1. What is Aerated Concrete?
Autoclaved Aerated Concrete (AAC) is a building material with outstanding thermal insulation,high loadbaring capacity at low weight and good workability.
Aerated Concrete is a well-proven material for almost 80 years and this in all climatic zones.Aerated Concrete is a high tech Calcium-Silicate-Hydrate produced out of Cao (contained in quicklime and cement),out of SiO2(contained in sand or PFA=Pulverized Fuel Ash ),anhydrite(gypsum),water and a trace of aluminium power(as aeration agent).
The raw materials are precisely dosed,mixed,poured into large moulds to form a "cake". The cake is pre-cured in climatized pre-curing chambers,cut to blocks or panels,steam cured in autoclaves at a temperature of 190°C(374°F).During the autoclaving process calcium silicate hydrate is formed.Finally the AAC is palletized.
More details of the production process follow.
Section1:,Anhydrite and Sand
1. Anhydrite (Gypsum)
Anhydrite as a power is supplied with silo trucks with a built-in compressor.It is blown into the silo for anhydrite powder and dosed with the dosing screw for anhydrite into the batcher for solids.
Crushed Anhydrite in lumps of 5-30 mm is added by the charging hopper for anhydrite lumps(3.12)and is added to the sand in the required relation.It is then ground together with the sand and water to form the "sand slurry".In special cases anhydrite can be ground dry in a separate mill to become anhydrite powder which is stored in a silo(3.0).
2. Sand (Quartz Sand)
Sand contains SiO2 and is supplied by truck or train.
An intermediate storage might be required.
This intermediate storage can be :
-Underground hopper with conveyors to the sand mill.
-Silo with conveyors to the sand mill.
-Store with or without roof for pay loader operation and additional storage in a heated mill building.
The intermediate storage-in the cold regions-must prevent freezing of the sand.The sand must be finer than 2 mm,otherwise screening is required.
Sand goes from charging hopper for sand,conveyors,dosing into sand mill and vibrating chute exactly dosed into the sand mill (wet mill)
Water is dosed into the mill in an exact proportion to the sand.
The sand mill is a ball mill with inside rubber lining for overflow of the slurry.
The overflow sand-water-suspension called"sand slurry" exits via a centric cylindric screen rotating with the mill(to separate oversize material)into the pump sump.
An abrasion resistant pump for sand slurry pumps the sand slurry into the storage tank for sand slurry with efficient agitator to prevent sedimentation of the solids.
The sand slurry pump pumps the sand slurry into the batcher for slurries.
Option:The density of the sand slurry can be measured between mill and storage tank for sand slurry by the density meter and the mill can be adjusted accordingly.
The mill charge (balls or cylpeps)made of high alloyed steel are continuously refilled by the mill charge feeder(4.13),so that the sand mill always runs with the same quantity of mill charge.
Section :Aluminium , Lime ,Cement , Water , Returns Slurry
3. Aluminium powder
The fine aluminium particles in connection with lime and water create tiny hydrogen bubbles.This causes the fine pore structure of the aerate concrete.
Aluminium powder or aluminium paste(coated aluminium power)is mostly supplied in drums,often in pre-weighed small plastics bags packed into drums.The aluminium mixing system mixes aluminium powder with water to form aluminium slurry.
The aluminium mixer is filled with the required water quantity and the pre-weight aluminium is dropped into the mixer for aluminium slurry.
Depending on the size of the mixer one or more batches of aluminium are filled into the mixer.
The aluminium dosing system doses aluminium into the batcher for aluminium slurry which is automatically discharged into the main mixer.
For security reason aluminium powder and paste should be stored and used in a separate room according to the safety instructions of the aluminium manufacturer.
Powderized quick lime
Usually fine ground quick lime is available.
This quick lime is supplied by silo trucks with built-in compressor.It is blown into the silo and dosed by a dosing screw into the batcher for solids(12.5).
Should the lime quality vary,then two or more lime silos are recommended.
Lime in lumps
Occasional lime is only available in the form of lumps of lime in the range of 20-40 mm of bigger.In such case a lime grinding plant has to be added.
Details upon request.
Powderized quicklime is stored in a silo
In the ideal case the cement factory is nearby and the cement is suppied by silo trucks with built-in compressor.It is blown into the silo for cement and dosed by a dosing screw into the batcher for solids.
