 |  | Compressed Earth Block - Volume I. Manual of production (GTZ, 1995, 104 p.) | ||
 |  | Production | ||
|  | Soil extraction | ||
| | Transport | ||
| | Stocking raw materials | ||
| | Manual preparation | ||
| | Motorized preparation | ||
| | Measuring out | ||
| | Mixing | ||
| | Compressing the blocks | ||
| | Curing and drying | ||
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GENERAL OBSERVATIONS
When deciding on how to extract the soil, several points must be taken into account. Is the extraction site on the production site itself or not? How much soil is needed and how can you avoid the risk of the soil type changing during extraction? Is the location accessible or will additional work be necessary? Is there any danger during extraction of causing a landslide? Will large holes be left behind, in which case dealing with these (by filling, levelling, landscaping etc.) needs to be allowed for.
HOW TO EXTRACT THE SOIL
For manual extraction, simple tools will suffice (shovels, picks, wheelbarrows). For mechanized extraction, a great deal of public works equipment is available, but is very expensive to purchase. The economic aspect will need to be precisely evaluated, both in terms of direct cost and the broader side-effects of the choice made. For the same cost, extraction time will differ greatly between manual and mechanized operations, as will the potential for creating jobs.
Depending on the site layout, certain pieces of equipment will be more suitable than others. A shallow, but wide quarry, for example, will need "raking machines" (such as dumper trucks, excavators, a bulldozer, scraper, agricultural tractor, etc.) If the quarry is deep' but narrow, machines such as mechanical diggers or loader-diggers for vertical digging will be more suitable. For more detailed information, there are numerous documents relating to public works to be consulted.
FIGURE
INTERMEDIATE OPERATIONS
This chapter deals essentially with processing operations specific to CEB production. Intermediate operations will, however, require transport and space, and these have to be taken into consideration for the brickworks to be efficiently run.
The data and outputs given below are indicative of the form of transport which will be best suited to each brickworks, from the simplest to the most sophisticated. Stocking materials and products will be addressed further on. It is difficult to give even approximate indications of the waste material excavated as this will be highly dependent on the context (the type of soil, the production location, proportions of materials used etc.). In general, it is fairly easy to find uses for waste, which includes rubble, rejects of screening, broken or sub-standard blocks, etc. It can be used for infilling, land drains, low temporary walls, etc. Recycling waste will take up part of the labour input and this should be checked to ensure that it is viable.
FIGURE
FIGURE
SOIL AND SAND
Both of these are generally stocked in bulk, but they can also be kept in storage bays if space is limited and to avoid them flowing and mixing together.
Keeping stocks in piles
The contents of a 5 m³ lorry will take up 9.5 m² on the ground, or approximately 1.7 m² per m³ soil or sand (taking account of settling).
FIGURE
Keeping stocks in storage bays
The sides must be strong enough to contain the soil.
FIGURE
WATER
Water is often stocked in 200 litre barrels. These are easy to find, cheap, and transportable. They can, for example, be placed under a roof gutter to catch rainwater.
FIGURE
Storage tank
A water tank with sides strong enough to resist the pressure of the water can also be built from CEBs with a waterproof render.
FIGURE
CEMENT AND LIME
Both of these are generally supplied in sacks, particularly cement. Here we use a "standard" 50 kg (= 42 l) sack of cement as a base.
FIGURE
The sacks should preferably be stocked in a secure area and protected from humidity, i.e. raised above the ground and kept away from walls to prevent the cement from absorbing humidity and to avoid destabilizing the walls (see sketch below).
Temporary external storage areas, protected by tarpaulin or plastic sheets, can also be used (as shown below).
FIGURE
FIGURE
GENERAL OBSERVATIONS
Soil preparation operations will play a crucial part in the ultimate quality of the blocks. These operations can sometimes make it possible to use soils which are unusable in their natural state, because they can include modifying the grain size distribution. Bearing in mind that extraction and transportation costs are generally high, this can allow useful economies to be made.
