Underground Void Filling by Cemented Mil Tailings

8/12/2019 Underground Void Filling by Cemented Mil Tailings

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Underground void lling by cemented mill tailings

Choudhary Bhanwar Singh , Kumar SantoshDepartment of Mining, Indian School of Mines, Dhanbad 826004, India

a r t i c l e i n f o

Article history:Received 14 March 2013

Received in revised form 22 April 2013Accepted 2 May 2013Available online 21 November 2013

Keywords:UndergroundCemented mill tailingsBackllingMetal miningSuper plasticizer

a b s t r a c t

Underground mining always create voids. These voids can cause subsidence of surface. So it is always ademand to ll the void in such a manner that the effect of underground mining can be minimized. Void

lling using mill tailings especially in metal mining is one of the best techniques. The tailings produced inmilling process have traditionally been disposed in tailing ponds creating a waste disposal and environ-mental problems in terms of land degradation, air and water pollution, etc. This disposal practice is moreacute in the metal milling industry where the ne grinding, required for value liberation, results in theproduction of very ne tailings in large percentage. This paper includes discussions on the effectivenessof different paste mixes with varying cement contents in paste backlling operations. The resultsrevealed that material composition and use of super plasticizer strongly inuenced the strength of cemented backll.

2013 Published by Elsevier B.V. on behalf of China University of Mining & Technology.

1. Introduction

Filling of the mine voids has multiple reasons such as, a simplemethod of tailings disposal, or as a void ller, in a few cases it isfollowed as an economic method for supporting the weak wallrocks, permit maximum ore recovery, safe and selection extractionof ore deposits without loss of ore and encountering dilution prob-lems and lastly, for creating a working platform in a few stopingoperations. Based on the specic purpose of backlling, the compo-sition of backll materials has been varied. According to Barrettet al. the purpose of the backll is not to transmit the rock stresses,but to reduce the relaxation of the rock mass so the rock itself willretain a load carrying capacity and will improve load shedding tocrown pillars and abutments [1]. This leads to less deteriorationin ground conditions in mine, improving operations and safety.

Cemented backll became popular when it was taken as ameans to support the weak wall rock. However, the high price of Portland cement has thrown open the challenge of economic via-bility. The consequence is that the researchers have tried to lookfor binder alternatives which have eventually resulted in the appli-cation of high density slurry and paste backll materials that haveimproved backll mechanical strength response, and reduced ce-ment consumption and water disposal.

The placement of backll underground directly reduces thequantity to be disposed on surface. This has direct operating andcapital cost benets and reductions in future rehabilitation costs.

There are two main types of cemented mill tailings as backll:hydraulic ll and paste backll. An adequate uniaxial compressivestrength for a backll in a typical mine is 0.72 MPa (100300 Psi), and common strength specication is 1 MPa after 28 days[2] . Hydraulic lls are slurry lls having a pulp density in the rangeof 55%75% solids weight for weight, Amaratunga et al. and Vileset al. state that as much as 30% of the total initial lls volume is lostby dewatering [3,4] . Hydraulic lls consist of classied coarse tail-ings along with a binder. The ne tailings are usually excluded fromthell because their removal improvesow characteristics and pro-vides better ll consolidation and subsequent water drainage. Thehigh water content allows the slurry to be transported by gravityor pumping at relatively high placement rates through boreholesand pipelines. Level preparation and clean-upcan be verytime-con-suming with this type of ll. The high binder dosage needed to cre-ate a hydraulic ll with good strength properties can be expensive.

Paste ll, on the other hand, has high solids content, usuallywith a pulp density in the range of 75%88% solids weight forweight [3]. Paste backll is cheap as comparison to rock ll orhydraulic ll [5] . This type of lling usually contains ne material.According to Archibald et al. and Slater as the concentration of neparticle (below 20 l m) increases, viscous stresses also increasesand paste become non-Newtonian in nature [6,7] . And it promotes just like Bingham ow conditions. This viscous character is a dy-namic property of paste. When the paste is stationary, the attrac-tive forces between particles or agglomerates form a three-dimensional structure, which extends to wall of the pipe. The shearstress, required to rupture this structure and initiate ow, is calledthe yield stress. Below this stress the material behaves like an elas-tic solid. As shear stresses and shear rates increase, the agglomer-

2095-2686/$ - see front matter 2013 Published by Elsevier B.V. on behalf of China University of Mining & Technology.http://dx.doi.org/10.1016/j.ijmst.2013.11.003

Corresponding author. Tel.: +91 9471191374.E-mail address: [email protected] (B.S. Choudhary).

