CA2241167A1

CA2241167A1 - Surface covering material

Info

Publication number: CA2241167A1
Application number: CA002241167A
Authority: CA
Inventors: Hendrik Johannes Van Vuuren; Kenneth Alfred Joubert
Original assignee: EVERMINE LIMITED
Current assignee: EVERMINE Ltd
Priority date: 1997-06-20
Filing date: 1998-06-19
Publication date: 1998-12-20
Also published as: EP1005441A2; WO1998058886A2; EA001141B1; BR9810446A; EA200000056A1; AP2000001737A0; WO1998058886A3; CN1261392A; AU8539998A; ZA985350B; PL337830A1; TR199903130T2

Abstract

A surface covering material is described which can be applied on to for example rock and coal surfaces (for convenience both rock and coal will further in this specification be referred to as "rock") in tunnels, stopes and pillars as well as around base plates of rock bolts to inhibit the breaking away of the rock covered thereby. The material comprises a mixture of a cementitious constituent, comprising a highly water absorbent cement blend, with a the second constituent which incorporates a water based polymer emulsion. The highly water absorbent cement blend can absorb at least its own mass of water and in some cases five times its own mass of water. The covering material will dry quickly in mines where there is high humidity and little air movement.

Description

Thi~ re~ion relate~ to sur~ace covering material Q _ I~ our South Afr~can Patent Specirication No 94/0532 there i~ de~ribed such ~ur~ace covering material~. Although the~e m~terial~ have ma~y excellent propertie~, they ha~e a ~eakne~s w~en u~ea underground.
The problem in mines is the hig~ hu~l~ity in the atmo~phere a~d the fac~ t~t there iQ orten very little airl,.o~e...~nt. In ~his situatio~, it haQ bee~ fo~nd that the ~foresaid ~aterlals take a ~air amount of time to dry and cure w~icn may be ~naccQptable in certain circumstances ~ c~ording to one a~pect of the prese~t inveneian there is provided a 6ur~ace co~ering material comp~ising a mixture af a c~mentitious constituent, comprisi~g a hi~hly wat~r ab~orbent cement blend, wlth a t~e ~econd con6tituent which incol~Lates a wacer based polymer emul~ion. This material can be applied on to for example rock and coal surface~ ~for conve~ience both rock and coal will fur~her in thi6 cpeci~ication be referred to a~ ~Irock~l~ in tunnel~, stope~ and pillars ~ well a~ aroun~ ba~e plates o~ rock bolt~ to inhibit the ~reaking away of the rock co~ered thereby.

The term "highly water abs~rbent" shoul~ be con-scrue~ in accordance with the ~ollowing:- Ordinary Portland cement ("OPC") ~ill ab~orb water in t~e P/Medal/74210 ~ollowing proportiuns, ~iz 100 gm OPC to about 38 ~m ~ watex A ~highly water absorbent ce~ent ble~d~ will ab~o~b a~ leas~ it8 OWI~ m~ss of water. The cementitious c~ns~i~uent preferably wlll ab~or~ at lea~t th~ee time~
its m~ o~ wa~er an~ i~ a p~eferred em~nAim~nt will absorb five ti~es iec ma~s of water~

Becau~e the ~ itious conxtitue~t i~ highly water absorbent, it can better ab80rb the liquid coLl~nent of the seeond con~tituent. Furthermore for o this reason che cementitiou~ constituent can o~ercom~
the problem whic~ would otherwi~e be encountered namely that the polymer coats ~ large p~~O~OLtion of the granule~ of the solid constituen~ thereby pt ~ve~Ling the formatio~ o~ an ade~uate amount of ettri~ite.

~he ~econa con~tituen~ may be a liqula con~ituen~
Alt~rnatively t~e ~econd constituent may ~e a dry material.