As we have seen in the chapters on STABILIZATION and EQUIPMENT, preparation is virtually indispensable for stabilized blocks in order to ensure an even distribution of the stabilizer, which will not work efficiently if the soil is sticking together. Even for non-stabilized blocks, any sods or tiny lumps of soil will prevent even compression and will then become weak spots inside the blocks. Preparation also enables any grain size distribution defects to be rectified. Grinding, for example, can fragment gravel, thus turning it into coarse sand; screening can remove a soil fraction such as stone or gravel which may be present in too great a quantity.
PULVERIZATION
The object here is to either break up lumps which are held together by clay (crushing) or to fragment stones and gravel (grinding). Applying fairly high pressure is sufficient for crushing, whereas grinding demands a hard impact.
SCREENING
In general, this is done to remove the particles which are too coarse. Mesh sizes typically go from 10 mm for presses which are sensitive to compression, to 20-25 mm for less sensitive presses, because of their higher compression force (F > 10 MPa).
FIGURE
MANUAL TECHNIQUES
Crushing can be carried out manually by breaking up the lumps of soil with a pestle or tamp. This process is cheap from the point of view of equipment, but it is also slow and painstaking. There are some simple manually-driven mechanisms using backwards and forwards motion or cranking handles. These can only crush the soil and have fairly low outputs relative to their cost.
Grinding by hand, although it does exist traditionally, is in practice very laborious, except for very small quantities.
Screening by hand, on the other hand, is very common. A wire-mesh fixed to a frame is either held at a slant by rigid supports, or suspended almost horizontally from a superstructure. The screen can therefore be shaken backwards and forwards, which increases output. Provided the soil is very dry, there are also hand-operated rotating screens with fairly good outputs, but which are quite expensive.
Crushing by hand
The soil is spread out and any lumps are broken up preferably on a hard surface.
FIGURE
Fixed manual screen
The soil is thrown onto the screen, which is fixed at an angle of about 50°. The angle can be modified, to allow more or less material to passing through.
FIGURE
Manual pendulum crusher
The crusher can be combined with a sieve so that all the processing operations are carried out at once. Not to be used with soils with too high a gravel content.
FIGURE
Suspended screen
The screen is at a slight angle to allow waste material to be removed and has a backwards and forwards motion.
FIGURE
GENERAL OBSERVATIONS (see chapter on EQUIPMENT)
Equipment specifically for preparing soil has not existed for very long; previously, preparation equipment was developed for the concrete industry or for agricultural purposes where conditions are different. For concrete, the material is reconstituted starting from pure, isolated ingredients (gravel and sand), whereas for CEB production, a product is obtained from a composite material (soil), where an ingredient has sometimes to be added or removed.
Agriculture is concerned with organic matter which is not as abrasive as soil. Agricultural equipment will therefore need to be slightly modified to avoid its getting very rapidly worn.
FIGURE
CRUSHING
Manual crushing is painstaking and moreover does not grind down the material. Mechanizing this process is therefore advantageous, particularly as a great deal of equipment specifically for soil is beginning to come onto the market.
"Tread-mill" crushers are suitable for fine soils with no stones or coarse gravel. They can only break up the lumps which are held together by clay and will not fragment any solid particles. This means that the grain size distribution of the soil is not modified. This type of machinery is suitable for treating dry soil, but can work with a soil the moisture content of which is close to the moisture content for compression limit (10 to 15%), in which case, it could also be used as a mixer.
Blade grinders are suitable for all soil types, even stony ones, since the hammers or cutters will split stones. This means that grinders do modify the grain size distribution of the soil, by increasing its fine graves and coarse sand content and eliminating stones and coarse gravel. The horse-power, apart from its impact on output, affects the extent to which the material will be broken down. Grinders work badly with wet soil which forms a crust inside the machine, blocking the feeding hopper and causing the hammers to wear more quickly. If necessary, the soil will have to be dried or at the very least the inside of the machine will need to be cleaned out very frequently. Nevertheless, this type of pulverizer is one of the most efficient.