International Journal of Mining Science and Technology 23 (2013) 893900

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ates gradually reorientate and disintegrate, resulting in a decreasein the viscosity of the backll material. This process is known asshear thinning. At very high shear stresses and shear rates, thereorientation and disintegration process reaches equilibrium, andthe viscosity becomes constant.

A super plasticizer is one of type of admixtures called waterreducers that are used for reduction in water requirement of mill

tailings. Water reduction results in undesirable effect on setting,bleeding, segregation and hardening characteristics. The superplasticizer is chemically different from normal water-reducers,and is capable of reducing water contents by about 30%.

The transportation of cemented mill tailings in the form of pastethrough pipelines is one of the main stages of paste backll oper-ations. One of the data-sets used for pipeline design purposes arethose correlating the yield stress of uid material changes withchanges in friction loss and the diameter of pipes and it is usedin the design of pumping energy requirements for the transporta-tion of paste backlls through pipelines [810] .

The addition of cement to cohesionless mill tailings backll re-sults in material which provides high strength and elasticity withtime [4,11,12] . The presence of sulfur in mill tailings reduces thestrength of backll after certain time. The production of hydrogenions causes sulfate attack that dissolves the calcium hydroxidefound in hydrating cement and the precipitation of gypsum andthus, causes expansion in cements [5,6,13,14] . The addition of ce-ment to tailings also decreases the permeability of tailings with -ner materials experiencing a greater percentage decrease [13] . Theeffect of cementing reactions is to reduce the porosity of the lland block drainage paths. Pulp density is a vital role playing in ce-mented mill tailings backll for strength and ow ability purpose.For strength purpose a high pulp density is ideal [3,14] .

2. Laboratory testing

A number of laboratory tests were carried out to study the ef-fect of material composition on the strength of cemented mill tail-ings. The main objectives of developing the backll laboratorytesting were:

First to identify a cost-effective backll mixture which will ful-ll the desired strength and deformation behavior of cementedmill tailing. As a function of binder content and cure time inuniaxial, the mix characteristics will be adjusted in such away that when underground opening is lled with this mixture,the lled structure will safely withstand strata loading, and willlimit underground and surface movements.

Second, to develop an understanding of the performance of cemented paste backll when exposed to superplasticizer.

2.1. Specimens properties

A mill tailing sample was taken from one of the undergroundmines. The basic properties of tailings are summarized in Table 1 .Chemical composition was determined by a scanning electronmicroscope method which is given in Table 2 . Fig. 1 shows the par-ticle size distribution of tailings, determined by sieve analysis.

2.2. Specimen unconned compression test

The purpose of the uniaxial compression tests was to obtainunconned compressive strengths (UCS) and moduli as a func-tion of binder content and cure time. The different percentageof cement was sampled for each type of test: 3%, 6%, 10% and20% by dry weight (cement:mill tailing). In all, sixty sampleswere cured in laboratory at pulp density 80% for 3, 7, 14, 21and 28 days at temperature 30 C. Other 24 samples were curedon laboratory for 28 days for different pulp density at 20 C.Again 24 samples were cured on laboratory for 28 and 90 daysfor different composition of superplasticizer at 20 C at pulp den-sity 77%.

The samples of 54 mm 110 mm diameter by length were castin wooden cylindrical molds ( Fig. 2). After allowing them to set for48 h, al1 of the samples were removed from the wooden molds andwere waxed at both ends to prevent moisture loss due to evapora-tion and possible oxidation of the samples.

Immediately before the testing, both ends of the samples ini-tially were done parallel by polish. The length, diameter andweight of the samples were measured. The sample was placedin the testing frame, its stroke control rate was 0.315 mm/minand brought into contact with the load cell by adjusting thehydraulic ram. When the sample was failed to load and defor-mation was noted. UCS was calculated with the Secant valueof Youngs modulus at 50% peak stress.

Table 1

Basic properties of mill tailings.

Parameter Value

Specic gravity 2.67pH in water 7.89Particle size distribution (%) Silt 12.22

Fine sand 86.82Medium sand 0.96

D10 71D30 125D50 140D60 150C u 2.11C c 1.47Permeability (cm/s) 4 [ 10 3

Table 2

Chemical composition of mill tailing (determined by SEM method).

