PowerPoint Presentation · About NAMWOLL - 2 2019/06/06 3 The Mining process Mine Pit Crushing and...

2019/06/06

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About NAMWOLL - 1

• The Team

➢ Bruce Stride – Managing Director;

➢ Riana Mulder – Personal Assistant to MD;

➢ Cheryl Willemse – Accountant;

➢ Gerrit Visser – Mine Subordinate manager;

➢ Fabian Adams – Process systems supervisor; and

➢ Charl Willemse – Mechanic and Safety Rep.

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➢ Dry separation system;

➢ Life of mine 1 million tonnes drilled reserves. Estimated total

reserves 3 million tonnes;

➢ The mine is 18km out of Garies, and the fine product

processing plant is in Garies and produces 5 different sizes

of Wollastonite product.

About NAMWOLL - 2

2019/06/06

3The Mining process

Mine Pit Crushing and Screening Plant Truck Loading Bin

Wollastonite Processing Plant

➢ Wollastonite is named after the English chemist and mineralogist William Hyde Wollaston (1766–1828) and is a calcium inosilicate mineral (CaSiOɜ) that may contain

small amounts of iron, magnesium, and manganese substituting for calcium.

➢ It is usually white but also found in a pearly grey colour.

➢ It forms when impure limestone or dolostone is subjected to high temperature and pressure sometimes in the presence of silica-bearing fluids as in skarns or

contact metamorphic rocks.

➢ Associated minerals include garnets, vesuvianite, diopside, tremolite, epidote, plagioclase feldspar, pyroxene and calcite.

➢ Some of the properties that make wollastonite so useful are its high brightness and whiteness, low moisture and oil absorption, low volatility and enhancement of flexural

and compaction strcngh. Wollastonite is used primarily in ceramics, friction products (brakes and clutches), metal making, paint filler and plastics.

➢ Despite its chemical similarity to the compositional spectrum of the pyroxene group of minerals where magnesium and iron substitution for calcium ends

with diopside and hedenbergite respectively it is structurally very different, with a third SiO4 tetrahedron in the linked chain (as opposed to two in the pyroxenes).

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4• What is Wollastonite?

Wollastonite - 1

Wollastonite - 2• What is Wollastonite?

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Wollastonite in nature. Fine Crystals. Wollastonite in nature. Cluster of crystals

with carnet and dioptase inclusions.Wollastonite cluster.

Wollastonite cluster. Wollastonite needles under a microscope. Wollastonite end product.

Wollastonite - 3

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Metallurgy application Metallurgy/ceramic

application

Construction/coating/

painting/friction application Plastic/painting/coating

application

Picture

Microscope

image

• What is Wollastonite? - continued

Wollastonite – 5

• Uses

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➢Wollastonite has industrial importance worldwide.

➢ It is used in many industries, mostly by tile factories which have incorporated it into the manufacturing of ceramic to improve many aspects,

and this is due to its fluxing properties, freedom from volatile constituents, whiteness, and acicular particle shape.

➢ In ceramics, wollastonite decreases shrinkage and gas evolution during firing, increases green and fired strength, maintains brightness

during firing, permits fast firing, and reduces crazing, cracking and glaze defects.

➢ In metallurgical applications, wollastonite serves as a flux for welding, a source for calcium oxide, a slag conditioner, and to protect the

surface of molten metal during the continuous casting of steel.

➢As an additive in paint, it improves the durability of the paint film, acts as a pH buffer, improves its resistance to weathering, reduces gloss,

reduces pigment consumption and acts as a flatting and suspending agent.

Wollastonite – 6• Uses - continued

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➢ In plastics, wollastonite improves tensile and flexural strength, reduces resin consumption, and improves thermal and dimensional stability at

elevated temperatures.

➢Surface treatments are used to improve the adhesion between the wollastonite and the polymers to which it is added.

➢As a substitute for asbestos in floor tiles, friction products, insulating board and panels, paint, plastics, and roofing products, wollastonite is

resistant to chemical attack, inert, stable at high temperatures and improves flexural and tensile strength.

➢ In some industries, it is used in different percentages of impurities, such as its use as a fabricator of mineral wool insulation or as an ornamental

building material.

➢Plastics and rubber applications were estimated to account for 25% to 35% of U.S. sales in 2009, followed by ceramics with 20% to 25%; paint,

10% to 15%; metallurgical applications, 10% to 15%; friction products, 10% to 15%; and miscellaneous, 10% to 15%. Ceramic applications

probably account for 30% to 40% of wollastonite sales worldwide, followed by polymers (plastics and rubber) with 30% to 35% of sales, and

paint with 10% to 15% of sales. The remaining sales were for construction, friction products, and metallurgical applications. The price of raw

wollastonite varied in 2008 between US$80 and US$500 per tonne depending on the country and size and shape of the powder particles.

