Note: Descriptions are shown in the official language in which they were submitted.
CA 0223.7.726 1 998 - 04 - 22
HIGH PU-LP DENSITY FAST SEl~I'ING AND HIGH EARlY STI~EN~TH
E~ACKFILL METHC~I) AND MAIERlAL
BACKGROUNl~ OF THE INVENTION
1. Field ol~ the Invention
S The present invention is directed to method and mater~al tor undergl~und mine bachC"ill
with high pulp density fast setting and high early strength backfill. More particularly,
it is directed to high crystal water content, fast setting and high early strength binding
material which is mixed with mine tailings, sands, ground sands, industrial solid waste
materials, or their mixture, a~d water to make a high pulp density back~ll slurry with
10 65 - 85~ pulp density. More particularly still, the slurry is then sent to the mine
stope through a pipeline either by gravity or by pumping. The backfill slurry in the
stope solidifies quickly to form a backfill body wi~ high early streng~. The backfill
body reaches more ~an 70% of its final strength in about 12 to 72 hours The present
backfill method may be widely usçd i~or upwards, downwards, and other mining
15 applications.
2. Prior Art
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As presently practised around the world, an important problem of using Portland
cement as binding material for mine backfill is to reconcile the requirements of
backfill body strength and the requirement tor transportation of the backfill slurry.
In order to increase the backfill body strength, the ratio of water to cement has to be
S low on the one hand, but on other hand, to increase tlowability of the backfill slurry,
much more water has to be used. The typical water to cement ratio is between 0.3
and 0.6 for Portland cement in order to get proper hydration, which is a relatively
small ratio of water needed for hydration. But in order to meet the re~luirc,llc--~ for
slurry transportation, pulp density of the slurry has to be less than 65 - 70%, to mal~e
10 it easily transportable to the mine stope through a pipeline. The excess amount of
water in the backFIll slurry will have to be removed in the stope. Coarse aggregate~s
such as s~nds, ground sands of coarse fractions from tailings are usually used in order
to make dewatering easier. In addition to this problem, the cement backfill body takes
7 - 28 days to reach the required strength. As a result, a long waiting period is
15 necessary in order to continue mining the ores beside the backt~llled body. The cyc1e
of drilling, blasting, ore transportation and backfill is prolonged.
There are other problems facing existing and tra lition~l Portland cement backflll
methods:
1. A large amount of cement in the slurry is carried away by water during the
20 dewal~ling process. This not only causes ellv~n~ nt~l problems, but also decreases
CA 02235526 1998-04-22
the strength of the backfill body.
2. Large spaces between the back~lll body and the roof of the stope cannot be
fully filled due to slurry volume loss during dewdle~ g. Multip1e backfilling
procedures are often require~ to fill up this space.
5 3. In order to create high permeability in the bacl~fiM body, only the coarse
fractions of the tailings can be used as aggregate. Tailing utilizatioD effciency is
therefore low, at less than 40~. The large quantity of unused fme tailings has to be
disposed of on land at the surface, which causes e.lYilollnlelllal problems on mine
surfaces.
10 4. The making of groun~ sands or purchase of sands to make up aggregates is
costly, if the arnount of tailings available is not sufficient for backfilll.
5. Due to the long solîdifying period of the bacln~ill body of between 7 and 28
days, means delay before the next mining operation may begin, thus production
efficiency is lowered.
15 In order to solve the technical problems listed a~ove, some mines have tried paste
backfill. The binding material is still Portland cement, but the pulp density of the
slurry has to be increased to more than 80%. Less water needs to be removed from
CA 02235526 1998-04-22
this paste slurry in the mine stope. As a result, the strength of the backfil1 body
increa~ses. However, due to the poor flow characteristics of the pa~ste, it raises a lot
of transportation problems and it can only be used in large vertical height mines where
gravity flow is used. Special mixing equipment such as 'double axis mixers' have to
S be used for mixing and special positive displacement pumps for paste slurry
transportation are required. The main problem~s associated with this method are: ~a)
A pressure filter is required for making paste~ where capita1 cost is high and the
process is complex, ~b~ Pipeline blockage occurs quite often due to too high pulp
density, so that the paste slu~g transportation through a pipeline is very difflcult; (c)
10 Both curing periods and operation cycles of mining are too long, since Portland
cement is used as the binding material; (d) Operating costs are high due to high
cement consumption; (e3 It is difficult to fill up all of the space in a stope, because
of the poor flow characteristics of the paste.
