ore Tailing Containing Gypsum as Backfill Material

Daiqiang Deng,1,2 Guodong Cao,¹ and Youxuan Zhang³

¹College of Civil Engineering and Mechanics, Xiangtan University, Xiangtan 411105, China
²College of of Mining Engineering, Guizhou Institute of Technology, Guiyang, Guizhou 550003, China
³Changsha Institute of Mining Research, Changsha 410012, China

Correspondence should be addressed to Guodong Cao; gdcao@xtu.edu.cn

Received 6 January 2021; Revised 6 March 2021; Accepted 29 March 2021; Published 8 April 2021

Academic Editor: Antonio G. De Lima

Copyright © 2021 Daiqiang Deng et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

The strength of the filling body is largely affected by the properties of the binder, mineral composition, fineness, and slurry concentration of tailing. In this paper, the rheological test was conducted to determine the slurry concentration of iron ore tailing containing gypsum. Then, the samples made from slurry and three binders, Portland cement, filling plant binder, and Huazhong binder, were tested, respectively. The effects of curing time, binder-tailing ratio by mass (b/t), and slurry concentration on compression strength were investigated. The sample made from Huazhong binder and iron ore tailing presented the largest compression strength.

1. Introduction

Tailings are produced as a lot of by-product in the mining industry. Large amount of open area is needed for the waste, and it has an important effect on the environment. However, voids occur after mined. Landslide may happen in the goaf zone. It is necessary to develop paste backfill technology to reuse waste and increase stability of land. About 60% of the waste will be reduced by the backfill.

The tailing is used as the raw material of the filling body. The physical and chemical properties of tailing, as a kind of artificial sandy soil, mainly depend on mineral composition and grade. Generally, due to quartz of high content, tailing particle of hard ore rock after mineral processing is hard. Instead, due to the ore of high content, the tailings of soft and fractured rock or oxidized ore usually are tiny and viscous. While sometimes ore is mixed with much soil, the average particle size also decreases. In the mine-tailing-filled engineering, the physical and chemical properties of different tailings are complicated and changeable. When using different binder materials, the mechanical property of filling body is diverse. Huang et al. [1] had found that the bind type had an observable influence on the mode I fracture toughness of backfill structure. The backfill material is always pumped in a pipe into the site, so an appropriate rheological property is needed. Zhang et al. [2] had found that the mineral admixture type and dosage affect the rheological and mechanical properties of cemented foam backfill. The strength of the filling body not only depends on the properties of tail but also depends on the type, content, and fineness of the binder [3, 4]. Jabulani et al. [5] investigated the effect of fly ash on the behavior of paste backfill produced by brine. The fly ash seems play a significant role than brine. Fall and Benzaazoua [6] studied the influence of Portland cement, fly ash cement, and slag cement on high sulfur tailings’ paste filling strength. It turned out that Portland cement had a better effect than fly ash cement and slag cement on the paste filling body. Furthermore, the chemical composition of the mixed water played a certain role in the strength properties of the cemented backfill. Other researchers [7–9] studied the strength characteristics of sulfur tailings’ backfill under different conditions. Cihangir et al. [10] and Yilmaz et al. [11] investigated the microstructure of the paste filling body and discussed the influence of the microstructure on mechanical properties and strength development. Some researchers [12–18] analyzed the coupling effect of temperature, water, and force on the strength of the filling body. They also evaluated various mechanical properties of backfill under other similar complex environments. Fall et al. [19] and Abdul-Hussain et al. [20, 21] analyzed the water pressure characteristics of cemented backfill. Moreover, they investigated the permeability of cemented backfill and cemented paste backfill under saturated and unsaturated conditions.

In this paper, the rheological behaviors of slurry were investigated to determine the concentration of tailing. Because there is some gypsum in iron ore tailing of chenchao, the usually used binder materials are unbefitting. Then, three binders, Portland cement 325# (PC), filling plant binder (FP), and Huazhong binder (HZ), were, respectively, used as the binder to make backfill samples. The compressive strength of backfill samples with different binder-tailing ratio by mass (b/t), slurry concentration, and curing time was compared.

2. Preparation of Raw Materials

The iron ore tailing of chenchao and three binders, PC, FP, and HZ, were used. The physical properties of three binders are shown in Table 1.

Table 1: Physical properties of the backfill material.

Material
Specific gravity
Loose bulk density (t/m³)
Compacted bulk density (t/m³)
Porosity (%)
Rest angle (°)

Tailing
2.772
1.290
1.590
42.60
33.73

PC
3.106
1.252
1.687
45.68
32.65

FP
2.985
1.367
1.703
42.95
34.28

HZ
3.262
1.389
1.792
45.06
33.32

In order to obtain the representative and uniform tailings, a rectangular material-receiving tank was dug at a tailing dam. Antiseepage color cloth was laid in the tank, and then, the tailing pumped from the mineral processing plant was drained into it by using a 4-inch white plastic tube, as shown in Figure 1. The tail paste will be settled naturally and water above the tailing mortar will be discharged. The physical properties of tailing were measured and shown in Table 1.

