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CORPORATE REFERENCE DOCUMENT
STANDARD SPECIFICATION
FOR
CONCRETE
Document Number : BRNA-SP-CS-012-03
NOTE
This document contains proprietary information belonging to Brown & Root NA Ltd.
It may neither be wholly or partially reproduced without the prior written permission
of Brown & Root NA Ltd.
Users of this document must always consult the appointed Custodian for advice. The
Custodian should be notified of any errors, omissions and suggested improvements.
BROWN & ROOT NA LTD DOC. NO.: BRNA-SP-CS-012-03
STANDARD SPECIFICATION FOR
CONCRETE PAGE 1 OF 53
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TABLE OF CONTENTS
Page No.
TABLE OF CONTENTS ....................................................................................................... 1
1.0 INTRODUCTION ...................................................................................................... 2
2.0 SCOPE ......................................................................................................................... 2
3.0 DEFINITIONS ........................................................................................................... 2
4.0 REGULATIONS CODES AND STANDARDS ...................................................... 2
5.0 OTHER REFERENCE DOCUMENTS ................................................................. 4
6.0 TECHNICAL REQUIREMENTS .......................................................................... 5
6.1 Materials ..................................................................................................................... 5
6.2 Storage of Materials .................................................................................................. 7
6.3 Concrete Properties ................................................................................................... 9
6.4 Concrete Mix Design ................................................................................................. 12
6.5 Quality Control and Testing ..................................................................................... 14
6.6 Batching, Mixing and Transporting Concrete ........................................................ 27
6.7 Formwork ................................................................................................................... 30
6.8 Reinforcement ............................................................................................................ 33
6.9 Built-in Items, Holes and Cavities ............................................................................ 34
6.10 Concreting .................................................................................................................. 35
6.11 Curing and Protection of Concrete .......................................................................... 42
6.12 Surface Treatment and Remedial Work ................................................................. 44
6.13 Concrete Finishes ....................................................................................................... 46
6.14 Corrosion Protection of Concrete ............................................................................ 48
6.15 Precast Concrete Flags, Kerbs Etc ........................................................................... 51
6.16 Setting Base Plates and Beams Plates ...................................................................... 51
7.0 DOCUMENTATION TO BE SUBMITTED .......................................................... 52
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1.0 INTRODUCTION
This Standard Technical Specification specifies the minimum technical requirements for
materials and workmanship of concrete Works.
2.0 SCOPE
The scope shall comprise provision and storage of materials, mixing, transporting, placing,
curing and testing of concrete with the exception of concrete for Prestressed Concrete
Cylinder Pipes (PCCP).
3.0 DEFINITIONS
None required.
4.0 REGULATIONS, CODES AND STANDARDS
Unless indicated otherwise in this Specification, the requirements of the following
regulations, codes and standards shall apply:-
American Society for Testing and Materials (ASTM)
ASTM C 29/C 29M Standard Test Method for Bulky Density ("Unit Weight") and Voids
in Aggregate.
ASTM C 33 Standard Specification for Concrete Aggregates.
ASTM C 40 Standard Test Method for Organic Impurities in Fine Aggregates for
Concrete.
ASTM C 117 Standard Test Method for Material Finer Than 75 Microns (Nr. 200)
Sieve in Mineral Aggregates by Washing.
ASTM C 123 Standard Test Method for Lightweight Particles in Aggregate.
ASTM C 127 Standard Test Method for Specific Gravity and Absorption of Coarse
Aggregate.
ASTM C 128 Standard Test Method for Specific Gravity and Absorption of Fine
Aggregate.
ASTM C 131 Standard Test Method for Resistance to Degradation of Small-size
Coarse Aggregate by Abrasion and Impact in the Los Angeles
Machine.
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ASTM C 142 Standard Test Method for Clay Lumps and Friable Particles in
Aggregates.
ASTM C 150 Standard Specification for Portland Cement.
ASTM C 227 Standard Test Method for Potential Alkali Reactivity of Cement-
aggregate Combinations (Mortar-bar Method).
ASTM C 289 Standard Test Method for Potential Alkali-Silica Reactivity of
Aggregates (Chemical Method).
ASTM C 295 Standard Guide for Petrographic Examination of Aggregates for
Concrete.
ASTM C 309 Standard Specification for Liquid Membrane-Forming Compounds
for Curing Concrete.
ASTM C 586 Standard Test Method for Potential Alkali Reactivity of Carbonate
Rocks for Concrete Aggregates (Rock Cylinder Method).
ASTM C 685 Standard Specification for Concrete Made by Volumetric Batching
and Continuous Mixing.
ASTM C 920 Standard Specification for Elastomeric Joint Sealants.
ASTM C 1105 Standard Test Method for Length of Change of Concrete Due to
Alkali-Carbonate Rock Reaction.
ASTM D 1190 Standard Specification for Concrete Joint Sealer, Hot-Applied
Elastic Type.
ASTM D 1751 Standard Specification for Preformed Expansion Joint Fillers for
Concrete Paving and Structural Construction (Non-extruding and
Resilient Bituminous Types).
ASTM D 1752 Standard Specification for Preformed Sponge Rubber and Cork
Expansion Joint Fillers for Concrete Paving and Structural
Construction.
British Standards Institution (BSI)
BS 12 Specification for Portland Cement.
BS 812 Testing Aggregates.
BS 882 Specification for Aggregates from Natural Sources for Concrete.
BS 1305 Specification for Batch Type Concrete Mixers.
BS 1377 Methods of Test for Soils for Civil Engineering Purposes.
BS 1881 Testing Concrete.
BS 3148 Methods of Test for Water for Making Concrete (Including Notes on
the Suitability of the Water).
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BS 3963 Method for Testing the Mixing Performance of Concrete Mixers.
BS 4016 Specification for Flexible Building Membranes (Breather Type).
BS 4449 Specification for Carbon Steel Bars for the Reinforcement of
Concrete.
BS 4483 Specification for Steel Fabric for the Reinforcement of Concrete.
BS 4550 Methods of Testing Cement.
BS 5075 Concrete Admixtures.
BS 5328 Concrete. Part 1: 1997. Guide to Specifying Concrete.
BS 5606 Guide to Accuracy in Building.
BS 5975 Code of Practice for Falsework.
BS 7263 Precast Concrete Flags, Kerbs, Channels, Edgings and Quadrant.
BS 8007 Code of Practice for Design Of Concrete Structures for Retaining
Aqueous Liquids.
BS 8110 Structural Use of Concrete.
BS 8666 Specification for Scheduling, Dimensions, Bending and Cutting of
Steel Reinforcement of Concrete.
BS EN ISO 4066 Construction Drawings. Bar Scheduling.
5.0 OTHER REFERENCE DOCUMENTS
Other relevant Specifications and documents referenced herein are listed below:-
American Concrete Institute (ACI)
ACI 207R Mass Concrete, Part 1 and Effect of Restraint, Volume Change, and
Reinforcement on Cracking of Mass Concrete, Part 2.
ACI 224R Control of Cracking in Concrete Structures.
ACI 304R Guide for Measuring, Mixing, Transporting and Placing Concrete.
ACI 305R Hot Weather Concreting.
ACI 308 Standard Practice for Curing Concrete.
ACI 309R Guide for Consolidation of Concrete.
ACI 347R Guide to Formwork for Concrete.
Brown & Root NA (BRNA)
BRNA-SP-MT-003 Standard Specification for Coatings and Linings.
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BRNA-SP-CS-012-03 April, 01
BRNA-SP-MT-005 Standard Specification for the Corrosion Protection of Buried
Concrete Structures.
Construction Industry Research and Information Association (CIRIA)
CIRIA Report 91 Early-age Thermal Crack Control in Concrete.
U.S. Corps Of Engineers (CRD)
CRD-C513 Rubber Waterstops.
CRD-C572 Polyvinyl Chloride Waterstops.
CRD-C621 Non Shrink Grout.
6.0 TECHNICAL REQUIREMENTS
6.1 Materials
6.1.1 Materials
Approved samples of all materials shall be kept in suitable containers, properly
labelled and stored on site for reference.
6.1.2 Cement
Ordinary Portland cement (OPC) shall comply with BS 12 or ASTM C 150, Type II.
OPC shall be used for all reinforced concrete. Tanking as specified in Section 6.14
shall be provided for all buried structures.
OPC shall be used for all mass concrete. The classification of sulphate exposure
given in Table 7 of BS 5328 : Part 1 shall be used as a guide:
Class 1 and 2 : OPC without tanking
Class 3, 4, and 5 : OPC with tanking
The above requirements do not apply to mass concrete used for non-structural
purposes.
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Any cement which is lumpy or partially set shall be rejected and removed from the
site.