In case the cement comes long distance and the supply is not regular,then a large quantity of cement should be stored in intermediate silos and from there be blown into the silo for cement
Cement dosing screw with variable speed for fine dosing.
Production water has to be cooled or heated according to requirements in order to reach the ideal process temperatur in the main mixer
Production water is dosed by the batcher for slurries.
7 Returns Slurry
Returns slurry is an important raw material for AAC production.Returns slurry is made out of the fresh cut-offs in the cutting line.All fresh cut-offs are recycled.
The cut-offs are mixed with water in the agitator and-once the required water-solids ratio has been reached-they are pumped into the storage tank for returns slurry equipped with effective agitator to prevent sedimentation of the solids.
Effective agitators prevent sedimentation of the solids
Dosing and Mixing
AAC is produced in large moulds.
Consequently dosing of raw materials is in charges.
Mixing Plant Control
The dosing and mixing system with its automatic mixing control is the brain of the plant and the key to a consistently good quality.
All important parameters of the raw materials are registered and stored and used for the production process.The system can be connected to a central computer and a quality control-an important benefit when certifying ISO 9000.
The correct water content of the mix has an important influence on the success of the operation.
Based on the slurry density the computer programme calculates the solids content of every charge which is contained already in the different slurries and compensates via water batcher or batcher for slurriesthe remaining water content.
The slurry densities(water-solids-ratio)for the sand slurry and the returns slurry can either be entered manually or (as an option) be measured with the density meter and transferred directly to the control system.
Computer Controlled Dosing
The mixing plant control weighs all raw material by means of the computer programme.The computer programme works as a "self-learning" system with highest precision.Every new charge will be compared with the previous one and in case of minor differences,these will be compensated.
Automatic mixing plant control is the key to consistently good results.
The temperature of the mix has high influence on the reaction of lime,cement and aluminium.Consistent temperatures in the main mixer are important for a consistently good quality of every AAC"cake".
The temperatures of all raw materials are automatically measured,the heat content of the mix is calculated and compared with the required heat content.The required difference heatwill automatically be compensated in form of hot or cold water.
As an option the computer can also consider the reaction heat of binders and aluminium as well as possible heat loss to the environment.
The batchers for the individual raw materials work on load cells and are controlled by a computer.
The main mixer is a special SANKON design for best mixing of all materials with good shears forces for mixing fine lime powder and to avoid lime lumps.
The main mixer is automatically washed in regular intervals.The wash down water is collected in a tank with agitator and is used repeatedly(pump for wash down water,and is then used for the returns slurry preparation.
Under the mixer is the slurry vibrator which emerges into the slurry and which improves the pore structure considerably.
The agitators for the returns slurry must run continuously and have to be connected to the emergency gen-set.
Mixer discharge into the mould
The cake is precured in heated precuring chambers(to be supplied by buyer).Upon request the preheated chambers can be equipped with many individual rolling doors and individual chamber heating,one for two moulds.
The whole form is only used during precuring.No part of the form whatever will go into the autoclave.
The intelligent transfer car transports the cake in the mould from the main mixer to the precuring"parking"places and form there-once cured-to the cutting line.With the "Smart" plant the transfer car also transports the cut cakes from cutting to the autoclaves.
Calcium Silicate Hydrate-the outstanding feature of Autoclaved Aerated Concrete(AAC)is formed in the auoclave with saturated steam and temperatures of 190°C(374°F).The crystal structure formed during autoclaving is significant for strength,shrinkage and water absorption of AAC.Steam entering the autoclave is initially condensating due to the difference of temperatures.This condensate is automatically drained in order to reduce the difference of temperatures between top and bottom of the autoclave.
Autoclaves are built to the proprietary specifications of SANKON.Part of these specifications are also steam connections,steam distribution,condensate outflow,vacuum connection,rail tracks and rail traverse.
The automatic autoclave control with PC and monitor as well as with special proportional motor valves controls automatically the whole autoclaving process.
Steam Boiler Plant
The steam boiler plant for approx,16 bar(230psi)with burner, chimney,feed water preparation, desalting,heat exchange,piping system,electric control and more accessories supplies steam for autoclaving,for hot water of section (Dosing and Mixing),for heating of the precuring chamber, the waiting area in front of the autoclaves as well as for the heating of the factory buildings.Part of the heat can be taken from the heat contained in the condensate.
Sorting and Palletizing
Production Process of Steel Reinforced Panels and Slabs
(as extension of block production)
Steel Reinforced Panels and Slabs
Steel reinforced panels are a good combination together with block production,usually the second step.