SCREENING
The mechanical screens currently available, whether vibrating or rotating, are rarely specific to CEB production. They often allow several grids to be used in combination in order to break the material down into various grain size fractions, which is rarely useful for CEBs, where at most only one or sometimes two grain sizes need to be isolated. Outputs are generally high and apply to large production units.
Mechanically-driven rotating screens can be relevant to medium to large sized units.
Vibrating screens are heavy and very high in energy consumption. They are relevant only to large production units.
Fixed screens loaded from loader-diggers can be an advantageous solution. The screens are simple and cheap. They can be made locally in craft workshops. The loader-digger, although relatively expensive, can be used at various stages in the production process (i.e. extraction, transport, pallet loading, etc.) Similarly, agricultural tractors equipped with forward buckets can be used.
GENERAL OBSERVATIONS
As we have already seen in the chapter on STABILIZATION, ensuring that the correct amounts of different materials are used is crucial, both for the quality of the product and for controlling production costs. Here we are not concerned with calculating quantities (which is covered in the chapters on SOIL and BLOCK-MAKING), but with how they are measured out, which can be either by weight or by volume of material.
MEASURING OUT BY WEIGHT
The amounts to be used are calculated as dry weights, but measuring out in the brickworks must take account of the moisture content, which is difficult to check in the case of materials such as sand, gravel, or earth. As the moisture content of cement, however, is insignificant, it can be measured out by weight without any danger of error. The scales used must be accurate to within 10 to 50 g depending on the quantities being weighed. The smaller the quantities, the more accurate the scales will need to be.
The operation must be carried out reliably (from the point of view of the operator and the scales), as well as efficiently (actions should be easy and quick), failing which there is no advantage to be gained from measuring out by weight. This approach has the advantage of measuring out material in a way which is precise and easily adjustable. For large production units, cement can be measured out by an automatic balance system (scales), identical to those used in concrete factories.
MEASURING OUT BY VOLUME
This is the most common and the simplest method. It has the disadvantage of being a little unprecise, depending on how wet and how loose the material is. This imprecision can be compensated for, however, by quality controls and by an experienced operator. Above all, measuring out containers of known capacity must be available.
There are two options:
- When using existing equipment (buckets, wheelbarrows, etc.), cheek the volumes with a relatively precise instrument (e.g. graduated bucket). These volumes are measured at the startup of production and will be used as the basis of calculations of quantities to be used. During production, volumes must be regularly checked to make sure that they have not changed (because of dents or different buckets or wheelbarrows being used, etc.).- Making measuring out containers (boxes for materials such as soil, gravel or sand) of the desired volumes, i.e. probably 30 to 601 capacity. If the box is too small, the same operation will have to be repeated too many times, and if it is too big, it will be too heavy. If mixing is done by hand, boxes with no base can be used, so the contents do not have to be lifted up. These should not exceed 100 to 1501 capacity. If a box is made for measuring out cement, its capacity will be approximately 5 to 10 litres. For large production units, measuring out can be done using feeding hoppers combined with a measuring out slide valve of precisely fixed capacity.
FIGURE
MEASURING OUT EARTH, SAND AND GRAVEL
For all these materials, the usual quantities range from about ten to about a hundred litres. The most suitable way of measuring out is generally by volume (using a bucket, a wheelbarrow, a measuring box etc.). After filling the measuring container, the surface must be levelled out using a straight edge (the handle of a shovel for example) to scrape it level with the top of the sides of the container.
MEASURING OUT WATER
It is difficult to calculate beforehand the precise volume of water which will be needed to reach the optimum moisture content for compaction, as this will depend on the natural moisture content of the various materials (soil, sand, etc.) which varies greatly. The operator must determine the optimum quantity of water using simple tests (e.g. the drop test, see QUALITY CONTROL) and by experience.