6.1.3 Aggregates
Fine and coarse aggregates shall be as defined by and be of the quality, shape and
nature required by BS 882. Potential alkali reactivity of aggregates shall be
determined in accordance with ASTM C 295, ASTM C 289, and ASTM C 586.
The moisture content of the aggregates shall be determined in accordance with BS
812: Part 2.
The grading of aggregates shall be as follows:
(a) Coarse Aggregate
Aggregates shall be graded according to the recommendations of BS 882,
Table 4:
• 10 millimetres maximum size, for screed finishes and small
components.
• 20 millimetres maximum size for all prestressed, reinforced and
precast concrete, benching, no-fines concrete and blinding concrete.
• 40 millimetres maximum size for all mass concrete.
(b) Fine Aggregate
Fine aggregates shall conform to BS 882, Table 5.
6.1.4 Water
Water used for mixing and curing concrete shall meet the requirements of BS 3148.
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6.1.5 Concrete Admixtures
(a) General
Before approval for the use of any admixture is given Contractor shall prove
its suitability for the work and its compatibility with the cement it is intended
to complement.
Only admixtures which can be administered in fixed calibrated amounts
through a mechanical dispenser or cachet, and which are added directly to
the mixing water shall be permitted.
Where more than one type of admixture is to be used for the same concrete
mix, each shall be dispensed separately.
(b) Water-reducing admixtures
Where, in the opinion of Owner, the workability of the mix is inadequate to
achieve an acceptable compaction and/or surface finish, or where excessive
bleeding of the concrete is in evidence, a water-reducing or high range water
reducing admixture complying with BS 5075 shall be used.
(c) Set-retarding admixtures
Where large quantities of concrete are to be placed at any one time or where
concreting is undertaken under hot weather conditions, Contractor may
include an approved set-retarding admixture to enable work to be properly
finished before premature setting has taken place. The admixture shall
comply with the requirements of BS 5075: Part 1.
(d) Admixtures containing chloride
Admixtures containing chloride shall not be used.
(e) Air-entraining admixtures
Air-entraining admixtures shall be in accordance with the requirements of BS
5075: Part 2.
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6.1.6 Reinforcing Steel
Reinforcement shall be either carbon steel bars conforming to BS 4449, or fabric
reinforcement conforming to BS 4483.
6.2 Storage of Materials
6.2.1 Cement
Cement shall be stored in a weatherproof building, bins or silos which shall exclude
moisture and contaminants. Cements of different types shall be stored separately.
Cement shall be fresh when delivered to site and the consignments shall be used in
the order of their delivery. Contractor shall mark the date of delivery on each
consignment and each consignment shall be stored separately and in such a manner
as to be easily accessible and identifiable.
Bagged cement shall not be stored higher than 10 bags at a temperature of not less
than 8°C. Bags shall be placed on dry boards above the floor. No bags of cement
shall be used unless the manufacturer's seals are intact at the time of mixing.
6.2.2 Aggregate
Aggregate stockpiles shall conform to the provisions of ACI 304R and be maintained
in a manner to avoid excessive segregation and to prevent contamination with other
materials or aggregates of different sizes.
The aggregates of various sizes shall be kept separate and away from all possible
contamination and shall be stored on a hard-standing area laid to falls or in bins,
provided with proper drainage.
Stockpiles shall be at least 2m in height and built in layers of not more than 1m in
thickness. No layer shall be allowed to 'cone' down over the under layer.
If aggregates of difference gradings are stockpiled in close proximity the stockpiles
shall be separated by bulkheads.
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All aggregates shall be handled from the stockpile or other source to the batching
plant in such a manner as to secure a typical grading of the material, care being taken
to avoid crushing the aggregates and that they remain free from extraneous matter.
All aggregates produced or handled by hydraulic methods and all washed aggregates
shall be stockpiled for draining at least 24 hours before being batched.
6.2.3 Reinforcing Steel
Reinforcing steel shall be stored on supports clear off hard laid floors in covered
areas with a waterproof overhead cover to screen stocks from contamination from
windblown dust. Delivery and storage shall be organised in such a manner as to
make identification easy. Supports shall be such that distortion of bars is avoided
and contamination and corrosion prevented.
Individual bundles of reinforcing bars shall be durably marked to identify source,
batch number, type and diameter.
Any reinforcement which becomes contaminated shall be sandblasted with clean
sand, and washed if necessary, not earlier than 3 days before its incorporation in the
Works.
6.2.4 Other Materials
Other materials shall be stored in such a manner as to avoid contamination and
deterioration and where a manufacturer's product is to be used any specific
recommendation regarding its storage shall be complied with.
6.3 Concrete Properties
6.3.1 General
All concrete, except where otherwise specified by Owner, shall comply with the
relevant provisions of BS 5328. Concrete for water retaining structures shall be in
accordance with BS 8007. Design of normal concrete shall be to BS 8110. The
grades of concrete appropriate for specific use shall, unless specified otherwise, be
selected from the preferred grades in BS 5328 which are adequate on grounds of
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strength and durability. As a guide the characteristic strength (fcu) for the concrete
elements shall, as a minimum, be as follows:
• Grade 40 - Prestressed concrete.
• Grade 30 - Reinforced concrete, precast concrete.
• Grade 20 - Mass concrete, floor screeds, benching.
• Grade 15 - Blinding concrete.
The meaning of the terms "grade" and "characteristic strength" is as defined in BS
5328.
6.3.2 Durability
The minimum cement contents shall be as follows:
• 360 kg/m³ of cement - for Grades 40, 30 and 20 concrete.
• 250 kg/m³ of cement - for Grade 15 concrete.
The maximum water/cement ratio for Grade 40 concrete shall be 0.40, for Grade 30
and 20 concrete shall be 0.45, and for Grade 15 concrete shall be 0.5.
In all cases of mix proportioning, the quantity of added water shall take account of
the moisture contained in the aggregates and shall be the minimum consistent with
the workability requirements.
6.3.3 Thermal Crack Control
In the first instance the thermal crack control shall be by means of the concrete mix
design and subsequently by the construction practice especially curing and protection
from drying. Note shall be taken of ACI 224R.
Where structural integrity of mass concrete element is likely to be impaired the
control of cracking shall be by provision of reinforcement. The amount of
reinforcement shall follow the recommendations of ACI 207R and CIRIA Report 91 -
"Early-age thermal crack control in concrete".
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6.3.4 Workability
For walls, columns, suspended slabs and beams, and grade beams the slump shall be
between 50 millimetres and 100 millimetres unless a high range water reducer is
approved for use, in which case the slump shall be between 150 millimetres and 200
millimetres.
For slabs cast against blinding or no-fines concrete and for foundations the slump
shall be between 50 millimetres and 100 millimetres unless a high range water
reducer is approved for use in which case the slump shall be between 125 millimetres
and 200 millimetres.
6.3.5 Air Content
All concrete shall have an air content of 4.5 + 1.5 percent.
6.3.6 Chloride Content
The maximum chloride ion content in the concrete resulting from the contribution of
the mix ingredients including water, aggregates, cement and admixtures shall be as
follows:-
Type of concrete Maximum chloride ion content
(percent by weight of cement)
Prestressed concrete 0.06
Reinforced concrete 0.10
Concrete with no embedded steel (mass
concrete, floor screeds, benching and
blinding)
0.60
6.3.7 Sulphate Content
The maximum sulphate content in the concrete, resulting from the contribution of the
mix ingredients including water, aggregates, cement and admixtures for all types of
concrete shall be 4.0 percent (S03) by weight of cement.
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6.3.8 No-Fines Concrete
Aggregate shall be 20 millimetres to 10 millimetres graded with no more than 5%
passing 10 millimetre sieve. Only sufficient water shall be added to ensure complete
coating of aggregate. One half of this water shall be placed into the mixer first, after
which the aggregate and cement shall be admitted. After partial mixing the balance
of the water shall be added until a consistent mix is achieved.
6.4 Concrete Mix Design
6.4.1 General
Contractor shall submit for Owner approval details of the proposed concrete mixes
including proportions of all materials, intended compacting factor, the average
strength to be attained in trial mixes and a target standard deviation. Following
approval the proposed mixes shall be used for carrying out laboratory trials. Subject
to any modifications agreed as necessary as a result of the laboratory trials,
Contractor shall carry out site trials on each mix under full scale production
conditions. The mix proportions resulting from site trials shall, subject to approval,
be used for constructing the Works.
6.4.2 Laboratory Trials
Contractor shall produce in the laboratory two batches from a trial mix for each grade
of concrete using cement and surface dry aggregates typical of the proposed source
of supply. Each batch shall contain the correct amount of cement and have a free
water/cement ratio at or below the maximum value. The workability of each batch
shall be determined. Provided that the slumps obtained fall within the specified
limits, and the requirements regarding cement content and free water cement ratio
have been met, Contractor may proceed to carry out site trials. For the purpose of
determining target mean strength of the concrete a design margin shall be added to
the characteristic strength for the particular grade of concrete. This design margin
shall not be less than 10N/mm².