In order to solve the above problems, research on new binding materials and low pulp
15 density backfill methods have made progress in China. Chinese patents ZL90
103141.0 and ZL91 103829.9, to Henghu Sun et al., have disclosed a new process for
metal mine backfill. These processes use so-called 'high water content' materials to
replace Portland cement as binder to form a low pulp density slurry with 15 - 70%
pulp density. The "high water content" material binder is made of two equal parts
20 termed A and B materials. Both slurry A cont~ining the A binding material and s1urry
B co~ -g the B binding material are sent to the mine stope through two separate
CA 0223.7.726 1 998 - 04 - 22
pipe1ines. The two slurries are then mixed together at a place close to the mine stope
for backfill. After 30 minutes7 the bacl~lll slurry solidifies in the stope without lusing
any water.
However, there are some problems associated with this method: (i) The ratio between
S A and B has to be exactly at one. Ch:lngin~ of this ratio may prevent the slurry from
solidifying; (ii) The A and B slurries have to be transported through two separate
pipelines. This directly increases the capital cost of the mining process; (iii) Since
the two slurries have to be mixed at a place close to the backfill stope in the mine,
s~ti~f~tory mixing requires that the pulp density of the slur~g must be less than 70%;
10 (iv) Due to the low solids content in the slurry, more hinder material is needed it
high strength is required. This increases the cost of the hackflll.
United States Patent No. 5,141,365 issued August 25, 1992 to Smart discloses that a
void in a mine is hackfilled by a backfill slurry comprising water, an inert filler, e.g.
mine tailings, and a binder, e.g. cement, lime or slag, to which a gelling agent, e.g.
15 sodium silicate, is added just before placement. The salient feature of this patent is
that the bachSII slurry is made of tailings, water, Portland cement7 lime and slag.
United States Patent No. 4,101,333 issued July 18, 1978 to Wayment discloses a
me~hod of ~ac~lling in underground mine operations by a mill tailings slurry which
is dewatered to provide a material with a controller water content to permit the
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dewatered material to be used as a backfill witnout requiring any substantial
dewatermg after placement and which material can, when desired, be mixed with
selected quantities of cement to provide a mortar for ba~ llin~ or surt'ace covering.
The salient feature of this patent is using de-watered tailings for mine backfill The
S dewatering of the backfi11 slurry underground in the mine is not necçss:lry. Port1and
cement is mixed with prepared backfill aggregate to make a backfill slurry.
Both of tne aboYe two Unite~ States patents use Portland cement as binding material,
and have the common disadvantage discussed above.
United States Patent No. 5,340,235 issued August 23, 1994 to Milliken discloses a
10 method for hydraulically b?,~filling empty mined salt cavities. The method comprises
combining at least one pozzolanically active waste material with an effective amount
of an ~lk~line earth metal in the form of an ~ lin~ earth metal hydroxide or jqlk~lin~
earth metal oxide and saturated brine to form a pozzolanic mixture, wherein the
relative proportion,s of said po~zolanically active waste material, ~lk~ earth metal
15 hydroxide or ~lk~line earth metal oxide and sdluldled brine are sufficient for reaction
under atmosphere conditions in said salt cavity to form a stable, low porosity, load
bearing pozzolanic cement; and hydraulically depositing said pozzolanic ~ ure in the
empty salt cavity
United States Patent No. 5,464,473 is~sued November 7, 1995 to Shiao discloses a
CA 0223.7.726 1998 - 04 - 22
backfill for an engineered barrier used to contain radinactive waste has a
predel~ ined amount of clayic material and a predelel ~I~ined amount of a
rein~olcement material with hydrophobic surface cl~lac~eristics. The reinforcement
material may include hydrophobic compounds selected from group con~i~tin~ of
S organic polymers or inorganic materials on which a 1ayer of hydrophobic compounds
is formed. The hydrophobic reillforcement material results in the backfill ~ i"f~in;l~g
a very low water permeability while providing high mechanical strength and other
properties suitable for use in a repository of radioactive waste.
