Specification for Concrete WorksContents 1

OIL&GAS PROJECT

Specification for

Concrete Works

Revison 0

REVISION SHEET
Entire Document Revised /  / Revised Sheets Only Attached
Rev. / Date / By / Review / Appr. / Remarks
Project: / OIL & GAS PROJECT
Title:
Specification for Concrete Works
Doc.No: / Rev:
0

Contents

1. SCOPE OF WORK5

1.1 DESCRIPTION OF TERMINOLOGY5

1.2 SITE CONDITIONS5

2. CODES AND STANDARDS6

2.1 AMERICAN SOCIETY OF TESTING AND MATERIALS6

3. CONCRETE STRENGTH7

4. CEMENT7

5. AGGREGATES7

5.1 ALKALI AGGREGATE REACTION8

6. WATER8

7. ADMIXTURES8

8. REINFORCEMENT8

9. SULPHATE RESISTING CONCRETE8

10. CONCRETE MIXES9

10.1 READY MIXED CONCRETE9

10.2 BATCHING AND MIXING ON SITE9

10.3 TRIAL MIXES9

11. TRANSPORTING CONCRETE10

12. PLACING CONCRETE10

13. COMPACTION11

14. CONCRETE IN HOT WEATHER11

15. CURING AND PROTECTION OF CONCRETE11

16. TESTING CONCRETE12

16.1 TESTING12

16.2 AGE OF CONCRETE CUBES FOR TEST12

16.3 EVALUATING TESTS12

17. DEFECTIVE WORK13

18. BENDING AND FIXING REINFORCEMENT13

18.1 WELDING REINFORCEMENT15

19. FORMWORK15

19.1 FORMWORK GENERALLY15

19.2 MATERIALS FOR FORMWORK15

19.3 FORMWORK FOR FAIR FACED CONCRETE15

19.4 CONSTRUCTION OF FORMWORK AND FALSEWORK16

19.5 REMOVAL OF FORMWORK16

20. FINISH TO SLAB16

21. TOLERANCES FOR IN-SITU CONSTRUCTION16

21.1 SCHEDULE OF TOLERANCES FOR IN-SITU CONSTRUCTION16

21.1.1 FOOTINGS AND PILES16

21.1.2 COLUMNS17

22. BLINDING17

23. CONSTRUCTION JOINTS18

24. FIBERMESH18

25. CORKJOINT18

Specification for Concrete WorksContents 1

1.Scope of Work

This specification covers general requirements for the construction of all concrete works.

The scope of work covered by this Specification includes procurement, construction and commissioning of all the structural works associated with the project:

a)Foundations and supports for all equipment, including, but not limited to:

  • pipelines and pipeline components
  • pressure vessels and associated equipment
  • pumps
  • buildings

b)Road and river crossings of pipelines

c)Reinforced concrete retaining walls

d)Rock mufflers

e)Access platforms

f)Compliance with all permitting, environmental protection, and local authority requirements.

For mass concrete refer to the Specification for Civil Work

1.1DESCRIPTION OF TERMINOLOGY

As used in this specification, the following definitions shall apply:

CUSTOMER:Company Limited

CONTRACTORContractor Limited

STANDARD(s):Shall mean standards, codes, bulletins, specifications, practices or other industry publications referenced herein.

1.2SITE CONDITIONS

The structural steel is used for pipe supports, pipe bridges and platforms which are used in the Project and would generally be in exposed conditions after the application of a corrosion protection system as specified in specification.

.1Average Rainfall:2,735 mm/year

.2Dry Season:Approximately April to September

.3Dry Bulb temperature:

  • Average18°C
  • Extremesminimum4°C

maximum30°C

.4Humidity:

  • Average87%
  • Extremesminimum50%

maximum100%

.5Average wet bulb temperature14.5°C

.6Elevation: 1,500 - 1,800 m amsl

2.CODES AND STANDARDS

Standards, Codes and References referred to herein form a part of the requirements of this specification in the manner and to the extent indicated.

Unless otherwise specified, the latest edition and addenda to these Standards, Codes and References in force at the time of execution of the agreement are to be used.

All concrete work shall be carried out in accordance with the American codes and standards. CONTRACTOR must acquaint himself with all such requirements. CONTRACTOR shall construct the work in strict accordance with this Specification.