MEASURING OUT CEMENT
The usual quantities will fluctuate between 5 and 15 kg. If measuring out is by weight, all that is needed are fairly precise scales. If a measuring box made to correspond to the volume required for a given degree of stabilization is being used, the surface should be scraped level with the sides without pressing the cement down. Actions should be as repetitive as possible so that the same amount is measured out each time. If measuring out is done by dividing up a full sack, e.g. 1/2, 1/3, 1/4, 1/5 of a sack, the contents of the sack should be divided up at in one go between the correct number of containers (usually buckets). Thus to obtain 1/3 of a sack, 3 buckets are needed for 1/4. 4 buckets, etc.
FIGURE
FIGURE
DETERMINING THE APPARENT DRY DENSITY OF A MATERIAL
A satisfactory result can be obtained by knowing the weight of a
litre of dry material. The figures obtained will be in kg/dm³ or in tons/
m³. This requires scales accurate to within 10 to 15 grams, a container for
measuring out exactly 1 litre and a way of drying out the material: a drying
kiln or oven, or a gas-burner and pan (maximum temperature: 105°C). The
material can also be spread out thinly and left to dry in the sun. The result
should be accurate to within 50 g/dm³.
GENERAL OBSERVATIONS (see also the chapters on SOIL, STABILIZATION and EQUIPMENT)
Mixing and preparation are important operations in the manufacture of a block. Obtaining a mix with the optimum moisture content for compaction is crucial to the quality of the product; for example, a 2% difference in moisture content can reduce the density of the block by nearly 100 kg/m³. The cement should be evenly distributed for its effect to be equal throughout the mix. The more homogenous the mix, the more the degree of stabilization can be reduced, i.e. lowering costs without affecting quality. Mixing should be done first dry, if dry materials (cement, sand, gravel) have to be added to the soil, followed by wet mixing, spraying the water on gradually. If water is added too quickly, it will be difficult to mix the dry and wet parts together. This applies both to stabilized and unstabilized blocks.
HAND MIXING
USING MANUAL MIXING TO MOVE THE
MATERIAL ALONG
MANUAL TECHNIQUE
The best way to proceed is to turn the pile over at least two or three times for the dry mix, and then a further two or three times gradually adding water. It is important to make sure that the shovel scrapes along the ground and picks up soil from the very bottom of the pile, at the same time making a vertical slope down which the soil from the top can flow and thus be mixed in. Soil should be poured from the first pile onto the top of the second pile, also to make it flow down. No more than 1/3 of a sack of cement should be mixed in at a time (see illustration on).
LAYOUT
Turning the soil can be exploited as a way of transporting the soil towards the press. This means locating stocks of dry material 6 or 8 metres from the press end the wafer stocks or supply halfway between the two, i.e. 3 or 4 metres from the stocks of material and the press. This approach ensures that the piles are well turned the required number of times (see sketch on p. 64).
MECHANIZED TECHNIQUES
The principles and objectives of mechanical mixing are identical to those of manual mixing, i.e. it is important to begin with dry mixing for 2 or 3 minutes for materials such as soil, sand, gravel, cement etc. and then to moisten the mix evenly by sprinkling (with a watering can), very fine spraying or vaporising the water. Wet mixing also takes 2 to 3 minutes.
The mixer can be filled using either buckets or measuring boxes which have to be emptied by hand, or using a sloping ramp for wheelbarrow access, or - for large production units - through measuring hoppers.
The formation of lumps of soil during mixing (generally wet mixing) must be avoided as these are difficult to compress. Lumps can form if the moisture content is too high and/or if the mixing time is too long, or again if an inappropriate system of blade-mixing is used. Checking the optimum moisture content (OMC) is crucial. For soils with a high clay content, the moisture content should be slightly higher than the OMC. For sandy soils, it will be slightly lower than the OMC.