United States Patent No. 4,059,963 issued November 29, 1977 to Wayment discloses
10 a method of backfilling in underground mine operations by a mill tailings slurry which
is dewatered to provide a material with a controlled water content to permit the
dewatered m~t~ l to be used as a bacffill without requiring any subs~lial
dewa~ g after placement and which material can, when desired, be mixed with
selected quantities of cement to provide a mortar for ba~lrfilling or surface covering.
United States Patent No. 4,746,249 issued May 24, 1988 to Haigh et al. discloses an
a4ueous slurry of backfill material e.g. slimes, includes a settable ttl~eri~l and an
activator therefor, e.g. pulverized fuel ash and lime, and a lubricant e.g. clay and a
plasticizer, e.g. a lignosulphonate so that the slurry can be pumped over long distances
but will then set to develop high early strength.
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United States Patent No. 5,106,422 issued April 21, 1992 to Bennett et al. discloses
a rapid-setting self-hardening backfill composition and a method of in~t~ tion. The
composition comprising a minor amount of Class C fly ash as a primary constituent
and other filler m~teri~l~ such as Class F fly ash in major amount. When such
5 materia1s are combined with water in control1ed amount, they produce a backfilling
material which is flowable and self-leveling for easy in~t~ tion in utility trenches and
simi1ar excavations in street and roadway surfaces to support re1atively heavy
co~ essive 10ads within relatively short periods of time without settling. The self-
hardening ini~al1y flowable ~ ures attain considerable strength for withst~n-~in~
10 traffilc loads without undue settling in time periods of about 4 hours. The rapid-setting
of the composition provides a rapidly ~t~in~l~le strength of the order of about 20 psi
within about 4 hours to permit overlaying a wearing course of paving material and
reopening of excavated areas of streets and roadways without undue traffic delays and
congestion. The bac~fillin~ composition ranges in amount from about 2 to 10 parts
15 by weight filler material to about 1 part by weight Class C fly ash with suffilcient
water to react with both Class C fly ash and filler material. The composition utilizes
by-products of coal-fired power stations to form a most economic b~ llling material
and method of utilization to provide both early strength and precisely controlled
pe~lllanent strength to permit ready reexcavation.
20 Other patents disclosin~ new binder materials for mine backfill are: United States
Patent No. 4,992,103, titled Cc.. ~ us Composition; United States Patent No.
CA 0223.7.726 1 998 - 04 - 22
4,798,628 titled Apparatus Delivering a Rapidly Setting Composition; and European
Patent No. 286~9, titled Rapid set composition.
The major differences among the above patents are that different binders are used.
In some, binder consumption is very high at 300 - 500 kg per cubic metre. This is
5 only used for special cases in coal mines due to high cost.
SUMMARY OF THE INVENTJON
The present invention endeavours to solve the problems described above. Salient
features of the method of the present invention are:
- Increase of tne backfill slurr,v pulp density to 65 - 85%.
10 - Use of all types of tailings, natural sands, ground sands and industrial solid
waste materials as aggregates.
- Use of various proportions of basic binding materials, accelerating reagents,
r~lardillg reagents, and suspension reagents to adjust the backfill slurry setting
speed, ~setting time, early strength, flow characteristics and transportation.
15 - Alteration of binder addition procedures and slurry making procedures to
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obtain the required results.
- Large quantities of tailings and industrial solid wastes can be used for mine
backfill.
- The making of high pulp density backfill slurry, such that underground de-
watering is not required in some cases.
- Existing backfill technology can be used for various mine conditions through
adjusting of the present method of making the present binding material
composition, and the method of producing the new backfill slurry and its
tran.~portation procedures.
