Part 4 Division 3 Concrete
Part 4 Division 3 Concrete
Part 4 Division 3 Concrete
Part 1. General
A. Unless otherwise stated in the Specification the latest edition of the following
standard specifications shall apply:
A. Concrete grades in this specification, e.g. grade 7,10 etc. are defined in
Section 03300
Part 2. Products
A. Materials, articles, samples and test certificates may conform with standards
other than the British Standards referred to in this Specification provided the
alternative standard is at least equivalent. In the event of a conflict of
interpretation between the alternative standard and the British Standard, then
the requirements of the British Standard shall prevail.
B. Materials used in the works shall be new, of the qualities and kinds specified
herein and equal to approved samples. Delivery shall be made sufficiently in
advance to enable further samples to be taken and tested if required. No
materials shall be used until approved, and materials not approved shall be
immediately removed from the site.
Part 1. General
1.1 Scope
A. Formwork including all temporary or permanent forms required for forming the
concrete, together with all temporary construction required for its support.
Part 2. Products
A. The surface finishes for formed surfaces shall be as specified on the drawings
to the following requirements:
Type Quality
Type Quality
D. Any concrete, the surface of which has been treated before being inspected
by the Architect, shall be liable to rejection.
Part 3. Execution
3.1 Preparation
A. The inside surfaces of forms shall, except for permanent formwork, be coated
with an approved material to prevent adhesion of the concrete. Release
agents shall be applied strictly in accordance with the manufacturer's
instructions and shall not come into contact with the reinforcement. The same
release agent shall be used for all concrete surfaces which will be visible on
completion of the works.
water used for washing out shall be formed so that they can be conveniently
closed before placing the concrete.
C. Before placing the concrete, bolts and fixings shall be in position, and cores
and other devices used for forming openings, holes, pockets, recesses and
other cavities shall be fixed to the formwork No holes shall be cut in any
concrete unless approved by the Architect.
E. Before any concrete is placed, all formwork shall be inspected and approved
by the Architect who must be notified by the Contractor 24 hours prior to
concreting. Approval does not relieve the Contractor of the responsibility for
the structural adequacy of formwork and supports.
3.2 Installation
B. Where internal metal ties are permitted, they or their removable parts shall be
extracted without damage to the concrete and the remaining holes filled with
drypack. No permanently embedded metal parts shall have less than 2"
(50mm) cover to the finished concrete surface or 3" (75mm) cover where the
structure is water retaining or exposed to sea-water.
C. If the formwork for a column is erected to the full height of the column, one
side shall be left open and shall be built-up in sections as placing of the
concrete proceeds.
D. Forms for beams, slabs and similar members shall be designed and
constructed so that the sides may be removed without disturbing the soffit
shutters or supports thereto.
of the Architect. Approval does not relieve the Contractor of the responsibility
for the adequacy of the method.
3.3 Removal
Part 1. General
1.1 Galvanising
A. After being cut and/ or bent to the dimensions shown on the drawings or
given in the bar schedules, all bar reinforcement and steel fabric unless
indicated otherwise on the drawings shall be prepared and hot-dip galvanised
in accordance with the requirements of BS 729 with a chromatin post-
treatment The temperature of the molten zinc bath shall not exceed
500"C.Softannea1ed iron tying wire shall also be hot-dip galvanised and
similarly treated. Steel reinforcement shall be clean, free from loose rust and
millscale at the time of galvanising. Unless instructed otherwise by the
Architect, reinforcement shall not be straightened nor bent after galvanising.
B. Steel bars to be used for reinforcement supports and spacers shall behot-dip
galvanised and treated in accordance with BS 729 as above. With the prior
approval of the Architect the Contractor may cut and bend this steel on site
provided 2 coats of an approved metallic zinc-rich paint is applied to the cut
end of the steel and to those areas where damage occurs to the galvanising
coating.
Part 2. Products
A. Steel used for concrete reinforcement shall comply with the following British
Standard Specifications:
BS Bar Description
Part 1. General
A. All concrete work shall be in accordance with the British Standard Code of
Practice BS 8110.
A. The Contractor shall be responsible for providing qualified personnel and site
equipment for all testing and sampling of concrete as instructed by the
Architect.
C. The tests will require the preparation of 4 cubes, each made from a single
sample taken from a randomly selected batch of concrete. Cubes shall be
labeled A,B,C,D, for any particular sample and in a numerical order for the
number of samples. A test result is defined as the mean compressive strength
of two cubes tested at 28 days.
i.e Test result X = (Comp strength cube A+ Comp strength cube B)/2
E. The number, frequency and location of tests shall be decided by the Architect,
but the maximum quantity of concrete that four consecutive test results shall
represent shall be limited to 13 yd3 (10 m3).
