SPECIFICATION FOR
PLANT LOCATION
NAOC PH BASE - NIGERIACode:3217.46.BASG.36912
PROJECT/UNIT
NEW PORT-HARCOURT BASE POWER GENERATION PROJECTPage 1 of
25Rev
0
SPECIFICATION FOR
CONCRETE WORKS
AT
NAOC PORT-HARCOURT BASE, NIGERIA
21/06/120Issued for ReviewH. DORDORD.AKANOR.OMIETIMI
DateRevDescription of RevisionPreparedCheckedApproved
CONTENTS
1.GENERAL1.1SCOPE
1.2REFERENCE DOCUMENTS
1.21 AGIP GENERAL SPECIFICATIONS
1.22 CODES AND STANDARDS
2.CLASS OF CONCRETE
2.1CLASS OF CONCRETE
2.2 USE OF CLASS OF CONCRETE
3.MATERIALS3.1 SPECIAL REQUIREMENTS
4.AGGREGATE GRAIN SIZE COMPOSITION4.1 SPECIAL REQUIREMENTS
5.MINIMUM QUANTITY OF CEMENT5.1 SPECIAL REQUIREMENTS
6.PRELIMINARY TESTS AND CHECKS OF THE SPECIFIED CONCRETE
MIXES
6.1 PRELIMINARY TESTS
6.2 CHECKING OF THE CHARACTERISTIC COMPRESSIVE ,STRENGTH
7.REINFORCEMENT AND FORMWORK
7.1SPECIAL REQUIREMENTS FOR REINFORCEMENT
7.2 SPECIAL REQUIREMENTS FOR FORMWORK
8.CONCRETING PROCEDURES
8.1CONCRETE MIXING
8.2CONCRETING IN HOT WEATHER
8.3TRANSPORTION OF CONCRETE
8.4BLINDING CONCRETE
8.5CONCRETE POURING
8.6TOLERANCES FOR FORMED SURFACES
8.6.1 Variations from plumb and alignment
8.6.2 Variations from the level or from the grade specified in
the drawings
8.6.3 Variations from plan alignment in relation to the
established . lines
8.6.3 Variations in sizes and location for sleeves
9.EXPANSION JOINTS
9.1PLAIN JOINTS FOR PAVING
9.2WATERTIGHT JOINTS
10.REINFORCED CONCRETE PITS
10.1SPECIAL REQUIREMENTS
11.TIGHTNESS TESTS FOR TANKS AND PITS
11.1SPECIAL REQUIREMENTS FOR TANKS
11.2SPECIAL REQUIREMENTS FOR PITS
1.0GENERAL
1.1 Scope
This document defines the specifications for concrete strengths,
classes of materials, strength tests, mixing and concreting
procedures for concrete work with reference to European Codes or
British Codes and Standards.
1.2Reference documents
1.2.1 AGIP General Specifications
27550.VAR.CIV.FUNSite Clearing and Excavation
27551.VAR.CIV.FUNFill
27552.VAR.CIV.FUNGeneral Concrete
27563.VAR.CIV.FUNSewers and Drainage
1.2.2 Codes and Standards
Unless otherwise stated, the latest editions of the following
codes and standards shall apply for all work to be carried out in
accordance with this Specification:
BS 12Specification for Portland cement
BS 146Specification for Portland blast furnace cement
BS 410Specification for test sieves
BS 412Testing aggregates
BS 812 VariousMethods of sampling and testing of mineral
aggregates from natural resources for concretes
BS 882Specification for aggregates from natural sources for
concrete
BS 1370Specification for low heat Portland cement
BS 1881Testing concrete
BS 3148Methods of test for water for making concrete (including
notes on the suitability of water)
BS 4027Specification for sulfate-resisting Portland cement
BS 4246Specification for high slag blast furnace cement
BS 4449Specification for carbon steel bars for the reinforcement
of concrete
BS 4483Specification for steel fabric for the reinforcement of
concrete
BS 4550Methods of testing cement
BS 5075Concrete admixture
BS 5080Structural fixings in concrete and in masonry
BS 5328Concrete
BS 5606Guide to accuracy in building
BS 5975Code of Practice for False work
BS 6588Specification for Portland pulverized-fuel ash cement
BS 6651Code of practice for protection of structures against
lightning
BS 8004Code of practice for foundations
BS 8007Code of practice for design of concrete structures for
retaining aqueous liquids
BS 8110Structural use of concrete
CP 102Code of practice for protection of buildings against water
from the ground
CP 2012 Part 1Foundation for reciprocating machines
Building Research Establishment Digest 250 Concrete in
sulphate-bearing soils and groundwater.
