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,