CONCRETING WORKS

1.0 OBJECTIVE

1.1 Is to define the requirements for the design, supply and execution g concrete works for the constructions under the contract no GTC.101/ED/01 Engineering, Procurement, Installation and Commissioning (EPIC) of Ras Laffan Utilization Project –Buildings and utilities and support service Phase 1-Utilities.

2.0 SCOPE

2.1 For foundation, substructure and superstructure of buildings and utilities at Base     Area, New Service Berth in Berth Area, FSO Marine and Telecom building.

3.0 REFERENCE

3.1 Project Approved Drawings

3.2 Qatar Petroleum Standard Specification for Civil Works Clause 3.8.1 3.17 to 3.22, 3.38

3.3 Qatar Construction Spec. Section 5, part 15

3.4 British Standards BS 5328, 1881

4.0 PROCEDURE

• The contractor shall obtain approval from QP for various grades of concrete as specified in the drawings. If QP wants, the contractor shall arrange for trial mix at approved concrete batching plant. The contractor shall submit the results of such trial mixes and obtain approval from QP.

• The contractor shall obtain approval from QP for the sources of all materials used in concrete including the ready mix batching plant by duly furnishing the valid calibration certificated of the batching plant issued by approved calibrating agencies and test certificates of all concrete ingredients form QP approved independent laboratories.

• Readymix concrete should conform to BS 5328, except for material, testing and design.

• Before concreting, necessary approval for rebars, formwork should be obtained from QP engineer. Clearance from electro mechanical shall be obtained. All the inserts, fixtures are in firmly position.

• Request for Inspection shall be submitted to QP engineer  in advance clearly mentioning the scope of concreting including the time, date, grade and quantity of concrete.

• All the equipment necessary for the proposed concrete should be made available in working condition at site. Proper lighting arrangements should be made available at concreting location if required.

• Adequate manpower shall be arranged at site for finishing the concrete before it takes initial setting.

• Ensure that the correct grade and required quantity of concrete is ordered and the delivery of concrete shall be such that there should not be any time gap which shall lead to cold joints in the freshly placed concrete.

• QP approved Independent Testing Agency should be readily available at site prior to commencement of concreting to conduct test on concrete. All the equipment used by the Independent Testing Agency shall have valid calibration certificate for each equipment.

• Temperature of concrete should be taken and it shall be within the permissible limits. If the temperature of concrete exceeds 32°C at the placing point, QP engineer should be informed and placing shall be at the discretion of QP engineer as it may create cold joint at the placement.

• Slump test in accordance with BS 1881 should be conducted before placing of concrete. Tests shall also be conducted when making test cubes and a record must be kept for all these tests. Slump test should be carried out at the rate of one test per load of concrete or one test per 10 cu. M of concrete delivered to site whichever is less.

• Samples for work cube test shall be taken at the rate of one sample from every load or one test for 15 cu.m of concrete whichever is less of a particular grade placed with a minimum of one sample taken every day that the mix is used. A sample consists of (6) Six cubes to be made, (3) three to be tested on (7) seven days and the balance (28) twenty eight days. Test cubes shall be crushed in presence of QP engineer and the results should be submitted to QP in an approved form giving the information like cube specimen mark, date of casting, date of testing, age, dimensions, compressive strength, weight of the cube etc.

• Concrete shall only be placed on surface ready to receive it. Concrete shall be placed gently to avoid segregation and care must be taken to see that the reinforcement is completely surrounded by the concrete and no void s or cavities left in the body of the concrete. It shall generally be deposited in horizontal layers to a compacted depth not exceeding 300 mm.

• Concrete shall not be thrown or dropped from a height exceeding 2 m and it shall be placed in final position and shall not be rehandled.

• Concreting shall be carried out continuously and fresh concrete shall not be placed against insitu concrete, which is more than 30 thirty minutes unless a construction joint is formed.
• The laying is shall be planned to ensure that a bay or panel is completed at an approved joint before the temperature raises above the permissible limits.

• At any case concrete shall not be placed in standing water in the formwork. The depth of layers and the time between placements of layer shall be such that each layer can be properly merged into preceding layer before initial set takes place.

• Concrete shall be thoroughly compacted by vibration during the operation of placing and thoroughly worked around the reinforcements, embedded fixtures and the corner of the formwork to form a solid mass free from voids.

• Vibration of the concrete shall not be applied by way of reinforcement. The duration of vibration shall be limited to that required to produce satisfactory compaction without causing segregation.

• Curing of concrete shall be made from the next day and if the weather is hot, proper protection arrangement shall be in place to protect the concrete from quick drying. Curing shall be arranged continuously as per requirement

• On completion of concreting, the site shall be cleaned and any splashes of concrete shall be removed to avoid setting and hardening.

5.0 RECORDS

5.1 Inspection reports

5.2 Checklist

5.3 Slump and cube log