FIGURE
GENERAL OBSERVATIONS (see chapter on EQUIPMENT)
Compression is of course the key operation in the manufacture of CEBs. Nevertheless, the quality of the product will depend heavily on what "goes into" the press (the type of soil and all the preliminary operations: preparation, mixing, retention time, etc.) as well as the way in which the products are going to be treated when they come out of the press (curing, storage, transportation, etc.) The various types and qualities of presses available obviously have some impact, but they are not necessarily crucial to the final result, the CEB.
The outputs suggested below are purely indicative and can vary enormously with different operators.
FILLING
Generally, moulds are designed to be completely filled with the mixed material. The soil therefore has to be scraped level with the sides of the mould. But with certain soils, the mould must not be completely filled, and in these cases the operator can often work "by eye", or he may be helped by some system for measuring out (a measuring box, a graduated bucket, etc.) There are also automatic mould levelling systems, (using brushes, a roller, a leveller etc.), generally fitted to rotating table presses. Some presses are equipped with an adjustable measuring system, either using sliding valves or tipping boxes. Such systems may be manual or mechanically-driven. If filling takes place from conveyor belts or hoppers connected to the mixer, such adjustable automatic measuring systems are indispensable. When the operator has access to the mould before compression takes place, he should preferably check on the content of the mould and, for example, top up or remove some material (if necessary) or press the soil down into each corner of the mould with his fingers (particularly for low pressure presses), and if necessary remove any stones, lumps or clods of soil (see illustrations below).
COMPRESSING THE BLOCK
If the press is fitted with a lid, it must be correctly positioned and soil must not get trapped in the angle between the mould and the lid as this can cause the lid to be displaced or the compression system to jam.
Some lids also precompress the soil in which case it is not so important to clean off the top of the mould. On the other hand, this type of lid has to be slammed down quite forcefully, taking care that no operator still has his hand in the way.
For manual presses, the force which has to be applied to the compression lever will depend on how much soil there is in the mould. This force should be neither too high nor too low. In the former case the operator will rapidly tire or the machine will be broken and in the latter, the block will be insufficiently compressed.
For motorized presses, the compression force remains uniform. It is therefore impossible to check during compression if the mould has been correctly filled.
FIGURE
FIGURE
REMOVING THE BLOCK FROM THE MOULD
With simple presses, the same piston both compresses and ejects the block. With more sophisticated presses, there will often be a second piston specifically for ejecting the block. This has the advantage of greater productivity, but the disadvantage of a higher risk of breakdowns or mechanical problems.
Once the block has been ejected, it must be picked up carefully as it is still fragile. The surface area of contact between the block and the hands should be as large as possible to keep pressure on the block to a minimum. The edges, which are fragile, should not be touched (see sketch on).
For large production units, the block will be ejected onto a moving belt, but here too it will often be picked up by hand at the end of the line. There are block pincers which reduce the risk of damaging the newly moulded block and which also enable one person to carry two blocks at a time.
USE OF SPECIAL BLOCKS
Special blocks, as we have seen, have a frog or a perforation allowing one to incorporate structural, or non-structural elements into the walls. They can also serve to make the blocks lighter and to reduce the amount of material used. Depending on the building system, however, the frogs or perforations may be filled with mortar. As the mix used for the mortar will be 1.5 times more stabilized than for the blocks, this could lead to additional costs for cement. Frogs and perforations are also used for decorative purposes (claustra work, etc.).
SPECIAL BLOCKS AND WAYS OF MAKING THEM
The way special blocks are made will depend on the press. If it
has interchangeable moulds it will be relatively easy to add all the possible
variations. If, on the other hand, there is no possibility of changing moulds,
it will nearly always be possible to insert a frog of the required
shape.
Where volumes are modified, in the same direction as the movement of
the piston (generally vertical), the shape of the latter should enable the
piston to slightly penetrate the mould, which will therefore be perforated.
MOULDS AND PISTONS
If the shape of the piston cannot be changed, vertical frogs which do not go the full height of the block can be used and then the superfluous part can be broken through by hand, although this has the disadvantage of leaving an irregularly broken surface.