(a)

(b)

Figure 1: The tailings sampling.

The particle size distribution of tailings was measured by a MASTERSIZER 2000 Laser diffraction particle size analyzer and shown in Figure 2.

Figure 2: Particle size distribution of tailings.

The chemical composition of the tailing is shown in Table 2. It contains about 22% CaSO₄.

Table 2: Chemical composition of tailings.

Chemical composition
TFe
SiO₂
Al₂O₃
MgO
Cu
S
P
CaSO₄
Other

Content (%)
8.74
27.80
5.96
7.35
0.034
5.30
0.09
22.09
22.64

3. Experiment

3.1. Rheological Test of Slurry

The filling process is downwards, so the viscosity of slurry should not be too small to prevent separation. The filling distance is long, and the viscosity should be not too large to guarantee flow under self-gravity. The viscosity is largely dependent on the slurry concentration of the tailing. The slump test is usually conducted to describe the flow performance of slurry [22, 23]. Therefore, slurries with 7 different concentrations were prepared, and their mix proportions are shown in Table 3. A slump test were conducted, as shown in Figure 3. The slump values are shown in Figure 4. With the advance of concentration, the slump increases.

Table 3: Mix proportion of slurry.

Series no.
Concentration (%)
Water (kg/m³)
Tailing (kg/m³)

1
74
493
1404

2
72
519
1334

3
70
543
1267

4
68
566
1203

5
66
588
1142

6
64
609
1083

7
62
629
1027

Figure 3: Slump test of slurry.

Figure 4: The slump-value-slurry-concentration curve.

Meanwhile, a rheometer was used to measure the yield strength and plastic viscosity of slurry, and the results are shown in Table 4. With the decrease of slurry concentration, the yield strength and plastic viscosity decrease. When the concentration is 74∼72%, the flow characteristics of slurry is bad and the slump is 20.0∼23.5 cm, making it difficult to flow under self-gravity. When the concentration is 70%, the slurry has a certain fluidity and the viscosity is large. When the concentration decreases to 68∼64%, the slump is 25.5∼27 cm. At this time, the fluidity of slurry is obviously improved. When the concentration is below 62%, the water-retaining property of slurry declines, and the bleeding phenomenon is obvious. Combining with rheological parameters and slump value, we determined the slurry concentration is 64%–68%.

Table 4: Rheological parameters of slurry.

Concentration (%)
74
72
70
68
66
64
62

Yield strength (Pa)
102.6
29.5
18.0
15.4
12.9
10.4
5.8

Plastic viscosity (Pa.s)
486.0
15.1
0.5
0.23
0.18
0.16
0.14

3.2. Production of the Filling Sample

36 series filling samples with 3 different b/t, 4 types of tailing concentrations, and 3 types of binders were prepared. The mix proportion is shown in Table 5.

Table 5: Mix proportion of the filling paste.

Series no.
b/t
Concentration (%)
Water (kg/m³)
Tailing (kg/m³)
Binder

PC (kg/m³)
FP (kg/m³)
HZ (kg/m³)

1
1 : 4
64
614
874
218
—
—

2
66
593
921
230

3
68
571
971
243

4
1 : 6
64
613
934
156

5
66
592
985
164

6
68
570
1038
173

7
1 : 8
64
612
967
121

8
66
591
1020
127

9
68
569
1075
134

10
1 : 10
64
612
988
99

11
66
590
1042
104

12
68
568
1098
110

13
1 : 4
64
613
871
—
218
—

14
66
592
919
230

15
68
570
968
242

16
1 : 6
64
612
932
155

17
66
591
983
164

18
68
569
1036
173

19
1 : 8
64
611
966
121

20
66
590
1018
127

21
68
568
1073
134

22
1 : 10
64
611
987
99

23
66
590
1041
104

24
68
568
1097
110

25
1 : 4
64
617
877
—
—
219

26
66
596
925
231

27
68
574
975
244

28
1 : 6
64
614
936
156

29
66
593
987
165

30
68
571
1041
173

31
1 : 8
64
613
969
121

32
66
592
1022
128

33
68
570
1077
135

34
1 : 10
64
613
990
99

35
66
592
1044
104

36
68
569
1100
110

The tailing and binder were firstly poured into the mixer and mixed for 3 min. Then, water was added and mixed for another 3 min. After the filling paste was prepared, it was poured into the mold. After one day, we removed the molds and put them into the curing room. The cubic filling sample with an edge length of 70.7 mm was fabricated.