The current edition of the building regulations and all
amendments thereto.
Standard method of detailing reinforced concrete published by
the Concrete Society and the Institution of Structural
Engineers.
2.0CLASS OF CONCRETE2.1Class of ConcreteThe class of concrete
will depend on the compressive cube strength determined at 28 days
tested to BS 1881.
2.1.1Compressive strength:15N/mm2(C15) -Blinding
2.1.2Compressive strength:20N/mm2(C20) - Road Crossings, Cable
Sleeves and Mass Concrete
2.1.3Compressive strength:25N/mm2(C25) -Structures and
Foundations
2.2Use of Class of Concrete The Class of concrete to be used in
the works shall be as shown on the relevant construction
drawings.
3.0 mATERIALS3.1 Special Requirements
3.1.1 Cement
Cement characteristics shall conform to BS 12, BS 146, BS 1370,
BS4027, BS 4246, BS 6588.
The type of cement to be used and the relevant strength shall be
specified on the design drawings and/or in other contract
documents.
3.1.2 Water
The water used for making concrete or cleaning out shuttering,
curing concrete or similar purposes shall be taken from the mains
supply wherever possible, and shall comply with the requirements of
BS3148: Where water is not available from the mains the Employers
approval shall be obtained before use.
3.1.3 Sand (Fine Aggregate)
Sand shall be in accordance with BS882 and come from rivers,
quarries, from natural sources or crushing of compact siliceous,
quartz, granitic or calcareous rock. The sand shall be clean, free
from silt and any other foreign matter that may affect the strength
and/or the normal curing time of the concrete.
The grain size shall be well graded within the following
range:
Sieve (BS410)% Passing
(by mass)
10mm100
5mm95-100
2.36mm80-100
1.18mm50-85
600(m25-60
300(m10-30
150(m2-10
The content in fines (passing through a sieve of 75(m) shall not
exceed the following values:
-3% by mass for natural sand
-5% by mass for sand produced by crushing.
Sand obtained by crushing can be added to natural sand in
suitable proportion in order to attain the above-mentioned
values.
Crushed-sand alone cannot be used unless previously approved by
the Employer.
Sea-sand if obtained from a quarry whose elevation is above the
maximum highest tide level can be used (subject to Employers
approval) providing the grain size is within the above-mentioned
range, and the salt content meets the requirements of BS812 and
BS1881.
3.1.4 Gravel or Crushed Stone (Coarse Aggregate)
Gravel shall be in accordance with BS 882 and come from a river
bed, quarry, or from a natural source of siliceous, quartz,
granitic or calcareous rock which is chemical inert, strong, hard,
durable and of limited porosity.
Gravels which come from the crushing of compact rock shall
comply with the requirements of BS 882.
All gravel and crushed stone shall be clean, free from silt or
any other foreign matter that may affect the strength and/or the
normal curing time of cement.
The limits of aggregate size are given in BS882 together with
the flakiness index and shall be strictly adhered to during the
selection and controlling of aggregates for a specific concrete
use.
3.1.5 Reinforcement
The characteristics of reinforcement shall conform to the
requirements of the BS4449. In particular, it shall be free from
apparent defects such as laminar separation, cracks, debarring and
burning, besides being clean and free from substances such as oil,
greases or earth that may impair its adhesion properties.
The type of steel to be used shall be specified on the relevant
design drawing.
Bar samples shall be subjected to tensile and bending tests by
an approved licensed laboratory in accordance with the requirements
of BS4449.
The use of a guaranteed strength reinforcement releases the
Contractor from the obligation of carrying out the above-mentioned
tests.
The characteristics of welded steel wire fabric shall conform to
the BS4483.
3.1.6 Admixtures
Any chemical admixtures use shall conform to the requirements of
BS5075.
