Prestressed beams are produced in steel or plywood moulds, hence the bottom and two sides are fair faced while the top is smooth or rough. The two ends have a rough character with the prestressing strands cut of flush with the concrete and sealed with epoxy paint. Moulds are generally manufactured by our fabricators in our work shop as steel moulds with sufficient rigidity to ensure that the units are produced within the needed tolerances.
Prestressed and normal reinforced beams and rectangular columns are produced in horizontal steel moulds, however only the base are made in full length and the side shuttering are moved down along the line for casting each individual beam. Circular columns are normally produced in vertical steel moulds.
Prior to casting, all cast in parts fixed in position and the mould is treated with a mould release agent. Hereafter reinforcement is kept in position and mould sides are fixed. All reinforcement will normally be prepared and prefabricated in our own workshop and placed in the mould using adequate spacers to ensure correct position and cover.
In cases were beams are prestressed, all beams with similar strand patterns are prepared for casting in the same line. All reinforcement will normally be prepared and prefabricated in our own workshop and placed in the mould using adequate spacers to ensure correct position and concrete cover.
The specially manufactured casting equipment is employed to pour concrete into the moulds. To ensure the highest quality possible, all concrete is mixed in our own mixer plants. From the batching plants the concrete is transported directly to the mould. All casting of the individual beam or column takes place in one continuous operation.
When the beams are prestressed, side moulds will be removed and fixed to the adjacent beam position (if any) and it will be casted in the same way until all beams on the same line are casted.
The concrete mix is evened out using a combination of both mould and and hand-held vibrators when casting both beams and columns.
When casting both beams and columns vibration will be by a combination of mould vibrators and hand-held vibrators.
After casting, all exposed surfaces will be covered with a tarpaulin to avoid vaporization.
Prestressed strands will be cut only after the concrete on the last casted beam has attained the prescribed strength of 40 N/mm2 which enable it to take the prestressing force.
With normal reinforced beams and columns the items will be demoulded 16-24 hours after casting and lifted to the stockyard for further curing. In the stockyard, the item will again be covered with tarpaulin or Hessian and kept in a humid environment for another 5 days.
Beams sides and soffit have a smooth fair faced surface off mould finish. The corbel of inverted T-beams and L-beams will have some minor blow-holes in the surface due to the casting method.
The beam top is usually fair faced, however, in cases where exposed reinforcement is needed, such as for composite structures, the surface will be made rough for better bondage to the top concrete.
Beam top is fair-faced, however in case exposed reinforcement, for composite structures, surface will be rough for better bond to the top concrete.
Quality control is performed according to BPC Group standard quality procedures in the well equipped laboratories. The testing equipment is calibrated and maintained at fixed intervals to ensure the test results are at par.
The material used in production of concrete undergoes inspection and testing as per company inspection procedures and British Standards. The reinforcement steel used in the panels is as per British Standards.
Comprehensive strength of concrete is determined by standard test cubes from the green concrete and these are tested in accordance with BS 1881: Part 108:1983 and BS1881: Part 116:1983.
All moulds are individually checked before casting. The final product is checked and inspected to ensure it meets the required finish and is free from any snags.
All elements are cured as per British Standards and company procedures. During the curing period, the elements are regularly watered and kept covered with polythene sheets to retain the moisture around panel.
A full schedule of company standard quality control procedures can be requested from the Quality Department.
As a special service, we can offer a full Quality Control Report for the individual project consisting of casting dates, cube test and other quality checks for the particular project. This service should be agreed with our sales department.
BPC Group Quality Control System and standard procedures have been certified to meet the requirements of ISO 9001:2000 standard covering design, manufacture and erection of the company's precast components. The ISO 9001:2000 certificate also ensures that the clients are guaranteed a good product and service throughout the entire project.
Quality Management System of BPC Bahrain, UPC Dubai and UPC Abu Dhabi has been certified by DNV
TRANSPORTATION AND INSTALLATION
Both columns and beams are normally transported on flat-bed trailers and lifted directly from the trailer into position.
Columns are placed in the foundation and aligned using jacks. When using pocket foundations, temporary support can be removed after final alignment and grouting.
When proper curing of grouting is obtained the columns are ready to receive Precast beams.
Beams can either be placed directly on the column or on shims depending on tolerances and surface quality of the column. In some cases a dowel bar is projected from the column into the beam and a slotted hole is then provided in the beam.