PSS Group SL Build

CONSTRUCTION METHOD

When calculating quantities for PSS Group SL Build, some allowance should be included for waste, although with good housekeeping on site waste would be minimal. There will be off cuts where special shapes are cut on site, eg pitched gables. Materials should be ordered in good time, recognising delivery lead times. When practical, minimise the between delivery to site and construction of PSS Group SL Build as this would reduce storage requirement on site.

The site should be prepared to receive the materials, by way of allocating an adequate access and lay down area, preferably adjacent to the actual construction. If materials are to be stored on site, they should be kept under cover or sheeted down.

Ensure that there is someone on site to take delivery of the materials. Mechanical equipment is not necessary for offloading as all packed PSS Group SL Build components are light enough to be manually portable.

CONSTRUCTION

Check that the base from which PSS Group SL Build is to be built is clean and level. Any steps in the level of the foundations should be multiples of 250 mm to co-ordinate with the standard block height. Set out and check the line(s) of the wall(s) to be built.

Move the pallets of PSS Group SL Build as close as practical to the point where they are to be erected and de -stack carefully, lifting each PSS Group SL Build Block cleanly up and away fro the pallet in order to minimize damage. Starting at the corners loosely lay out the base course or PSS Group SL Build Blocks, identifying where any cut blocks will occur – preferably in the middle of a wall rather than the end or corner.

Again, starting from the corners lay the second course to interlock with the base course of PSS Group SL Build Blocks in a stretcher bond, avoiding coincidence ot vertical joints between courses as far as possible.

PSS Group SL Build is manufactured to close tolerances, and the interlocking joint detail is designed to ensure a tight integrated connection. A proper interlock is achieved by lining up the interlocking joint and pushing the PSS Group SL Build Block firmly and uniformly into place. PSS Group SL Build Blocks should not be twisted or pushed into place on a skew. Check the position and alignment of the corners before cutting any closure blocks for the base and second courses. Insert any end pieces for corners or an opening progressively, as each course is laid.

When using the PSS Group SL Build 250 system, offset the second or third course of PSS Group SL Build Blocks 125mm to stagger the alignment of the crosswall connections, particularly when the concrete is to be pumped.

 

PSS Group SL Build

CONSTRUCTION METHOD

This will improve the stability of the wall during placement of concrete. Continue laying courses of  PSS Group SL Build up to the level determined for the first concrete pour, maintaining a pattern of stretcher bon construction. Use up all the PSS Group SL Build Blocks from one pallet before opening a new pallet. It is easier, quicker and tidier to incorporate all individual PSS Group SL Build Blocks as the work proceeds. Check for the positions and height of door, window and any other apertures so that these are constructed as PSS Group SL Build construction progresses.

SUPPORT

The tight interlocking mechanism of PSS Group SL Build components provides a relatively stable formwork system which achieves substantial extra rigidity from corner and crosswall constructions. When the height of concrete to be placed in one pour is less than one meter on a level base, it may be practical to place the concrete without additional bracing or support. When the height of concrete to be placed is greater than one metre, props or bracing should be provided at corners and at approximately two metre intervals along a free-standing wall so that the maximum length of unsupported wall does not exceed four meters.

The level of temporary support will vary depending upon the design and location of each project. On exposed sites or in conditions of strong or gusting winds it may be prudent either to reduce the exposed area of unfilled PSS Group SL Build Block system or provide additional bracing to counteract the effect of such winds. For this reason it is inadvisable to leave areas of unfilled PSS Group SL Build Block System for long periods before concreting, in case of deteriorating weather conditions.

Where lintel blocks are installed , check that they are adequately supported and braced if necessary.

 

REINFORCEMENT

Place and fix any specified steel reinforcement as work proceeds, ensuring the minimum depth of cover is established. If designed with full reinforcement (e.g. a basement, swimming pool), it is recommended that the wall is build and concreted in stages of c. one meter to allow for close monitoring of the concreting process.

In standard building applications the only steel reinforcement required will be for lintels over the various openings. Reinforcing bars may be located below the metal spacers or through the holes in the metal spacers as required. Should it prove necessary to include shear links in a reinforcement cage it may be more practical to remove the metal wires from the PSS Group SL Build lintel to allow positioning of either the reinforcing cage inside the lintel block, or alternatively a standard steel section in lieu of reinforced concrete In such cases it is recommended than an additional course of PSS Group SL Build Blocks be laid over the lintel to prevent the concrete spreading the unsupported lintel sidewalls.

 

PSS Group SL build

CONSTRUCTION METHOD

When a section of PSS Group SL Build has been completed ready for concrete, check line, level, and plumb of al walls. Check the positions of apertures. Check also that steel reinforcement is in place, and that any bracing or support is secure. Particular care must be taken with long lintels to prevent movement of the lintel bocks which form, in effect slender beams. Without full support of the PSS Group SL Build system lintel constructions are more susceptible to movement or distortion.

 

BUILDERS WORK

Install any ducts required through the wall for services and if necessary seal any gaps between the duct and the cut formwork. This will prevent any leakage of concrete when filling the wall, and eliminate cold bridging in the completed construction.