10 Using the backfill technology of the present invention, full tailings from a mine mill
can be used as aggregates. In prior methods, when using Portland cement as binder,
the tailings must be classified to remove fine tailings; only about 40% of the tailings
with particle si~s larger than 37 microns can be used as aggregates. In the present
backfill technology, all tailings without classification can be used for backfill. R~Ckfill
15 slurry may be made by mixing any kind of tailings with water to make a slurry with
65 - ~5% pulp density by weight. It is then sent to the mine stope through one
pipeline rather than two pipelines. The weight of the present binding material added
to the backfill slurry is between 0.5 and 20% by weight. If there are no tailings
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available for bacffill, natural sands, ground sands, industrial solid waste materials or
a mixture of thereof may be u~sed as aggregates. The natural sands include river
sands, ~sea sands, sands from mwnlai~s. The ground sands are made from grinding
rock into particle sizes of 0.04 - 5 mm. The industrial solid waste mq~ could be
S iron smelter slag, power plant slag and various industrial waste slags.
According to the present invention, there is provided a high pulp density fast setting
and high early strength backtill material and method for use in undergfoulld mines
COII~hiSillg: one part of mine tailings, natural sands, ground sands, and solid industrial
waste materials as aggre~ate; a binding material of between O.S and 20% by weight
10 mixed with water to form a slurry with 65 - 85% pulp density by weight; and
transporting the slurry to the stope of a mine through a single pipeline.
Preferably, the present binding material is composed of six groups of components in
the following ratios:
Component 1 can be one of, or a ~ e of sulpho-ah~ e cement clinkers, ferro-
15 ~lumin~t~ cement clinkers, fluo~ e cement clinkers and high ~hlmin:~t~ cementclinkers, in any ratio. The concentration of component 1 in the binding material is
between 40 - 90% by weight~ pl~rel~ly at 45 - 80% by weight and best at 50 - 70%
hy weight.
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12
Component 2 can be one of, or a mixture of anhydrite and gypsum, in any ratio. The
concentration of component 2 in the binding material is between 5 - 50% by weight,
prerelably at 10 - 40% by weight and best at 15 - 40% by weight.
Component 3 can be one of, or a mixture of lime and hydroxide lime in any ratio.
5 The concentration of component 3 in the binding material is up to 30% by weight,
preferably at 3 - 25% by weight and best at 5 - 20% by weight.
Component 4 can be one of, or a mixture of KCI, NaCI, CaC12, MgC12, ZnCI2,
Na2C03t K2C03, Li2C0~, Li cc,..l~inii.g chemical compounds, Na2S04, K2S04,
A12~S04)3, Na2S203, Na~, Na3P04, NaN03, K1~03, all alkalis, triethanolamine,
10 tri-isopropanolamine, c~balllide, in any ratio. The concentration of component 4 in
the binding material is up to ~0 by weight, preferably at 0.05 - 6% by weight and
best at 0.2 - 5% by weight. Component 4 is used as accelerating or/and high early
strength reagent.
Component S can be one, or a llli~lule of sugars, molasses, lignosulphonates, tartaric
15 acid, tartrates salts, citric acid, citrate salts, boric acid and borate salt, in any ratio.
The concentration of component S in the binding material is up to 2% by weight,
preferably at 0.05 - 1% by weight and best at 0.1 - 1% by weight. Comp~nent S is
used as rel~ding or/and dispersion reagent.
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Component 6 can be one of, or a ~ ur~ of bentl-nite, lime~stone, tlyash, silica fume,
slag powder, cement, talc powder, clay powder, baux~te powder, anhydrite, gypsum,
lime and hydroxide lime, in any ratio. The concentration of component 6 in the
binding material is up to 31)% by weight, preferably at 0.1 - 10% by weight and best
5 at 0.5 - 5% by weight.
In another aspect of the present invention, there is provided a me~hod for producing
a binding material for high pulp density, fast setting, high early strength b~
comprising: mixing of the above six groups of components in preselected ratios; an~
making and grinding the components to pass 100 Tyler mesh. P~ bly, the ratios
10 of the six components are:
(a) component 1: 45% - 80% by weight;
(b~ component 2: 10 - 40% by weight,
(c~ component 3: 3 - 25% by weight;
~ d) component 4: 0.05 - 6% by weight, whereby component 4 is used as
15 accelerator or/and high early strength reagent;
(e~ component S: 0.1)5 - 1% by weight, wheleby component 5 is used as re~der
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14
or/and dispersion reagent; and
~f) component 6: 0.1 - 10% by weight.