Chemical component Percentage(% by weight)

Element Percentage(% by weight)

Na2O 5.88 Na 6.72MgO 6.23 Mg 6.20Al2O3 9.83 Al 8.97SiO2 42.31 Si 35.55SO3 4.89 S 3.79K2O 1.1 K 1.67CaO 9.08 Ca 11.76TiO2 1.46 Ti 1.58MnO 2 0.34 Mn 0.47Fe2O3 17.43 Fe 21.29NiO 0.1 Ni 0.13ZnO 1.35 Zn 1.89

0.1

1

10

100

0.01 0.1 1 10

Grain size (mm)

Fig. 1. Grain size distribution of tailings.

894 B.S. Choudhary, S. Kumar / International Journal of Mining Science and Technology 23 (2013) 893900


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3. Results and discussion

3.1. Effect of cement content and curing time on UCS and Youngsmodulus

The unconned UCS was calculated as the mean value of themaximum stresses obtained during the testing of three samplesof the same mill tailing and cement mixture. The secant values of Youngs modulus were calculated at the point corresponding to50% of the compressive strength value. Different UCS (kPa) and

Young Moduli (MPa) were obtained for different cement propor-tions and curing time.

Fig. 3a shows the relationship between UCS and cement per-centage and Fig. 3b shows Youngs modulus and cement percent-age respectively for different curing period. These gures clearlyshow the compressive strength and Youngs modulus of the ll.Both increase with cement content and curing time as expected.

Compressive strength and elasticity are relatively low for 3% of ce-ment in mill tailing, with a notable increase starting to occur forsome mixes with a cement dosage higher than 6%. All samplesgradually gained strength and elastic modulus up to 28 days of curing. These results agree with the reports by Belem et al. [15] .The UCS increases nonlinearly with the cement dosage for all ce-ment mill tailing composition. Modulus values also follow thesame trend, increasing nonlinearly with binder dosage for all ce-ment mill tailing composition. The rate of increase in UCS andmodulus values was higher in the initial 21 days compared withits increment after 21 days.

High strength values were obtained in the samples containinghigh amount of cement. It can also be seen from Fig. 3a that cementhas high strength gain in the corresponding sample at curing

Fig. 2. Sample preparation in the wood mold.

0

1.00

2.00

3.00

4.00

5.00

6.00

7.00

3 6 10 20Cement (%)

For 3 daysFor 7 daysFor 14 daysFor 21 daysFor 28 days

0100200300400500600700800900

3 6 10 20Cement (%)

(a) UCS (b) Youngs modulus

Fig. 3. Effect of cement and curing time on UCS and Youngs modulus.

2.01.51.00.50

100

50

200

150

300

250

350

Strain (%)

(a) 3% cement

U C S ( k P a )

1.51.00.50

1000

500

2000

1500

2500

Strain (%)

(c) 10% cement

U C S ( k P a )

2.01.00.50

3000

6000

4000

7000

Strain (%)

(d) 20% cement

U C S ( k P a )

1.5

1000

2000

5000

1.51.00.50

Strain (%)

(b) 6% cement

800

1400

1000

1600

S t r e s s

( k P a )

400

600

1200

200

Curing 3 days

Curing 7 days

Curing 14 days

Curing 21 days

Curing 28 days

Fig. 4. Typical stressstrain curves for paste backll specimen for different curing period containing.

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28 days. Therefore, it can be concluded that longer curing periodalso plays an important role for increasing the strength and moduliof paste backll. Fig. 4 shows the stressstrain curve for differentcement composition and curing period.

3.2. Effect of pulp density on UCS

Fig. 5a shows the relationship between UCS and different pulpdensities for 28 days curing period at 6% of cement dry weight

composition at 20 C. Fig. 5b shows the relationship between mod-uli and pulp density.

When pulp density 83.3% was used then result of UCS of thissample after 28 days curing in laboratory was 566 kPa, whichwas 135% more compared with UCS of sample with pulp density66.7%. Similarly, Youngs modulus of pulp density 83.3% samplewas 86% more as compared with that of the sample with 66% pulpdensity. Therefore, it can be inferred that the compressive strengthand Youngs moduli of the backll samples are related to the pulpdensity. It was also noticed from Fig. 4 that there was no more dif-ference in strength values for the samples with pulp densities be-tween 83.3% and 80%. This may be due to the required amount of water to react with cement and develop bonds between tailingmaterials. The strength of the backll decreases as the pulp densitydecreases mainly because of the subsequent increase in overall

U C S ( k P a )

Y o u n g

' s m o d u l u s

( M P a )


Fig. 5. Effect of pulp density on UCS and Youngs modulus.

