SCOPE: Manufacturing the precast concrete element. Basically this method
statement explain the procedure adopted for carrying out various processes involved in the manufacturing of precast element at the manufacturing facility of M/s Abu Dhabi Precast Concrete Plant LLC, as per the approved shop drawings provided by the Main Contractor. The process of precast element manufacturing involves:
* Preparation of Platforms
* Approval of Concrete Mix-Design, Admixtures and curing compound
* Approval of Third party for Quality Control of Concrete.
* Installation of Reinforcement and Formwork
* Curing and Shifting of the Concrete Elements.
* Painting of precast Elements
* Shifting of the Precast Concrete elements to site.
* Risk Assessment
Preparation of Platforms:
In order to ensure sufficient Quality Control during the operations of formwork, reinforcement, concreting, curing and dispatch; the Platforms for manufacturing the precast elements are divided into 3 bays:
* Concreting bay
* Curing bay
* Dispatch bay
Concreting Bay: The area of the platform required for concreting is decided based on the number of elements to be delivered and the time required beforeshifting the concreted elements to curing platforms. The platform for casting the precast elements is prepared such that the top level of the platform surface is within ±1mm in order to ensure the platform and this arrangement shall not allow moving during the installation of reinforcement and concreting operations. The Concreting Bay will be provided with the arrangements for curing.
Curing Bay: After ensuring that the precast element have obtained enough strength to be shifted to Curing Bay from the Concreting Bay; the precast elements will be shifted to Curing bay and the curing is continued for further period of 7 days. Upon conformance that the 7days concrete strength test results are complying and upon completion of curing the precast concrete elements will be shifted to Dispatch Bay with Green Tag (of QC
Check) fixed to each element.
Dispatch Bay: Only the precast concrete elements having Green Tag and stacked in the Dispatch Bay will be shifted to site.
Approval of Concrete Mix-design, Admixtures and Curing Compound:
The concrete mix design along with admixtures,concrete mixing plant and curing compound will be submitted for the approval of the Engineer. Only approved material shall be incorporated in permanent works.
Approval of Third Party for Quality Control of Concrete
As per the Project requirement if need Third party agency will be engaged to ensure that the concreting operations at the manufacturing facility of precast elements are complying with the contract quality control requirements and the test reports will be submitted to the Engineer for record.
The qualifications and the profile of Third Party Testing Agency will be submitted for the approval of the Engineer.
Installation of Reinforcement & Form Work
The outer formwork is cleaned and shuttering oil is applied prior to installation.The formwork is self supporting. The Formwork is installed and necessary checks of dimensions and verticality are carried out by the formwork foreman and checked by the Production-incharge and then QC Inspector. Silicon jelly is used to arrest the gaps. Reinforcement cut and bent as per approved reinforcement shop drawing shall be fixed in position with the help of chairs and spacers. Any inserts mentioned in the shop drawings shall be installed with proper lugs and sufficient concrete cover is maintained.
For arrival of concrete the QC inspector will ensure that the Concrete Mix checking the temperature, slump/workability of the Concrete, collection of concrete samples (a set of six(6) nos.per sample) and testing seven(7)days and Twenty Eight (28) days strength, in accordance with Contract Specifications. The test results of each pour shall be submitted for Engineer’s review and approval. Concrete will be placed in layers of 30cm inside the formwork and 40mm needle vibrators will be used for uniform compaction of concrete.
Curing and Shifting of the Concrete
The elements concreted shall be covered with moist hessian cloth until the outer formwork is removed. Outer formwork is removed after the minimum concrete strength achieved . The precast elements will be shifted upon concrete strength test results confirms that the concrete has attained
the required strength for shifting these elements to Curing Bay. The Curing of the precast concrete elements will continue for the remaining period i.e. 7days. Upon testing the concrete samples and confirming that the concrete attained required strength the precast elements will be Bitumen painted and labeled with QC Check (Green Tag) and shifted to Dispatch Bay. The precast elements in Dispatch Bay with Green Tags only shall be
allowed for shifting to site.
Shifting of the Precast Concrete
elements to site:
Precast elements approved for shifting to site will be shifted to site using flat bed trailers or A Frame Trailers. The purpose made arrangements in the Concrete will be used for lifting the precast elements. Care shall be taken to avoid any damages to the precast elements or the embedded utilities in the elements, during loading, transportation and unloading. The precast elements shall be placed on a level firm ground at site, in
order to avoid any damages.