In yet another aspect, the me~od of making high pulp density, fast setting and high
early strength backfill slurry for underground backfill comprises using one of, or a
5 mixture of mine tailings, natural sands, ground sands and industrial solid waste
materials at any ratio as backfill aggregate; mixing the backfill aggregate, water and
material together uniformly to make a slurry with pulp density of 65 - 85 % by weight;
and transporting the slurry to the mine stope through a single pipeline by l~u114~illg or
by gravity; wherein the ratio of the binding material to the backfil1 aggregate is
between 1:5 and 1: 100 by weight.
A preferred method for prep~on of high pulp density7 fast setting and high early
strength backfill slurry comprises the fol10wing steps: mixing one of, or a mixture
of mine tailings7 natural sands, ground sands and industrial solid waste m~terial~7 in
any ratio7 with water to form a homogenous and uniform sand slurry with a pulp
15 density of 63 - 82% by weight; adding binding material to the sand slurry through a
feeder and mixing the slurry for 2 - 8 mim~tes in a ~ ur~ to form a backfill slurry
with pulp density of 65 - 85% by weight; wherein the ratio of the newly invented
binding material added to the backfill slurry is from 1:5 to 1:100 by weight7 and
tran~sporting the bacloSII slurry to the stope in the mines through a pipeline by
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pumping or by gravity.
In another aspect, the ~ ~d~ion of high pulp density, fast setting and high early
strength backfill slurry for underground backfi11 comprises the following steps: mixing
one of, or a mixture of mine tailings, natural sands, ground sands or industrial solid
S waste materials, in any rativ, with water to torm a homogenous and uniform sand
slurry with a pulp density of 63 - 82% by weight; transporting the sand slurry to a site
close to the stope in the mine through a pipeline by pumping or by gravity, at which
site, adding binding material to the sand slurry inside the pipeline through a feeder,
wherein the binding material added is well-mixed with the sand slurry through a
10 turbulent flow pattern inside the pipeline on its way to the stope; and wherein the
formed backf111 slurry has a pulp density of 65 - 85 ~ by weight, and the ratio of the
binding material added to the backfill slurry is from 1:5 to I:100 by weight.
Another method of providing binding material comprises: mixing components 1, 2 and
3 as defined above to form another component 7 as a binding material, wherein the
15 c(J-Ice~ alion by weight of each component in the binding material is as follows:
component 1 40 - 90%; component 2 5 - 50%; component 3 3 - 30%; grin~ling the
component 7 to pass tOO Tyler mesh; mixing cvmponent 4 with component 6 in a
ratio of 1 to up to 5 by weight, then grinding the l~ ure to pa~ss 70 Tyler mesh and
packaging the result separately to form (accelerating reagent) component 8; mixing
2() component 5 with component 6 in a ratio of 1 to up to 5 ~y weight, respectively, then
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16
grinding the lllixlul~ to pass 70 Tyler mesh and pack~ging the result separately to form
~re~rding reagent) component 9.
Depending on the distance at which the slurry will have to be transported, a binding
material required with a shorter setting time, typically between S and 50 minutes, can
be made by mixing component 7 with component 8 in a ratio of (95 - 100):~0 - 5);on the other hand, with a longer setting time, typically between 40 and 120 minutes,
the binding material can be made by mixing the component 7 with component 9 in aratio of (97 - 100):(0 - 3), when the slurry transportation distance is long.
A method for making the high pulp density, fast setting and high early strength
10 backflll slurry for underground backfill comprises: mixing one of, or a mixture of
mine t~ilin~, natural sands, ground sands and industrial solid waste materials at any
ratio with water to form sand slurry with a 63 - 82% of pulp density by weight in a
station at the surface before it is transported to underground, then transported to a
p1ace c10se to the back~lll stope through a pipe1ine by pumping or gravity; adding the
lS binding material to the formed sand slurry in a pipeline through a feeding system, and
mixing the binding material well with the sand slurry by turbulent flow inside the
pipe; wherein the ~ tily of the binding material added is about 2 - 20% of the sand
slurry by weight.