4. Experimental Results and Discussion

A uniaxial compression test was conducted to measure the uniaxial compression strength of every series after curing time of 3, 7, 28, and 60 days. The load was applied at a constant loading rate of 0.5 MPa/s until the sample was broken. For every series, the average UCS of 3 samples was calculated.

4.1. Effect of Curing Time on UCS

The effect of curing time on UCS of the sample with 66% tailing concentration is shown in Figure 5. Although the UCS of all samples of three binders increases with curing time, the increase rate is different.

(a)

(b)

(c)

(d)

Figure 5: Variation of UCS with curing time at different b/t. (a) b/t is 1 : 4. (b) b/t is 1 : 6. (c) b/t is 1 : 8. (d) b/t is 1 : 10.

When the curing time is 3 days and b/t is 1 : 4 (Figure .5(a)), the UCS of HZ is slightly larger than others, but for the other 3 series, their UCS is almost the same. When the curing time is 7 days and the dosage of binder is surplus (Figures 5(a) and 5(b)), the UCS of HZ is the largest and the UCS of PC is the lowest, but when the dosage of the binder decreases (Figures 5(c) and 5(d)), the UCS of FP is larger than others. However, after 60 days curing time, regardless of b/t, the UCS of HZ used sample is largely higher than others.

4.2. Effect of b/t on UCS

The effect of b/t on UCS of the sample with 66% tailing concentration is shown in Figure 6. Regardless of curing time, the UCS of HZ increases with the increase of b/t. However, for PC and FP, the b/t has no obvious effect. The UCS of PC and FP at all curing ages is less than 2 MPa. There are two reasons: On one hand, the size of iron tailing of chenchao is small, so its specific surface area (SSA) is large. The SSA of HZ is larger than the others, so the increase of contact area leads to the increase of reaction rate. On the other hand, the iron tailing of chenchao has only 27.8% SiO₂, but the contents of CaSO₄ and MgO exceeds 24% and 7%. The flocculation of Ca+ has a negative effect on the strength of cementitious material.

(a)

(b)

(c)

(d)

Figure 6: Variation of UCS with b/t. (a) 3 d curing time. (b) 7 d curing time. (c) 28 d curing time. (d) 60 d curing time.

4.3. Effect of Slurry Concentration on UCS

The effect of slurry concentration on UCS of the sample with b/t of 1 : 4 is shown in Figure 7. In spite of curing time, the UCS of HZ increases with the increase of slurry concentration. The UCS of HZ is the largest, and the UCS of PC is the lowest. Nevertheless, the UCS of PC and FP has no obvious change with the increase of slurry concentration.

(a)

(b)

(c)

(d)

Figure 7: Variation of UCS with slurry concentration. (a) 3 d curing time. (b) 7 d curing time. (c) 28 d curing time. (d) 60 d curing time.

5. Conclusions

36 series samples were conducted. The effects of curing time, b/t, and slurry concentration were investigated. The following conclusions were obtained:

(1)Regardless of curing time, b/t, and slurry concentration, the UCS of HZ is larger than the others(2)The UCS of all samples increases with the curing time(3)The UCS of HZ increases with the increase of b/t and slurry concentration, but the UCS of PC and FP has no obvious variation

HZ is a new kind of mine tailing filling material, which is made of blast furnace slag powder and some additives. Compared with PC and HZ, it has the advantages of early strength increasing quickly, late strength stability and reliability, and small dosage. At the same level of filling body strength, HZ dosage is just about 30∼60% of PC. Hence, for iron tailing with gypsum of high content, the HZ is a more suitable binder.

Data Availability

The [DATA TYPE] data used to support the findings of this study are included within the article.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Acknowledgments

This work was supported by the NSFC Projects of China (51764009), the Guizhou Province Science and Technology Support Plan Project (Grant No. [2018]2836), the Provincial Natural Science Foundation of Hunan (2020JJ5538), the Scientific Research Fund of Hunan Province Education Department (20A475 and 19C1736), and the High-level Talent Gathering Project in Hunan Province (2019RS1059). The authors are grateful for the financial support for this research.

References

S. Huang, E. Yan, K. Fang et al., “Effects of binder type and dosage on the mode I fracture toughness of cemented paste backfill-related structures,” Construction and Building Materials, vol. 270, pp. 235–246, 2021.

S. Zhang, L. Yang, F. Ren et al., “Rheological and mechanical properties of cemented foam backfill: effect of mineral admixture type and dosage,” Cement and Concrete Composites, vol. 112, pp. 163–175, 2020.

M. Benzaazoua, M. Fall, and T. Belem, “A contribution to understanding the hardening process of cemented pastefill,” Minerals Engineering, vol. 2, pp. 456–466, 2003.