The use of admixtures may be used to improve the workability of
the concrete provided that the approval of the Employer is obtained
and that the use of such admixtures does not impair the quality of
the concrete.
4.0 AGGREGATE GRAIN SIZE COMPOSITION
4.1 Special RequirementsThe grain size composition of concrete
aggregates shall be expressed as a percentage by mass of each
component passing through square mesh sieves, and shall normally
range between the maximum and minimum values indicated in the
BS882.
Before transporting the aggregate supplies to the site, the
Contractor shall submit for agreement with the Employer the grain
size values to be used in the concrete mixes.
Aggregates shall be from approved sources and test certification
shall be provided for each source.
Coarse aggregate shall be limited to 20mm nominal size.
5.0 MINIMUM QUANTITY OF CEMENT
5.1Special RequirementsUnless otherwise specified in the Design,
the minimum quantity of cement refers to one (1) m3 of concrete mix
for each grade of concrete, shall be as follows:
Characteristic compressive strengthMinimum Cement Content
kg/m3
20 N/mm2220
25 N/mm2255
35 N/mm2300
These minimum quantities of cement stated above shall always be
complied with.
Should it be necessary to increase the quantities of cement from
those specified, to achieve the characteristic compressive
strength, the mix shall be redesigned in accordance with BS8110
with due regard for the placing, workability and shrinkage, etc. of
the concrete mix.
Any changes to the concrete mix shall be submitted to the
Employer for his approval in writing before use on site, but this
approval does not relinquish the Contractor from his responsibility
and/or costs for providing the characteristic compressive
strength.
6.0 PRELIMINARY TESTS AND CHECKS OF THE SPECIFIED CONCRETE
MIXES
6.1Preliminary TestsPreliminary tests shall be carried out by
the Contractor prior to casting, and according to the schedule
submitted to and approved by the Employer.
For each grade of concrete, and according to the required
consistency and workability requirements, the Contractor shall
carry out preliminary tests to establish the optimum design mix
with regard to the required strength and workability.
The tests therefore shall be made to check the following in
accordance with BS5328.
-aggregates with different mechanical characteristics
-aggregates with different grain size composition
-quantity of water
-quantity of cement
-density of fully compacted concrete.
It should be noted that, with the same quantity of cement, the
highest strength within any given grade is attained by a concrete
where:
-total water (including aggregate water) to cement ratio is 0.50
or less);
-the hardest aggregates are incorporated;
-the highest density is attained by a good aggregate
distribution, reducing voids to a minimum.
In the case of a low water concrete having poor workability, for
its intended use, the quantity of cement can be increased provided
that the initial water to cement ratio remains unchanged.
Following the Manufacturers recommendations concrete workability
can be improved by using liquefying admixtures.
The use of such products shall in no way impair the strength
properties of the concrete; in this connection, a series of
strength tests using the liquefying admixture shall be
performed.
The optimum mix shall be determined by preliminary tests
performed not later than 30 days before the start of the casting of
concrete and shall be constantly monitored and checked throughout
the casting operation.
The preliminary determination of the strength of each class of
concrete only has the purpose of defining the optimum mix.
The final acceptability of the concrete however shall depend
upon its characteristic compressive strength, which shall be
determined on test samples obtained during the casting operation
and in accordance with the requirements of BS1881.
The preliminary tests shall be carried out on a series of cubes
subjected to 7 and 28 days of curing, 1 tested at 7 days, 2 tested
at 28 days, 1 spare to be tested at 56 days in the event of failure
at 28 days.
The cube test results shall prove the quality of the concrete
obtained regarding its density and workability, etc., and shall
ensure that the concrete mix used will reach the required
characteristic compressive strength specified.
6.2 Checking of the Characteristic Compressive Strength
Checking shall be carried out in accordance with the
requirements of BS1881.
The check shall be carried out on four samples at a time.
The type of samples, their preparation and curing shall conform
to the requirements of the previous chapter 6.1. of this
Specification.
The sampling frequency shall comply with the requirements set
out in the Project specification; however, not less than 1 set
(one) of samples per 50m3 and/or for each day of casting shall be
taken, unless otherwise agreed upon with the Employer.
