Basic Ideas :
1. Minimize the Waste from Production Line of Fiber Cement Process.
2. Minimize the Waste from Back Water / Decantation /Waste Water Tank
3. Basic Fundamental of Cement Reactivity to Water and Filler / Aggregrate.
Concepts :
1. Up grade from old process methode to new once ( countinues methode ).
2. Minimize to usage of utility - Electricity.
3. Minimize the raw material damages in the line process - low yeild
Action :
Still in my Project ..........( hope will be realised ....... )
Application :
On new machine / new project
About Me
- Frangky Welly W
- Project, Plant Engineering and Process Consultant to Fiber Cement or Calcium Silicate Board and both Light Concrete AAC and NAAC-CLC
Sunday, November 28, 2010
Sunday, November 21, 2010
MAK- Fiber is 3D-reinforcement solution
What is MAK-Fiber ?
MAK-Fiber is an Organic Synthetic Fiber was applied to Fiber Cement and Board Manufacture which binds with aggregate or filler in mixture components.
MAK-Fiber is creating a highly cohesive 3-dimentional network with enhanced mechanical performance and durability.
Why used MAK-Fiber ?
The use of MAK-Fiber in Fiber Cement or Board can or able to replace Asbestos fiber.
However, it has been clarified that asbestos remarkably injures human health, for example, it causes cancer of the lung and the use of asbestos has been therefore becoming to be legally restricted or prohibited in many countries.
Benefits with MAK-Fiber
Strength without brittleness
The strongly fiber – bound 3D structure and cohesive action of MAK-Fiber allow
+ Cementitious matrix tensile strength due to high fiber elastic modulus.
+ Crack and micro-crack preventive during curing time .
+ Effective bridge mechanism provided the use of fiber with the optimal aspect
ratio ( a very wide range of length-diameter ratios are available)
+ Chemical and mechanical adherence to the cementitious matrix
Thermal and Chemical resistance
MAK-Fiber recognized high resistance to most chemical and physical agents provides a durable reinforcement solution
+ Long term stability
+ Resistance to outdoor exposure ( no rust or UV alterations)
+ Resistance to biological agent ( growth of mildew, fungi,etc)
+ Resistance to cement alkalinity, acids and organic solvents
+ Thermal Resistance
Applications of MAK-Fiber
- Fiber Cement and Board Sheet Manufacture
To replace an asbestos fiber and substitution to cellulose fiber.
Can be applied to both Air Cure and Autoclave Process.
Improves to Strength, Flexibility and Bending of the Fiber Cement and Board
product.
Anti-uv and high temperature , cold resistance ability.
Recommended usage conditions of MAK-Fiber
Please contact to Frangky
MAK-Fiber is an Organic Synthetic Fiber was applied to Fiber Cement and Board Manufacture which binds with aggregate or filler in mixture components.
MAK-Fiber is creating a highly cohesive 3-dimentional network with enhanced mechanical performance and durability.
Why used MAK-Fiber ?
The use of MAK-Fiber in Fiber Cement or Board can or able to replace Asbestos fiber.
However, it has been clarified that asbestos remarkably injures human health, for example, it causes cancer of the lung and the use of asbestos has been therefore becoming to be legally restricted or prohibited in many countries.
Benefits with MAK-Fiber
Strength without brittleness
The strongly fiber – bound 3D structure and cohesive action of MAK-Fiber allow
+ Cementitious matrix tensile strength due to high fiber elastic modulus.
+ Crack and micro-crack preventive during curing time .
+ Effective bridge mechanism provided the use of fiber with the optimal aspect
ratio ( a very wide range of length-diameter ratios are available)
+ Chemical and mechanical adherence to the cementitious matrix
Thermal and Chemical resistance
MAK-Fiber recognized high resistance to most chemical and physical agents provides a durable reinforcement solution
+ Long term stability
+ Resistance to outdoor exposure ( no rust or UV alterations)
+ Resistance to biological agent ( growth of mildew, fungi,etc)
+ Resistance to cement alkalinity, acids and organic solvents
+ Thermal Resistance
Applications of MAK-Fiber
- Fiber Cement and Board Sheet Manufacture
To replace an asbestos fiber and substitution to cellulose fiber.
Can be applied to both Air Cure and Autoclave Process.
Improves to Strength, Flexibility and Bending of the Fiber Cement and Board
product.
Anti-uv and high temperature , cold resistance ability.
Recommended usage conditions of MAK-Fiber
Please contact to Frangky
How To Elimination or Protected Cellulose From Alkalinity of the Cement ?
Key words :
Cellulose is not permanently resistant to the alkalinity of the cement.
Sizing to the Cellulose Fiber.
Background :
In the Papermaking Process ( in the first started from china as early as AD 768 ) , why to sized the cellulose fiber ?
- To improve the water resistance of the paper surface
- To improve the Surface Strength
- To Improve printability of paper
Basic Fundamental:
Cellulose a complex carbohydrate, (C6H10O5)n, that is composed of glucose units, forms the main constituent of the cell wall in most plants, and is important in the manufacture of numerous products, such as paper, textiles, etc.
Cellulose is Hydrophilic (water-loving)
Hydrophilic literally translates as "water loving" or "water friend." Hydrophilic substances are attracted to, and dissolve well within, water.Hydrophilic is typically used to describe a property of a molecule, and refers to the likelihood of its bonding with the hydrogen molecule in water. A hydrophilic molecule is not just soluble in water but also in other polar solvents; it will dissolve less readily in oils and other hydrophobic solvents. Hydrophilic molecules are charge-polarized so that one end is positive and the other negative.A hydrophilic molecule or portion of a molecule is one that is typically charge-polarized and capable of hydrogen bonding, enabling it to dissolve more readily in water than in oil or other hydrophobic solvents. Hydrophilic and hydrophobic molecules are also known as polar molecules and nonpolar molecules, respectively. Some hydrophilic substances do not dissolve. This type of mixture is called a colloid. Soap, which is amphipathic, has a hydrophilic head and a hydrophobic tail, allowing it to dissolve in both waters and oils.
An approximate rule of thumb for hydrophilicity of organic compounds is that solubility of a molecule in water is more than 1 mass % if there is at least one neutral hydrophile group per 5 carbons, or at least one electrically charged hydrophile group per 7 carbons
History
As the process of sizing had and has the intent of making the paper suitable for printing, it would seem slightly ironic that some processes of sizing would make printing paper a problem for the continued existence of that paper and those who would preserve them. Sizing processes started early on in the papermaking processes, with historians citing that items, such as starch, were early sizing agents used on paper. Dade Hunter in papermaking through Eighteen Centuries corroborates this by writing, “The Chinese used starch as a size for paper as early as A.D. 768 and its use continued until the fourteenth century when animal glue was substituted.” The early modern paper mills Europe, which produced paper for printing and other uses, the sizing agent of choice was gelatin, as Susan Swartzburg writes in Preserving Library Materials, “Various substances have been used for sizing through the ages, from gypsum to animal gelatin.” Hunter describes the process of sizing in these paper mills in the following:The drying completed, the old papermakers dipped their paper into an animal size that had been made from the parings of hides, which they procured from the parchment-makers. It was necessary to size that paper so that it would be impervious to ink, but sizing was more needed in writing than in printing papers. Many books of the fifteenth century were printed upon paper that had not been sized, this extra treatment not being essential for a type impression. The sizing was accomplished by a worker holding a number of sheets by the aid of two wooden sticks, and dipping the paper into the warm gelatinous liquid. The sheets were then pressed to extract the superfluous gelatine. This crude method of sizing the paper was extremely wasteful as many sheets were torn and bruised beyond use. The sizing room of the early paper mills, was, for this reason, known as the ‘slaughter-house.’With the advent of the mass production of paper, the type of size used for paper production also changed. As Swartzburg writes, “By 1850 rosin size had come into use. Unfortunately, it produces a chemical action that hastens the decomposition of even the finest papers.” In the field of library preservation it is known “that acid hydrolysis of cellulose and related carbo-hydrates is one of the key factors responsible for the degradation of paper during ageing.” Some recent professional work has focused on the specific in the degradation involved in the deterioration of paper that has had a rosin sizing process, and what amount of rosin affects the deterioration process, in addition to work on developing permanent paper and sizing agents that will not eventually destroy the paper. An issue on the periphery to the preservation of paper and sizing, is washing, which is described by V. Daniels and J. Kosek as, “The removal of discolouration in water is principally effected by the dissolution of water-soluble material; this is usually done by immersing paper in water. In such a process, surface level items applied to the paper, such as size in early paper making processes as seen above, have the possibility of being removed from the paper, which might have some item specific interest in a special collections library. With later processes in paper making being more akin to “engine sizing,” as H. Hardman and E. J. Cole describe it, “Engine sizing, with is part of the manufacturing process, has the ingredients added to the furnish or stock prior to sheet formation, the concern for the removal of size is less, and as such, most literature focuses on the more pressing issue of preserving acidic papers and similar issues.