2. the strength determined from any test result is not less than the
specified characteristic strength minus:
If only one test result fails to meet the second requirements then that test
result may be considered to represent only the particular batch of concrete
from which that test was taken provided the average strength of the group
satisfies the first requirement.
If more than one test result in a group fails to meet the second
requirement or if the average strength of any group of four consecutive
test results fails to meet the first requirement then all the concrete
represented by all such samples shall be deemed not to comply with the
strength requirements.
G. All test cubes shall be labeled as described herein, and shall, approximately
24 hours after casting, be transported to the Ministry of Public Works Quarry
for curing and testing. Test results shall be forwarded to the Architect.
H. The Architect may require the testing of additional cubes for special purposes
including the time at which to strike formwork and the strength of concrete
under hot weather conditions. These additional cubes shall be made and
tested in accordance with BS 1881, but the methods of sampling shall be
varied to suit the purpose for which they are required. Sampling where
possible shall be at the point of placing and the cubes shall be stored so far
as possible under the same conditions as the concrete in members to which
they relate. The extra cubes shall be clearly identified at the time of making
and shall not be used as part of the normal quality control or compliance
procedures.
I. The cement content of any batch of concrete shall be not less than the
specified minimum value minus 5% of that value, not more than the specified
maximum value plus 5% of that value, unless otherwise approved by the
Architect.
1. Slump Test
If the first test result fails to meet the specified limits a second set of results
shall be tested. Two failures constitutes a rejection of that batch of concrete.
K. Any additional tests required by the Architect to comply with this specification
as a result of failure of routine tests shall be performed at the expense of the
Contractor.
Reports of each test taken shall be supplied to the Architect and shall contain
the following:
L. Should any of the results of the specified works tests be unsatisfactory, the
Architect may take one of the following actions:
M. The Contractor shall note that the target strength for the concrete mix design
shall be substantially greater (in the order of 10 N/sq mm) than the specified
characteristic compressive strength. To ensure that no more than 5% of the
concrete falls below this value the Architect may instruct the contractor to take
one or both of the following steps in the event of test cubes failing to meet the
required standard:
A. The Architect shall instruct the Contractor to make a loading test on the works
if in the opinion of the Architect such a test is necessary. The test shall be in
accordance with BS81l0, and shall be carried out as soon as possible after
the expiry of 28 days from the time of placing the concrete.
B. The test loads to be applied shall be specified by the Architect and shall be
equal to the characteristic imposed load and shall be maintained in place for
24 hours. If any of the final dead load is not in position on the structure,
compensating loads shall be added as directed.
C. During the tests, struts and bracing strong enough to supportthewhole load
should be placed in position leaving a gap under the members to be tested,
and adequate precautions should be taken to safeguard persons in the
vicinity of the structure.
F. If, within 24 hours of the removal of the test load the part of the works under
test does not show a recovery of at least 85% of the maximum deflection
shown during the 24 hours under load, the loading shall be repeated. The
structure shall be considered to have failed to pass the test if the recovery
after the second loading is not at least 85% of the maximum deflection shown
during the second loading.
G. If the result of any test is not satisfactory, the Architect shall instruct that the
part of the works concerned shall be taken down or cut out and reconstructed
to comply with the Specification, or that other measures shall be taken as
directed. The Contractor shall conduct the test and shall take down or cut out
and reconstruct the defective work or shall execute remedial measures as
directed.
I. If the structure does not satisfy the conditions of the test, and the daily drop in
water level continues, the period of test may be extended for a further 7 days
at the discretion of the Architect The Contractor shall execute any remedial
measures as required by the Architect.
Part 2. Products
2.1 Cement
A. Unless otherwise noted, cement shall comply with BS 12 and BS 146 or equal
approved.
B. Neither masonry cement nor high alumina cement shall be used in structural
concrete.
C. All cement shall be fresh when delivered to the site, and unless delivered in
bulk, shall be in the original sealed bags or drums of the manufacturers. It
shall be stored in a suitable weatherproof building of ample size, with raised
floors giving adequate protection against the effects of moisture from any
source. Manufacturers' certificates shall be submitted to the Architect on
request.
F. If in the opinion of the Architect any cement has become injuriously affected
by damp or other causes, it shall at once be removed from the site.A1lcement
shall remain stored at the sole responsibility of the Contractor.