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6.4.3 Site Trials
Trial mixes shall be made at site under full scale production conditions. The
proportions of materials used, including the water content and any admixtures, shall
agree with the mix proportions determined by the laboratory trial mixes. Three
batches of concrete for each grade of concrete shall be produced, using the same
plant and mixing time proposed by Contractor for use in the Works.
For each grade of concrete the following shall be carried out:
• The workability of each of the three batches shall be determined immediately
after mixing by the slump test specified in BS 1881: Part 102 or compacting
factor in BS 1881: Part 103 as appropriate.
• Two (a pair) test cubes or cylinders from each of the three batches shall be
made, cured, stored and tested at seven (7) days and twenty-eight (28) days
after casting in accordance with the method described in BS 1881.
The relationship between cube and cylinder strength shall be as stated in Section
6.5.7.
A site trial mix for a particular grade and type of concrete shall be considered
satisfactory provided that:
i. The slumps fall within the specified limits, and
ii. none of the strengths of the test specimens is below the specified
characteristic strength,
or
iii. the average value of the three consecutive test results taken from the trial mix
is equal to or greater than the target mean strength, and
iv. the difference in strength between two test specimens divided by their mean
value does not exceed 15%,
where a test result is the average of two (pair) test specimens.
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If the results for any mix meet these requirements and the mix complies with all other
specified concrete properties, the mix will then be approved for use in the Works.
If the results for any mix fail to meet these requirements Contractor shall re-design
that mix and make further site trials as above.
6.5 Quality Control and Testing
6.5.1 General
Quality control charts shall be prepared and maintained as a record of all the concrete
testing activities undertaken. These charts shall, where applicable, show the extreme
limits of acceptable values and all test results whether within or outside the
acceptable limits. Quality control charts shall be prepared and submitted on a weekly
basis.
6.5.2 Cement
Cement shall be sampled and tested at the manufacturing plant in accordance with
the requirements of BS 4550. A test certificate shall be provided with each delivery
of cement to the site. Additionally, any cement which has been stored on the site in
bags for 3 or more months, or stored in bulk for 6 or more months shall be sampled
and the samples tested for compliance with this Specification.
Any cement failing to meet the requirements of this Specification shall be rejected
and removed from the site.
6.5.3 Aggregates
Aggregates shall be sampled and tested as specified.
The tests shown in Table 6.1 shall be carried out at the stated frequencies at the
aggregate production plant.
The tests shown in Table 6.2 shall be carried out at the stated frequencies at the
concrete batching plant.
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The following action shall be taken if the test results fail to conform with
requirements of this specification.
(a) Fine Aggregate
(i) Grading
Where the amount retained on any sieve is outside the range of acceptable
values in BS 882, the fine aggregate shall be re-sampled and re-tested. If the
second test results in values outside those limits the stockpiles shall be
rejected, removed from the aggregate storage area and replaced with material
conforming to the Specifications.
(ii) Moisture Content
When the moisture content of the fine aggregate changes by 0.5% or more,
the concrete batching plant scale settings for fine aggregate and water shall
be adjusted either directly or by means of a moisture compensation device.
(iii) Contamination by Chemicals
Where the chemical contents are outside the ranges shown in Table 6.2 the
aggregate stored at the batching plant shall be either washed until the
chemical content requirements are met, or removed and replaced by material
conforming to this Specification.
(b) Coarse Aggregate
(i) Grading
When the amount passing any sieve is outside the specified limits, the coarse
aggregate shall be re-sampled and re-tested. If the second sample fails to
meet the required limits, the material stockpiled shall be removed from the
aggregate storage area and replaced with material conforming to this
Specification.
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(ii) Moisture content
The test results and remedial actions for coarse aggregate shall be treated in
the same way as for fine aggregate with the proviso that, if the variation in
water content results in the specified water/cement ratio being exceeded, the
in-situ concrete strength of batches placed before the adjustment shall be
sampled and tested in accordance with BS 1881: Part 120.
Notwithstanding the results of this test, as soon as it is determined that the
maximum water/cement ratio defined in this Specification has been
exceeded, concrete work shall cease until full compliance with this
Specification is achieved.
(iii) Particle shape
If the sample tested does not conform to the requirements of BS 812: Part
105, Section 105.1 another sample shall be taken and tested. If this sample
fails, the material stockpiled shall be removed from the aggregate storage
area and replaced with material conforming to this Specification.
(iv) Contamination by Chemicals
Where the chemical contents are outside the ranges shown in Table 6.2 the
aggregate stored at the batching plant shall be either washed until the
chemical content requirements are met, or removed and replaced by material
conforming to this Specification.
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TABLE 6.1
TESTS FOR AGGREGATES AT THE PRODUCTION PLANT
Test Code or
Name
Test Description
Test Requirements
Minimum Frequency
ASTM C 127
Specific gravity and
absorption of coarse
aggregate
Coarse agg.: Min. bulk saturated
surface dry (ssd) specific gravity
2.4, max. absorption 2.5%
1/1000T (Once per
1000 tonnes used - or
part thereof produced)
ASTM C 128
Specific gravity and
absorption of fine
aggregate
Fine agg.: Min. bulk ssd specific
gravity 2.4, max. absorption
1.8%
1/1000T or part
thereof
ASTM C 142
Clay lumps and friable
particles
With chert:
Fine aggregate: max. 5.0%
Coarse aggregate: max. 5.0%
Without chert:
Fine aggregate: max. 3.0%
Coarse aggregate: max. 3.0%
1/500T or part thereof
BS 812:
Part 105
Flakiness index
Elongation index
(Coarse aggregate)
15% Max.
15% Max.
1/1000T or part
thereof
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TABLE 6.1 (continued)
TESTS FOR AGGREGATES AT THE PRODUCTION PLANT
Test Code or
Name
Test Description
Test Requirements
Minimum Frequency
ASTM C 29/
C 29M
Weight and voids in
aggregate
Results used for determining
concrete mix design
1/2000T or part
thereof
BS 812:
Part 121
Soundness of
Aggregate by use of
sodium sulphate or
magnesium sulphate
Use of magnesium sulphate:
Fine aggregate: Max. 18%
Coarse aggregate: Max. 18%
1/1000T or part
therefore
ASTM C 131
Resistance to
Degradation of small-
size coarse aggregate
by abrasion and
impact in the Los
Angeles machine
Coarse aggregate: Max. 50% at
500 revolutions
1/2000T or part
thereof
BS 812:
Part 118
Sulphate content
Max. 0.4%
1/500T or part thereof
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TABLE 6.1 (continued)
TESTS FOR AGGREGATES AT THE PRODUCTION PLANT
Test Code or
Name
Test Description
Test Requirements
Minimum Frequency
BS 812:
Part 117,
Appendix C
Chloride content
Fine aggregate: Max. 0.012%
1/500T or part thereof
ASTM C 289
Potential reactivity of
aggregate (Chemical
method)
ASTM C 33, Sections 7.3 and
11.2
1/2000T or part
thereof
ASTM C 586
Potential alkali
reactivity of carbonate
rocks for concrete
aggregates (rock
cylinder method)
ASTM C 33, Sections 7.3 and
11.2
1/2000T or part
thereof
Quantab test
strips
"Quick" chloride
content
Fine aggregate: Max. 0.012%
Coarse aggregate: Max. 0.005%
1/250T or part thereof
ASTM C 295
Petrographic
examination of
aggregates for
concrete
ASTM C 33, Sections 7.3 and
11.2
Once at start of each
aggregate source
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TABLE 6.1 (continued)
TESTS FOR AGGREGATES AT THE PRODUCTION PLANT
Test Code or
Name
Test Description
Test Requirements
Minimum Frequency
ASTM C 227
Potential alkali
reactivity of cement-
aggregate
combinations (mortar
bar method)
ASTM C 33 Sec. 7.3 and 11.2
Once at start of each
aggregate source
ASTM C 1105
Length change of
concrete due to alkali-
carbonate rock
reaction
ASTM C33 Sec. 7.3 and 11.2
Once at start of each
aggregate source
ASTM C 117 Material finer than nr
200 sieve in mineral
aggregate by washing
Fine aggregate: 3.0% Max.
Coarse aggregate: 1.0% Max.