FIGURE
If the change in volume is perpendicular to the movement of the piston (i.e. a horizontal frog), there will be no difficulty in inserting a frog with good results.
HORIZONTAL VOIDS
MAKING A FROG
Frogs should be strong (from solid wood, solid metal shapes, etc.). They are placed either right inside the mould, or attached to the lid or compression plate, or fixed to a piece of sheet iron placed between the lid and the soil. The sheet iron serves as a guideline and enables frogs to be quickly and precisely located. The sheet iron and the frogs have to conform to the dimensions of the mould, with a little to spare. For example, for a block measuring 29.5 × 14 × 9 cm, the piece of sheet iron will measure 29.1 × 13.6 and be 1 to 2 mm thick.
MEASURING OUT TO FILL THE MOULD
The mould no longer contains only loose, mixed (compressible)
material, but also a compact (non-compressible) foreign body. This means that
the compression ratio has to be reduced. This can be done either by adjusting
the machine, or by reducing the volume of loose earth being put into the
mould.
Some system for measuring out (a graduated bucket, a measuring box,
etc.) will save time.
FIGURE
TRANSPORTING SPECIAL BLOCKS
The frog or perforation lowers the strength of the block, particularly when it has just been moulded. To prevent weak blocks from breaking, they should be transported with the frog, which should be removed only when the blocks have been stacked for curing. At least two of each of the same shaped frogs will therefore be needed, or production will be slowed down. For strong blocks, these precautions are not necessary (see illustration above).
GENERAL OBSERVATIONS
Curing conditions and principles have been reviewed in the chapter on STABILIZATION. They greatly influence the final quality of the block. Briefly, for very slightly stabilized blocks (< 3 to 4 %), drying should not be allowed to take place too quickly, as this would cause shrinkage cracks. Unstabilized blocks should also be sheltered from direct sun and wind, but not kept in a humid environment. For cement (or lime) stabilized blocks, the presence of water within the block is crucial for the stabilizer to attain its maximum strength. High temperatures will also help in this respect. Not only do the blocks have to be sheltered from direct sun and wind, but they also have to be kept in a hot, humid environment with the help of tarpaulins or heat-absorbent (black, for example) plastic sheets, which can be sealed off as hermetically as possible. The duration of this humid, hot curing stage will also depend on the climate, but should be not less than 7, and if possible 14, days.
The differences between curing, drying and final storage lie in the way these are carried out, but not necessarily in the way the blocks are placed, unless they are too fragile when newly moulded. For cement-stabilization, complete curing takes 28 days. For lime-stabilization theoretically it takes 6 months (but the blocks can be put into use after maximum 2 months).
SEPARATE STACKING (FOR CURING, DRYING, STORAGE)
If the freshly moulded blocks are fragile, they cannot be stacked very high. A specific area will have to be set aside for wet curing close to the press (3 to 5 m) to reduce handling distance which can damage the blocks. The blocks can be handled after 2 days' curing. The curing areas therefore need to be able to hold the equivalent of 2 days' production.
The first day's blocks will be stacked on half of the area and the second day's on the other half. On the morning of the third day, the first day's blocks are removed to the area set aside for drying in order to make room for stacking the third day's blocks. Similarly, on the morning of the fourth day, the second day's block's are removed, and so on.
Special care must be taken when stacking special blocks which can have serious weak spots.
DIRECT STACKING
If the blocks are strong enough as they come out of the press, they can support being stacked 10 to 15 high. This type of stacking will require transporting straight from the mould over a greater distance than for separate stacking (10 to 50 m). If the ground is very flat, they can be transported using flat wheelbarrows or on pallets.
TIGHTLY PACKED ON THE GROUND
The ground must be flat and hard or the stacks will not be straight. The blocks are placed either on their lower face, or on their side. For fragile blocks, with separate stacking, blocks should not be stacked more than 5 or 6 high. If they are strong enough, and stacked directly, they can be piled 10 to 15 high. Crisscrossing the blocks between each layer has the advantage of keeping them straight, but may cause depressions which can break the blocks. Small, finger-wide spaces can be left between the piles, which avoids having to slide them together and risk damaging them.