The ~urf~ce co~ering material i~ pre~erably appli~d by beir~g :3prayed on to the rock ~ur~ace. For this purpo~e the constituent-~ are pre~erab1y mix~d prior to be1 ng ~prayed on ~o the rc~ck ~iur~ace . 'rhe mi~cture will normally have a limi~ed pot life and there~ore will ha~re to be 6praye~:1 within a certain period, no~mally about twenty to tIlir~y'minutes a cer m$xirlg.

P/Menal/74210 CA 0224ll67 l998-06-l9 Where the cecond con~tituent is a dried material, the two co~stituent~ ar~ conveniently mixed or blended tog~ther and the water added to the mixture in the a~ G~iate amount. Altern~t~ely, the mixture o~ the dry materi~ls and water ma~ be ~prayed on ~o ~he surface by ~ proces~ ~imilar to t~e "Gunite" ~-v~

The cementitiou~ and ~econd con~tituent~ are pre~era~ly mixed in the raclo of 1: 3. ~All ratio~ and percentages refexre~ tO in this ~peci~ication are on the ba~i~; o~ ma6~3:mas~2 ~

Th~ c~m~ntitiou~ co~titu~nt preferably compri~es high-alumina cement, OPC and anhydrite g~psum (anhydr~us calcium ~ulphate) ~onming the bul~ of the mixture together with soda a~h, lithium carbonate and ~odium fluoride and conveniently in addi~ion N~tra~ol~250HR or Cellosize0QP 52~00. The ~tem6 men-tioned above a~ formlng t~e bulk o~ ~he mixture m~y - con~titure 99~ or more o~ the ~ix~ure We have found that ~he minor constituentc react with She major co~tituents to provi~e the highly water absor~e~t chara~teri~tic to the csmentitiou~ con~titu~nt.

The OPC may co~prise between 40~ and 52~ and pre~erably about 47~ o~ the cementitious con~tituent.
2S Tl~e high alu~ na cement may cornprise between 18~ and 28%
and preferably about 23-~ of ~he cementitiou~ con~t~u-ent. The anhydriee gyp~3um may com~ri~e between 279c P/Medal/74210 and 31% and prèferably about 29~ of the ceme~titious con~tituent.

The sodium fluoride i~ preferably a ligh~ 95 technical grade ~odium fluoride.

~he soda a~h should be ~inely ground ~da ash.
~he ~oda a~h and the ~odlum ~luori~e may each comp~i~e between o,25~ and 0,35~ prefe~a~ly about O,3% O~ the cementitiou~ con~tituent~ T~e lithiurn r;~-hr~n:lte an~l Natrasol ~or Cellosize1 may each compri~e betw4~n 0, 09 and 0,15~ and preferably about 0,1~ of the cementitiou~
con~tituent.

Pre~erably the ~econd conseituent further comprise~
a fire retarda~t. A pre~erred fire re~ardant c~mprises antimony ~rioxide and chlorinate~ paraffin, the la~ter p~eferably being that ~ld under the trade name "~ere-clor~ 70n. Thi~ fire retardanc preferably con~titu~e~
a~o~ to 20~ of t~e ~econ~ con~ uent The cnlor-inated para~fin c~nveniently constitute~ between 8~
and 12~, preferably between 10~ and 11~ and most preferably about 10,7~ of the ~econd constituent while the antimony trioxide conveniently constitutes between 3~ and 7~, preferably betw~en 5~ and 5,5~ and mo~t pre~ierably about 5,4~ of the second constituent.