0.5 1.0 1.50100

200

300400

Strain (%)

S t r e s s

( k P a ) 500

600700

PD 83.3%PD 80.0%PD 77.0%PD 74.0%PD 71.4%PD 66.7%

Fig. 6. Typical stressstrain curves at different pulp density for 6% of cement (dryweight).

2 5 70

20

Shear strain (%)9

10

40

30

50

70

60

S h e a r s t r e s s

( k P a )

8 1063 41

Normal stress 19.60 kPa Normal stress 35.28 kPa Normal stress 47.00 kPa Normal stress 58.80 kPa Normal stress70.56 kPa

Fig. 7. Curves of shear strain and shear stress from the direct shear test.

20 40 600

20

Normal stress (kPa)

80

10

4030

50

7060

S h e a r s t r e n g

t h ( k P a ) y=0.5697 x+17.4

R2=0.928

Fig. 8. Normal stress and shear strength from the direct shear test.

Table 3

Effect of cement addition on porosity and UCS.

Cement content in mil l ta il ing (%) Porosi ty (%) UCS (kPa)

3 60.000 173.446 59.184 635.2510 58.696 1702.80

20 55.556 5159.30

173.44635.25

1702.8

5159.3

0

1000

2000

3000

4000

5000

6000

55 56 57 58 59 60 61Porosity (%)

U C S ( k P a )

Fig. 9. Effect of porosity on UCS for curing 3 days.

Table 4

Effect of SP on compressive strength and Youngs modulus for 28 and 90 days curing.

Time Composition UCS (kPa) Youngs modulus (MPa)

28 days 94:6:0.2 654.26 214.2096:4:0.2 545.91 165.3694:6:0 313.64 124.8497:3:0.3 130.16 150.90

90 days 94:6:0.2 938.90 234.0096:4:0.2 892.10 198.6094:6:0 586.10 170.2097:3:0.3 331.87 97.30



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porosity caused by the water-lled voids. On drying these samplesair voids were created which were likely to decrease the strengthof samples. On the contrary, the higher the pulp density ratio the

stronger the samples. This is due to greater cement particle inter-locking with mill tailing and less air voids creation. Fig. 6 alsoshows the stressstrain curve at different pulp density for 6% of cement.

3.3. Shear strength parameters

Normal stresses required for testing were estimated by dividingthe applied load by the area of the shear box. Peak shear strengthwas determined from plots of shear stress versus shear strain.Internal friction angle was obtained using a linear best-t line fromthe plot of peak shear strength versus normal stress. The residualfriction angle was obtained using a similar best-t line. Fig. 7shows the variation of shear stress with shear strain. Fig. 8 shows

the shear strength with normal stresses which gives internal fric-tion angle 30 and cohesion 17.4 kPa.

3.4. Effect of porosity

The effect of cement addition on porosity is given in Table 3 andeffect of porosity on UCS is given in Fig. 9. Porosity had decreasedwith addition of cement in mill tailing due to neness of cement.So when cement was mixed in mill tailing and then void ratio of mill tailing decreased. The higher UCS had been found in lowerporosity due to greater particle interlocking and the presence of more cement per unit volume of backll.

3.5. Effect of super plasticizer

The results of all the UCS tests due to variation of superplasti-cizer are summarized in Table 4 and Fig. 10. Fig. 10 shows the var-iation in the UCS and Youngs moduli with the variation of composition of paste backll with superplasticizer for 28 and90 days curing. Fig. 10a shows the maximum compressive strength654.26 kPa (just double) of the composition MT:C:SP containing94:6:0.2 ratios as compression to compressive strength

313.64 kPa of composition MT:C:SP containing 94:6:0 ratios (con-trol binder) respectively for 28 days curing. Compressive strength

654.3

545.9

313.6

130.2

938.9892.1

586.1

331.9

0100200300400500600700800900

1000

94:6:0.2 96:4:0.2 94:6:0 97:3:0.3

Composition (MT:C:SP)

U C S ( k P a )

For 28 days

For 90 days 214.2

165.36

124.84150.9

234

198.6

170.2

97.3

0

50

100

150

200

250

94:6:0.2 96:4:0.2 94:6:0 97:3:0.3Composition (MT:C:SP)

Y o u n g

' s m o d u l u s

( M P a )


Fig. 10. Effect of super plasticizer on UCS and Youngs modulus for different curing days.