ON LATHS
Placing blocks on laths is used only for blocks which are very fragile when freshly moulded. Laths create spaces between the layers, so that a hand can be slipped between them without spoiling the blocks. The other advantage is the possibility of achieving good stacking even on a ground surface which is not very smooth or flat. The blocks are placed on their sides 3 to 6 high. Disadvantages are that this takes up a large area and uses up a great deal of wood (for the laths).
ON PALLETS
This type of transportation has the advantage of being very easy. Machinery for lifting pallets (pallet transporters, cranes, etc.) can take loads of up to 1.5 tonnes, or the weight of 200 blocks, and piles approximately 5 blocks high. Forklift trucks can take heavier loads.
SPREAD OUT ON THE GROUND
This kind of stacking is suitable only for unstabilized blocks. The blocks are directly stacked on their sides, with spaces between them to allow air circulation, 2 blocks taking up the width of 3. To steady the piles, blocks are crisscrossed but there is no risk of their breaking since the load is reduced.
FIGURE
STOCK MANAGEMENT
Whichever way the blocks are laid out, it is important to be able to count them easily. It should also be easy to find their date of manufacture in order to be able to check on the duration of the curing stages.
Stacks can correspond either to a day's production or to a number which is a convenient multiple (e.g. 500 or 1,000 blocks). The choice will be determined by the space limitations of the production site and the rate of demand for the blocks. In general, stacks equivalent to one day's production take up more space than stacks of a convenient number. But if demand for the blocks is high, they must be usable as soon as the curing stage is over, in which case, stacking by day's production is preferable.
Note: data refers to 29.5 × 14 × 9 cm blocks.
Tightly packed blocks, placed on
their lower face
Separate and direct stacking
Ground surface area: 5.25 m² - 125 blocks per
layer.
First stage curing: 500 blocks stacks, 38 cm. high, i.e. 4 blocks
high, tarpaulin covered area 4m².
Second stage curing: 2000 block
stacks, 1.52 cm high, i.e. 16 blocks high, tarpaulin covered area 17m².
Tightly packed blocks, placed on
their sides
Separate and direct stacking
Ground surface area: 3 m² - 100 blocks per layer.
First
stage curing: 500 blocks stacks, 0.7 m. high, i.e. 5 blocks high, tarpaulin
covered area 11m².
Second stage curing: 1000 block stacks, 1.4 cm high,
i.e. 10 blocks high, tarpaulin covered area 16m².
Blocks on laths, placed on their
sides
Separate stacking (fragile blocks)
Ground surface area: 1.1 m² - 40 blocks per layer.
First
stage curing (only): 200 blocks stacks, 0.86 m. high, i.e. 5 blocks plus lath,
tarpaulin covered area 9.5 m², 38 m. of 4 × 4 laths
Blocks on pallets, placed on their
sides
Direct stacking
Ground surface area: 1.2 m² - 40 blocks per layer.
First
stage curing: 200 blocks stacks, 0.85 m. high, i.e. 5 blocks high + pallet,
tarpaulin covered area 6.6 m².
The pallets must be strong and easy to slide onto the transporter.
Blocks on pallets, placed on their
lower faces
Direct stacking using a 3-ton fork-lift truck
Ground surface area: 1.2 m² - 24 blocks per layer (7th
layer only 16 blocks).
400 blocks stacks (3 tons), 0.75 m. high, i.e. 17
blocks high + pallet, tarpaulin covered area 11 m².
The pallets must be
strong and easy to slide onto the transporter.
Widely spaced blocks, placed on
their sides
Direct stacking, unstabilized blocks
Ground surface area: 5.4 m² - 100 blocks per layer.
1000
blocks stacks, 0.4 m. high, i.e. 10 blocks high, tarpaulin or mat covered area
(to provide shelter from direct sun and wind) 10 m² (1.7 × 6
m).
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