Experience proves that panels and slabs are more successful in conjunction with a "building system" offered by experienced builders.Such "building system"is usually developed and designed by the builder in a cooperation with AAC producers and/or the customers of the builder.
Such "building system"can be for industrial buildings,schools,commercials,dormatories,multifamily buildings or just homes.AAC panels are successfully used in seismic areas.
Steel wire(mostly 6-9 mm or 1/4 or 3/8" thick)are supplied as coils.The wire should be rust protected.
The coil goes into the wire straightening and cutting machine where the wire is cut to longitudinal or cross bars.
The coil goes into the automatic mat welding machine to form a mat.Two mats are welded together to form a cage(cage welding machine.
Spacers-in dimension to the distance-are welded to connect the two mats.
1 cage per panel is used.
Reinforced Assembly and Rust Protection
The individual cages are fixed onto an assembly frame.The assembly frame has the size of a mould and consists of the mould size frame and cross beams to hold the cages.
At the assembly places the cages are fixed with holding pins to the cross beams.
Cross beams and holding pins for the cages.
One set of reinforcement for one mould is now assembled and is on the assembly frame conveyor however the cages still require corrosion protection and are dipped with the anticorrosion coating lift into the anticorrosion coating plant.The anticorrosion paint(usually water based)dires on the dryer.
Smaller AAC production plants use manual coating where the individual cage is dipped and coated and is then dryed on racksbefore being fixed into the assembly frame.
The assembly frame(107.0)with the coated cages is lifted by the assembly frame lifter(111.0)on a mould and is extracted with the same machine after precuring prior to cutting.The pins are unlocked to release the reinforcement into the cake.
Anti-corrosion coating of the cages
The cake with the precisely placed reinforcement runs through the cutting line and is cut to panel dimensions.
Assembly frame with cages is set on the mould.
Damming Wall System (Option)to adapt the Mould Length during Production of Short Length Panels
It is advised that the mould length is shortened(adapted)once short panels are produced.Damming walls are used.
The damming wall inserter or a slewing pillar crane sets the damming wall into the mould prior to mould closing.When closing the mould the damming wall is fixed(squeezed)into the mould.
Ready panels are handled with the palletizing and sorting machine and can be checked and stacked with the panel.
Depending on type and length the panels are put together to form a pack or a bundle.They are covered with plastic film,straps and wooden squares in order to facilitate fork lift handing.
Some panels require finishing such as sawing with the panel saw to size or milling or drilling.
JQF-6 Autoclaved aerated concrete cutting machine is one of JQF-4.25 series product. It is a constant cutting developed from moving cutting. The machine is composed of longitudinal cutting machine and transverse cutting machine trolley and guid rail. And, the horizontal cutting machine has been modified from fixed swing, spring tension to frame swing and cylinder tension, and there is contact surface on the frame swing, which increase the service life, and remove the deform defect by the spring tension, it improves the cutting accuracy.
When the casting blank is lift to the cutting trolley after turn 90° and de-mold, it will be moved to the work station of longitudinal cutting machine and transverse cutting machine to have six surface cutting for the casting blank. First, it will be cut 4 surfaces horizontally by the longitudinal cutting machine, and then it will be moved to the transverse cutting machine by the first trolley, and then cut vertically by the transverse cutting machine, and then it will be moved by the first trolley under the hanger which will lift it to the steam curring cavity and go back after the curring, meanwhile the cutting waste will be moved to the waste slurry mixing tank. It takes around 5 minutes to finish the cutting, the second trolley works together after the first trolley, it will move the cutting waste to the tank when the first trolley goes forward.
Single machine function:
Longitudinal cutting machine: It cut 4 surface for the casting blank (2 sides and upper and lower horizontal surface), the blank size after cutting is 600mm wide and 1200mm high, and it will be cut horizontally base on product required, and it will mill the tenon on the both end
Transverse cutting machine: It is used to cut the both end of the casting blank, the length will be determined base on the requirement, and it will cut vertically from upper to lower base on the thickness requirement
Trolley: It is used to move the casting blank to the cutting work station and move the cutting waste to the mixing tank
Waste clean trolley: It is a special trolley to move the cutting waste to the waste slurry mixing tank
The guid rail is used only for the trolley running.