Wollastonite - 7• Uses continued

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Application Field Specific Application Wollastonite Function

Ceramic Industry Various ceramics, glass and moulds • Reduce the burnt temperature;

• Shorten the burnt period;

• Reduce the firing shrinkage. Improve deflection and cracking;

• Optimisation of porcelain glaze glossiness and sleek flatness;

• Improve the mechanical strength abrasion and scratch resistance.

Metallurgical Industry Protection slag for heat insulation material

and cast steel

• Ensuring composition stabilized and uniformity of slag;

• Better adapted to steel types;

• Reducing the possibility of steel surface embrittlement and longitudinal cracking;

• Strong absorbsion and dissolving capacity of impurity;

• The viscosity varies little along with temperature in the process of continues casting;

• Lubrication and protection without effecting the crystallisation and cooling of casting billet;

• Reduces fluoride pollution and equipment corrosion.

Building Materials Industry Calcium silicon plate, cement fibrolite plate,

fire insulation board

• Being innocuous, flavourless and non-radioactive it reduces pollution and production costs;

• Increases shock resistance, flexural strength and abrasive resistance;

• Good corrosion resistance, sound and heat insulation and fireproofing.

Rubber and Plastics Industry Styrene butadiene rubber • Increases wear and scratch resistance;

• Increases shock strength and enables products to enjoy high electrical and thermal insulation;

• Increases thermal and dimensional stability;

• Increases surface finish quality;

• Good reinforcing function;

• Increases the tensile strength, tearing strength, elongation at break, wear resistance;

• Improves moistening and dispersion.

Coating and Paint Industry Anticorrosive paint, thermal insulation

coating, construction paint

• Wear, corrosion and ultra violet resistance;

• Make paint show higher surface gloss and better water proof corrosion and buffers ph-value;

• Improve thermal stability;

• Reduce consumption of cementing substance.

Our Product - 1 (Specifications of the various Wollastonite sizes)

The Company produces 4 different sizes of Wollastonite Product:

1. -100 MICRON

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CHEMICAL ANALYSIS %

Calcium CaO 46.5 – 47.5

Magnesium MgO 0.16 – 0.3

Silica SiO2 48 – 49.5

Sodium Na2O Trace

Potassium K2O3 0.08 – 0.88

Phosphorus P2O5 0.01 – 0.05

Titanium TiO2 0.03 – 0.04

Iron Fe2O3 0.5 – 0.55

Aluminium Al2O3 0.8 – 0.9

L.O.I 2.6 – 2.7

PHYSICAL PROPERTIES %

pH 9.8 - 10

Moisture (110 dec C at 24 hrs) 0.5


Oil Absorption 23-25g/100g

Refractive Index 1.63

Hardness moh 4.5 – 5.0

Whiteness SABS 137 Dry 80 – 85

Specific gravity 2.8 – 2.9

Melting Point 1540c

Appearance White

Shape Acicular

PARTICULAR SIZE DISTRIBUTION MICRON

Retained on cumulative

250 micron 0.00

150 micron 0.09%

75 micron 10 – 12%

45 micron 22 – 25%

Our Product – 2 (Specifications of the various Wollastonite sizes)

2. -150 Micron

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CHEMICAL ANALYSIS %

Calcium CaO 46.5 – 47.5


Silica SiO2 48 – 49.5

Sodium Na2O Trace




Iron Fe2O3 0.5 – 0.55


L.O.I 2.6 – 2.7


pH 9.8 - 10








Melting Point 1540c

Appearance White

Shape Acicular



250 micron 0.05%

150 micron 6-8%

100 micron 15-17%

75 micron 39-44%

45 micron 72-74%


3. -1200 Micron (<1.2mm)

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CHEMICAL ANALYSIS %

Calcium CaO 44 - 45.5


Silica SiO2 49 - 51

Sodium Na2O Trace




Iron Fe2O3 0.4 – 0.5


L.O.I 3.5 – 3.7


pH 9.8 - 10







Melting Point 1540c

Appearance Wollastonite/Garnet/Calcite

Shape Acicular/round mixed


2000 micron Trace

1600 micron 4.4%

1000 micron 30.90%

710 micron 44.60%

500 micron 60.10%

425 micron 66.60%

250 micron 83.80%

150 micron 92.60%


4. -25 Micron

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CHEMICAL ANALYSIS %

Calcium CaO 44 - 45.5


Silica SiO2 49 - 51

Sodium Na2O Trace




Iron Fe2O3 0.4 – 0.5


L.O.I 3.5 – 3.7


pH 9.8 - 10








Melting Point 1540c

Appearance White

Shape Acicular



75 micron 0.00%

45 micron 0.00%

25 micron 0.5%

10 micron 28 – 30%

Wollastonite vs Artificial Fibres

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Type of Fibre Diameter

[pm]