Implementation on Fiber Cement making
Cellulose Fiber Sized in Fiber Cement Process :
Chemically treating cellulose fibers to impart the fibers with hydrophobicity and/or durability, and making cellulose fiber reinforced cement composite materials using the Chemical / Additive treated cellulose fibers which the cellulose fibers are treated or sized with specialty chemicals that impart the fibers with higher hydrophobicity by partially or completely blocking the hydrophilic groups of the fibers.
This technology advantageously provides fiber cement building materials with the desirable characteristics of reduced water absorption have advantage reduced rate of water absorption, lower water migration, lower water permeability so the final products made from these materials have improved freeze-thaw resistance, reduced efflorescence, reduced dissolution and re-deposition of water-soluble matrix components in natural weathering.
Using fiber sizing almost to improve other product properties to the physical and mechanical of final product.
More information : sent to my Email
Cellulose is not permanently resistant to the alkalinity of the cement.
Sizing to the Cellulose Fiber.
Background :
In the Papermaking Process ( in the first started from china as early as AD 768 ) , why to sized the cellulose fiber ?
- To improve the water resistance of the paper surface
- To improve the Surface Strength
- To Improve printability of paper
Basic Fundamental:
Cellulose a complex carbohydrate, (C6H10O5)n, that is composed of glucose units, forms the main constituent of the cell wall in most plants, and is important in the manufacture of numerous products, such as paper, textiles, etc.
Cellulose is Hydrophilic (water-loving)
Hydrophilic literally translates as "water loving" or "water friend." Hydrophilic substances are attracted to, and dissolve well within, water.Hydrophilic is typically used to describe a property of a molecule, and refers to the likelihood of its bonding with the hydrogen molecule in water. A hydrophilic molecule is not just soluble in water but also in other polar solvents; it will dissolve less readily in oils and other hydrophobic solvents. Hydrophilic molecules are charge-polarized so that one end is positive and the other negative.A hydrophilic molecule or portion of a molecule is one that is typically charge-polarized and capable of hydrogen bonding, enabling it to dissolve more readily in water than in oil or other hydrophobic solvents. Hydrophilic and hydrophobic molecules are also known as polar molecules and nonpolar molecules, respectively. Some hydrophilic substances do not dissolve. This type of mixture is called a colloid. Soap, which is amphipathic, has a hydrophilic head and a hydrophobic tail, allowing it to dissolve in both waters and oils.
An approximate rule of thumb for hydrophilicity of organic compounds is that solubility of a molecule in water is more than 1 mass % if there is at least one neutral hydrophile group per 5 carbons, or at least one electrically charged hydrophile group per 7 carbons
History
As the process of sizing had and has the intent of making the paper suitable for printing, it would seem slightly ironic that some processes of sizing would make printing paper a problem for the continued existence of that paper and those who would preserve them. Sizing processes started early on in the papermaking processes, with historians citing that items, such as starch, were early sizing agents used on paper. Dade Hunter in papermaking through Eighteen Centuries corroborates this by writing, “The Chinese used starch as a size for paper as early as A.D. 768 and its use continued until the fourteenth century when animal glue was substituted.” The early modern paper mills Europe, which produced paper for printing and other uses, the sizing agent of choice was gelatin, as Susan Swartzburg writes in Preserving Library Materials, “Various substances have been used for sizing through the ages, from gypsum to animal gelatin.” Hunter describes the process of sizing in these paper mills in the following:The drying completed, the old papermakers dipped their paper into an animal size that had been made from the parings of hides, which they procured from the parchment-makers. It was necessary to size that paper so that it would be impervious to ink, but sizing was more needed in writing than in printing papers. Many books of the fifteenth century were printed upon paper that had not been sized, this extra treatment not being essential for a type impression. The sizing was accomplished by a worker holding a number of sheets by the aid of two wooden sticks, and dipping the paper into the warm gelatinous liquid. The sheets were then pressed to extract the superfluous gelatine. This crude method of sizing the paper was extremely wasteful as many sheets were torn and bruised beyond use. The sizing room of the early paper mills, was, for this reason, known as the ‘slaughter-house.’With the advent of the mass production of paper, the type of size used for paper production also changed. As Swartzburg writes, “By 1850 rosin size had come into use. Unfortunately, it produces a chemical action that hastens the decomposition of even the finest papers.” In the field of library preservation it is known “that acid hydrolysis of cellulose and related carbo-hydrates is one of the key factors responsible for the degradation of paper during ageing.” Some recent professional work has focused on the specific in the degradation involved in the deterioration of paper that has had a rosin sizing process, and what amount of rosin affects the deterioration process, in addition to work on developing permanent paper and sizing agents that will not eventually destroy the paper. An issue on the periphery to the preservation of paper and sizing, is washing, which is described by V. Daniels and J. Kosek as, “The removal of discolouration in water is principally effected by the dissolution of water-soluble material; this is usually done by immersing paper in water. In such a process, surface level items applied to the paper, such as size in early paper making processes as seen above, have the possibility of being removed from the paper, which might have some item specific interest in a special collections library. With later processes in paper making being more akin to “engine sizing,” as H. Hardman and E. J. Cole describe it, “Engine sizing, with is part of the manufacturing process, has the ingredients added to the furnish or stock prior to sheet formation, the concern for the removal of size is less, and as such, most literature focuses on the more pressing issue of preserving acidic papers and similar issues.
Implementation on Fiber Cement making
Cellulose Fiber Sized in Fiber Cement Process :
Chemically treating cellulose fibers to impart the fibers with hydrophobicity and/or durability, and making cellulose fiber reinforced cement composite materials using the Chemical / Additive treated cellulose fibers which the cellulose fibers are treated or sized with specialty chemicals that impart the fibers with higher hydrophobicity by partially or completely blocking the hydrophilic groups of the fibers.
This technology advantageously provides fiber cement building materials with the desirable characteristics of reduced water absorption have advantage reduced rate of water absorption, lower water migration, lower water permeability so the final products made from these materials have improved freeze-thaw resistance, reduced efflorescence, reduced dissolution and re-deposition of water-soluble matrix components in natural weathering.
Using fiber sizing almost to improve other product properties to the physical and mechanical of final product.
More information : sent to my Email
Non Asbestos ?” It’s Not Only Economical But a Better Products”
Summary
Fibre cement sheets are most economic for roofing and wall building.