If ready mixed concrete is used one set of samples per delivery
shall be taken.
7.0 REINFORCEMENT AND FORMWORK
7.1Special Requirements for Reinforcement
The requirements of the standard concerning carbon steel bars
used for reinforcement shall be complied with in respect of
construction, tolerances, joints, bends and spacers.
The minimum covering thickness of concrete shall comply with
recommendations of BS8110 and/or be as shown on the detail
drawings.
Bars shall be installed in accordance with the number, size,
shape and position specified in the detail drawings and/or design
documents.
Bars shall be tied together using annealed iron wires at all
intersection points, to form rigid cages that will maintain their
position without distortion or twisting during the placing and
compaction of the concrete.
Prefabricated spacers of concrete or plastic type approved by
the Employer, shall be inserted between the bars and internal
surfaces of the formwork, so that the required concrete cover
thickness is maintained during the placing and compaction of the
concrete.
Contractor shall attach certified manufacturers material data
sheet for reinforcement bars to be used on this project.
Characteristic strength test will also be carried out on samples of
reinforcement bars.
7.2Special Requirements for Formwork1)Timber or steel may be
used for formwork at the Contractors convenience or according to
the material he has available and shall comply with BS5975.
Formwork shall be able to withstand the weights of the
structure, of the workers, and fixed and mobile equipment for the
placing and compaction of the concrete, as well as any other loads
or stresses.
Moreover, formwork shall be erected to prevent distortion or
misalignment during concreting, and shall be built to allow the
striking of the formwork in accordance with the provisions of
BS8110. Care shall be taken in the design, erection and dismantling
of the formwork and its supports when heavy loads, wide spans, or
similar unusual features are involved.
The formwork surface in contact with the concrete shall be
smooth and free from projections, indentations, undercuts or
unevenness, care being taken to accurately mate the boards so that
the required finished surfaces may be obtained.
Unless otherwise specified, all edges and corners of exposed
concrete shall be chamfered using timber fillets (25mm).
2)PVC or fibre cement pipes of either round or square section
may be used to provide anchoring pockets for bolts and similar
items. Their outside surfaces shall be greased before concreting to
facilitate their removal after the concrete has set.
Inserts shall be provided with holes for fixing anchor bars
together with bottom plugs, when necessary. The pockets so formed
shall be thoroughly cleaned before the anchor is installed; pockets
shall be filled with polystyrene foam or similar to prevent any
damage to the concrete.
3)The dismantling of formwork shall only be effected after the
concrete has been sufficiently cured, and shall be carried out with
appropriate care, avoiding shocks or sudden stresses.
In particular, before any formwork is dismantled a check should
be made of the concrete pouring records to ascertain the weather
conditions that existed when the concrete was cast in order to
ensure that the concrete has sufficiently cured and that all the
other appropriate conditions have been fulfilled.
Concrete strength checks may also be advisable prior to
dismantling, by performing tests with a portable sclerometer, even
though such tests shall not be regarded as final.
Formwork shall not be removed unless the correct number of days
has elapsed since the date of the last casting, as specified in the
BS8110 for each type of structure, considering a day to be a 24
hour unit.
4)The time of concrete curing and the dismantling dates shall be
those adopted for normal pouring and curing conditions; otherwise
they shall be extended in accordance with the requirements of
BS8110.
5)In addition to the precautions already indicated for
dismantling, care shall be taken to avoid chipping or otherwise
damaging the concrete surface.
Upon completion of the formwork removal, all protruding iron
stays shall be removed.
Any damage or unevenness in the structural finish, shall be
reviewed by the Contractor and a recommendation for the remedial
work involved, shall be presented to the Employer for his approval.
This shall not in any way relieve the Contractor of his
responsibility to the contracted works, and all the remedial works
agreed, shall be at the Contractors expense.
8.0 CONCRETING PROCEDURES
8.1Concrete MixingNormally, mechanical means shall be used for
concrete mixing, and hand mixing shall only be allowed for small
works, if approved by the Employer.
Concrete mixing equipment shall be sufficient for the size of
the structures to be constructed and the concreting schedules,
taking into account the need to ensure a continuous supply of
concrete for each structure.