The e~ulsio~ i~ preferably an acrylic emul~ion binder, con~eniently a vinyl acetate ethylene copolymer P/Medal/74210 and preferably that which is c~mmercially available un~er the cra~e name "Air~lex~ 300". Thi~ material ~0 ~16 a ~inder ~or the applied ~urface covering la~er giving i-~ov~d fle~ibility, ela~t~city and ten~ile strength ~o the cured 6urface co~eriny layer. ~n addition it proviaes im~rove~i at9he~3lon tO the rock ~urface. The vinyl acetaee ethyle~e copolymer conveni-ently con~titute~ betw~en 60% an~ 75~, preferably bet~een 65~ and 70~ and mw~t proferably about 67,6~ of the second constit~ent . A pla~ticizer i~ preferably included to improve the flexibilicy and re~ilience of the material once ~t ha~
cured. I~ par~icular the pla~icizer will a~sist in provi~ing re6ilience and ~lexibility over small radii ~uch as are encounterea at roc~ edges during rockma~s dsforTnation~ under 610q~ and rapiCi loat~ing con~5itions.
preferred plasticizer is dibutyl p~thala~e The pla~ticizer may con~-tit~te between 5~ and 10%, preferab-ly between 7% and ~ and mo~t preferably about 7,8~ or the second con~tituent.

A ~actericide for pre~enting g~owth of bacteria and e~zym~s ~ay be pro~ided. Thi~ is conve~iently in the ~orm o~ Che material commercially obt~ hle under the trade name nMetatin- G.~ nly a ~mall amount of the bacterici~e need be adaea an~ ~hi~ may be les~ than 1~, conveniently between o,1~ an~ ~, 2~ and pre~erably about 0,13~ o~ the ~econd con~ti~uenc.

P~Me~al~74210 An anti-f~aming a~en~ i~ al~o pre~erably added to pre~ent ro~mi~ a~d con~equent tr~ppin~ o~ air in the product and re~ultant reduction in the strenyth of t~e set pro~uc~ TwO pre~erred an~ oaming agents are ~VALOID~ 513 a~ ~PW only a S~Rll a~ount of ~uch agent need be p~ovi~ea an~ chis may be less than ~,5~ an~ conveniently between O,1% and 0,3~ of the cecond eonstituent. The amount o~ anti-roa~i n~ agent ean be adju~ted and in particular suppl~m~nted on inapectio~ during th~ mixture of the product.

The co~rin~ material i~ preferably provided with a thickener ~hich preferably fonm~ thixotropic ~i~cosity build zAInd help~ tc~ vt~nt ~ag . Pref erably thi~
provided in the second c~n~tituent. A preferred thic~e~er is ATTAG~0 50 It ls preferably added as a 15~ aqueou~ ~uspension T~i5 ~u~pe~io~ ~olu~io~ may comp~ise between 2~ ana 4~ an~ pre~erably about 2,7~ or the second constituent.

The seeond constituent ~ay further co~ri~e a relaA
ti~ely 3m~ mount of water con~3tituting conveniently betwee~ 2~ and 10~, m~re cGnve.~iently bet~een 4,~
and 6~ and pre~erably about 5,4~ o~ the mass of the second constituent. Alternatively, as menti~ed ab~ve, the ~econd constituent may be a dry material fonmed prefera~ly ~y drying the e~ ion as well as any other liquid cont~;ning m~te~ials an~l ~hen ~len~ling this ~r~e~l proauct wi~h any rurcher solid ma~erial~.

P/Medal / 7~s2 10 According to another aspect of the invention there is provided the ~econd con~tituent of the ~lrfa~e covering material set out above. According to a rurther a~pect o~ the in~ention there i~ provided the ~eme~tl~ious co~s~ituent o~ ~he ~urface covering mate~ial ~e~ o~ a~ove.

.

Accor~ing to yet another aE;pec!t Of the invention there i8 provided;~ method of reinforcing a rocl~ surface in a ~ine comprioing applying a layer of the above naterial to the said surface and permitting it to set.

Examples of the ~urface ~overing material will now be de~cribed by way of example.

~x~qPr.~: T

A cur~ace covering material comprices a ~irst cem-~n~itious constituent and a s~cond liquid constituent.