0.2 0.4 0.6 0.8 1.00

100200300

400

500600700800

Strain (%)

S t r e s s

( k P a

)

0.2 0.4 0.6 0.8 1.00

200

400

600

800

1000

1200

Strain (%)

S t r e s s

( k P a

)

1.2

0.2% SP mixed withMT:C (94:6)0.2% SP mixed withMT:C (96:4)

No SP mixed withMT:C (96:4)0.3% SP mixed withMT:C (97:3)

(a) 28 days (b) 90 days

Fig. 11. Typical stressstrain curve after 28 and 90 days of curing for the different percentage of composition.

Fig. 12. Slump test of backll with superplasticizer.

493

338

0

100

200300

400

500

600

Without SP With SP(0.2%)

Y i e l d s

t r e s s

( P a )

Fig. 13. Effect of superplasticizer on yield stress.

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of another binder in which MT:C:SP containing 96:4:0.2 ratioswere also 74% more strength as compression to that control binder.But effect of superplasticizer was not good in binder which con-tains MT:C:SP containing 97:3:0.3 ratios. Compressive strength130.16 kPa of this binder was less than half value of compressivestrength of control binder. Fig. 10b shows Youngs modulus214.19 MPa of binder which contains MT:C:SP containing94:6:0.2 ratios were also 70% more than that of the Youngs mod-ulus of control binder. This type of increment in compressivestrength and stiffness had happened due to renders a lower poros-ity hardened material and increased the rate of cement hydrationin well dispersed cement so that between cement mill tailing bet-ter particle packing and denser structure upon hardening in pastescontains admixture superplasticizer [16,17] .

Fig. 10 clearly shows the variation of curing time on its strengthand moduli. Increment on strength due to curing varies from 50%to 100% for different composition. This has happened may be dueto long term hydration between cement and mill tailing. Fig. 11produced unclear stressstrain relationship for 28 and 90 dayscuring.

The cement paste backll mixture MT:C:SP containing 94:6:0.2developed the highest unconned compressive strength over a90 days curing period and showed the maximum stiffness develop-ment as compared with those of paste backll specimens withoutadmixture. But the cement paste backll mixture MT:C:SP contain-

ing 96:4:0.2 also developed the required unconned compressivestrength over a 90 days curing period and showed the maximumstiffness development as compared with those of paste backllspecimens without admixture. So for economical purpose thiscomposition would be the best.

4. Rheological tests

4.1. Experimental procedure

Cylindrical mould was used for determination of slump valuedue to many advantages over the cone slump test [18] . Therewas no required standard for the cylinder test. Cylinder was madeby PVS with the length 115 mm and diameter 102 mm. The bothsides of the cylinder were opened so that slumped material is100% consistent during lifting. And one strong smooth steal plateon top of cylinder was used for lling with sample. The cylinderwas lled with sample, and the cylinder lifted slowly and evenly.The change in height between the cylinder and deformed materialwas measured ( Fig. 12 ). The midpoint of the slumped material wastaken as the representative height and measured with a scale. Den-sity and concentration were measured at the time of testing.

The results of the slump tests performed with 6% (dry weight %)cements with 0.2% superplasticizer and without superplasticizer(Fig. 13 ). Results obtained from the tests are: the yield stress of

Table 5

Vicat needle test result.

Binder content Additive Water of total weight (%) Setting time (min)

Initial Final

94:6 (MT:C) None 23 65 125SP 0.2% of dry weight 23% of total weight 45 120

Fig. 14. Flow characteristics of mill tailing when 0.2% of superplasticizer mixed with MT:C (94:6).

Fig. 15. Flow characteristics of mill tailing when there is no superplasticizer used inMT:C (94:6).

Fig. 16. Flow characteristics of mill tailing when 0.2% of superplasticizer mixedwith MT:C (96:4).



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backlls without superplasticizer is 493 Pa with slump height25.6 mm; the yield stress of backlls with superplasticizer is338 Pa with slump height 41.51 mm. It had been seen that therewas more difference (155 Pa) on the yield value and also betweenslump height (15.91 mm), while 23% of water was present in bothconditions. So uidity increased due to superplasticizer.