1/500T or part thereof
BS 812:
Part 103
Sieve or screen
analysis fine and
coarse aggregate
BS 882: Tables 4 (coarse) and 5
(Fine)
1/250T or part thereof
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TABLE 6.1 (continued)
TESTS FOR AGGREGATES AT THE PRODUCTION PLANT
Test Code or
Name
Test Description
Test Requirements
Minimum Frequency
ASTM C 40
Organic impurities in
fine aggregate for
concrete
ASTM C 33, Sec. 6.2
1/1000T of part
thereof
ASTM C 123
Light weight pieces in
aggregate
Fine aggregate: Max. coal and
lignite 1.0% per ASTM C 33,
Sec. 11.1.8
Coarse aggregate: Max. coal
and lignite 0.5% per ASTM C33,
Sec. 11.1.8
1/1000T or part
thereof
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TABLE 6.2
TESTS FOR AGGREGATES AT THE CONCRETE BATCHING PLANT
Test Code or
Name
Test Description
Test Requirements
Minimum Frequency
ASTM C 117
Material finer than
Nr 200 sieve in
mineral aggregate by
washing
Fine aggregate: 3.0% Max.
Coarse aggregate: 1.0% Max.
Once every 2 weeks
and following periods
of inclement weather
BS 812:
Part 103
Sieve or screen
Analysis fine and
coarse aggregate
Once every 2 weeks
and following periods
of inclement weather
BS 1881:
Part 118
Sulphate content
Max. 0.4%
Once per week
Quantab test
strips
"Quick" chloride
content
Fine aggregate: Max. 0.012%
Coarse aggregate: Max. 0.005%
Once per week and
following periods of
inclement weather
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TABLE 6.2 (continued)
TESTS FOR AGGREGATES AT THE CONCRETE BATCHING PLANT
Test Code or
Name
Test Description
Test Requirements
Minimum Frequency
Speedy
moisture
Moisture content
coarse and fine
aggregate (quick test)
To verify batching proportions
Daily, prior to
commencing batching
or changing weather
conditions
ASTM C 566
Total moisture content
of aggregate by drying
To verify batching proportions
Once per week and
following rain or
inclement weather
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6.5.4 Water
The water used for making concrete shall be sampled and tested once per week in
accordance with BS 3148.
6.5.5 Concrete Batching Plant
The weight batching machines used shall be approved types accurate to within 2%
and shall be kept in good condition.
The accuracy of each materials’ measuring component of the batching plant shall be
checked once per week. Additionally, if the properties of the fresh concrete have
altered in a manner that could be attributed to mix proportion errors, the measuring
components shall be checked. The results of all such tests and necessary adjustments
to the plant shall be notified to Owner.
A daily concrete batching report shall be prepared and submitted to Owner detailing
the type and source of cement used, the quantities of any admixture used, the
required aggregate and water weights per cubic metre, the amount of free moisture in
each size of aggregate, the batched aggregate and water weights per cubic metre.
6.5.6 Fresh Concrete
Fresh concrete shall be sampled in accordance with BS 1881: Part 101.
(a) Slump
The slump of fresh concrete shall be tested in accordance with BS 1881: Part
102. One slump test shall be performed at the start of each individual pour
and thereafter repeated on random batches of each 50 cubic metres or part
thereof produced, or when samples for compressive strength determination
are taken, or when required by Owner.
(b) Air Content
The air content of the fresh concrete shall be determined in accordance with
BS 1881: Part 106. The frequency of sampling and testing shall be whenever
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strength specimens are prepared or as required by Owner. If a single test
result is outside the limits of this Specification immediate steps shall be
taken to correct the batching of the admixture.
(c) Density of Fresh Concrete
The density of the fresh concrete shall be determined in accordance with BS
1881: Part 107 and shall be tested whenever strength specimens are prepared.
(d) Temperature
The temperature of the fresh concrete shall be taken and recorded each time a
slump test is performed or as required by Owner.
6.5.7 Concrete Strength
Samples of fresh concrete shall be taken from the batched mixes, prepared as test
cubes or cylinders, and cured and tested in accordance with BS 1881.
For the purpose of establishing cube compressive strength (based on 150mm x
150mm x 150mm cube) from cylinder compressive strength (based on 150mm
diameter x 300mm length cylinder) the following relationship shall be used:
Cube strength = cylinder strength x 1.15.
Forty samples shall be made initially in eight random samples each day for the first
five days of structural concreting of each grade of concrete. Thereafter one random
sample shall be taken from each 50 cubic metres, each individual pour, or each
individual structural element for each grade of concrete.
The test results shall be examined individually in any consecutive set of two and the
mean strength of each set calculated. Test results shall be fully in accordance with
BS 5328: Part 4, Clause 3.16.
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The standard deviation shall be calculated on a continuous basis over suitable time
increments to include at least 40 results. The actual mean strength, minus 1.64 times
the standard deviation, shall be greater than the characteristic strength.
In compliance with BS 5328: Part 1, Clause 10 where the results for any mix do not
conform to the above requirements no further concrete of that mix shall be placed
until adjustments have been made to the mix proportions. Should any test result give
a strength 3 Newtons per square millimetre or more below the specified characteristic
strength, Contractor shall test the in-situ concrete in accordance with BS 1881: Part
120.
If this test conforms to the strength requirements the concrete shall be deemed
satisfactory. Should the results be less than the characteristic strength minus 3
Newtons per square millimetre the concrete shall be cut out and replaced.
6.5.8 Records of Concreting
Contractor shall submit daily returns in respect of all concrete placed during the
previous day.
The returns shall give for each location in the work:
• The position of the pour (e.g. bay or lift reference number).
• The grade of the concrete placed.
• The total volume of concrete placed and the number of batches used.
In addition, Contractor shall maintain an accurate and up to date record showing
dates, times, weather and temperature conditions when each part of the work was
concreted.
Results of all tests on concrete shall be recorded and identified with the parts of the
work to which they relate.
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6.6 Batching, Mixing and Transporting Concrete
6.6.1 General
The batching, mixing and transporting of concrete shall comply with the applicable
sections of BS 1305, BS 5328, ACI 304R. The concrete batching plant shall be
capable of providing concrete at the rate necessary to comply with the construction
schedule.
6.6.2 Batch Proportions
Only with the approval of Owner shall aggregates be volume batched and in no case
shall cement be volume batched. Contractor may, however, so proportion the mix
that each batch shall use a whole bag or bags of cement, the weight of which is
known precisely. Where permission has been given for volume batching of
aggregates, all gauge boxes shall be accurate and strongly constructed and due
allowance shall be made for bulking of the aggregates in assessing the correct volume
to be used. For volumetrically batched aggregates, the provisions of ASTM C 685
shall apply.
6.6.3 Moisture Content
The batch plant shall be equipped with a moisture meter which shall accurately
indicate the moisture in the fine aggregate. The plant shall be capable of
automatically compensating for varying fine aggregate moisture content.
6.6.4 Mixing Concrete
Concrete shall be mixed in a batch type or continuous mixer tested in accordance
with BS 3963 and having a minimum performance within the limits of Table 6 of BS
1305. Continuous mixers shall be fed with materials which have been proportioned
wholly by weight. For the purpose of testing continuous mixers, one cubic metre of
concrete sampled during continuous operation shall be taken as the batch referred to
in BS 3963 and the batch capacity shall be assumed to be over 0.625m³. Concrete
mixed in batch type mixers shall be mixed for a time approved by the Owner who
will take into account the manufacturer's prototype test report and the test report for
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the particular mixer for the mix proportions and the appropriate performance limits
of Table 6 of BS 1305.
The speed and rate of feed of continuous mixers shall correspond with the values on
the test report for the mix proportion and performance limits of Table 6 of BS 1305.
The drums or pans of all mixers shall revolve at the speed used for testing in
accordance with BS 3965 within a tolerance of plus or minus one revolution per
minute.
All mixers shall be properly maintained in good working order in every respect.
For each mixer proposed, the contractor shall provide a copy of the manufacturer's
specification and statement of performance capability.
The amount of concrete mixed in any one batch shall not exceed the rated capacity of
the mixer.
The whole of the mixed batch shall be removed before materials for a fresh batch
enter the drum.
On cessation of work, including all stoppages exceeding 20 minutes, the mixers and
all handling plant shall be washed out with clean water.
Concrete mixed as above shall not be modified by the addition of water or otherwise
in order to facilitate handling or for any other purpose.
6.6.5 Concrete Production Records
The batch plant shall be equipped with an automatic recorder which shall, as a
minimum, record the following information: grade of concrete, date, time,
cumulative production for each grade of concrete for the day, truck number, cement
and aggregate scale tare, individual weights of cement, each aggregate, admixture,
water and the moisture compensator setting.
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6.6.6 Separation of Constituent Materials
Separate bins or compartments shall be provided for each size of aggregate and type
of cement.
Coarse aggregates shall be separated into the following sizes and stored separately:
40-20 millimetres, 20-10 millimetres and 10-5 millimetres.