The ple~lion method for high pulp density, fast setting and high early strength
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backfill slurry for underground backfill comprises: mixing of mine tailings, natural
sands, ground sands and industrial solid waste materials in any ratio, with component
7 ~as described above~ to form backfill material mixture; then adding water to the
above ~ ure to make a slurry with 65 - 85% pulp density by weight, and
S transporting the slurry to a place close to the bacl~'ill stope through the pipeline by
pumping or gravity, wherein (accelerating reagent ~) component 8 ~described above)
is added in an amount of 0 - 5% the weight of the formed slurry; wherein the backfill
slurry is made uniform by the turbulent flow inside the pipe.
Another L~ ~dlion method for high pulp density bacfflll slurry comprises: adding
10 one of, or a ~ lure of natural sands, ground sands or industrial solid waste materials,
in any ratio, to low pulp density tailings from mine processing mills to make a denser
slurry with 62 - 80% pulp density sand sluny by weigl~; adding the binding material
(described above) to the slurry through a feeding system with a quantity fiom 2 to
20% of the weight of the formed slurry to form a backfill slurry with 65 - 85% pulp
15 density.
DETAILED DESCRiPTION (}1~ THE INVENTION
EXAMPLE 1
Tailings from a gold mine is COI cen~ted from 20 - 30% solids to above 70% pulp
CA 02235526 1998-04-22
18
density slurry. The present binding material is added through a measuring and mixing
device to the formed tailing slu~y at a ratio of the binding material to the formed
tailing slurry being 1 to 30. After mixing for 5 minutes, the slurry is sent to the
underground mine through a pipeline. Samples modules (4" x 8n) with dirfel~n t
S setting time are made for testing setting time and compressive strength. The result is
shown as below:
The present binding m~tçri~l composition is as follows:
1. Sulph~ min~te cement clinkers 65%
2. Gypsum 20%
3. Hydroxide lime 5%
4. CaC12 3 %
5. Na2CO3 2%
6. LiOH 0.4%
7. Rf ntonite 4.6%
15 The initial setting time: 40 minutes
The final setting time: 180 minutes
Testing time: 8 hours I day 3 days 7 days
Strength, psi: 19.6 52.3 67.8 87.4
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19
EXAMPLE 2:
A slurry with 7~% pulp density by weight is made by mixing natural sands with
water.
Mixture 1 is made of sulpho-alumim~te cement clinkers and ferro-alumin~te cement
5 clinkers at a ratio of 1:1
Mixture 2 is made of gypsum and anhydrite at a ratio of 2:8
Mixture 3 is made of hydroxide lime and lime at a ratio of 3:7
The binding material is composed of:
1. Mixture 1 65%
2. Mixture 2 20%
3 . Mixture 3 8%
4. K2C03 0.8%
5. NaCI 0 7%
6. 1,i2C03 0.2%
7. Molasses 0.3%
8. Flyash 5.0%
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The above material is well mixed and ground to pass 100 Tyler mesh to make the
binding material, which is then added to the above 75 % pulp density sand slurry with
amount of 4% of the weight of the formed sand slurry. The mixture is tnen well
mixed for S - 8 minutes and filled to exp~.rim~nt~l modules at 20 C. The result is
S s} own ~elow:
The iI~itial setting time: 36 minutes
The final setting time: 1~6 minut~s
Testing time: 6 hours 1 day 3 days 7 days 28 days
Strength, psi: 23.2 112.6 157.8 192.5 220.7
10 EXAMPLl~ 3:
Mix diy tailings with slag at a ratio of 1~ round the Illixlur~ to 0.04 - 5 mm.