Various production technologies are :
1. The sieve cylinder process ( paper mill machine – Cylinder Mould) – Modified
and patent by Hatschek
Where thin fibre cement layers are formed on a felt
– Flat and Corrugated Sheet – Good Strength
2. The flow on process ( paper mill machine – Fourdrinier Type )
Is much simpler uses cheaper fibres and needs less investment
- Flat and Corrugated Sheet - Lower Strength than cylinder process
3. Air Cure / Autoclave curing
Provides dimensional stability and next day ready to sales because both of the stability
and process of aggregate in the mixture sheet was done which in 8-10 hours comparing with
air curing needed 28 days to get ready all the stability of the sheet.
4. New technique to process Non Asbestos Fiber Cement .
The process are improvement of traditional techniques.
The price is availability related to raw material.
Using existing equipment and the low investment of utilize / support equipment.
Why Non Asbestos Fiber Cement Product ????
http://www.osha.gov/SLTC/asbestos/
1. Sieve cylinder process
This process with operations almost everywhere on the globe.
Mechanisms ;
- A very thin slurry of water, binder and fibres is mixed and is introduced into each one
of the sieve cylinder vats.
- The rotating sieve cylinder collects a thin layer of 0.2 to 0.35 mm of the solid materials
whilst most of the excess water passes through the wire mesh of the sieve cylinder.
- The thin layer "emerges" from the slurry and is further dewatered and compressed by
the couch roller as it is transferred to a felt.
- The thin layers of all the various sieve cylinders are collected on the felt which runs with
a speed of approx. 60 - 130 m/ over dewatering vacuum boxes to the accumulating size
roller.
- The size roller accumulates layer after layer until the programmed number of
revolutions and the required sheet thickness is reached and the automatic cut-off
mechanism cuts through the layers.
- The sheet thickness is double-checked by high-precision laser control. The sheet drops
onto the take-off conveyor.
- Should the thickness differ from the preset thickness the slurry density and/or the felt
speed is adjusted.
- The sheet needs to be cut to exact size and runs through a cutting system with rotating
knives or even better through a high precision cutting press where the sheet can be cut
to any irregular Shape.
- Until this production step the sheet is still flat or to be corrugated.
Flat sheets
Are preferably compressed to improve their strength and, if required, to receive an embossed surface in
form of stone texture or wood grain. Flat sheets are best and most economically compressed in a
stacking system press with a specific pressure of 50 - 300 kg/cm² (700 - 4000 psi)
Sheets may also be embossed directly on the forming roller without additional pressing or in a roller press with minimal pressing.
Corrugated sheets
Are corrugated with a suction corrugators while on the cross conveyor bridge. The corrugators picks up the flat sheet by suction after cutting and during the cross motion contracts and corrugates the sheet to exact shape. The sheet is placed onto a corrugated steel mould.
Type to making corrugated;
- Uncompressed sheets are stacked with the steel mould as a mixed pile. Compressed sheets
run on a corrugated perforated process steel mould through a single sheet press.
- The compressed corrugated sheets are stacked on the usual corrugated steel moulds to
form a mixed pile. The empty perforated process steel mould remains in the closed press
cycle. It is washed and returned to the corrugator for immediate repeated press use.
Sheets precuring, curing and finishing
After a defined precuring time ( depending on the cement to be used) - the sheets are hard enough for
further handling. They are then demoulded and palletized for 2 to 4 weeks' aircuring, or high-pressure
steam cured in autoclaves for about 12 hours.
What are the benefits of the sieve cylinder system?
There must be many benefits as it is the mostly used process!
- High strength due to many individual layers
- The many layers allow good and easy moulding (corrugated, hand moulding)
- Easy to operate
Are there any disadvantages?
- Large water surplus (which is recycled)
- Requires suitables fibres to run the process
- Risk of delamination (minor)
2 Flow-on sheet production
The flow-on sheeting plant is similar to the sheeting plant using the sieve cylinder machine.
The difference is how the layer is formed on the felt: The slurry is much thicker, i. e. the solid content is higher and the slurry flows directly onto the felt via a distributor mechanism ( head box in Paper machine )
This distributor mechanism is either ;
a) A large box similar to the sieve cylinder vat where the felt is forming the wall of the vat and
the layer is drawn to the felt by a vacuum box
or
b) A distributor box ( head box ) on top of the felt which forms a thin layer in the gap between
the felt and the distributor box and is dewatered by means of both foil blade and vacuum box
.
What are the benefits Flow On?
- The sheeting machine is much simpler.
- There is only little excess water which saves a sophisticated water recuperating system.
- The slurry can be composed by any available raw materials and fibres.
- There is no need for process related tricks to keep the binders and fibres together ( still have
and more easily ).
- There is a reasonably good ratio of fibre distribution in DM (Direct machine) or CM ( Cross
machine ) direction.
Are there any disadvantages Flow On?
_ The slightly lower strength of the sheets as there are less layers and the strength is approx.
90 - 95 % of the sieve cylinder system.
- The higher risk of delamination due to the thicker layers, especially for corrugated sheets
- Risk of different density in the sheet
- The lower production capacity (similar to a 2 sieve cylinder machine) because of the need for a
longer dewatering time of this layer and the difficulty of forming more than one layer on the
felt.
- The flow-on system is successfully used for flat but rarely for good corrugated sheets.
Note : To minimize the disadvantages of flow on machine must do the any
modification and combined with additive - modified by Frangky Welly )
3 Curing
The curing process are
- Aircuring
Aircuring is the conventional cement hardening similar to all other cement-based products
After 8 - 12 hours the sheet is hard enough for further handling but needs another 28 days to
reach its full strength.
Benefit: - no extra investment
Disadvantages: - reduced dimensional stability - i. e. shrinkage
- 3-4 weeks curing time, needs high working capital ( ware house area )
- Autoclaving
Autoclaving creates a completely different hydrated material, i.e. "high temperature calcium
silicate hydrate" of a superior crystal structure.
In fact the aircuring system forms already a semi-crystallized silicate hydrate, but the high
temperature in the autoclaves forms various crystal structures - preferably the tobermorite
structure - which give the sheet unique properties and opens a market for new applications.
Cement is mixed with fine silica in the ratio of approx. 40-45 % cement and 50 -55 % SiO2.
Precuring is aircuring as described before but final curing is in the autoclave. At approx.
180 -185 °C and at saturated steam corresponding to 12 bar (170 - 180 PSI) calcium silicate
hydrate is formed. The crystal structure provides highly preferred properties to the sheet,
especially to the flat sheet.
Why Using Autoclave ?
Benefits: - extreme dimensional stability
- Less material cost as cement is partly substituted by silica sand
- Immediate final curing, i.e. the sheet can be sold within 24 hours after production
- Reduction of working capital.
Disdavantages:
- Increased investment - depending on the process.
- sand grinding (could in some cases be replaced by using silica powder)
- Autoclaves and accessories
- Steam boiler
4 The New technique to process Non Asbestos Fiber Cement
WHY ???
“ It’s Not Only Economical But a Better Products
http://ecohomesite.com/
http://www.osha.gov/SLTC/asbestos
4.2. What are the raw materials typically used?
4. 2.1 Fibres
The most critical material as they may dictated the price and quality of the sheet.
- Cellulose fibres bleached or unbleached
. as reinforcement for the sheet
. as the process fibre to help the process work in connection with other man-made fibres
Cellulose (for aircured process) is not permanently resistant to the alkalinity of the cement. Therefore small quantities of components which retard the alkalinity of the cement are added.
The cellulose alone is used in a process with autoclave-curing where a calcium silicate hydrate is formed which has a low alkaline matrix.
Cellulose can be blended with long lasting man-made fibres like PVA (Poly-Vinyl-Alcohol) or an organic syntetic fiber ( MAK- Fiber ) depending on the required physical properties of the fibre cement products.