6.6.7 Interlock of Discharge Gates or Valves
Batcher discharge gates or valves shall be interlocked with the batcher charging gates
or valves such that the discharge gates or valves cannot be opened before the
charging gates or valves are fully closed.
Accurate automatic admixture dispensers shall be provided and interlocked into the
batching sequence. The location of the discharge of the admixture shall be in
accordance with the manufacturer's recommendation.
6.6.8 Sampling Facility and Batching Tolerance
The plant shall be arranged so as to facilitate the inspection of all operations at all
times. Provisions shall be available to obtain representative samples of the materials
as batched.
The batching scales shall be accurate when static load tested to plus and minus 0.4
percent of the total capacity of the scale.
6.6.9 Transporting Equipment
All concrete shall be transported in vehicles that comply with the requirements of
ASTM C 94, and the recommendations of ACI 304R, Chapter 5.
6.6.10 Mixing times
The cement and aggregates shall be thoroughly mixed dry. Mixing shall be
continued, after addition of water, for not less than two minutes and until concrete of
uniform colour and consistency is obtained.
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6.7 Formwork
6.7.1 General
Formwork shall be designed and constructed in accordance with the requirements of
BS 5975 and shall ensure that the finished concrete members conform accurately to
the dimensions, lines and elevations shown on the drawings and to the specified
tolerances.
Top formwork shall be provided to slopes of 30 degrees or more from horizontal.
Contractor shall submit details of formwork to Owner for review and approval in
advance of concreting.
Formwork shall be of such strength and rigidity as to carry the weight and pressure
from the fresh concrete to be placed on or against it, together with all constructional,
wind or other load likely to be imparted to it, without producing deformation of the
finished concrete in excess of the specified tolerances.
All formwork shall be sufficiently tight without plugging to prevent loss of grout
during the vibration of the concrete.
The faces of formwork shall be clean, free from protrusions, adhering grout and other
imperfections or defects.
6.7.2 Form Ties
Form ties shall be factory fabricated, removable or snap-off metal ties which will
neither allow formwork deflection nor spall the concrete when removed. The ties
shall be provided with backing plates to distribute loads evenly to the formwork.
Bolt or tie systems which, when removed, leave a hole through the member, shall not
be permitted in liquid retaining structures. Ties shall be fitted with devices that will
leave holes in the concrete surface not less than 6 millimetres nor more than 25
millimetres in diameter. Bolts and rods that are to be completely withdrawn from the
finished concrete shall be coated with an approved non-staining bond breaker prior to
concreting.
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6.7.3 Boxouts
Boxes for forming holes shall be constructed to be easily removable without
damaging the concrete during removal. They shall be properly vented to permit the
escape of entrapped air and shall be capable of being sealed subsequently to prevent
the loss of grout. The use of polystyrene blocks for forming holes shall not be
allowed unless used purely as a void filler within otherwise rigidly constructed
boxes.
6.7.4 Inspection Holes
Openings in formwork for inspection and cleaning-out shall be formed so that they
can be completely sealed before the placing of concrete.
6.7.5 Formwork Props
All props shall be supported on adequate sole plates and shall not bear directly on or
against previous concrete. They shall be capable of being released gently without
shock to the supported formwork. No appliance for supporting the formwork shall be
built into the permanent structure.
6.7.6 Chamfers
All outward projecting 90 degree corners shall have a 25 millimetre x 25 millimetre
chamfer unless shown otherwise on the drawings.
6.7.7 Formwork Removal
Formwork shall not be removed before the minimum allowable times given in Table
6.3 have elapsed after placing concrete.
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TABLE 6.3
MINIMUM PERIOD BETWEEN PLACING CONCRETE
AND REMOVAL OF FORMWORK
Element Time (Days)
Beam sides, walls, columns 1½
Slabs (props left under) 4
Beam soffits (props left under) 7
Removal of props to slabs 10
Removal of props to beams 16
6.7.8 Treatment of Formwork
Forms, other than retained-in-place metal forms, shall be coated with form oil (mould
oil) or form release agent before the concrete is placed. The coatings shall be
approved commercial formulations of satisfactory and proven performance. They
shall not bond with, stain or adversely affect the concrete surfaces and shall not
impair subsequent treatment of concrete surfaces depending upon the bond or
adhesion, nor impede the wetting of surfaces to be cured with water or curing agent.
Forms for unexposed surfaces that are to be treated with a waterproof membrane
shall be moistened with water immediately before placing concrete. Surplus oil on
form surfaces, reinforcing steel and construction joints shall be removed before
placing the concrete.
Where a concrete surface is to be permanently exposed only one release agent shall
be used throughout the entire area. Release agents shall be applied evenly. Where
the concrete surface is to receive an applied finish, care shall be taken to ensure
compatibility between the release agent and the finish.
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6.8 Reinforcement
6.8.1 Preparation
Reinforcement shall be wire brushed and cleaned to remove all loose millscale, rust,
grease and dust before it is placed in position.
Bending dimensions, cutting and scheduling shall be in accordance with BS 4466.
6.8.2 Site Fixing
Reinforcement shall be fabricated to the shapes and dimensions shown and shall be
fixed in strict accordance with the Drawings. Cutting and bending shall be in
accordance with BS 4466 and shall be done without the application of heat and in a
temperature no less than 5°C. Suitable precautions shall be taken by Contractor to
prevent displacement of the reinforcement during the placing and compaction of the
concrete. The placement of reinforcement with kinks or bends shall not be permitted.
6.8.3 Supports
Where required to support and retain the reinforcement in its correct position,
Contractor shall provide templates, stools or other supports.
Precast concrete support blocks for reinforcement shall be manufactured from Grade
30 concrete of 10 millimetre maximum aggregate size to ensure the correct cover
thickness. They shall be cured before use and carefully stored on the site to avoid
contamination. Plastic supports may be used subject to the approval of Owner.
Where precast concrete support blocks are used, they shall be wedge-shaped, not
larger than 90 millimetres by 90 millimetres, of a thickness necessary to provide the
required cover and with an embedded hooked stainless steel tie wire for anchorage.
If the formed surface is exposed to view, the precast concrete support block shall be
the same quality, texture and colour as the finished surface.
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6.8.4 Cover and Laps
Cover to reinforcement shall be in accordance with the drawings. Cover shall be
maintained over ties, stirrups and lap splices. Except where shown otherwise the lap
length for high yield steel shall be in accordance with BS 8110. Laps and joints in
reinforcement shall be made only at the positions shown on the drawings or as agreed
by the Owner.
6.8.5 Tie Wire
All intersections of bars shall be tied with 16 gauge black annealed iron wire and
shall have the loose ends pointing away from the formwork, such that they do not
project into the specified concrete cover.
6.8.6 Welding
Welding of bar reinforcement at intersections or for the joining of bars shall not be
permitted.
6.8.7 Mesh Laps
Wire mesh fabric reinforcement shall not be continuous across joints. Lap splices
shall be at least one full mesh plus 50 millimetres, staggered to avoid continuous laps
in either direction, and securely wired.
6.9 Built-in Items, Holes and Cavities
Contractor shall be responsible for the co-ordination of all requirements as regards provision
of holes, chases, cavities and fixings.
Where reinforcing bars at the specified spacing would foul holes of size less than 250
millimetres x 250 millimetres the full length of the bar shall be moved to one side. Bars shall
be positioned to provide the specified cover to the face of the hole. In the case of holes
exceeding 250 millimetres x 250 millimetres the bars shall be cut on site and lapped with
additional equivalent bars, or placed as shown on the drawings.
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Embedded items shall be fabricated and installed to satisfy design requirements. Where
pipes, sleeves, water bars or other items are built into concrete, they shall be rigidly secured
in position to prevent movement. Inserts for anchoring structural, architectural, electrical and
mechanical fixtures and fittings shall be cast in-situ with the concrete according to the
manufacturer's instructions and shall be free from external coatings which might reduce the
bond.
Where in-situ casting is not suitable or is constrained by the proximity of construction
equipment box-outs may be used. Contractor shall submit for approval of Owner on a case
by case basis his proposals for using box-outs.
Embedded items which are galvanised shall not be tied to or in contact with reinforcing steel.
Dissimilar metals shall not be in contact within the concrete. Concrete cover to embedded
items shall not be less than the cover to the reinforcement and the concrete shall be worked
around the items so as to achieve full compaction.
Bolts, hooks and other fixings shall be embedded in concrete, or holes shall be drilled and
fitted with threaded expanding anchors to receive the bolts. Contractor shall ensure that
bolts, hooks and other fixings are accurately positioned. Holding down bolts for machinery
shall be set to template.
Wherever possible, Contractor shall build in all pipework and metalwork which passes
through walls and floors, and he shall ensure that it is thoroughly encased in concrete.