Longitudinal cutting machine
Max outside size
Length:10410mm Width:2870mm Height:2550mm
Weight : According to the actual production
Cutting wiring diameter
Longitudinal cutting wire: φ0.5mm
Transverse cutting wiring: φ0.8mm
Transverse cutting machine
Max outside size
Length:6900mm Width:3155 mm Height:4000mm
Vertical cutting reducer
Type: K87-17.1-YEJ5.5-B31-0 Qty:1PC
Install type: B31
transmission ratio: i=17.1
Type: YEJ112M-4 Qty:1PC
Rotate speed:1450 r/min
Lifting time:Single stroke121.5/s
Lifting time:Single stroke,upper 73s,lower48.5s
Cutting swing (transverse cutting)
Cutting wiring diameter: φ0.8mm
Cutting trolley, waste remove trolley
Max outside size
Length:4200mm Width:1650mm Height:1140mm
All the main parts of the longitudinal cutting machine, transversed cutting machine and cutting trolley are made of square and rectangular steel tube, it has good rigidity, long service life and convenient structure, which is easy to install and adjust
Longitudinal cutting machine: It is composed of Longmen frame, beam, the vertical beam axis, cutting, slotting device, longitudinal steel wiring and wiring cutting tensioning device
Transverse cutting machine: It is composed of Longmen, transverse frame, frame beam, a guide shaft ( a guide sleeve for special lubricants bearings, without refueling ), transverse swinging device, vertical cutting transmission system ( lifting by the sprocket chain composition) and cutting wiring
Cutting trolley: It is composed of trolley body, cutting frame, wheels and running device, etc. It is driven by the speed reducer.
The longitudinal cutting machine is tighten by the tension device and there is cutting wiring or cutter in the both sides, the front is used to cut the casting blank and the back i used to modified, in order to make ure the width is 600mm. The horizontal cutting has 5 grades, it cut in the angle of 39°48ˊ. The advantage is the cutting material will come down stably that there will no crack happen, and avoid any destroy. Each wiring has accurate scale to position, in order to make sure the product accuracy
The transverse cutting will start when the casting blank is put on the workstation. The program is that the vertical and horizontal cutting is synchronized. When it is cutting vertically, itis from upper to lower, the power is the reducer of K87-17.1-YEJ5.5-B31-0, the transmission reducer drives the chain wheel to make it cut from upper to lower. Transverse cutting is started by KD05-7.55-Y5.5-4P-M4-A+B, and it will have repeated motion with the help by the eccentric mechanism swinging device, and the cutting wiring in the both end will cut it to the required length and the middle part will be cut as the product required. The cutting wiring is tightened by the cylinder and the accuracy is positioned by the scale, the cutting time from upper to lower is 121.5 seconds
The cutting trolley is special used for moving the cutting material, it is driven by the reducer.
Longitudinal cutting machine, transverse cutting machine and trolley is made of steel structure, it is installed already before ex-factory. It just need to fix some parts that loose during the shipping.
Longitudinal cutting machine
Install cutting wiring, and connect to the air supply.
Transverse cutting machine
Install cutting wiring, and connect to the power supply of the reducer.
Put the trolley onto the guild rail, and connect the wheel to the gearing, connect to the reducer power supply, it then can run.
Trial running, trial cutting and adjustment:
The cutting trolley is run on the guid rail, and the 4 wheels run stably.
Trial cutting and adjustment
In case of any difference happens during the trial cutting, just refer to the scale to adjust the cutting wiring position.
Longitudinal cutting machine
The horizontal error can be upper or lower adjusted, the section mold is 5mm, longitudinal cutting error (600mm) , longitudinal cutting wiring or cutter can be left and right adjusted.
Transversed cutting machine
The error can be left and right adjusted, the section mold is 10mm.
The swing speed is controlled by the frequency converter (Note: It should be done when start)
Maintenance and repair:
Clean the waste in each part after the each production shift.
Remove the dust on the cutting wiring, scale, chain wheel and chain.
Loose the cutting wiring.
Add oil for the reducer per wee.
Check the oil level of the reducer, and add it on time if it is lower the level.
Chain wheel uses 90# industrial wheel oil.
KW series reducer uses 90# industrial wheel oil.
Tighten the parts and replace each destroyed parts.
Check the power supply in case of any electricity leakage, check the cutting wiring and replace the destroyed parts.
Shut off the power after the production
In case the wiring is broken during the production, stop the machine to replace, and no one is allowed to stand in the permitted line.