M. Fall, M. Benzaazoua, and S. Ouellet, “Experimental characterization of the influence of tailings fineness and density on the quality of cemented paste backfill,” Minerals Engineering, vol. 1, pp. 125–136, 2004.

S. Jabulani, Mahlaba, P. Kearsley, and R. A. Kruger, “Effect of fly ash characteristics on the behaviour of pastes prepared under varied brine conditions,” Minerals Engineering, vol. 8, pp. 1313–1324, 2011.

M. Fall and M. Benzaazoua, “Modeling the effect of sulphate on strength development of paste backfill and binder mixture optimization,” Cement and Concrete Research, vol. 2, pp. 381–391, 2004.

M. Benzaazoua, T. Belem, and B. Bussière, “Chemical factors that influence the performance of mine sulphidic paste backfill,” Cement and Concrete Research, vol. 32, no. 7, pp. 1133–1144, 2002.

B. Ercikdi, H. Baki, and M. İzki, “Effect of desliming of sulphide-rich mill tailings on the long-term strength of cemented paste backfill,” Journal of Environmental Management, vol. 115, no. 3, pp. 5–13, 2013.

B. Ercikdi, A. Kesimal, F. Cihangir, H. Deveci, and İ. Alp, “Cemented paste backfill of sulphide-rich tailings: importance of binder type and dosage,” Cement and Concrete Composites, vol. 31, no. 4, pp. 268–274, 2009.

F. Cihangir, B. Ercikdi, A. Kesimal, A. Turan, and H. Deveci, “Utilisation of alkali-activated blast furnace slag in paste backfill of high-sulphide mill tailings: effect of binder type and dosage,” Minerals Engineering, vol. 30, no. 4, pp. 33–43, 2012.

E. Yilmaz, T. Belem, B. Bussière, and M. Benzaazoua, “Relationships between microstructural properties and compressive strength of consolidated and unconsolidated cemented paste backfills,” Cement and Concrete Composites, vol. 33, no. 6, pp. 702–715, 2011.

S. Ouellet, B. Bussière, M. Aubertin, and M. Benzaazoua, “Microstructural evolution of cemented paste backfill: mercury intrusion porosimetry test results,” Cement and Concrete Research, vol. 37, no. 12, pp. 1654–1665, 2007.

O. Nasir and M. Fall, “Coupling binder hydration, temperature and compressive strength development of underground cemented paste backfill at early ages,” Tunnelling and Underground Space Technology, vol. 25, no. 1, pp. 9–20, 2010.

D. Wu, M. Fall, and S. Cai, “Coupled modeling of temperature distribution and evolution in cemented tailings backfill structures that contain mineral admixtures,” Geotechnical and Geological Engineering, vol. 30, no. 30, pp. 935–961, 2012.

D. Wu, M. Fall, and S. J. Cai, “Coupling temperature, cement hydration and rheological behaviour of fresh cemented paste backfill,” Minerals Engineering, vol. 42, no. 2, pp. 76–87, 2013.

N. Abdul-Hussain and M. Fall, “Thermo-hydro-mechanical behaviour of sodium silicate-cemented paste tailings in column experiments,” Tunnelling and Underground Space Technology, vol. 29, no. 3, pp. 85–93, 2012.

W. Xu, Q. Li, and Y. Zhang, “Influence of temperature on compressive strength, microstructure properties and failure pattern of fiber-reinforced cemented tailings backfill,” Construction and Building Materials, vol. 222, pp. 776–785, 2019.

E. Yilmaz, T. Belem, and M. Benzaazoua, “Effects of curing and stress conditions on hydromechanical, geotechnical and geochemical properties of cemented paste backfill,” Engineering Geology, vol. 168, no. 2, pp. 23–37, 2014.

M. Fall, D. Adrien, J. C. Célestin, M. Pokharel, and M. Touré, “Saturated hydraulic conductivity of cemented paste backfill,” Minerals Engineering, vol. 22, no. 15, pp. 1307–1317, 2009.

N. Abdul-Hussain and M. Fall, “Unsaturated hydraulic properties of cemented tailings backfill that contains sodium silicate,” Engineering Geology, vol. 123, no. 4, pp. 288–301, 2011.

N. Abdul-Hussain and M. Fall, “Unsaturated hydraulic properties of cemented tailings backfill that contains sodium silicate,” Engineering Geology, vol. 4, pp. 281–290, 2011.

S. Clayton, T. G. Grice, and D. V. Boger, “Analysis of the slump test for on-site yield stress measurement of mineral suspensions,” International Journal of Mineral Processing, vol. 70, no. 1-4, pp. 3–21, 2003.

S. Yin, A. Wu, K. Hu, Y. Wang, and Y. Zhang, “The effect of solid components on the rheological and mechanical properties of cemented paste backfill,” Minerals Engineering, vol. 35, pp. 61–66, 2012.