6.10 Concreting
6.10.1 General
The finished concrete shall be dense and free from honeycombing. Any free water
shall be removed from locations where concrete is to be placed before placing the
concrete. Any flows of water shall be diverted away from the Works without
washing over freshly deposited concrete. All debris and foreign material shall be
removed from the interior of the formwork. Runways shall be provided for wheeled
concrete-handling equipment, such equipment shall not be wheeled over
reinforcement nor shall runways be supported on the reinforcement. Reinforcement,
embedded items and formwork shall be inspected and approved before the placing of
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concrete. Wind blown contaminants (such as salt and dust) shall be removed from all
embedded items, reinforcement and formwork prior to the placing of concrete.
6.10.2 Transport
Transport of concrete from the mixer to the forms shall be in accordance with BS
5328: Part 3, Clause 4.10.
6.10.3 Chutes and Drop Pipes
Concrete may be placed directly from a truck mixer or other transporting equipment.
The chutes attached to this equipment may be used provided that the clear free fall
from the end of the chute is no greater than 1 metre and that the slope of the chute
does not exceed 1 vertical to 1 horizontal. When transferring concrete vertically
from higher to lower elevations, drop pipes (trunking) shall be used.
6.10.4 Buckets and Skips
Concrete buckets and skips may be used provided that the equipment is designed to
discharge concrete of the slump required, the discharge gates are tight against
escaping grout when closed and that any free fall of concrete does not exceed 1
metre.
6.10.5 Pumps
The delivery pipe shall be steel or heavy duty flexible hose and the concrete shall be
supplied continuously to the pump. The pump shall be of adequate capacity and
power to ensure delivery of a continuous supply of concrete. Whenever the supply of
concrete to the pump is interrupted for more than 1 hour the chutes, pumps, pipes and
any other means of distribution shall be thoroughly flushed out with water and
cleaned, and shall be flushed with water immediately prior to the resumption of
concreting. All wash water used shall be discharged outside the formwork and clear
of any freshly placed concrete. When pumping is complete, the concrete remaining
in the pipeline shall be ejected without contaminating the concrete in place. At all
times when pumping concrete Contractor shall provide adequate alternative
arrangements for placing the concrete in case of a breakdown of the pumping
equipment.
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6.10.6 Placing and Compacting Concrete
Concrete shall be placed and compacted in accordance with the recommendations of
ACI 304R, Chapter 6 and ACI 309R.
No concrete shall be placed until Contractor has obtained the approval to do so from
Owner. Process control sheets shall be developed jointly between Contractor and
Owner to administer the procedures for inspection and approval.
Concrete shall be handled from mixer to forms in a continuous manner until the
approved pour has been completed and shall be deposited as close as possible to its
final position in the forms and in layers not exceeding 500 millimetres. The total
time taken from the addition of water to the mix until the completion of finishing
operations on any batch of concrete shall not exceed 2 hours and be within 30
minutes of the discharge from the agitator.
Temporary or permanent stoppages of work shall only be made against stop ends and
between specified or approved construction joints.
Each batch of concrete shall be consolidated by internal vibrators according to the
manufacturer's recommendations with respect to effective radius and time of
vibration. The vibrators shall be withdrawn immediately water or a thin film of
mortar begins to appear on the surface of the concrete. Vibrators shall be withdrawn
slowly from the concrete.
Vibrators shall be inserted vertically at uniform spacing to ensure that the effective
vibrated areas just overlap.
Vibrators shall not be used for moving concrete within the forms.
Slabs 100 millimetres thick or less shall be compacted by vibrating beams or other
approved techniques and not by internal vibrators.
Contractor shall ensure that for all concreting operations sufficient vibrators are
available to facilitate continuity of the placing and that stand-by vibrators are
available in the event of breakdowns. Concrete placing shall cease in the event of a
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total breakdown of the vibration equipment and shall be reduced with partial failure
of the equipment. Concrete that has not been properly compacted shall be rejected.
Concrete which is transported in truck mixers or agitators, or concrete which is truck
mixed shall normally be placed within 90 minutes.
6.10.7 Hot Weather Concreting
When the temperature of fresh design mix concrete exceeds 30°C with the
consequence that workability is adversely affected, mixing and placing of the
concrete in question shall be terminated.
Special precautions shall be taken to ensure the concrete temperature at placing is
maintained below 30°C. These precautions may include:
• Protecting all aggregate stockpiles, water lines and tanks as well as the mixer
from the direct rays of the sun.
• Mixing water cooled by the addition of ice to the storage tanks.
• Concreting carried out during the cooler parts of the day or during the night.
• Cooling all chutes, formwork and reinforcement by watering when possible,
or otherwise protecting the site of placing from the direct rays of the sun.
Any water so used shall be removed before placing the concrete in the
formwork.
• Providing wind shields during periods of drying winds.
To minimise the possibility of plastic shrinkage of the fresh concrete the rate of
evaporation of water from the surface of the concrete shall be measured according to
ACI 305R and if this exceeds 1.0 kilogram per square metre per hour, the concrete
shall be protected immediately after placing.
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6.10.8 Concreting in Cold Weather
Concreting at ambient temperatures below 2°C may be carried out only if the
following conditions are met:
• The aggregates and water used in the mix shall be free from snow, ice and
frost before placing concrete.
• The formwork, reinforcement and any surface with which the fresh concrete
will be in contact shall be free from snow, ice and frost and shall be at a
temperature above 0°C.
• The initial temperature of the concrete at the time of placing shall be at least
5°C.
• The temperature at the surface of the concrete shall be maintained at not less
than 5°C at any point, nor should water curing be applied until the concrete
reaches a strength of 5N/mm² as confirmed by tests on cubes matured under
similar conditions.
The Contractor shall take precautions to prevent the temperature of any concrete
falling to 0°C during the first five days after placing.
Concreting is not to be carried out when the air temperature is below 2°C on a falling
thermometer or 1°C on a rising thermometer.
6.10.9 Time Between Pours
The time between successive vertical lifts shall not be less than 3 days and not more
than 7 days. The time between placing concrete in adjacent pours separated by
construction joints shall not be less than 21 days.
6.10.10 Floor Slabs on Grade
Immediately before placing concrete, the capillary water barrier or subgrade under
slabs in buildings shall be covered with a vapour barrier unless membrane
waterproofing is indicated. Punctures and tears during subsequent operations shall
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be patched. Edges shall be lapped not less than 100 millimetres and ends not less
than 150 millimetres. Patches and lapped joints shall be sealed with a pressure-
sensitive adhesive or pressure-sensitive tape, not less than 50 millimetre wide and
compatible with the membrane.
6.10.11 Construction Joints
Before commencing construction of any structure, Contractor shall submit for Owner
approval drawings showing full details of construction joints including their location
and lift heights. No construction joints shall be formed which are not shown on
approved drawings.
Construction joints shall be provided with water stops where shown on drawings,
where joints in concrete elements are in contact with ground soil, and wherever
construction joints occur in liquid retaining structures. Water stops shall be properly
installed and joined to other water stops at the ends of the joints to provide a
continuous barrier to the passage of water in the finished structure.
To ensure control in the placing of concrete slabs Contractor shall provide control
boards to form panels not larger than 15 square metres in plan area. These shall be
lifted as concreting proceeds. Where ready-mixed concrete is used, the control
boards shall be positioned so as to enclose a volume of concrete equal to that
delivered by each truck.
Horizontal construction joints in walls shall be formed along straight lines coinciding
with the full height of the formwork. Construction joints shall be formed normal to
the surface of the retained concrete.
As soon as possible after concreting, and while the surface is still green, the surface
of the concrete forming the joint shall be freed of loose aggregate and sprayed with a
fine spray of water to prevent the formation of laitance. Where laitance has not been
removed before the concrete has hardened it shall be removed by use of an approved
power operated hammer. Subsequently all excess water shall be removed by a jet of
compressed air and the surface left clean to receive further concrete.
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6.10.12 Water stops
Water stops shall be an approved polyvinyl chloride (PVC) or rubber proprietary
brand conforming to U.S. Corps of Engineers CRD-C572 or CRD-C513. The
minimum web thickness shall be 4.5 and 10 millimetres for PVC and rubber water
stops respectively. Site jointing and all fixing shall be strictly in accordance with the
manufacturer's recommendations. All cruciform and T-joints shall be standard
manufactured items.
6.10.13 Joint Sealant
Joint sealant shall conform with the requirements of ASTM C 920 and ASTM D
1190 elastomeric joint sealant. The concrete surfaces adjacent to the joint sealant
shall be clean, dry and free from oil or other foreign matter and shall be prepared in
accordance with the manufacturer's instructions. The sealant shall completely fill the
rebates designated for it and shall be fully bonded to the concrete along both sides of
the joint. It shall be debonded from the back face of the joint by means of an
approved bond breaker.