2.1American Society of Testing and Materials

ASTM C 227-90 / Test Method for Potential Alkali Reactivity of Cement-Aggregate Combinations (Mortar-Bar Method)
ASTM C 289-94 / Test Method for Potential Alkali-Silica Reactivity of Aggregates (Chemical Method)
ASTM C 150-78a / Sulphate Resisting Cement

3.Concrete Strength

All cast in place reinforced concrete shall have a minimum compressive strength of 30MPa at 28 days unless stated otherwise on the drawings.

All cast in place mass concrete shall have a minimum compressive strength as specified in Specification for Civil Work .

4.Cement

Unless specified otherwise, cement shall be Ordinary Portland cement complying with Portland Cement.

All cement shall be delivered in the sealed and branded bags of the Manufacturer or in properly designed and approved bulk containers. The cement shall be stored in a suitable building or silo, well protected from the weather and from dampness, in a manner which will prevent deterioration or contamination. The cement store shall be arranged so that batches of cement can be used in the order in which they have been delivered.

No cement which is in any way affected by dampness or aeration shall be used in the work. Any cement which is unfit for use shall be removed from the site promptly.

Sulphate Resisting Cement (Type V cement) to ASTM C 150-78a shall be used for Sulphate Resisting Concrete. Refer to Section 9.

5.Aggregates

Aggregates shall comply with the requirements of PBI NI-2 1971 and shall be sampled and tested.

Coarse aggregate is aggregate which will be retained on a 5 mm sieve, fine aggregate is aggregate which will pass a 5 mm sieve. The fine and coarse aggregate shall be combined in such proportions as will give a well graded mixture capable of producing a dense concrete with a workability suitable for the type of work and for the means of compaction to be used.

Coarse aggregate shall be clean sound crushed rock of the sizes required for the various mixes. It shall be of a good shape with no more than 10 percent elongated or flaky particles. It shall be hard and free from weathered rock.

Fine aggregate shall be clean sand, free from shells, silt, clay, salt and other impurities. Subject to satisfactory grading tests and trial mixes CONTRACTOR may use manufactured sand in place of natural sand.

Aggregates shall be stored on clean hard surfaces or in bunkers in such a manner as will effectively keep the different sizes separate and will prevent contamination and excessive segregation. Provision shall be made to drain off rainwater from the stockpiles.

Samples of aggregates shall be taken from the stockpiles and tested either on site or by an approved local testing Authority. Such tests shall be at CONTRACTOR’S expense. Weekly tests shall be made to determine the moisture content of the aggregate and a record of the results shall be kept as part of the CONTRACTOR’S Quality Assurance procedures.

5.1Alkali Aggregate Reaction

Aggregates which are likely to cause an alkali aggregate reaction shall not be used. Samples of aggregate shall be tested in accordance with ASTM C 289-94. Potentially reactive aggregate shall be further tested in accordance with ASTM C 227-90.

6.Water

Water shall be clean fresh water free from chemical or organic impurities. Tests for water shall be carried out in accordance with PBI NI-2 1971. If it should be necessary to store water on site, care shall be taken to prevent contamination.

7.Admixtures

If admixtures are to be used they should be included with the concrete mix test procedures. Admixtures shall be used strictly in accordance with the Manufacturer's instructions. When admixtures are used the amount of water added to the mix shall be adjusted to maintain suitable workability.

8.Reinforcement

Reinforcement for concrete shall be either mild steel or high tensile steel bars or mesh. It shall be free from rolling defects and of the full specified size. It shall be clean and free from loose rust, scale, oil and grease.

The Manufacturer's Certificate of origin and test certificates for each consignment for use in the work shall be checked by the CONTRACTOR for compliance with the specification and kept as part of the CONTRACTOR’S Quality Assurance procedures. The certificates must show the chemical analysis of the steel and the results of the tensile and bending tests. Upon delivery of reinforcement, two specimens, 60 cm long, of each size of bar or mesh shall be taken to an approved testing authority for testing.

Mild steel reinforcement shall have a minimum yield strength of 24 kg/mm2 (235 MPa) and shall comply with the SII (Indonesian Industry Standard), Class TP-24.

High tensile steel reinforcement shall be hot rolled deformed bars with a minimum yield or 0.2% proof stress of 40 kg/mm2 (390 MPa). It shall comply with the SII, Class TD-40. Steel mesh or fabric reinforcement shall comply with the requirements of the Indonesian Concrete Regulations (PBI NI-2, 1971) and shall have a minimum yield strength of 50 kg/mm2 (490 MPa).