2.2 Aggregates
A. Generally:
B. Fine aggregate:
C. Coarse aggregate
3/1611 (5mm) and not less than 25% nor more than 55% is smaller
than 3/811 (10mm).
D. All-in aggregate
E. Storage of aggregates
F. Testing of aggregates
2.3 Water
A. Water shall be potable, clean, fresh and free from organic and inorganic
matter in solution or suspension in the concrete. Water shall be obtained from
an approved source and must not be obtained from a well, excavation,
underground source or the sea.
B. Only water of approved quality shall be used for washing out formwork, curing
concrete, and similar purposes. Water for making concrete shall be tested in
accordance with BS 3148.
2.4 Admixtures
A. Suitable admixtures may only be used in structural concrete mixes with the
prior approval of the Architect. The amount added and the method of use
shall be to the strict instructions of the manufacturer and the approval of the
Architect.
Part 3. Execution
A. For the specified grade of concrete the Contractor shall design the mix in
accordance with BS 8110 and within the limits indicated in Table C.2 below:
B. The cement content of the mix shall not exceed 500 kg/m3 (844 pcy) without
the approval of the Architect.
C. The total chloride content of the concrete mix shall not exceed 0.35% of
chloride ion by weight of cement for concrete made with ordinary Portland
cement. The chloride content shall be measured in accordance with BS 1881.
D. The total sulphate content of the mix shall not exceed 4.0% of sulphur trioxide
by weight of cement. The sulphate content shall be measured in accordance
with BS 1881.
3.3 Workability
A. The workability of the fresh concrete should be such that the concrete is
suitable for the conditions of handling and placing so that after compaction it
surrounds all reinforcement and fills the formwork, subject to the approval of
the Architect.
BS 1305 and checked against accurate weights and volumes when required
by the Architect
E. Mixers which have been out of use for more than 30 minutes shall be
thoroughly cleaned before any fresh concrete is mixed. Unless otherwise
agreed by the Architect the first batch of concrete through the mixer shall then
contain only two-thirds of the normal quantity of coarse aggregate. Mixing
equipment shall be thoroughly cleaned before changing types of cement.
F. During hot weather the Contractor shall ensure that the constituent materials
of the concrete are sufficiently cool to prevent the concrete from stiffening in
the interval between its discharge from the mixer and compaction in its final
position.
G. Trial mixes: where trial mixes are required, three separate batches of
concrete shall be made using materials likely to be typical of the proposed
supply and preferably under full scale production conditions. If circumstances
make this inconvenient, the batches may be mixed in a laboratory unless this
is specifically precluded by the Architect. Sampling and testing should be in
accordance with BS 1881 and BS 5328.
H. The workability of each of the trial batches should be determined and three
cubes made from each batch for test at 28 days. A further three cubes from
each batch shall be made for testing at an earlier age if required. The trial mix
proportions should be approved if the average strength of the nine cubes
tested at 28 days exceeds the specified characteristic strength by 10 N/sq
mm or the nine tests at a earlier age indicate that is likely to be exceeded by
this amount
I. During production the Architect may require trial mixes to be made before a
substantial change is made in the materials or in the proportions of the
materials to be used.
A. Ready mixed concrete as defined in BS 5328, batched off the site, may be
used only with the agreement of the Architect and shall comply with all
requirements of the Specification and Contract.
C. When truck mixed concrete is used, no water may be added to the mix at the
site, without the express approval of the Architect, and in no circumstances
shall water be added in transit.
D. Mixing shall continue for not less than 100 revolutions at a rate of not less
than 7 revolutions per minute.
E. Any ready-mix truck containing concrete which has been rejected by the
Architect for whatever reason shall be removed from the site and deposited
elsewhere. Under no circumstances will any addition of material such as
cement, aggregate or water and remixing of the original batch be allowed.
C. Concrete shall not be placed in any part of the structure until the approval of
the Architect has been given. A minimum of 24 hours notice shall be given
prior to any concrete placement.
G. Concrete shall not be dropped into place from a height exceeding 3' (1.0m).
When trunking or chutes are used they shall be kept clean and used in such a
way as to avoid segregation. In general, trunking or chutes shall not be more
than 20° from vertical.
I. All cement slurry and other material used to lubricate pump pipes shall be run
to waste and not deposited in the works.