Specific Gravity

[g/cm²]

Tensile Strength

[Mpa]

Elastic Modulus

[Gpa]

Ultimate Elongation

[%]

Metallic

Steel

Glass

E Glass

AR Glass

5 – 1000

-

8 – 15

8 - 20

7.85

-

2 – 54

2.70

200 – 2600

-

2000 – 4000

1500 - 3700

195 – 210

-

72

80

0.5 – 5

-

3.0 – 4.8

2.5 – 3.6

Synthetic

Acrylic (Pan)

Aramid (e.g Kevlar)

Carbon (low modulus)

Carbon (hight modulus)

Nylon (polyamide)

Polyester (e.g. PET)

Polyethylene (PE)

Polyethylene (HHPE)

Polypropylene (PP)

Polyvinyl acetate (PVA)

5 – 7

10 – 12

7 – 18

7 – 18

20 – 25

10 – 8

25 – 1000

-

10 – 200

3 - 8

1.18

1.4 – 1.5

1.6 – 1.7

1.7 – 1.9

1.16

1.34 – 1.39

0.96

0.97

0.90 – 0.91

1.2 – 2.5

200 -1000

2000 – 3500

800 – 1100

1500 – 4000

965

280 – 1200

80 – 600

1000 – 4000

310 – 760

800 - 3600

14.6 – 19.6

62 – 130

38 – 43

200 – 800

5.17

10 – 18

5.0

80 – 150

3.5 – 4.9

20 - 80

7.5 – 50

20 – 4.6

2.1 -2.5

1.3 – 1.8

20

10 – 50

12 – 100

29 – 4.1

6 – 15

4 - 12

Natural – Organic

Cellulose (wood)

Coconut

Bamboo

Jute

15 – 125

100 – 400

50 – 400

100 - 200

1.50

1.12 – 1.15

1.50

1.02 – 1.04

300 – 2000

120 – 200

200 – 440

250 – 350

10 – 50

19 – 25

33 – 40

25 – 32

20

10 – 25

-

1.5 – 1.9

Natural – Inorganic

Asbestos

Wollastonite

0.02 – 25

25 – 40

2.55

2.87 – 3.09

200 – 1800

2700 4100

164

303 - 530

2 – 3

-

Physical properties of selected fibres:


Glass fibres

• Glass-fibre-reinforced cementitious composites (GFRC) have been developed primarily for the production

of thin sheet components. (Mainly as exterior building-façade panels ACI 544 IR 2002), with a paste or

mortar matrix and approx. 5% fibre content see Bentur and Mindess (2006). Conventional glass fibres have

been found to lose strength very quickly due to the high alkalinity of the cement based matrix. From a

structural duration point of view, the most interesting type of glass fibre is the one produce from alkali

resistant glass, AR-GFRC. The chemical composition of this type of glass differs from conventional

borosilicate glass fibres (E-glass) and soda-lime-silica glass fibres (A-glass), mainly by the inclusion of the

highly chemically resistive, ceramic material zirconium.

• Most commercially manufactured GFRC composites will experience reduction in tensile and flexural

strengths and ductility if exposed to an outdoor environment. The strength of fully-aged GFRC

composites will decrease to about 40% of the initial strength and the strain capacity will decrease to

about 20% of initial capacity prior to aging. Furthermore exposure to natural moisture and temperature

cycles will result in cyclical volumetric dimensional changes. The two major ageing mechanisms are: 1)

chemical attack and 2) growth of hydration products between the glass filaments. (Bentur and Mindess

2006). Even though commercial AR-GFRC does have higher resistance than E-glass to a chemical attack in

the form of an alkaline environment, it is not completely immune and strength reductions have been

observed, see Bentur and Mindess. Regarding the second mechanism the hydration product primarily

responsible for composite embrittlement i.e. loss of toughness is calcium hydroxide, which fills the voids

between the glass filaments. Addition of polymer solids at a minimum of 5% by volume of total mix, may

party inhibit the embrittlement of the glass fibre. ACI544 IR (2002).