9.Sulphate Resisting Concrete

Sulphate Resisting Concrete is to be used where specified and in all places where the concrete is likely to be in direct and continuous contact with geothermal fluids, e.g. rock mufflers, drains.

10.Concrete Mixes

CONTRACTOR shall submit full details of the concrete mix prior to construction to the Customers for review.

CONTRACTOR shall provide concrete that satisfies the Specification at all times. If at any time the concrete does not satisfy the requirements specified, delivery shall cease until remedial action has been effected. The cost of any mix alteration, including increase in cement content, shall be at CONTRACTOR’S expense.

All concrete shall be batched by weight.

The maximum water/cement ratio shall be 0.55.

10.1Ready Mixed Concrete

Ready mixed concrete shall comply with the requirements of PBI NI-2 1971.

CONTRACTOR shall be responsible for ensuring that the concrete complies with this Specification including quality control, regularity of delivery and continuous supply of concrete. If any of the requirements of this Specification are not complied with CONTRACTOR shall change the Supplier or stop using ready mixed concrete.

10.2Batching and Mixing On Site

The size of each batch shall not exceed the rated capacity of the mixer. The mixer shall be charged in a manner which will assist the blending of the materials. If it should be necessary to charge cement separately from the other ingredients, a longer mixing time may be required to obtain proper uniformity of the mix.

The time of mixing shall be sufficient to ensure the production of uniform concrete throughout the batch. In drum mixers the concrete shall be mixed for not less than two minutes. In pan mixers of one cubic metre capacity or less the mixing time shall be not less than 80 seconds and a further 80 seconds for each cubic metre of additional capacity.

All the concrete of one batch shall be discharged before the materials for the next batch are charged. No water shall be added to the concrete after it has been discharged from the mixer.

Mixing by hand is only allowed for small quantities for minor non-structural works. When mixing by hand, the heap of materials shall be turned at least three times before the addition of the water. The water shall then be added by sprinkling while the materials are being turned and the concrete shall be turned at least three more times after the addition of the water so that it is thoroughly and uniformly mixed throughout.

10.3Trial Mixes

Before any concrete is placed in the Works, trial mixes shall be made and tested to confirm that the strength, workability and cohesion of the various mixes of structural concrete comply with the Specification. If a change in the mix proportions becomes necessary additional trial mixes shall be made and tested.

The necessary labour, materials and plant for making and testing the trial mixes shall be provided at CONTRACTOR’S expense. More than one trial for each grade of concrete may be necessary at the beginning of the work. Each trial mix made on site shall be used for trial mixes only and shall not be used in any permanent structural work.

The concrete from the trial mixes shall first be inspected for cohesion and segregation and the workability shall be checked to ensure that it is suitable for the type of work and means of compaction to be used. If these properties are satisfactorily tested cubes shall be made in accordance with PBI NI-2 1971 and the consistency of the concrete tested by means of the slump test.

The following records of each trial mix shall be kept as part of the CONTRACTOR’S Quality Assurance procedures:

a)Type and grading of aggregates.

b)Source of aggregates.

c)Type and brand of cement.

d)Type, brand and quantity of admixtures.

e)Quantity of each constituent used in the trial mix and the equivalent weights required for one cubic metre of concrete.

f)Brief description of appearance and properties (e.g. workability, cohesion segregation) of the concrete.

g)The results of all tests.

11.Transporting Concrete

Concrete shall be transported from the mixer to the point of placing in such a manner as will prevent significant alteration in its properties, i.e. uniformity, temperature, cohesion workability and final strength. CONTRACTOR shall provide sufficient plant, equipment and labour to transport the concrete continuously and without delay.

12.Placing Concrete

No concrete shall be placed until the reinforcement has been checked and approved by the CONTRACTOR’S Quality Assurance team. The forms shall be cleaned before concrete is placed.

Concrete shall be placed without delay and within fifteen minutes of leaving the mixer. It shall be placed in such a manner as will avoid segregation and prevent displacement of the reinforcement. Concrete from barrows shall be tipped to guide the concrete vertically into deep forms such as columns and walls.

The maximum permissible time between water being added to the concrete mix at the batch plant and deposition in its appointed location is 1 hour and 30 minutes.

Concrete shall be placed continuously between construction joints. The working face shall be kept plastic and free from cold joints, fresh concrete shall be placed against it before the initial set of the previously placed concrete.

In deep sections the concrete shall be placed in layers of about 50 cm depth without inclined layers.

CONTRACTOR shall have materials and labour available to make additional construction joints in case of rain or breakdown in concrete supply.