Note:
MAK- Fiber is suitable for both the air cured process and for the autoclave process
More information regarding this MAK- Fiber please contact to Frangky Welly W ( frangww@yahoo.com)
4. 2.2 Binders
- Portland cement
Is the most commonly used cement
- other preferred cement types are low alkaline cements like slag cement using steel furnace
slag.
- Other options for special sheets could be:
- Gypsum or anhydrite
- Lime-based binders
4.2.3 Siliceous Compounds
The siliceous compound SiO2 is unavoidable in the autoclave curing process where SiO2 with CaO and H2O forms calcium silicate hydrate.
Other siliceous compounds are added in small quantities to affect and determine the physical properties of the fibre cement products:
- Silica fume
- Amorphous silicates
- Perlite , expanded ( to get low density of product )
- Vermiculite, expanded
- Mica
- Bentonite
- Kaolin / Clay
- Slag
4.2.4 Others / Additive
- Water
- Flocculant
- Bonding Aid
- Defoamer
Note : Both Flocculant and Bonding Aid ( Floren series - by MAK )
4.3 Equipment
- Using existing Equipment
- Modification on Close Loop line and additing the feeding line for chemicals application and all
chemicals preparation equipment.
Note :
How to Up Grading Your Product ?
I will support and guidance to do it
Frangky Welly W
http://www.osha.gov/SLTC/asbestos,
Fibre cement sheets are most economic for roofing and wall building.
Various production technologies are :
1. The sieve cylinder process ( paper mill machine – Cylinder Mould) – Modified
and patent by Hatschek
Where thin fibre cement layers are formed on a felt
– Flat and Corrugated Sheet – Good Strength
2. The flow on process ( paper mill machine – Fourdrinier Type )
Is much simpler uses cheaper fibres and needs less investment
- Flat and Corrugated Sheet - Lower Strength than cylinder process
3. Air Cure / Autoclave curing
Provides dimensional stability and next day ready to sales because both of the stability
and process of aggregate in the mixture sheet was done which in 8-10 hours comparing with
air curing needed 28 days to get ready all the stability of the sheet.
4. New technique to process Non Asbestos Fiber Cement .
The process are improvement of traditional techniques.
The price is availability related to raw material.
Using existing equipment and the low investment of utilize / support equipment.
Why Non Asbestos Fiber Cement Product ????
http://www.osha.gov/SLTC/asbestos/
1. Sieve cylinder process
This process with operations almost everywhere on the globe.
Mechanisms ;
- A very thin slurry of water, binder and fibres is mixed and is introduced into each one
of the sieve cylinder vats.
- The rotating sieve cylinder collects a thin layer of 0.2 to 0.35 mm of the solid materials
whilst most of the excess water passes through the wire mesh of the sieve cylinder.
- The thin layer "emerges" from the slurry and is further dewatered and compressed by
the couch roller as it is transferred to a felt.
- The thin layers of all the various sieve cylinders are collected on the felt which runs with
a speed of approx. 60 - 130 m/ over dewatering vacuum boxes to the accumulating size
roller.
- The size roller accumulates layer after layer until the programmed number of
revolutions and the required sheet thickness is reached and the automatic cut-off
mechanism cuts through the layers.
- The sheet thickness is double-checked by high-precision laser control. The sheet drops
onto the take-off conveyor.
- Should the thickness differ from the preset thickness the slurry density and/or the felt
speed is adjusted.
- The sheet needs to be cut to exact size and runs through a cutting system with rotating
knives or even better through a high precision cutting press where the sheet can be cut
to any irregular Shape.
- Until this production step the sheet is still flat or to be corrugated.
Flat sheets
Are preferably compressed to improve their strength and, if required, to receive an embossed surface in
form of stone texture or wood grain. Flat sheets are best and most economically compressed in a
stacking system press with a specific pressure of 50 - 300 kg/cm² (700 - 4000 psi)
Sheets may also be embossed directly on the forming roller without additional pressing or in a roller press with minimal pressing.
Corrugated sheets
Are corrugated with a suction corrugators while on the cross conveyor bridge. The corrugators picks up the flat sheet by suction after cutting and during the cross motion contracts and corrugates the sheet to exact shape. The sheet is placed onto a corrugated steel mould.
Type to making corrugated;
- Uncompressed sheets are stacked with the steel mould as a mixed pile. Compressed sheets
run on a corrugated perforated process steel mould through a single sheet press.
- The compressed corrugated sheets are stacked on the usual corrugated steel moulds to
form a mixed pile. The empty perforated process steel mould remains in the closed press
cycle. It is washed and returned to the corrugator for immediate repeated press use.
Sheets precuring, curing and finishing
After a defined precuring time ( depending on the cement to be used) - the sheets are hard enough for
further handling. They are then demoulded and palletized for 2 to 4 weeks' aircuring, or high-pressure
steam cured in autoclaves for about 12 hours.
What are the benefits of the sieve cylinder system?
There must be many benefits as it is the mostly used process!
- High strength due to many individual layers
- The many layers allow good and easy moulding (corrugated, hand moulding)
- Easy to operate
Are there any disadvantages?
- Large water surplus (which is recycled)
- Requires suitables fibres to run the process
- Risk of delamination (minor)
2 Flow-on sheet production
The flow-on sheeting plant is similar to the sheeting plant using the sieve cylinder machine.
The difference is how the layer is formed on the felt: The slurry is much thicker, i. e. the solid content is higher and the slurry flows directly onto the felt via a distributor mechanism ( head box in Paper machine )
This distributor mechanism is either ;
a) A large box similar to the sieve cylinder vat where the felt is forming the wall of the vat and
the layer is drawn to the felt by a vacuum box
or
b) A distributor box ( head box ) on top of the felt which forms a thin layer in the gap between
the felt and the distributor box and is dewatered by means of both foil blade and vacuum box
.
What are the benefits Flow On?
- The sheeting machine is much simpler.
- There is only little excess water which saves a sophisticated water recuperating system.
- The slurry can be composed by any available raw materials and fibres.
- There is no need for process related tricks to keep the binders and fibres together ( still have
and more easily ).
- There is a reasonably good ratio of fibre distribution in DM (Direct machine) or CM ( Cross
machine ) direction.
Are there any disadvantages Flow On?
_ The slightly lower strength of the sheets as there are less layers and the strength is approx.
90 - 95 % of the sieve cylinder system.
- The higher risk of delamination due to the thicker layers, especially for corrugated sheets
- Risk of different density in the sheet
- The lower production capacity (similar to a 2 sieve cylinder machine) because of the need for a
longer dewatering time of this layer and the difficulty of forming more than one layer on the
felt.
- The flow-on system is successfully used for flat but rarely for good corrugated sheets.
Note : To minimize the disadvantages of flow on machine must do the any
modification and combined with additive - modified by Frangky Welly )
3 Curing
The curing process are
- Aircuring
Aircuring is the conventional cement hardening similar to all other cement-based products
After 8 - 12 hours the sheet is hard enough for further handling but needs another 28 days to
reach its full strength.
Benefit: - no extra investment
Disadvantages: - reduced dimensional stability - i. e. shrinkage
- 3-4 weeks curing time, needs high working capital ( ware house area )
- Autoclaving
Autoclaving creates a completely different hydrated material, i.e. "high temperature calcium
silicate hydrate" of a superior crystal structure.
In fact the aircuring system forms already a semi-crystallized silicate hydrate, but the high
temperature in the autoclaves forms various crystal structures - preferably the tobermorite
structure - which give the sheet unique properties and opens a market for new applications.