Polyvinyl alcohol fibres (PVA)

• High strength PVA fibres have been developed mainly for asbestos replacement. PVA fibres can have a

modulus of elasticity on the same order of magnitude as that of a cementitious matrix. Due to the strong

chemical bonding though, they tend to rupture instead of being pulled out from the concrete matrix.

Bentur and Mindess (2006). Zheng and Feldman mention that autoclaving has a considerably negative

effect on both tensile strength and elastic modulus of these fibres.

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Natural fibres

• Much of the research on the use of natural fibres in cementitious composite has been motivated by the

need of a low cost fibre and the availability of such fibres which are high in strength. Wood fibres derived

from bamboo or sugar cane have been used for the production of low cost cementitious composites. Other

natural fibres are e.g. jute, sisal and coconut fibres.

• Natural fibres are sensitive to changes in moisture content and may suffer deterioration or petrification

due to the alkaline environment and the continuous cement hydration. In e.g. cellulose pulp fibres a

moisture increase is associated with reductions Young’s modulus and strength, but an increase in

toughness. This effect would most likely be true for other natural fibres as well. Bentur and Mindess (2006)

• Combination of micro and macro fibres, so called hybrid fibre reinforcement, may not lead to a hardening

behavior, although from a durability point of view it may be an important concept. The micro fibres

effectively counteract the line cracks from shrinkage and drying and also prevent micro cracks from

widening. Macro fibres on the other hand arrest the crack growth at localized cracking, thus producing a

material with loss moisture permeability.

• Although steel fibres, up to now, have been subjected to more research than any other type of fibre and

have been shown to provide cementitious composites with enhanced tensile behavior, they do have some

drawbacks. If for instance aesthetics is important a negative attribute is that with time rust colored

patches may develop. Perhaps more serious is that due to daily use and environmental exposure the fibres

may protrude from the surface as this wears down. One interesting variant of the steel fibre is the so

called “engineered fibre”. This twisted fibre with square or triangular cross section has the characteristic

of exhibiting more resistance the more it is pulled out Naaman (2003).

• Development of fibres made of other materials with properties comparable to those of steel fibres is a

continuous process. Synthetic materials are lighter than steel and in general they have tensile strengths

equal to or higher than that of the steel fibre e.g. polypropylene with tensile ranging from 500-1200 MPa.

One drawback for most synthetic fibes is the relatively low elastic modulus (expect perhaps for PAN carbon

fibres) which may lead to larger elongations over time than has been observed in steel fibres. Thus, crack

width reductions in the range of those achievable with SFRC (cracks due to loading0 may be difficult with

some of the currently available synthetic fibres, although PVA fibres used in ECC is an exception. In

addition even for high modulus synthetic fibres, there is a tendency for creep, see Peijs et al (2000).

Another drawback is the relatively short time that research has been focused on e.g. synthetic fibre for

structural application. This means that it is not fully known how some of these fibres will behave over

time, especially in the alkaline environment of concrete. It should also be mentioned that fibres made of

synthetic materials most probably will exhibit poorer fire resistance than steel fibres. This must be

considered during the design process to ensure proper load bearing capacity corresponding to given

requirements. In combination with more heat resistive load bearing materials though, synthetic fibre (e.g.

polypropylene) will melt and are believed to provide an escape route for the steam in the concrete, thus

preventing fire spalling.

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Influences of wollastonite on the chemical properties of concrete

• Studies were made on cement concrete and cement-fly ash concrete mixes incorporating wollastonite as partial substitute of

cementitious material and sand respectively.

• Improvements in compressive (28-35%) and flexural strength (36-42%) at 28 and 56 days respectively were observed by incorporation

of wollastonite (10%) in concrete mixes.

• By incorporation of wollastonite, reduction in water absorption, drying-shrinkage and abrasion loss of concrete, and enhancement in

durability against alternate freezing-thawing and sulphate attack were observed.

• Because of high concrete strength and abrasion resistance, a better utilization of concrete cross section is possible.

• Alternatively, thickness of pavement slab can be reduced by incorporation of wollastonite micro-fibres in concrete mixes.

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Contact details

• Riana Mulder at the Mine – 027 652 1703

• Bruce Stride – 0825624421

• Agent in Johannesburg – Garry Burgess – 082 565 4155

• Elaine Beylefeld (CEO of Incubex, holding company of Namwoll) – 083 297 0735

• Mine address -

• Registered address – Knightsbridge Manor, Block H, Ground Floor, #001A, 33 Sloane Street,

Bryanston, 2191

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