6.10.14 Joint Filler
Joint filler shall be of an approved proprietary brand conforming to ASTM D 1751 or
ASTM D 1752 and shall be installed according to the manufacturer's instructions.
The joints shall be filled with one thickness of the material to the dimensions shown
on the drawings.
6.10.15 Bond Breaker
Bond breaking material shall be compatible for use with the approved joint sealant
and joint filler and shall be applied at the interface between sealant and filler as
shown on the drawings. The bond breaker shall completely span the interface
between filler and sealant.
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6.10.16 Floor Screeds
Floor screeds shall be constructed to the lines, elevations and crossfalls shown on the
drawings and shall consist of Grade 20 concrete with 10 millimetre maximum size
aggregate.
6.10.17 Concrete Benching
Concrete for benching in manholes and structures shall consist of Grade 20 concrete
with 20 millimetre maximum size aggregate. It shall be placed with low workability
to the shape required and, while still green, shall be finished with not less than 50
millimetres of Grade 20 concrete with 10 millimetre maximum size aggregate to a
steel trowelled finish and to the contours shown on the drawings.
6.10.18 Concreting on "no-fines" Concrete
The exposed surfaces of no-fines concrete upon which, or against which, further
concrete is to be placed shall be completely covered with an approved breather type
membrane complying with the requirements of BS 4016. Care shall be taken to
ensure that the paper is not cut or torn during the erection of formwork or the fixing
of reinforcement. The laps of adjacent sheets of building paper shall not be less than
200 millimetres. In the event of cuts or tears in the paper, patches with a minimum
overlap of 200 millimetres shall be used to cover the damaged area and care taken
during concreting to ensure that none of the grout from the concrete being placed
escapes into the no-fines concrete.
6.11 Curing and Protection Of Concrete
6.11.1 General
Concrete shall be cured for a minimum period of 7 days in accordance with the
requirements of ACI 308.
Immediately after placing, the concrete shall be protected from premature drying,
mechanical injury and from the effects of rain or flowing water. All materials and
equipment needed for curing and protection shall be available at the point of concrete
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placing prior to the concreting operations. Concreting shall not proceed without this
provision.
No fire or excessive heat shall be permitted near or in direct contact with the concrete
or formwork at any time during the curing process.
6.11.2 Moist Curing
Concrete surfaces shall be maintained continuously wet for the entire curing period.
If the water stains or discolours the concrete surfaces which are to be permanently
exposed, the concrete surfaces shall be cleaned. If the forms are removed before the
end of the curing period, curing shall be carried out as on unformed surfaces, using
suitable approved materials.
6.11.3 Curing Compound
Curing compound shall only be used with the approval of Owner.
The curing compound shall conform to ASTM C 309R, Type 1 - D Class A or B.
Curing compound shall not be used on surfaces that are to receive any subsequent
treatment which is dependent upon adhesion or bonding to the concrete. Styrene
acrylate or chlorinated rubber compound meeting Class B requirements may be used
for surfaces which are to be painted. Curing compound shall be applied to formed
surfaces immediately after the forms are removed and prior to any patching or
surface treatment except the cleaning of loose sand, mortar, and debris from the
surface.
For slabs the curing compound shall be applied to slab surfaces as soon as the
finishing operations are complete.
The compound shall be applied in a one-coat continuous operation by mechanical
spraying equipment, at a uniform coverage in accordance with the manufacturer's
instructions. Two coats may be required due to wind conditions or surface texture
and shall only be applied with the approval of Owner. Concrete surfaces which have
been subjected to rainfall within 3 hours after curing compound has been applied
shall be resprayed at the coverage specified for the initial application.
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Surfaces permanently exposed to view shall be shaded from direct rays of the sun for
the duration of the curing period. Surfaces coated with curing compound shall be
kept free from pedestrian and vehicular traffic, and from other sources of abrasion
and contamination during the curing period.
6.11.4 Impermeable Sheeting
Exposed concrete surfaces shall be covered with impermeable sheeting, properly
secured to prevent removal by wind and the development of air spaces beneath it.
Joints in the sheeting shall be lapped by at least 300 millimetres.
6.11.5 Limitation of Temperature Differentials
The temperature differentials in concrete elements greater than 0.5 metre thick shall
be limited to a maximum permissible between the core and the surface of 20°C.
6.12 Surface Treatment and Remedial Works
6.12.1 General Requirements
All exposed faces of concrete shall be hard, dense, smooth and free from
honeycombing, air and water holes and other blemishes.
6.12.2 Surface Defects
Within 24 hours of the removal of the formwork surface defects shall be remedied as
follows:
• For permanently exposed surfaces, fins shall be removed by rubbing down
and all grit and dust therefrom thoroughly washed off with clean water.
Holes left by the removal of tie rods shall be reamed and filled with an
approved proprietary brand non-shrink mortar.
• For all surfaces, honeycomb and other defects shall be cut back to sound
concrete and to a depth of not less than 25 millimetres. The edges of the
repair area shall be cut perpendicular to the surface of the concrete and the
area of repair cleared of all loose material. The prepared area shall be
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thoroughly dampened and the repair shall be completed using an approved
proprietary brand non-shrink cementitious repair mortar thoroughly tamped
into place. In lieu of patching, a small shotcrete gun may be used. The
patches shall be finished flush with adjacent surfaces. The air temperature
shall be above 15 degrees centigrade while making the repair and during the
following 72 hours curing period.
6.12.3 Treatment other than for Surface Defects
Defective areas which, in the opinion of Owner, cannot be remedied by the treatment
specified above shall be cut back until sound concrete is encountered. The limits of
the cut back area shall be directed by Owner.
The sides of the cavity created and any reinforcement shall be cleared of all loose
material, oil, grease and other deleterious material. Formwork shall be erected to
restore the affected surface to the lines and level required and the cavity filled with
concrete of the grade required in the final Works. Before filling with new concrete
the existing concrete surfaces of the cavity shall be dampened with water. Any
excess water shall be removed before concreting.
Care shall be taken to ensure that the correct cover to reinforcement is achieved, that
the finished surface is flush with the surrounding surfaces and that the replacement
concrete is properly compacted.
6.12.4 Replacement of Concrete
As and when directed by Owner, Contractor shall cut out and replace concrete for
any of the following reasons:
• The concrete does not conform to the Specification.
• Deleterious materials or materials which are likely to produce harmful
effects have been included in the concrete.
• Honeycombed or damaged areas occur.
• The finished concrete sizes are not in accordance with the drawings within
the tolerances specified.
• The setting-out is incorrect.
• The steel cover has not been maintained.
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• The protection, including curing, of the concrete during construction was
inadequate, resulting in damage.
• The work of making good or other remedial measures have not been carried
out to Owner satisfaction.
• Deformation of or damage to the Works has taken place due to inadequate
formwork or to premature or excessive loading.
6.13 Concrete Finishes
6.13.1 Formed Finish - F1
This shall be the standard of finish to all concrete formed surfaces that are to be
concealed in the completed work or by other construction, unless otherwise indicated
or specified.
The surface treatment shall comprise the filling of any depressions greater than 12
millimetres deep, including tie-rod holes, and the removal of any fins exceeding 6
millimetres in height by rubbing down with carborundum stone.
The surface so formed shall be within plus or minus 12 millimetres of the required
line and level. Abrupt irregularities shall not exceed 6 millimetres and gradual
surface irregularities shall not exceed plus or minus 6 millimetres when measured
with a 1.5 metre straight edge.
6.13.2 Formed Finish - F2
F2 form finishes shall generally comprise all concrete surfaces that are exposed
either to air or water or that are to be covered with a coating material applied directly
to the concrete, or a covering material bonded to the concrete such as waterproofing,
and are not included in the classification for F3 finishes. The surfaces shall be
formed using close fitting good quality plywood or steel faced boarding with true
arises without visible offsets or bulges. Any fins greater than 6 millimetres in height
shall be rubbed down with carborundum stone. The surfaces so formed shall be
within plus or minus 3 millimetres of the required line and level. Abrupt
irregularities shall not exceed 6 millimetres and gradual irregularities shall not
exceed plus or minus 3 millimetres when measured with a 1.5 metre straight edge.
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6.13.3 Formed Finish - F3
F3 form finishes shall generally comprise those surfaces which convey water or
against which water is impacted.
The formed surfaces shall comply with the requirements for F2 finishes with the
exception that abrupt irregularities and fins shall be no more than 3 millimetres in
height.