Cement is mixed with fine silica in the ratio of approx. 40-45 % cement and 50 -55 % SiO2.
Precuring is aircuring as described before but final curing is in the autoclave. At approx.
180 -185 °C and at saturated steam corresponding to 12 bar (170 - 180 PSI) calcium silicate
hydrate is formed. The crystal structure provides highly preferred properties to the sheet,
especially to the flat sheet.
Why Using Autoclave ?
Benefits: - extreme dimensional stability
- Less material cost as cement is partly substituted by silica sand
- Immediate final curing, i.e. the sheet can be sold within 24 hours after production
- Reduction of working capital.
Disdavantages:
- Increased investment - depending on the process.
- sand grinding (could in some cases be replaced by using silica powder)
- Autoclaves and accessories
- Steam boiler
4 The New technique to process Non Asbestos Fiber Cement
WHY ???
“ It’s Not Only Economical But a Better Products
http://ecohomesite.com/
http://www.osha.gov/SLTC/asbestos
4.2. What are the raw materials typically used?
4. 2.1 Fibres
The most critical material as they may dictated the price and quality of the sheet.
- Cellulose fibres bleached or unbleached
. as reinforcement for the sheet
. as the process fibre to help the process work in connection with other man-made fibres
Cellulose (for aircured process) is not permanently resistant to the alkalinity of the cement. Therefore small quantities of components which retard the alkalinity of the cement are added.
The cellulose alone is used in a process with autoclave-curing where a calcium silicate hydrate is formed which has a low alkaline matrix.
Cellulose can be blended with long lasting man-made fibres like PVA (Poly-Vinyl-Alcohol) or an organic syntetic fiber ( MAK- Fiber ) depending on the required physical properties of the fibre cement products.
Note:
MAK- Fiber is suitable for both the air cured process and for the autoclave process
More information regarding this MAK- Fiber please contact to Frangky Welly W ( frangww@yahoo.com)
4. 2.2 Binders
- Portland cement
Is the most commonly used cement
- other preferred cement types are low alkaline cements like slag cement using steel furnace
slag.
- Other options for special sheets could be:
- Gypsum or anhydrite
- Lime-based binders
4.2.3 Siliceous Compounds
The siliceous compound SiO2 is unavoidable in the autoclave curing process where SiO2 with CaO and H2O forms calcium silicate hydrate.
Other siliceous compounds are added in small quantities to affect and determine the physical properties of the fibre cement products:
- Silica fume
- Amorphous silicates
- Perlite , expanded ( to get low density of product )
- Vermiculite, expanded
- Mica
- Bentonite
- Kaolin / Clay
- Slag
4.2.4 Others / Additive
- Water
- Flocculant
- Bonding Aid
- Defoamer
Note : Both Flocculant and Bonding Aid ( Floren series - by MAK )
4.3 Equipment
- Using existing Equipment
- Modification on Close Loop line and additing the feeding line for chemicals application and all
chemicals preparation equipment.
Note :
How to Up Grading Your Product ?
I will support and guidance to do it
Frangky Welly W
http://www.osha.gov/SLTC/asbestos,
Global Suppliers of Alternative Products – Non-Asbestos
Some information related to Non Asbestos Products
Everite Group, South Africa – fiber-cement flat sheet and roofing. http://www.everite.co.za/
Etex Group, Belgium – fiber-cement roofing, boards, siding; affiliates worldwide. http://www.etexgroup.com/
Parry Associates, UK – microconcrete roofing; design and engineering firm that has worked with local and international clients in 80 countries. http://www.parryassociates.com/
Worldroof, Belgium – recycled polypropylene and high-density polyethylene and crushed stone. http://www.belgiantechnologies.com/content/index.php?lang=4∂=2&cat=2⊂=&product=568
Kuraray, Japan – manufacturer of PVA fiber used to make fiber-cement by companies in countries including Ukraine, Nigeria, Turkey, Vietnam, Thailand, Malaysia, Mexico, Colombia, and Brazil.
Unitika, Japan – manufacturer of PVA fiber used in fiber-cement. http://www.unitika.co.jp/e/home.htm
Weyerhaeuser, US – wood products company developing fiber-cement markets using wood pulp. Contact: Brian Wester brian. wester@weyerhaeuser.com ,
Fiber Cement Forum, Norway – expanding markets for use of waste materials silica fume, flyash, and rice husk ash in fiber-cement products. Contact: Henning Thygesen henning.thygesen@elchem.no
Saint-Gobain, France – developing fiber-cement products using polypropylene and cellulose for use in Brazil, India, etc. Contact in Brazil: João Carlos Duarte Paes abifibro@terra.com.br
BRAZIL
http://www.engeplas.com.br/ – Engeplas + Ecotop – recycling dental tubes plastics +aluminum
http://www.onduline.com.br/ vegetable fiber + asphalt/betume
http://www.tecolit.com.br/ (fibers + asphalt)
http://www.viralata.org.br/ (recycling paper + asphalt)...this is a cooperative of poor people ...social inclusion program
ibicunha@brturbo.com (long life packs - milk box recycling) http://www.rbrepresentacoes.com/produto_lista.asp ceramic tiles
MALAYSIA
UAC Berhad http://www.uac.com.my/ Siding, interior boards, ceiling panels.Hume Cemboard http://www.humecemboard.com.my/ Siding, interior boards, ceiling panels.
TAIWAN: (ceiling and interior boards, siding)
Taisyou International Business Col, Ltd. http://www.taisyou.com.tw/e/e-index.htm
L.H. Fortune Co., Ltd.Wellpool Co., Ltd. http://www.wellpool.com.tw/cg/ch/
KOREA
Byucksan http://www.byucksan.com/byucksan_e/intro.htm
Kumgang Korea Chemical Co., Ltd. http://www.kccworld.co.kr/korea/
INDONESIA
Nusantara Building Industries http://www.nbi.co.id/
Eternit Gresik http://eternitgersik.com/
others
AUSTRALIA, NEW ZEALAND
James Hardie http://www.jameshardie.com/index.htm
CSR Fibre Cement http://www.csr.com.au/Corporate/default.asp
others
James Hardie http://www.jameshardie.com/index.htm
Aptech Manufacturing Corp., Angeles and Pampanga, plantation wood/rattan wastes Fabricemtech, Lucena and Quezon, plantation wood and bagasse
GC Enterprises, Zamboanga, yemane and palo verde
San Nicolas Multipurpose Coop., Candon and Ilocos Sur, giant ipil-ipil and tobacco stalks
R-II Builders, National Capital Region, plantation wood
Cemboard Systems Inc., Lipa and Batangas, yemane
Phela Resources, Genaral Samtos City, yemane
Boalan Agri-Resources, Zamboanga del Sur, yemane and palo verdeCruzayco Corp., Kambankalan, Negros Occ., yemane
Cagayan Wood Works Manufacturing Corp.,
Solana and Cagayan, yemane
Caraga Women's Cooperative, Butuan City, yemane and rattan wasteEarn Corporation, Bay and Laguna, yemaneVillarica Forest Products, Samal Island and Daval, yemaneZementboard Cooperative, Korondal and South Cotabato, yemaneVersaboard Enterprises, Angeles and Pampanga, bagasseAlenter Cane Corp., Cebu, rattan wastesLemon Products Int'l./Victorians Marketing, Imus and Cavite, rattan wastes
Reference: The Wood Wool Cement Board Industry in the Philippines: http://sres.anu.edu.au/associated/fpt/nwfp/woodwool/woodwoolphil.html#anchor5666869
Everite Group, South Africa – fiber-cement flat sheet and roofing. http://www.everite.co.za/
Etex Group, Belgium – fiber-cement roofing, boards, siding; affiliates worldwide. http://www.etexgroup.com/
Parry Associates, UK – microconcrete roofing; design and engineering firm that has worked with local and international clients in 80 countries. http://www.parryassociates.com/
Worldroof, Belgium – recycled polypropylene and high-density polyethylene and crushed stone. http://www.belgiantechnologies.com/content/index.php?lang=4∂=2&cat=2⊂=&product=568
Kuraray, Japan – manufacturer of PVA fiber used to make fiber-cement by companies in countries including Ukraine, Nigeria, Turkey, Vietnam, Thailand, Malaysia, Mexico, Colombia, and Brazil.