Add water into the ~ ule to make a slurry of 72% solids. Mix sulpho-al~min~te
cement clinkers and ferro~ min~te cement cli~ at ratio of 1:1 and grind the
lui~lul~ to pass 100 Tyler mesh to produce component 1. The proportions for the
15 present binding l-ldlelial are:
1. Component 1 ~0%
2. Anhydrite 28 ~
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3. Lime 8%
4. Limestone 4%
The materials listed above is ground to pass 100 Tyler mesh to ~orm the binding
material. lt is then added to the formed sand slurry which is with 72% of pulp
5 density. The quantity added of the binding material is 5% of the weight of slurry.
After mixing for S - 8 ~llhl~lles, the slurry is filled to a few modules for strength
testing. The result is as follows:
The initial setting time: 50 minll~s
The final setting time: 200 minutes
Testing time: 6 hours 1 day 3 days 7 days 28 days
Strength, psi~ 18.8 87.8 138.3 167.1 lX8.9
EXAMPLE 4:
The binding material composed as shown in table 1, which is ground to pass totally
100 Tyler mesh, is separately mixed with classified tailing and alluvial sand slurries
of 68%, 72% and 76% of pulp density. The ratios of the classified tailings alluvial
sand to the binding material, Portland cement type 10, Poltland cement type 30, slag
cement 10 - 90 are 15:1, 30:1, 45:1, respectively. The composition and strengths
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measured are shown in the following table 1:
EXAMPLE 5:
Mix dry tailing from the mine mill with ground sand at a ratio of the tailing to ground
sand being 70:30. This formed ~ ure is then mixed with water to form sand s1urry
S with pulp density of 70 wt. % . The binding material to be used, which is the same as
in example 4, is added and mixed with the sand slurry to form backfill slurry. The
backtill slurry is then transported through pipeline to a place where is about 30 - 50
meters from the backfill stope. The accelerating reagents such as sodium carbonate,
lithium hydroxide and the suspension such as be-~ ile are added through measuring
10 devices. The quantities added of sodium carbonate, lithium hydroxide and b~nlollile
are 3%, 0.02% and 5% of the weight of the bacffill slurry, respectively. These
reagents are well mixed with the backfill slurry by a turbulent tlow inside the pipeline~
The slurry is then filled to the stope.
EXAMPLE 6:
15 Add sand, ground sand and ground industria1 solid waste material at an equal quantity,
to tai1ing s1urry with pu1p density of 20 - 30% by weight from the mine mi11 to make
sand slurry wi~ pulp density of 72% by weight. The binding materia1, same as in
examp1e 1, is added to the formed sand s1uny. The weight of binder is 6% of the
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23
Table I
SUMMARY OF::~IYDRA~ B~AC~II;L STRENGTH, PSI
Classihed t~;lin~ a~ IIiiyiaI sand
B d R~tio Pulp Deo~it~
m er S~d:b~d~
~e Cl-c~ifi~ Talngs a~uvials~d
68% 72% 72% 76%
~ ~r 69.7 151.0 89.3 146.7
The present 15-1 3~Y 93.7 178.7 108.1 185.1
binding material ~ 7 ~ 105 0 195 3 115 0 191 5
recipe
28~ 209.4
I I ~y 26.6 70.9 35.3 55.3
Sulph~ ~IIlmin ~ 30-1 3~y 38.7 94.2 50.6 86.0
cemen~ clinker 60%
2. 7~y 43.1 92.7 57.5 86.8
Anhy~i~e 28% 28~y 105.3
Lime 10% 1 ~y 151 42.6 25.0 29.7
45- 1 3 ~y 24.4 56.4 34.2 41.4
CaC03 2%
7~y 28.7 66.1 35.5 45.4
28~y 74.5
Portland Cement 15:1 Iday o o 6.1 12.5
Type 30 3 ~Y 1.5 2.2 14.8 29.6
7~y 6.1 8.3 29.8 42.3
28~y 20.1 24.3 37.3 66.2
Portland Cement 15:1 I day o o o 8.9
Type 10 3 ~Y 0 06 14.0 28.3
7~y 2.1 18.3 24.2 43.1
28~y 21.3 24.3 36.S 67.4
Slag Cement 15:1 ' d~y o o o o
10-90 Binder 3~y 12.4 11.5 0 0
7 ~y 28.5 26.3 7.6 9.4
28~y 60.0 67.0 24.7 28.5
CA 02235526 1998-04-22
24
weight of the formed sand slurry. After mixing for 5 - 8 minutes to form backfill
slurry, the unirolll.ed backfill slurry is transported to the mine through a pipeline by
pumping and filted in the stope The 3 days strength of tne sample i'rom the bacl~ïll
body in the stope is above 80 psi.