In the event that the formed surfaces require treatment following the removal of
formwork, all fins over 3 millimetres in height shall be rubbed down with
carborundum stone and the formed surfaces treated with a filling paste comprising
one part ordinary Portland cement and two parts well graded sand passing a Nr. 30
sieve, with water added to give the consistency of thick paint. After the surface has
been thoroughly wetted and allowed to approach surface dryness, the mortar shall be
vigorously applied to the area by clean burlap pads or by cork or wood-floating, to
completely fill all surface voids. Excess grout shall be scraped off with a trowel. As
soon as it can be accomplished without pulling the mortar from the voids, the area
shall be rubbed down with burlap pads having on their surface the same sand-cement
mix specified above but without any mixing water, until all of the visible grout film
is removed. The finish of any area shall be completed in the same day, and the limits
of a finished area shall be made at natural breaks in the surface. The surface shall be
continuously moist cured for 48 hours.
6.13.4 Rough Slab Finish - U1
Immediately after consolidation, slabs shall be screeded with straight edges to bring
the surface to the required finish level with no coarse aggregate visible. The
resulting rough slab finish should be suitable to receive fill and mortar setting beds
for tile, terrazzo and other bonded applied cementituous floor finishes.
6.13.5 Wood Float Finish - U2
Wood float finish shall be applied to monolithic slab surfaces that are to receive
trowel and other finishes and slab surfaces which are to be covered with bituminous
waterproofing or elastomeric membrane roofing.
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Wood float finishes shall be formed by smooth floating the accurately levelled and
screeded surface. Care shall be taken to ensure that the concrete is worked no more
than is necessary to produce a uniform surface free from screed marks.
6.13.6 Steel Trowel Finish - U3
Trowel finish shall be applied to monolithic slab surfaces that are to be exposed to
view and slab surfaces that are to be covered with resilient flooring, paint, or other
thin-film finish coating systems.
Immediately following the wood floating, the surface shall be steel-trowelled to
produce a smooth, dense surface free from blemishes including trowel marks. In lieu
of hand finishing, an Owner approved power finishing machine may be used in
accordance with the directions of the machine manufacturer. A final hard steel
trowelling shall be done by hand.
6.13.7 Non-Slip Finish - U4
Brush finish shall be given to exterior concrete platforms, steps and ramps. After
wood floating, the surface shall be lightly steel-trowelled, and then brushed with a
fibre-bristle broom.
6.14 Corrosion Protection of Concrete
6.14.1 General
Corrosion protection of buried concrete structures shall be in accordance with the
"Standard Specification for the Corrosion Protection of Buried Concrete Structures".
External surfaces of reinforced concrete structures and pre-cast concrete units buried
or in contact with the ground, shall be protected by plastic membrane.
Alternatively, concrete surfaces of small structures in contact with the ground shall
be coated with a cold applied liquid coating.
Mass concrete used for structural purposes may or may not be tanked depending on
the degree of exposure to sulphate attack (see Section 6.1.2).
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Mass concrete used for fill or other non-structural purposes does not require tanking.
The blinding course beneath reinforced concrete shall be overlain with a water and
vapour proof polyethylene membrane. A cold applied adhesive plastic membrane
shall overlap the foundation membrane to form an effective seal. The membrane
shall fully encase the underground structure before backfilling. The tanking system
used shall be suitable for effective protection against aggressive salts in a hot, wet
environment and shall be tested, installed, formed and completed in accordance with
the manufacturer's instructions. Chamfers or fillets shall be formed to ensure
continuity of membranes that cover right angle concrete joints. To ensure the
tanking system is not damaged when erecting formwork and reinforcement
Contractor shall use a sandwich foundation sealing system incorporating the
impervious barrier between two layers of blinding concrete. To ensure that the
tanking system is not damaged during backfilling Contractor shall use a protective
covering as described in Section 6.14.6.
6.14.2 Materials
Plastic membranes for tanking shall be of a proprietary brand especially designed and
manufactured for the purpose of tanking, and shall comprise a chemically inert
backing sheet with a bituminous adhesive on one side, with a minimum combined
thickness of 1.5 millimetres. The width of roll shall not be less than one metre.
Plastic membranes below structural bases shall be of two types:
• Polyethylene sheeting with a minimum thickness of 1.0 millimetres.
• Textured high density polyethylene membrane with a minimum thickness of
1.5 millimetres and minimum friction angle of 31o between the membrane
and both the underlying blinding concrete and the overlying structural
concrete.
Textured high density polyethylene membrane shall be used where the structure is
designed to resist horizontal forces unless otherwise shown on drawings.
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The cold applied liquid coating shall be as detailed in "Standard Specification for the
Corrosion Protection of Buried Concrete Structures" and "Standard Specification for
Coatings and Linings".
Storage of all materials shall be in accordance with manufacturer's recommendations.
6.14.3 Surfaces to be Protected
All surfaces to be tanked shall have a smooth finish, free of sharp projections or
hollows. Cured concrete bases and pre-cast concrete units shall be dry and swept
free of sand, dust and stones.
6.14.4 Priming
Prior to application of tanking, the concrete shall be primed with a compatible primer
recommended and obtained from the manufacturer of the plastic membrane.
The area to be primed at any one time shall not exceed that which can have the
tanking applied before the primed area becomes contaminated with wind-blown sand
and dust.
6.14.5 Application of Tanking
The membrane shall be applied with the adhesive face over the dry primed surface.
Adjacent rolls of the membrane shall overlap by a minimum of 50 millimetres, and
end-to-end joints shall overlap by at least 100 millimetres.
All overlaps and joints shall be firmly pressed or rolled to ensure that the joint is
water tight.
On all internal or external corners or angles, a 300 millimetres wide reinforcing strip
of the same tanking material shall be applied. On internal angles the reinforcing strip
shall be applied over a fillet of primed mortar or sealing compound.
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6.14.6 Protective Covering for Tanking Membrane
The protective covering shall be a tough, hard, impact resistant bituminous board
containing stone dust filling and chippings and shall have at least one smooth face. It
shall be a minimum of 3 millimetre thick, rot-proof, water repellent and resistant, and
impervious to groundwater chemical attack. It shall also be proof against attack from
insects, rodents and termites and shall not be capable of supporting or hosting
vegetable or microbial growth. It shall be supplied in sheets no larger than 2 metres
by 3 metres.
The protective covering shall generally be held against the structure by the weight of
the soil behind. If any fixing to the structure is required, it shall be accomplished
without any damage to the waterproof tanking material. Contractor shall seal the
joints between boards with a strong adhesive tape.
6.15 Precast Concrete Flags, Kerbs, etc.
Precast concrete units shall be obtained from an approved manufacturer or cast at the Site of
the Works in accordance with the requirements of BS 7263. They shall be true to dimension
and shape, with true arises and with smooth exposed faces free from surface blemishes, air
holes, crazing and other defects, whether developed before or after building-in. Units shall be
tested for water absorption in accordance with BS 7263 and shall display no greater
absorption than that specified under Clause 13 of BS 7263: Part 1.
6.16 Setting Base Plates And Bearing Plates
6.16.1 General
After being set up and checked for alignment, level and verticality, base plates and
bearing plates shall be set with a proprietary non-shrink grout or mortar in
accordance with manufacturer's recommendations.
The plates shall be set and anchored to the correct alignment and elevation using
metal wedges, shims and/or setting nuts. Concrete and metal surfaces in contact with
the bedding shall be clean and free from oil and grease. Concrete surfaces shall be
free from laitance and shall be dampened.
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6.16.2 Non-shrink Grout
Non-shrink grout shall comply with the requirements of CRD-C621 with a minimum
28 day compressive strength of 35 N/mm².
Mixing and placing shall conform with the manufacturer's recommendations. Forms
shall be used to retain the grout and the surface finish attained shall conform with
that of the structural surfaces surrounding it. The grout shall be placed quickly and
continuously completely filling the void without segregation or bleeding.
6.16.3 Slip Bearings
Slip bearings shall comprise two (2) layers of approved proprietary, preformed
bearing strips of dense extruded polyethylene sheet each 1.5 mm thick. Material
minimum safe load capacity shall be 0.1 N/mm². The maximum coefficient of
friction shall be 0.28.
The concrete surface shall be prepared, and the bearing material bonded to the
concrete surface in accordance with the manufacturer's recommendations.
7.0 DOCUMENTATION TO BE SUBMITTED
Contractor shall submit the following documentation to Owner for review and approval:-
7.1 Reports
Materials management reports for quality control of all aggregate and concrete testing
activities.
Quality control documentation reports for daily concreting records.
7.2 Technical Data
Test certificates for cement and reinforcing steel.
Manufacturer's technical data sheets for all proprietary products.
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Quality control documentation and calculations for concrete mix design details.
Loading and calculations relating to design of formwork.
General arrangement drawings of construction joints and identifying sequence of
construction.