Unitika, Japan – manufacturer of PVA fiber used in fiber-cement. http://www.unitika.co.jp/e/home.htm
Weyerhaeuser, US – wood products company developing fiber-cement markets using wood pulp. Contact: Brian Wester brian. wester@weyerhaeuser.com ,
Fiber Cement Forum, Norway – expanding markets for use of waste materials silica fume, flyash, and rice husk ash in fiber-cement products. Contact: Henning Thygesen henning.thygesen@elchem.no
Saint-Gobain, France – developing fiber-cement products using polypropylene and cellulose for use in Brazil, India, etc. Contact in Brazil: João Carlos Duarte Paes abifibro@terra.com.br
BRAZIL
http://www.engeplas.com.br/ – Engeplas + Ecotop – recycling dental tubes plastics +aluminum
http://www.onduline.com.br/ vegetable fiber + asphalt/betume
http://www.tecolit.com.br/ (fibers + asphalt)
http://www.viralata.org.br/ (recycling paper + asphalt)...this is a cooperative of poor people ...social inclusion program
ibicunha@brturbo.com (long life packs - milk box recycling) http://www.rbrepresentacoes.com/produto_lista.asp ceramic tiles
MALAYSIA
UAC Berhad http://www.uac.com.my/ Siding, interior boards, ceiling panels.Hume Cemboard http://www.humecemboard.com.my/ Siding, interior boards, ceiling panels.
TAIWAN: (ceiling and interior boards, siding)
Taisyou International Business Col, Ltd. http://www.taisyou.com.tw/e/e-index.htm
L.H. Fortune Co., Ltd.Wellpool Co., Ltd. http://www.wellpool.com.tw/cg/ch/
KOREA
Byucksan http://www.byucksan.com/byucksan_e/intro.htm
Kumgang Korea Chemical Co., Ltd. http://www.kccworld.co.kr/korea/
INDONESIA
Nusantara Building Industries http://www.nbi.co.id/
Eternit Gresik http://eternitgersik.com/
others
AUSTRALIA, NEW ZEALAND
James Hardie http://www.jameshardie.com/index.htm
CSR Fibre Cement http://www.csr.com.au/Corporate/default.asp
others
James Hardie http://www.jameshardie.com/index.htm
Aptech Manufacturing Corp., Angeles and Pampanga, plantation wood/rattan wastes Fabricemtech, Lucena and Quezon, plantation wood and bagasse
GC Enterprises, Zamboanga, yemane and palo verde
San Nicolas Multipurpose Coop., Candon and Ilocos Sur, giant ipil-ipil and tobacco stalks
R-II Builders, National Capital Region, plantation wood
Cemboard Systems Inc., Lipa and Batangas, yemane
Phela Resources, Genaral Samtos City, yemane
Boalan Agri-Resources, Zamboanga del Sur, yemane and palo verdeCruzayco Corp., Kambankalan, Negros Occ., yemane
Cagayan Wood Works Manufacturing Corp.,
Solana and Cagayan, yemane
Caraga Women's Cooperative, Butuan City, yemane and rattan wasteEarn Corporation, Bay and Laguna, yemaneVillarica Forest Products, Samal Island and Daval, yemaneZementboard Cooperative, Korondal and South Cotabato, yemaneVersaboard Enterprises, Angeles and Pampanga, bagasseAlenter Cane Corp., Cebu, rattan wastesLemon Products Int'l./Victorians Marketing, Imus and Cavite, rattan wastes
Reference: The Wood Wool Cement Board Industry in the Philippines: http://sres.anu.edu.au/associated/fpt/nwfp/woodwool/woodwoolphil.html#anchor5666869
Substitutes for Asbestos-Cement Construction Products
by Barry Castleman
Substitutes for these asbestos products are not limited to products that simply replace asbestos with another material (e.g., PVA ,and cellulose in fiber-cement roofing sheet). There are also a number of wholly different products that can replace the asbestos products. A number of substitutes for asbestos-cement products are included in the following table.
Asbestos Product
Substitute Products
Asbestos-Cement Corrugated Roofing
Fiber-cement roofing using: synthetic fibers (polyvinyl alcohol, polypropylene)
and vegetable/cellulose fibers (softwood kraft pulp, bamboo, sisal, coir, rattan
shavings and tobacco stalks, etc.); with optional silica fume, flyash, or rice husk
ash Microconcrete (Parry) tilesGalvanized metal sheetsClay tilesVegetable fibers
in asphaltSlateCoated metal tiles (Harveytile)Aluminum roof tiles (Dekra Tile)
Extruded uPVC roofing sheetsRecycled polypropylene and high-density
polyethylene and crushed stone (Worldroof)Plastic coated aluminumPlastic
coated galvanized steel.
Asbestos-Cement Flat Sheet (ceilings, facades, partitions)
Fiber-cement using vegetable/cellulose fibers (see above), wastepaper, optionally
synthetic fibersGypsum ceiling boards (BHP Gypsum)Polystyrene ceilings,
cornices, and partitionsFaçade applications in polystyrene structural walls (coated
with plaster) Aluminum cladding (Alucabond) BrickGalvanized frame with plaster
-board or calcium silicate board facingSoftwood frame with plasterboard or
calcium silicate board facing.
Asbestos-Cement Pipe
High Pressure:Cast iron and ductile iron pipeHigh-density polyethylene
pipePolyvinyl chloride pipeSteel-reinforced concrete pipe (large sizes)Glass
-reinforced polyester pipe Low Pressure:Cellulose-cement pipeCellulose/PVA
fiber-cement pipeClay pipeGlass-reinforced polyester pipeSteel-reinforced
concrete pipe (large diameter drainage)
Asbestos-Cement Water Storage Tanks
Cellulose-cementPolyethyleneFiberglassSteelGalvanized ironPVA-cellulose fiber-
cement, Asbestos-Cement Rainwater Gutters; Open Drains (Mining Industry)
Galvanized ironAluminumHand-molded cellulose-cementPVC
Substitutes for these asbestos products are not limited to products that simply replace asbestos with another material (e.g., PVA ,and cellulose in fiber-cement roofing sheet). There are also a number of wholly different products that can replace the asbestos products. A number of substitutes for asbestos-cement products are included in the following table.
Asbestos Product
Substitute Products
Asbestos-Cement Corrugated Roofing
Fiber-cement roofing using: synthetic fibers (polyvinyl alcohol, polypropylene)
and vegetable/cellulose fibers (softwood kraft pulp, bamboo, sisal, coir, rattan
shavings and tobacco stalks, etc.); with optional silica fume, flyash, or rice husk
ash Microconcrete (Parry) tilesGalvanized metal sheetsClay tilesVegetable fibers
in asphaltSlateCoated metal tiles (Harveytile)Aluminum roof tiles (Dekra Tile)
Extruded uPVC roofing sheetsRecycled polypropylene and high-density
polyethylene and crushed stone (Worldroof)Plastic coated aluminumPlastic
coated galvanized steel.
