This article is about Fabrication Method Statement for Precast Concrete Panels.
Precast Concrete Panels Method Statement for Fabrication
1. Scope:-
• Detailed description for all manufacturing processes starting from casting moulds preparation till the delivery of the product to job site.
• Quality Control is briefly mentioned in this methodology, for more details, refer to the following documents: ISO-QP-8.2.4 and GEN-QP-001.
2. References:-
• PCI-MNL-116.
• SAES-Q-012
3. Moulds Preparation:
• The mould stopper sides will be fabricated from steel channels and / or wooden timber, the mould dimension and details will be as per the latest approved shop drawings.
• The QC shall ensure that the basic mould is ready as per the shop drawing, level and free face deterioration which could impair the quality of the finished concrete bottom surface.
• The moulds will be thoroughly cleaned and an approved oil base releasing agent will be applied manually.
4. Placement Of Embeds and Reinforcing steel rebars:
• The steel guide to fix the electrical boxes at both surfaces of the mold and timber guide to fix the block outs and recesses.
• Fixing the embedment (Recess, Elec. Boxes, Pipes … etc … ) at the bottom of the moulds.
• Reinforcement will be fabricated in the steel workshop according to the detailed approved shop drawings considering the (Grade, type, diameter, black/FBE coated, length, number, spacing … ).
• Reinforcement cages will be transferred to the production area and placed in the moulds.
• Proper concrete cover will be considered using the plastic spacers.
• Elec. Pipes, boxes with different sizes, sockets and block outs to be fixed inside the moulds.
5. Concrete Pouring & placing:
• Cleaning the moulds using the air pressure prior to cast.
• The freshly batched concrete as per approved concrete mix design is delivered from the Batch Planet to the production area in a Truck Mixer.
• Pouring concrete using concrete bucket lifted by overhead crane.
• Spreading the concrete all over the mould.
• Vibration of the concrete will be done using the table vibrator or the hand (poker) vibrator as agreed by the QC in-charge and in complies with the mould structure.
• For the external panels, first the outer-skin (white concrete) will be casted and compacted by the table vibrator, immediately after casting, a layer of the polystyrene thermal insulation with a specific thickness will be provided over the concrete, then finally, the inner-skin (grey concrete) will be casted and the concrete will be compacted by hand vibrator to avoid causing damage in the outer skin.
• Smoothing the concrete surface will be done using the hand trowel.
6. Concrete curing:
• 6-2- Curing by watering:
• The water curing will be applied to every part of the concrete surface by covering the whole surface closely by wet burlap sheets until the compressive strength reached 70o/o of the specific strength but not less than 7 days after placement.
• Prior to demoulding, a temporary bracing to be fixed in order to avoid cracks in the openings corners using a special socket connected to the RFT of the panel.
• For the Tilting Table, panels to be lift vertically and transferred to the stock area using the (A-frame) truck.
• In case of lifting horizontally, a flatbed truck is used to transfer the panels to the stock area.
• All concrete elements are to be handled carefully and slowly to avoid damage during transit.
• Precast Concrete Panels should be clearly identified to allow traceability & correct erection positioning.
8. Storage:
• Storage area should be relatively level and firm.
• Panels will be stocked in panel rack with enough space to keep the surface of panel safe.
• In case of horizontal stocking for some elements. Only panels with same lengths and with no larger recess should be stacked together and directly on top of each other.
• Wooden spacers should be used; all spacers should be stacked exactly on top of each other.
9. Transportation & Delivery:
• The Precast concrete element will be loaded on A-frame truck or flat bed as per the element type.
• The QC shall ensure that all repairs are carried out under his direct supervision.
• All loads have to be secured with appropriate ropes, straps or chains.