The position of wall ties and other concrete inserts should be marked out prior to concreting, to check for positioning and ensure that such items will clear the PSS Group SL Build Block spacers. (Note: Once the concrete is placed, there is relatively little time to set out and install any inserts before the concrete hardens) If such inserts can be fitted securely and without impeding the flow of concrete, they may be fitted prior to concreting.

The wall thickness of the PSS Group SL Build Block must not be reduced (e.g. Chased for services ) before the concrete has been cast as any reduction will substantially weaken the strength of the formwork system,

 

BUILDING SCHEDULE

The area of PSS Group SL Build that can be built at any one time may be as little or as much as practical. Whether it is the single course of a wall, or the complete storey height, construction of a building will depend upon project requirements and resources available. For access, control and flexibility of operations, it is better to plan for long runs of wall at lower lifts heights rather than short lengths of wall at high heights. The MAXIMUM height of wall that can be pored at any one time is three meters.

 

In most cases, the area of PSS Group SL Build erected at any one time is likely to be determined by the quantity of concrete that is to be placed in the following operation.

For intermediate pours the most practical level of concrete is just above the level of the polystyrene bridges and below the top of the PSS Group SL Build Block. At this level the concrete surface will be regular and continuous to facilitate a good construction joint, and the risk of concrete clogging the interlock detail at the top of the PSS Group SL Build Block will be reduced.

CONCRETING

A successful concreting operation is the key to the success of the PSS Group SL Build system. Concrete must be specified as a structural grade (minimum 25N/mm² strength at 28 days) and pump grade concrete with a minimum cement content of 300kg/m³ and a slump of 75-100mm. 10Mm aggregate size should be used , this specified concrete mix will help the flow of concrete.

Design strength of concrete may vary dependent upon the structural design and performance required. Specification of
pump grade mix serves to ensure that the formwork system will fill fully under the natural flow of the concrete and consequently vibration is not required to achieve adequate compaction.

The structural engineer will confirm concrete specification and requirements for steel reinforcement.
Placing concrete by means of a concrete pump is recommended as the most practical and efficient method of carrying out the work.

When ordering the concrete pump, check with the supplier that the concrete specification is suitable for the equipment to be used and check also what site facilitates are required. A supply of water and some cement to prime the pump  are normal requests.

Before placing concrete, check there is a clear working area for delivery of concrete and that adequate staging is provided if necessary to maintain a clear view inside the PSS Group SL Build system.
Provide protection for the top edges of the PSS Group SL Build systems to prevent concrete contamination and physical damage from concrete spillage and accidental impacts. Check that the interior of the PSS Group SL Build System is clear of all debris and loose articles before starting to concrete.

Check that the concrete is the mix specified and is well mixed before commencing to fill the PSS Group SL Block. It is recommended that a swan-neck discharge nozzle is used when placing concrete from a boom pump as this will reduce the momentum of concrete at  discharge point and make placement much easier.

Concrete should be placed first at the corners, and the PSS Group SL Build filled progressively towards the middle of the wall.
The concrete should be allowed to drop vertically and freely under gravity into the cavity of the PSS Group SL Build system.
After corners concrete should be placed at window openings up to sill level and the rest of the shutter should be filled in 1meter pours until the pour is complete.

Keep a lookout for signs of movement of the wall construction during the concrete operation and also for any significant leakage of concrete grout through the PSS Group SL Build Block joints or builders work penetrations.
The maximum height poured should be up to first floor level throughout the concrete pour close attention must be paid that the concrete flows smoothly and fill the system progressively and completey.

Care should be taken to ensure that any reinforcement is properly surrounded with concrete without displacement of the steel. Where T16 steel has been specified care should be taken to ensure the concrete has passed and filled the shutter.
If there is any doubt that the flow of concrete has been obstructed, a tamping rod may be inserted and the concrete tamped down.

After concreting a section of wall , check that line and level are correct. Should any movement have taken place, it may be corrected  by adjusting the PSS Group SL Build trestles and by placing a temporary bracing support. While the concrete is still wet, hose down any spillage off the exposed  face of the PSS Group SL Block.

PSS Group SL Build

CONSTRUCTION METHOD

Where the construction joints are to be formed, the top surface of wet concrete may be flushed to remove any contamination and expose clean aggregate to form a good clean joint with the next batch of concrete. When the concrete is set, the exposed surface should be clean and any contamination should be removed to expose clean aggregate to which the fresh concrete will bond.

When the concreting is finished, cover any exposed concrete surface with damp hessian or polythene to prevent the concrete from trying out too quickly. The expanded polystyrene faces of PSS Group SL Build Blocks will protect the concrete from freezing weather conditions and also from very hot weather which could otherwise cure the concrete to quickly. B

By providing insulation against internal temperature fluctuations the PSS Group SL Build system is an excellent curing medium for concrete. As the concrete cures, excess  moisture will pass through the expanded polystyrene in the form of water vapour that will dissipate in the open  atmosphere. It is consequently, preferable to allow some time before applying any wall finishings that would act to slow down the drying out  process.