Generally, a mechanical means shall be used for measuring the
concrete materials, and the concrete composition shall be constant
and identical with those that proved to be the optimum during the
preliminary tests for each class of concrete.
8.2 Concreting in Hot Weather
The temperature of concrete at the time of placement shall not
exceed 30C, but for concrete items in excess of 30m3 and/or 900mm
thickness, the temperature of concrete at the time of placement
shall not exceed 25C. Any concrete with a temperature in excess of
the above figures shall not be used. All mixing and curing shall be
in accordance with ACI 305R-91.
The Contractor shall make adequate provision before normal
production concrete commences for the means of keeping within this
temperature limit, taking into account the anticipated site
temperatures during the period of concrete production.
Normal provisions for reducing the concrete temperature are as
follows:
a)Shading of mixing plant and trucks.
b)Shading of aggregates and water tank.
c)Painting white the mixing plant, trucks, water tank and cement
silo.
d)Insulating the water tank and supply piping.
e)Using flaked ice in lieu of mixing water.
f) Concreting at night.
8.3 Transportion of Concrete
The transportation of concrete to the pouring areas shall be
effected by the most suitable, and usually mechanical means, to
avoid segregation of the concrete.
Unless the means of transport is equipped with a mixer, no
longer than 15minutes shall elapse from the time concrete is loaded
to the time it is placed (dumpers, chutes, buckets or the like)
concrete shall never be unloaded from a height exceeding 1.5
metres.
Concrete may also be poured using mechanically driven pumps, in
which case liquefying additives may be added, subject to the
Employers written approval, provided the procedure and requirements
of paragraph 6.2. are adhered to.
After each interruption of the work, the pump and piping shall
be flushed with pressurized air and water. Care should be taken to
ensure that excess water does not enter the areas to be
concreted.
On arrival at the delivery area the temperature of the concrete
shall be taken to check that it complies with sub-clause 8.2.
8.4 Blinding Concrete
All foundations, whatever the nature of the soil, shall be laid
on a bed of blinding concrete (grade C15) with a minimum content of
220kg of Portland cement for one m3 of mixture.
The minimum thickness of the concrete blinding shall be 50mm and
it shall be laid to the specified levels.
It shall extend 50mm beyond the edge of the foundation
perimeter, unless otherwise specified on the construction
drawings.
8.5 Concrete Pouring
8.5.1Prior to concreting, checks shall be carried out to
determine that:
-the steel reinforcement fully complies with the construction
drawings with regards to the number, location and diameter of the
bars, their bending, joints, offsets, laps, spacing, cover and
tying, and that the cages are fastened so as to ensure their
stability during concreting;
-all the formwork has been thoroughly cleaned and all foreign
matter has been removed;
-all inserts, as indicated on the construction drawings, have
been correctly located inside the shuttering;
-that all bolts, stays, sleeves, plates, pipes, etc. have been
correctly positioned to the proper levels, position and alignment,
on both horizontal and vertical structures, above and below ground,
as required for the subsequent erection of any permanent or other
temporary equipment;
-the formwork and any other tiling and cement material is kept
damp, especially during hot weather;
-all flaws, distortions, cracks, etc., caused by board shrinking
and/or settling have been properly eliminated from timber formwork,
particularly during hot weather;
-all appropriate, mobile and stationary equipment has been
properly installed for concrete lifting, conveying and
distribution, to ensure concreting as scheduled without
interruption; avoid shock loading and/or vibration from this
equipment which could affect concrete stability and curing;
-where large pours are involved, requiring several days to
complete, the limit of the daily pour shall be scheduled so that
the construction joint occurs in the most appropriate location,
depending on the type of structure.
8.5.2The Contractor shall submit for approval to the Employer a
precise pouring schedule. The Employer may also issue specific
pouring instructions.
8.5.3Concrete shall be laid in layers and shall be compacted
using vibrators, without displacing the steel reinforcement.
The concrete, particularly in cases where the water-cement ratio
is lower than 0.45, and in cases where concrete with higher
characteristics are used, shall be vibrated within 15 minutes of
placing, using compressed air, electrical or mechanical equipment
working at frequencies ranging between 8000-12000 vibrations per
minute, taking into account the fact that vibrating frequency is a
function of aggregate particle size and reinforcement density.