A 1000 kg ~ix of the ~olid con~tituent comprises ;-P/Medal/74210 ~C~ t;Q~ 2 ;~ kg High Alumina cement 230, o 23, o OPC 470,00 47,0 Anhydri~ce Gyp~um ( anhydrous Calcium ~ul~hate) 292, 0 29, 2 Finely Ground Soda A~;h .P./V.S P 3,0 0,~
S~ditlm Fl~loride 95~ light tech-nical gr~de 3, 0 0, 3 ~ithium carbonate (99~ pure)1, 0 0,1 Na~rasol~ 250 H.R. 1, 0 ~,1 1000 100, 0 We have found that 100 gm of this cementitiou~
m~xture will absorb at lea~t 500 gm ~ater. It is there~ore highly wa~er abEiorbent.

The li~auid con~ituen~ compri~e~:-P~Medal/~4210 ~es~
Airflex 300 - Emulsion binder67,5~
dibutyl phth~late plasticizer 7,81 ~ntimo~y trioxide ~l~m~ retardant5,38 Cereclor 70~ rlame recardant10,77 15~ a~ueous s~o~-ution of Attagel anti-sag ag~nt 2,69 ~ccicide bac~ericide 0,13 Anti-~oam 0,26 Water 5~39 100, 00 The comp~nent~ of the second constituent ar~ mixed togecher ~n a high ~peed mixer ~ntil the flame retardanc~ are dl~persed, i. e . for betw~en ten to twe~ty mlnu~es ac amb~ent temperature.

Ihe cementitious ana liquid constl~uent~ are n~w mi~ed together at ambient te~perature in a nopper o~ a ~ecial ~prayer in a ratio o~ tnree par~ liqu~d con~tituent to o~e part cementitiou~ con6tituent The mixture i8 ~tirred continually until it l~ ufied. ~he mixture will ~et within about thirty ~inutes and there~ore should be used within about twenty minute~ 0~
~i xi ng . The mlxture is ~prayed on to the rock surf ace to provide a layer o~ not les~ than 2,0 mm thick. The P/Medal~7~210 - - CA 0224ll67 l998-06-l9 ~praying rate of the mixture is between two and three hu~dred litre~ per hour.

We have ~ound that the cement constituent ab~orbs the water in the second constituent so that the ~ur~ace layer wlll dry ~o a dry film even in condicion~ Or loo~
hlnn~ y ,QO that lt, ~he ~llrrace layer, will ~u~e ~u~ficiexltly to be ~elf-~uppo~i~g within fif~een ~n~nutes and ~o be a~le tO gi~re initial ~upport ~or th~
rocl~ within two to three hour~. When fully cured, which will n~rmally take abo~t twenty eight day6, the layer will have a uni-axial tensil~ ctrength o~ ~ot le~~
than 1,5 ~nega-pascal~. The layer i8 al80 adequately flexible having an elongation o~ between fift~ and ~ixt~
per cent. These characteri~tic~ enable the layer to fO~II a conf;n~m~nt for the rock to control the di~i~te-~ration of the rock ~urface and to improve stability o~
the rock mas~. Thi~ i~ becau~e che ~lexible layer w~ll assis~ in disslpaci~g e~ergy relea~e, will a~ist in controlling ~he rock de~ormation and ~ill keep the key ~locks in place thereby a~QiQting in reducing rock falls and furth~r will as~ict in holding the rock coherently even when there i6 a high rate of en~rgy release. Of courae thia atrength i~ limited and under extremely high force~ the layer will ~ail. It, the cured layer, ~ill ha~e sdcquat~ adhe~ion to most rock ~ubstrates found in the mine~.

PJMedal/74~10 The ~praying machinery and the hopper can ~e cleaned ~ith water and the waste water can run aw~y a~d join other water in the mine~. It i~ not necessary to provide toxic liquid for the cle~ning o~ the par~. The conBtituent~ for producing the ~u~ace covering layer and the mechanical eguip~ent for this purpo~e are relatively i n~Y~rn~ ive.

R~,MPT ,R T I

Th~ constituents are ~ormed a~ in RY~mple ~. A
~pray nozzle ~itted with a mixing dQ~ice on itB inlet ia u~ed. The mixing de~ice comprises a static ~piral mlxer CompriBing spiral segment~ ~rrsnged so tha~ each con~ecuti~e segmen~ rotate~ the mix pa~ing through tube in a direction opposite to that o~ the previou~ ~e~ment.