13.Compaction

CONTRACTOR shall provide, and maintain in good working order, a sufficient number of power driven vibrators and spares for the rate at which concrete is to be placed. The vibrators shall be of types, sizes and powers suitable for the various parts of the work on which they will be used.

All concrete shall be carefully compacted by vibration to the maximum practicable density so as to thoroughly fill the forms and surround and embed the reinforcement without voids.

Compaction by hand is not permitted.

In general, vibration shall be continued until the mass of concrete becomes plastic, mortar begins to come to the surfaces and air bubbles cease to appear. Over-vibration causing segregation or surface laitance shall be avoided. If signs of over-vibration occur before the concrete is fully compacted, the water content of the concrete shall be reduced appropriately.

The vibrator shall be worked systematically so that all the concrete is properly vibrated. In deep sections immersion vibrators shall be inserted vertically and shall penetrate through the layer of concrete into the previous layer in order to work the successive layers together. They shall be withdrawn slowly to prevent the formation of voids. They shall not be placed against the reinforcement or other embedded fixtures.

Vibrators must not be used to make the concrete flow horizontally; they must be kept a sufficient distance back from the working face to prevent horizontal flow.

After the concrete has been properly vibrated it shall be left completely undisturbed while setting, except for surface finishing.

14.Concrete in Hot Weather

CONTRACTOR shall take precautions to avoid the harmful effects of hot weather on the properties of the plastic concrete and on the quality and strength of the hardened concrete.

15.Curing and Protection of Concrete

During its initial hardening period, of not less than seven days, the concrete shall be protected from the harmful effects of sun, wind, rain or running water and from mechanical injury. All exposed surfaces shall be kept continuously damp during this period.

Intermittent wetting and drying will not be acceptable. Special care shall be taken when column forms are stripped early.

Curing compounds may be used. The surface of the concrete shall be damp when the compounds are applied. Curing compounds shall be of a type which will have no adverse effect on any finishes to be applied to the concrete nor on the appearance of fair faced concrete. Curing compounds shall be applied strictly in accordance with the Manufacturer's instructions.

The methods of curing adopted shall be suitable for the part of the work and the prevailing weather conditions. Under certain conditions of sun, humidity and/or drying wind it may be necessary to cover the freshly placed concrete immediately after compacting before the surface moisture dries out.

16.Testing Concrete

16.1Testing

.1Inspection and testing shall be performed either on site or in an approved testing laboratory. Record of the results shall be kept as part of the CONTRACTOR’S Quality Assurance procedures.

.2Tests of cement and aggregates shall be performed to ensure conformity with specified requirements.

.3CONTRACTOR shall provide and maintain, in good condition at all times, sufficient steel moulds and curing facilities.

Number of Concrete Test Cubes Required:
Volume of Concrete Placed in Day / Numbers of Cubes
5 cubic meters or less / 6
5 to 10 cubic meters / 12
10 to 20 cubic meters / 15
each 10 cubic meters thereafter / 3 additional

.4One (1) slump test shall be taken for each set of test samples. Test in accordance with PBINI-2 1971.

.5CONTRACTOR shall co-operate with the testing laboratory to facilitate their work. CONTRACTOR shall provide and arrange for access to the concrete mixing plant by the testing laboratory. The CONTRACTOR shall notify the name of the testing laboratory to OWNER for review. CONTRACTOR shall provide, for the testing laboratory at the project site, an insulated lockable box of sufficient size to store equipment, concrete cubes and CONTRACTOR shall supply whatever labour is required in the preparation of test samples.

.6The actual making, handling, transporting and curing of the test samples shall be carried out by the testing laboratory only, and shall be in accordance with PBINI-2 1971.

16.2Age of Concrete Cubes for Test

When only six concrete test cubes have been cast on one day, three shall be tested at 7 days and three shall be tested at 28 days. When 12 or more test cubes have been cast on one day, six shall be tested at 7 days and the remaining test cubes shall be tested at 28 days.

16.3Evaluating Tests

When the result of the 7-day test is unsatisfactory, CONTRACTOR may elect to remove and replace the defective concrete without waiting for the 28 day test. If the result of 28 day test is unsatisfactory as determined by the CONTRACTOR’S Quality Assurance procedures, the volume of the concrete represented by the set of tests shall be immediately liable to be rejected and CONTRACTOR shall stop all concrete work at its expense and shall not proceed until the problem has been rectified to the satisfaction of the CONTRACTOR’S Quality Assurance Manager.