Asbestos-Cement Flat Sheet (ceilings, facades, partitions)
Fiber-cement using vegetable/cellulose fibers (see above), wastepaper, optionally
synthetic fibersGypsum ceiling boards (BHP Gypsum)Polystyrene ceilings,
cornices, and partitionsFaçade applications in polystyrene structural walls (coated
with plaster) Aluminum cladding (Alucabond) BrickGalvanized frame with plaster
-board or calcium silicate board facingSoftwood frame with plasterboard or
calcium silicate board facing.
Asbestos-Cement Pipe
High Pressure:Cast iron and ductile iron pipeHigh-density polyethylene
pipePolyvinyl chloride pipeSteel-reinforced concrete pipe (large sizes)Glass
-reinforced polyester pipe Low Pressure:Cellulose-cement pipeCellulose/PVA
fiber-cement pipeClay pipeGlass-reinforced polyester pipeSteel-reinforced
concrete pipe (large diameter drainage)
Asbestos-Cement Water Storage Tanks
Cellulose-cementPolyethyleneFiberglassSteelGalvanized ironPVA-cellulose fiber-
cement, Asbestos-Cement Rainwater Gutters; Open Drains (Mining Industry)
Galvanized ironAluminumHand-molded cellulose-cementPVC
Process and Mechanisme to get Green Sheet on the Hatschek Machine
The success of fibre cement by the Hatschek process :( From paper mill Cylinder Mould Type )
• Formation in thin paper like films that are placed one on the other until the desired sheet
thickness is reached.
• Formation of the sheet by this means distributes the reinforcing fibres in two dimensions
taking best advantage of the reinforcing fibres to increase the in-plane strength of the
sheet.
• Thus the strength of sheets made in this fashion is approximately 50% greater than
sheets formed to full thickness in one action in the filter press process.
Sheet formation on the Hatschek Machine occurs in 4 stages1. Initial formation of a filter layer on the surface of the sieve
2. Building of a very watery layer of fibre cement over the filter layer as the sieve rotates
in contact with the slurry in the vat
3. Low intensity dewatering of the wet film as it transfers to the felt and
4. High intensity dewatering of the film as it passes through the nip of the accumulator
roller.
Introduction The Hatschek machine :( Modification and using cylinder mould machine (frangky )
1. First developed for the production of asbestos cement in the 1890’s when it was patented by
the inventor, Ludwig Hatschek.
2. The machine is still used in the same basic form today and although modern Hatschek
machines are much more productive than the early models
Mechanism to build green sheet on the Hatschek machine as follows
1. Clean sieve is pulled under the slurry in the vat, water from the slurry runs through the
sieve depositing a soft porous film of fibre and cement on the surface of the sieve.
2. The sieve carrying the film exiting the vat is brought into contact with the felt stretched
tightly across the sieve. This removes much of the water from the film by forcing it back
through the film. The solid film floats on this layer of water and is transferred to the felt
partly in response to the effect of removal of water and partly because the felt has a greater
affinity for the film than the sieve.
3. The film is carried on the felt to an accumulator roll to which it is transferred by further
removal of water at high pressure.
4. A sufficient number of films are wrapped on the accumulator roll to form a sheet of the
desired thickness, the stack of films is then removed from the roller and laid out flat to form
the sheet. The action of dewatering successive films in contact with each other under
pressure is sufficient to bind the films together to form a contiguous solid sheet.
Detailed Mechanism of Film FormationFormation of the film takes place as follows
1. A filter layer of fibres forms on the surface of the sieve within a short distance the
immersion of the sieve into the water.
2. The film continues to build up on the sieve but now contains a lower proportion of fibres
and a greater proportion of the non-fibrous materials.
3. The film is dewatered and stripped from the sieve on to the felt driving the sieve.
The position of formation of the filter layer Two possibilities exist,1. The fibre orientation screw runs counter to the sieve direction and throws the slurry onto
the sieve above the immersion point. In this case most of the formation of the filter layer
occurs before the sieve enters the slurry.
2. The fibres orientation screw runs in the same direction as the sieve that may be fitted with
a rubber flap extending 50 mm or so beneath the surface of the slurry. In this case the
formation of the filter layer takes place just below the rubber flap.
Raw material in to processThe feed to a Hatschek machine is
1. Fibres
2. Portland Cement
3. Ground minerals
4. Water.
Formation of the Filter LayerFormation :
Typical sieve apertures are around 0.4mm (400 um) and clearly the non-fibrous material is significantly smaller than the sieve apertures and so would wash through the sieve.
Fibres on the other hand are able to bridge the wires of the sieve although any fibre presenting perpendicular to the sieve surface could also pass lengthwise through it.
Entrapment of the non-fibrous materials therefore depends on the formation of a filter layer of fibres on the surface of the sieve.
Process Making Fiber Cement old type and improvement
Process Making Fiber Cement old type and improvement
Asbestos fiber cement techhology about 120 years ago, Ludwig Hatschek made the first asbestos reinforced cement products, using a paper-making sieve cylinder machine on which a very dilute slurry of asbestos fibers (up to about 10% by weight of solids) and ordinary Portland cement (about 90% or more) was dewatered, in films of about 0.3 mm, which were then wound up to a desired thickness (typically 3-6 mm) on a roll, and the resultant cylindrical sheet was cut and flattened to form a flat laminated sheet, which was cut into rectangular pieces of the desired size.
For over 100 years, this form of fiber cement found extensive use for roofing products, pipe products, and walling products, both external siding (planks and panels), and wet-area lining boards.
Asbestos cement was also used in many applications requiring high fire resistance due to the great thermal stability of asbestos.The great advantage of all these products was that they were relative lightweight and that water affected them relatively little, since the high-density asbestos/cement composite is of low porosity and permeability.The disadvantage of these products was that the high-density matrix did not allow nailing, and methods of fixing involved pre-drilled holes.Although the original Hatschek process (a modified sieve cylinder paper making machine) dominated the bulk of asbestos cement products made, other processes were also used to make specialty products, such as thick sheets (say greater than about 10 mm which required about 30 films). These used the same mixture of asbestos fibers and cement as with the Hatschek process, although sometimes some process aid additives are used for other processes.
For example, fiber cement composites have been made by extrusion, injection molding, and filter press or flow-on machines.
Two developments occurred around the middle of the last century that had high significance to modern replacements of asbestos based cement composites.
The first was that some manufacturers realized that the curing cycle could be considerably reduced, and cost could be lowered, by autoclaving the products.
This allowed the replacement of much of the cement with fine ground silica, which reacted at autoclave temperatures with the excess lime in the cement to produce calcium silica hydrates similar to the normal cement matrix.
Since silica, even when ground, is much cheaper than cement, and since the autoclave curing time is much less than the air cured curing time, this became a common, but by no means universal manufacturing method.
A typical formulation would be about 5- 10% asbestos fibers, 30-50% cement, and about 40-60% silica.
The second development was to replace some of the asbestos reinforcing fibers with cellulose fibers from wood.
This was not widely adopted except for siding products and wet-area lining sheets.
The great advantage of this development was that cellulose fibers are hollow and soft, and the resultant products could be nailed rather than by fixing through pre-drilled holes.
The siding and lining products are used on vertical walls, which is a far less demanding environment than roofing.
However, cellulose reinforced cement products are more susceptible to water induced changes, compared to asbestos cement composite materials. A typical formulation would be about 3-4% cellulose, about 4-6% asbestos, and either about 90% cement for air cured products, or about 30-50% cement and about 40-60% silica for autoclaved products.