4.2. Setting time procedure

Setting time was determined by Vicat needle test (penetrationtest). Specimens for the Vicat needle test were cylindrical cup with70 mm in diameter and 40 mm high. After being lled with paste,pulp density was 80%. The standard test method, the Vicat needletest, was used to determine the initial and nal setting time of hydraulic cement. The initial setting was determined for the needleto reach a penetration depth of 5 mm in standard Vicat apparatus.The nal setting took place when the needle does not visibly pen-etrate into the paste, i.e., the specimen had a solid structure.

Table 5 shows the initial and nal setting time for paste inwhich one was without superplasticizer and other was with

superplasticizer. The data indicates that initial time setting of pastewith superplasticizer was less as compared with paste withoutsuperplasticizer. The nal setting time of both pastes was aboutthe same while superplasticizer paste was wet as comparison topaste without superpasticizer. So for the same slump value, timesetting would be reduced in superplasticizer paste than pastewithout superplasticizer.

4.3. Flow ability test

For the ow behavior test, one galvanized iron sheet with120 cm length was used at inclination of 20 as shown in Figs. 1417 . Figs. 1417 show the ow characteristics of backll material.The result of the test was performed with 4 different compositions.

In the rst experiment for the ow test, 0.2% of superplasticizerwas used in MT:C containing 94:6 ratios binder. In the secondexperiment, no superplasticizer was used for the same combina-tion. In the third experiment, 0.2% of superplasticizer was used inMT:C containings 96:4 ratios respectively. In the fourth experi-ment, 0.3% of superplasticizer was used in MT:C containing 97:3ratios respectively. It was found that there was signicant differ-ence on the uidity of different compositions. At 0.2% of superp-lasticizer in mill tailing, cement (94:6 ratios) binder, the uidityincreased compared with the other compositions. And in othercompositions some part of paste had owed and some part hadnot owed. Higher uidity in the rst case was observed due toelectrostatic repulsion between particles, causing dispersion. Inthe 3rd and 4th experiment an insufcient amount of cement

may be available to react with main hydration (i.e., calcium silicatehydrates or CSH) to produce effective dispersion at later stage.

Fine particles in the compositions played an important role withsuperplasticizer for uidity purpose.

The rheological behavior of two paste backlls characterized inthis study was yield-pseudo plastic. The superplasticizer controlsnot only the rheological behavior of paste backll, but also theiryield stress. Yield stress measurements in slump test method

showed reliable results for superplasticizer as comparison withnon superplasticizer paste backlls. Based on the results of this re-search, it can be said that the use of superplasticizer in backllmaterials will be economical because this will not only increasesthe strength but also aids in the rheological characteristics of pastebackll materials.

5. Conclusions

The following conclusions may be drawn from the above study:

(1) Predominant oxides found in the mill tailing samples areSiO2 , Fe2O3, Al2O3, CaO, Na2O, MgO, SO3, and TiO 2. The pres-ence of CaO at 9% in the mill tailing samples indicates thegood pozzolanic characteristics of mill tailing.

(2) Particle size distribution shows that the percent of ne sandis 86.82%. For paste backll purpose at least 15% of mill tail-ing less than 20 l m is required.

(3) Coefcient of permeability of mill tailing is 4.08 10 3 cm/s, which is very less and after cement addition its value willagain decrease. So it is not good for drainage in hydraulicbackll purpose without any occulants. This is good forpaste backll purpose.

(4) The Pulp density is a critical determining factor in thestrength of cemented backll. Increase in its value signi-cantly increases the backll strength.

(5) It has been observed that increase in cement contentincreased the backll strength.

(6) Superplasticizer also played a good impact for increment onbackll strength with cement content.

(7) Flow ability increased with mixing of superplasticizer. Set-ting time was not affected due to superplasticizer.

References

[1] Barrett JR, Coulthard MA, Dight PM. Determination of ll stability mining withbackll. In: 12th Canadian Rock Mechanics Symposium, Sudbury: 1978.

[2] Petrolito J, Anderson RM, Pigdon SP. A review of binder materials used instabilized backlls. CIM Bull 2005;98(1085):85 .

[3] Amaratunga LM, Hein GG, Yaschyshyn DN. Utilization of gold mill tailings as asecondary resource in the production of a high strength total tailings past ll.CIM Bull 1997;90(1012):838 .

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Fig. 17. Flow characteristics of mill tailing when 0.3% of superplasticizer mixed with MT:C (97:3).

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