The constituents are f~d ~epara~ely tO the no~zle and the mixing de~lce blend~ the CWo con~ticue~t p~lor tO entering the spray nozzle which now applies the blen~l to the surface o~ the rock to bQ coat~d.

BXAMP~E III

The cementitiou-~ constituent i~ a~ de~cribed in ~xample I. A blend o~ liquid polymer~ and plasticizers are dried in an air drier to remove the ~ater. Thi forms a dry powder. The dry powder is then blended with the rem~ solids of the ~econd con~ltuent.

P/M~dal/74210 The cem~neitiou and 6econd con~ituents are then ~lended with one anoth~r. The hydrating water ix now added to the m~xture in the mine at the ~ite ~here it i~ requirQd to coat the rock. ~he product i~ stirred and then applied as ~entioned i~ RY~mr1 e I.

EXAMPLE IV

The dry mixture Or ~he first and second con~tituent~ is preparea a~ descri~ed in Bxample III.
The dry ~i~cu~e and water a~e applied under preosure to ~he ~ock ~urfa~e ~y mean~ of a "Gunite" noz~le. ~hi~
nozzle i~ ~itted in~ide with a perforated nanifold through which water i~ introduced under pressure to be mixed with th~ colid material that i~ pneumatically conveyed to the nozzle. Ihe mixture i~ a~plied to the rock surface.

~ he rock covering materials applied in accordance with Examples I~. III a~ Iv have the same ad~antag~s as th~e as descr~ed in ~xample I.

The invention is not limited to the preci8e detail~
set ~orth in the example~. The constitue~ts of the material may vary or be altered. For example hydrophil-lic fibres or glas~ fibre~ o~ between 6ay 0,5 and 12 ~n may be add~d to the material to increa~e the tensile ~trength of the cured layer e~pecially in the post failure stage. Alternati~e fla~e retardants, ~acteri-P~Medal/74210 cide~ and anti-foaming agents may be u~ed. Fhrther ad~icional water may be added to lower the ~i~co~ity of the seco~ constituent.

I~ de~i~e~ a foamin~ age~t may be added to the cecond constituen~ (a~ the anti-foaminy agent L~--W~ed) ~o that a ~o~mea layer of ~he material mdy be 8~rayed on to the cured or partially cured layer. ~hi~ ~oamed layer may be about thirty five to seve~ty ~i~e and ~referably fifty millimetre~ thick. The ~oa~ed layer 1~ will p~ovide t~enmal insulation for the rock walls and will inhibi~ heat from the r~ck enteri~g into the worki~y ~paces of the mine.

P~Medal~7~210

Claims

1. A surface covering material comprising a mixture of a cementitious constituent and a second constituent characterised in that the cementitious constituent comprises a highly water absorbent cement blend and the second constituent incorporates a water based polymer emulsion.

2. A material as claimed in claim 1 characterised in that the cementitious constituent will absorb it own mass of water.

3. A material as claimed in claim 2 characterised in that the cementitious constituent will absorb about five times its own mass of water.

4. A material as claimed in claim 1, 2 or 3 characterised in that the cementitious mixture comprises high-alumina cement, ordinary portland cement and anhydrite gypsum (anhydrous calcium sulphate) forming the bulk of the mixture together with soda ash, lithium carbonate and sodium fluoride.

5. A material as claimed in claim 4 characterised in that it further comprises Natrasol~250HR or Cellosize~QP
52000.

6. A material as claimed in claim 4 or 5 characterised in that the high alumina cement, ordinary portland cement and anhydrite gypsum constitute 99% or more of the cementitious constituent.

7. A material as claimed in claim 4, 5 or 6 characterised in that the ordinary portland cement comprises between 40% and 52% and preferably about 47% of the cementitious constituent.