S EXAMP~E 7:
This is a comparison between the binding mqteri~l and Portland cement type 10, type
3~ Firstly, natu~ sands are mixed with water to form various pulp density sand
slurries of 68%, 70%, 72%, 74%, 76% and 78% respectively. Secondly, the present
binding material, Portland cement type 10 and Portland cement type 30 are added into
the formed sand slurries with various sand to binder ratios of 15:1, 20:1, 25:1, 30:1
and 35 :1, respectively, with a mixing time of 5 - 10 minUtes~ The formed slurries a re
poured into 4" x 8" cylinder respectively. The strengths have been measured at a
compressive testing, machine in 1 day, 3 days, 7 days and 28 days, which are listed
in the following table 2.
15 Table 2 shows that the compressive strengths of using the present binding material are
much higher than the compressive strengths of either using the Portland cement type
10 and type 30. Especially, very high early strengths have been achieved by using the
present binding materia1. And 1 part of the binding material by weight used can
replace 3 times of the Portland cement to get nearly the same compressive strength
CA 02235526 1998-04-22
Table 2
SUM~IARY OF UNCONFlNED COM:PRESS~VE STRENGl'~
ALLUVIA.L SAND BACKF~LL
Binder Sand: binder
68% 70% 72% 74% 76~/. 78%
I d~y 51.2 79.1 111.4 151.0 131.8 143.9
The present 15-1 3d~y 65.0 99.8 125.0 178.7 143.9 179.9
binding material ~ 7d~y 75.3 105.8 145.1 195.3 178.9 192.0
recipe 28d~y 69.5 122.5 156.0 209.4 175.8 190.5
I d~y 25.5 39.9 54.9 70.9 66.8 74.5
Su~pho~ 20: 1 3 d~y 40.0 58.8 71.7 94.2 88.0 95.7
cemell~clinlcer S0% 7d y 49.4 58.5 79.8 92.7 93.7 105.0
A~hydrite30% 28d~y 55.4 67.7 84.5 105.3 114.7 113.4
3. I d~y 18.6 24.6 33.4 42.6
Lime IS%
4. 25: 1 3 d~y 28.2 34.2 47.7 56.4
5CaC03 2% 7~r 33.1 41.1 51.8 66.1
NuCO3 1% 28 d~y 37.1 42.1 60.0 74.5
6. I d-g 12.4 16.8 22.2 31.3 49.2 49.2
NaCI 1%
7 30:1 3d y 19.6 23.8 34.4 41.8 64.8 68.7
Sugar 0.2% 7 d-y 26.0 28.0 41.3 46.3 78.3 78.3
LiOH 0.0S% 28 d~y 29.7 33.4 43.0 51.0 84.0 85.6
Benl~ 0.7S% I d~y ~ . 36.2 34.9
35:1 3d~y . , . , 4~.4 48.7
7 d~y ~ 53.3 55.1
28 ~y ~ ~ ~ ~ 64.2 63.6
Portland Cement 15 1 It~y o o 6.1 , 12.5 17.8
Type 30 3d~y 13.5 11.4 14.8 ~ 29.6 40.8
7 d~y 20.3 17.6 29.6 ~ 42.3 69.4
28 d~y 24.7 24.8 37.3 ~ 66.2 95.0
Portland Cement 15:1 Id~y O I O O 0 8.9 11.5
Type 30 3d~y 8.8 lo.l 14.0 12.6 28.3 34.7
7d-y 16.1 13.8 24.2 18.3 43.1 54.
28d~y 20.5 25.1 36.5 36.9 67.4 68.
CA 02235526 1998-04-22
26
within 7 days.
Table 2 also shows very good properties of using the present binding m~t~ l, which
can not be achieved with using Portland cement or any otner traditional binding
material in the mining backfill ~leld.