A. During hot weather the Contractor shall ensure that the constituent materials
of the concrete are sufficiently cool to prevent the concrete from stiffening in
the interval between its discharge from the mixer and compaction in its final
position. Alternatively the Contractor may incorporate in a mix a plasticiser of
a make and in a proportion which has been shown by laboratory tests and full
scale trial to be to the satisfaction of the Architect, to eliminate detrimental
effects of high temperature without introducing any other detrimental effect,
and for which he takes full responsibility in these two respects.
B. The following may be used to keep the temperature of concrete below the
above limitations:
C. The Architect shall have the power to order the suspension of concrete
production and/or laying when the shade temperature exceeds 86°F (30°C) if
he is not satisfied that the precautions being taken or intended by the
Contractor are adequate to:
1. Prevent the temperature of the concrete rising above 86° F (30° C) or;
2. Avoid any detrimental effect in the use of a plasticiser. This power of
the Architect shall not relieve the Contractor of his responsibilities.
D. Concrete shall not be laid during heavy or prolonged rain. Suitable protection
shall be readily available to protect the concrete after placement during
adverse weather conditions.
3.9 Compaction
B. Immersion vibrators shall be capable of producing not less than 10,000 cycles
per minute, and in the opinion of the Architect be of suitable diameter to
deliver an effective radius of action.
C. Vibration shall not be applied by way of the reinforcement and contact with all
reinforcement and inserts shall be avoided, so far as is practicable.
B. The position and detail of any construction joints not described in the contract
shall be subject to the approval of the Architect, and shall be arranged to
minimise the possibility of the occurrence of shrinkage cracks.
C. Construction joints not shown on the drawings and elsewhere shall with the
approval of the Architect be in accordance with the following:-
D. The upper surface of lifts of concrete walls and columns shall be horizontal
and if the formwork extends above the joint on the exposed face it shall be
cleaned of adhering concrete before the next lift is placed. The concrete
placed immediately above a horizontal construction joint shall contain only
two-thirds the normal quantity of coarse aggregate, shall not be the first batch
through the mixer, and shall be thoroughly compacted and worked against the
existing concrete.
E. Where sections of the work are carried out in lifts, the reinforcement
projecting above the lift being cast shall be adequately supported to prevent
movement of the bars during the casting and setting of the concrete.
F. All laitance, loose material and cement paste shall be removed by wire
brushing while the concrete is still green, to expose, but not dislodge, the
coarse aggregate, and no further roughening shall then be required. Where
this is not possible, it shall be removed by mechanical means without
damaging the aggregates, provided the concrete has been in position for
more than 24 hours. The roughened surface shall then be washed with clean
water and a 1:1 slurry of cement and concretes and shall, wherever possible,
be well worked in immediately before the fresh concrete is placed.
A. All areas of internal floor slabs shall be power-floated and power -toweled to
provide a durable and smooth surface, unless otherwise indicated on the
drawings.
B. Power-toweling shall not be started until surface moisture has evaporated and
the concrete is firm enough to take the weight of the machine. Sufficient
machines shall be provided to ensure that the whole of the area laid is
finished before the concrete becomes unworkable.
C. The tolerance on surface regularity shall be 1/8" (3mm) under a 10' (3m)
straight edge. Notwithstanding this requirement, the slabs shall be finished to
provide a surface which is visually smooth to the satisfaction of the Architect
3.14 Lintels
A. Unless otherwise stated, lintels shall be a minimum of 8" (200mm) deep and
shall have a minimum bearing of 8" (200mm) on each side of the opening
below them and shall be reinforced as follows:
C. These lintels are to be used only when the block work height over the opening
is greater than or equal to the opening width. Where additional loads from
floors, roofs, beams, etc., are within this height, purpose designed lintels are
to be used.
B. The strength of the concrete and the stresses produced by the loads shall be
assessed only by the Architect Materials and plant shall not be stacked on
any newly constructed floor without the permission of the Architect
Part 1. General
B. Immediately after compaction, concrete shall be protected from the sun, wind
and rain, and be prevented from drying out by one of the following methods
for a period of at least 4 days:
C. If the concrete being cured is exposed to the sun, the curing compound shall
be a proprietary product containing white pigment or be an aluminised
compound. The curing compound shall be kept clear of any construction joint
surfaces and be compatible with floor finishes, adhesives for tiles, etc.
Part 1. General
C. A copy of all 28 day cube test results relating to members cast off the site
shall be sent to the Architect as soon as they become available. Where the
Architect requires tests to be carried out, no members to which the tests
relate shall be dispatched to the site until the tests have been satisfactorily
completed.