Asbestos fibers had several advantages. The sieve cylinder machines require fibers that form a network to catch the solid cement (or silica) particles, which are much too small to catch on the sieve itself. Asbestos, although it is an inorganic fiber, can be"refined"into Asbes, They are stable at high temperatures. They are stable against alkali attack under autoclave conditions. Hence, asbestos reinforced fiber cement products are themselves strong, stiff (also brittle), and could be used in many hostile environments, except highly acidic environments where the cement itself is rapidly attacked chemically. The wet/dry cycling that asbestos roofing products were subjected to, often caused a few problems, primarily efflorescence, caused by the dissolution of chemicals inside the products when wet, followed by the deposition of these chemicals on the surfaces of the products when dried. Efflorescence caused aesthetic degradation of roofing products in particular, and many attempts were made to reduce it. Because the matrix of asbestos reinforced roofing products was generally very dense (specific gravity about 1.7), the total amount of water entering the product even when saturated was relatively low, and the products generally had reasonable freeze thaw resistance. If the density was lowered, the products became more workable (for example they could be nailed) but the rate of saturation and the total water absorption increased and the freeze thaw performance decreased.
Alternative Fiber Cement Technologies In the early 1980's, the health hazards associated with mining, or being exposed to and inhaling, asbestos fibers started to become a major health concern. Alternatif Fiber Semen Technologies . Manufacturers of asbestos cement products in the USA, some of Western Europe, and Australia/New Zealand in particular, sought to find a substitute for asbestos fibers for the reinforcement of building and construction products, made on their installed manufacturing base, primarily Hatschek machines. Over a period of twenty years, two viable alternative technologies have emerged, although neither of these has been successful in the full range of asbestos applications.
In Western Europe, the most successful replacement for asbestos has been a combination of PVA fibers (about 2%) and cellulose fibers (about 5%) with primarily cement (about 80%), sometimes with inert fillers such as silica or limestone (about 10- 30%). This product is air-cured, since PVA fibers are, in general, not autoclave stable. It is generally made on a Hatschek machine, followed by a pressing step using a hydraulic press.
This compresses the cellulose fibers, and reduces the porosity of the matrix. Since PVA fibers can't be refined while cellulose can be, in this Western European technology the cellulose fiber functions as a process aid to form the network on the sieve that catches the solid particles in the dewatering step. This product is used primarily for roofing (slates and corrugates). It is usually (but not always) covered with thick organic coatings. The great disadvantage of these products is a very large increase in material and manufacturing process costs. While cellulose is currently a little more expensive than asbestos fibers at $500 a ton, PVA is about $4000 a ton. Thick organic coatings are also expensive, and hydraulic presses are a high cost manufacture step.
Asbestos fiber cement techhology about 120 years ago, Ludwig Hatschek made the first asbestos reinforced cement products, using a paper-making sieve cylinder machine on which a very dilute slurry of asbestos fibers (up to about 10% by weight of solids) and ordinary Portland cement (about 90% or more) was dewatered, in films of about 0.3 mm, which were then wound up to a desired thickness (typically 3-6 mm) on a roll, and the resultant cylindrical sheet was cut and flattened to form a flat laminated sheet, which was cut into rectangular pieces of the desired size.
For over 100 years, this form of fiber cement found extensive use for roofing products, pipe products, and walling products, both external siding (planks and panels), and wet-area lining boards.
Asbestos cement was also used in many applications requiring high fire resistance due to the great thermal stability of asbestos.The great advantage of all these products was that they were relative lightweight and that water affected them relatively little, since the high-density asbestos/cement composite is of low porosity and permeability.The disadvantage of these products was that the high-density matrix did not allow nailing, and methods of fixing involved pre-drilled holes.Although the original Hatschek process (a modified sieve cylinder paper making machine) dominated the bulk of asbestos cement products made, other processes were also used to make specialty products, such as thick sheets (say greater than about 10 mm which required about 30 films). These used the same mixture of asbestos fibers and cement as with the Hatschek process, although sometimes some process aid additives are used for other processes.
For example, fiber cement composites have been made by extrusion, injection molding, and filter press or flow-on machines.
Two developments occurred around the middle of the last century that had high significance to modern replacements of asbestos based cement composites.
The first was that some manufacturers realized that the curing cycle could be considerably reduced, and cost could be lowered, by autoclaving the products.
This allowed the replacement of much of the cement with fine ground silica, which reacted at autoclave temperatures with the excess lime in the cement to produce calcium silica hydrates similar to the normal cement matrix.
Since silica, even when ground, is much cheaper than cement, and since the autoclave curing time is much less than the air cured curing time, this became a common, but by no means universal manufacturing method.
A typical formulation would be about 5- 10% asbestos fibers, 30-50% cement, and about 40-60% silica.
The second development was to replace some of the asbestos reinforcing fibers with cellulose fibers from wood.
This was not widely adopted except for siding products and wet-area lining sheets.
The great advantage of this development was that cellulose fibers are hollow and soft, and the resultant products could be nailed rather than by fixing through pre-drilled holes.
The siding and lining products are used on vertical walls, which is a far less demanding environment than roofing.
However, cellulose reinforced cement products are more susceptible to water induced changes, compared to asbestos cement composite materials. A typical formulation would be about 3-4% cellulose, about 4-6% asbestos, and either about 90% cement for air cured products, or about 30-50% cement and about 40-60% silica for autoclaved products.
Asbestos fibers had several advantages. The sieve cylinder machines require fibers that form a network to catch the solid cement (or silica) particles, which are much too small to catch on the sieve itself. Asbestos, although it is an inorganic fiber, can be"refined"into Asbes, They are stable at high temperatures. They are stable against alkali attack under autoclave conditions. Hence, asbestos reinforced fiber cement products are themselves strong, stiff (also brittle), and could be used in many hostile environments, except highly acidic environments where the cement itself is rapidly attacked chemically. The wet/dry cycling that asbestos roofing products were subjected to, often caused a few problems, primarily efflorescence, caused by the dissolution of chemicals inside the products when wet, followed by the deposition of these chemicals on the surfaces of the products when dried. Efflorescence caused aesthetic degradation of roofing products in particular, and many attempts were made to reduce it. Because the matrix of asbestos reinforced roofing products was generally very dense (specific gravity about 1.7), the total amount of water entering the product even when saturated was relatively low, and the products generally had reasonable freeze thaw resistance. If the density was lowered, the products became more workable (for example they could be nailed) but the rate of saturation and the total water absorption increased and the freeze thaw performance decreased.
Alternative Fiber Cement Technologies In the early 1980's, the health hazards associated with mining, or being exposed to and inhaling, asbestos fibers started to become a major health concern. Alternatif Fiber Semen Technologies . Manufacturers of asbestos cement products in the USA, some of Western Europe, and Australia/New Zealand in particular, sought to find a substitute for asbestos fibers for the reinforcement of building and construction products, made on their installed manufacturing base, primarily Hatschek machines. Over a period of twenty years, two viable alternative technologies have emerged, although neither of these has been successful in the full range of asbestos applications.
In Western Europe, the most successful replacement for asbestos has been a combination of PVA fibers (about 2%) and cellulose fibers (about 5%) with primarily cement (about 80%), sometimes with inert fillers such as silica or limestone (about 10- 30%). This product is air-cured, since PVA fibers are, in general, not autoclave stable. It is generally made on a Hatschek machine, followed by a pressing step using a hydraulic press.
This compresses the cellulose fibers, and reduces the porosity of the matrix. Since PVA fibers can't be refined while cellulose can be, in this Western European technology the cellulose fiber functions as a process aid to form the network on the sieve that catches the solid particles in the dewatering step. This product is used primarily for roofing (slates and corrugates). It is usually (but not always) covered with thick organic coatings. The great disadvantage of these products is a very large increase in material and manufacturing process costs. While cellulose is currently a little more expensive than asbestos fibers at $500 a ton, PVA is about $4000 a ton. Thick organic coatings are also expensive, and hydraulic presses are a high cost manufacture step.
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