8. A material as claimed in claim 4, 5, 6 or 7 characterised in that the high alumina cement may comprise between 18% and 28% and preferably about 23% of the cementitious constituent.

9. A material as claimed in any one of claims 4 to 8 characterised in that the anhydrite gypsum comprises between 27% and 31% and preferably about 29% of the cementitious constituent.

10. A material as claimed in any one of claims 4 to 9 characterised in that the soda ash comprises between 0,25% and 0,35% and preferably about 0,3% of the cementitious constituent.

11. A material as claimed in any one of claims 4 to 10 characterised in that the sodium fluoride comprises between 0,25% and 0,35% and preferably about 0,3% of the cementitious constituent.

12. A material as claimed in any one of claims 4 to 11 characterised in that the lithium bicarbonate comprises between 0,09% and 0,15% and preferably about 0,1% of the cementitious constituent.

13. A material as claimed in any one of claims 4 to 12 characterised in that the Natrasol comprises between 0,09% and 0,15% and preferably about 0,1% of the cementitious constituent.

14. A material as claimed in any one of the preceding claims characterised in that the second constituent further comprises a fire retardant.

15. A material as claimed in claim 14 characterised in that the fire retardant comprises antimony trioxide and chlorinated paraffin.

16. A material as claimed in any one of the preceding claims characterised in that the emulsion is an acrylic emulsion binder.

17. A material as claimed in claim 16 characterised in that the emulsion is a vinyl acetate ethylene copolymer.

18. A material as claimed in claim 17 characterised in that the vinyl acetate ethylene copolymer constitutes between 60% and 75%, preferably between 65% and 70% and most preferably about 67, 5% of the second constituent.

19. A material as claimed in claim 18 characterised in that a plasticizer is included.

20. A material as claimed in claim 19 characterised in that the plasticizer is dibutyl phthalate.

21. A material as claimed in claim 19 or 20 characterised in that the plasticizer constitutes between 5% and 10%, preferably between 7% and 8% and most preferably about 7,8% of the second constituent.

22. A material as claimed in any one of the preceding claims characterised in that a bactericide for preventing growth of bacteria and enzymes is provided.

23. A material as claimed in any one of the preceding claims characterised in that an anti-foaming agent is added to the second constituent.

24. A material as claimed in claim 23 characterised in that the foaming agent comprises less than 0,5% and conveniently between 0,1% and 0,3% of the second constituent.

25. A material as claimed in any one of the preceding claims characterised in that the covering material is provided with a thickener which preferably forms thixotropic viscosity build and helps to prevent sag.

26. A material as claimed in claim 25 characterised in that the thickener is provided in the second constituent.

27. A material as claimed in claim 26 characterised in that the thickener is added as a 15% aqueous solution which preferably comprises between 2% and 4% and preferably about 2, 7% of the second constituent.

28. A material as claimed in any one of the preceding claims characterised in that the first and second constituents are mixed in the proportions of one to three.

29. For use in a covering material as claimed in claim 1, a cementitious constituent characterised in that it comprises high-alumina cement, ordinary portland cement and anhydrite gypsum (anhydrous calcium sulphate) together with soda ash, lithium carbonate and sodium fluoride.

30. A cementitious constituent as claimed in claim 29 characterised in that it further comprises Natrasol~250HR or Cellosize~QP 52000.

31. For use in a covering material as claimed in claim 1, a second constituent characterised in that it comprises a liquid constituent.

32. For use in a covering material as claimed in claim 1, a second constituent characterised in that it comprises a dry solid constituent.

33. A method of reinforcing a rock surface in a mine characterised in that a layer of the surface covering material as claimed in any one of claims 1 to 28 is applied to the said surface and permitted to cure.

34. A method as claimed in claim 33 characterised in that the surface covering material is applied to the said surface by being sprayed on to the surface.

35. A method as claimed in claim 34 when dependant upon claim 32 characterised in that the dry constituent and water are sprayed on to the said surface by a "Gunite"
process.