Vibrators shall be inserted and drawn out slowly, at a speed not
exceeding 80 to 100mm per second, to prevent the formation of voids
inside the concrete. Furthermore, contact between vibrators and any
reinforcing rods shall be avoided.
The depth of each layer to be vibrated shall not exceed 40mm,
which shall include 10mm of the previous layer.
Vibration shall cease as soon as a cement grout appears on the
surface. Any further vibration may result in the segregation of the
concrete constituents.
Where closely spaced reinforcing bars are found, blade vibrators
shall be used, the blade length being 200mm or less.
Pouring shall be continuous and fill the whole section both
vertically and horizontally, so that no curing occurs at any of the
contact surfaces of the concrete sections during the pour.
This provision shall be strictly complied with until each
structural unit shall have been completed, or at least until the
pre-determined interruption limits have been reached.
To comply with this provision, concrete mixing, transportation
and casting capacity shall, if necessary, be temporarily increased
wherever large or otherwise unusual structures are to be cast.
All horizontal surfaces shall be flat and float finished in
accordance with that specified. Surfaces in contact with the
formwork shall be smooth, compact, uniform, free from colour
patches, voids or burrs, after the formwork has been
dismantled.
8.5.4Normally no interruption of concreting operation shall be
allowed.
Any interruption which should become necessary shall be
authorized by the Employer.
Any surfaces affected by the resumption of concreting shall be
carefully chiselled, washed and grouted.
8.5.5During and/or after concreting, care shall be taken to
ensure that:
a)No person or equipment is allowed on any structure, or part
thereof, before it has adequately cured.
b)Excessively high temperature conditions do not prevent proper
curing.
c)Since the daily ambient temperatures are normally going to
exceed the allowable concrete temperatures in sub-clause 8.2 strict
curing control shall be applied in accordance with ACI305R-91
Concreting in Hot Weather.
For large pours in particular the Contractor shall provide
calculations to Employer to show that the method of curing will
control the temperature and gradients within the concrete mass.
All concreting shall be carried out wherever possible during the
coolest period of the day. Any temporary protection shall not be
removed until the curing process is almost complete and/or that
specified in BS8110.
Concrete shall be protected from heat and wind by any such means
as may adequately lower the temperature, whether directly or
otherwise, over the concreted surfaces.
In addition, as soon as sufficient hardness has been attained to
prevent washing out, all finished surfaces shall be continuously
wetted throughout the day, particularly where intense heat
prevails. Insulation shall be used on the appropriate surfaces
where necessary.
d)Concreting records shall be kept up-to-date by the Contractor,
stating when each structure, or part thereof, is undertaken and
completed, the grade of concrete used, and the weather conditions
prevailing during concreting up to completion of the curing.
A copy of these records shall be delivered daily to the
Employer.
8.6Tolerances for Formed Surfaces
Unless otherwise specified in the contractual documents,
concrete works shall conform to the tolerance limits as stated in
BS5606.
8.6.1Variations from plumb and alignment
To the arises and surfaces of columns, pillars and walls:
in any 3m of length
6mm
maximum for the entire length
25mm
8.6.2Variations from the level or from the grade specified in
the drawings
To the surfaces and arises of slabs, ceilings and beam
soffits:
in any 3m of length
6mm
maximum for the entire length
18mm
8.6.3Variations from plan alignment in relation to the
established lines
To buildings (or supporting structures) as a whole and to the
related pillars, walls and partitions:
in any 3m of length
12mm
maximum for the entire length
25mm
8.6.4Variations in sizes and location for sleeves
For floor and wall openings 6mm
9.EXPANSION JOINTS9.1Plain Joints for PavingJoints shall be 15mm
wide and shall extend the full length of the concrete paving.
Polystyrene foam shall be used to fill the joint up to 25mm
below the upper concrete surface, the remaining 25mm shall be
sealed with a hydrocarbon-proof sealant or equivalent, approved by
the Employer.
The Manufacturers recommendations shall be carefully followed
for the application of the sealant.
9.2Watertight JointsWhen the joint is required to be watertight
(water tanks, basins, etc.), water stops buried in concrete shall
be used so as to allow for expansion or shrinkage of the
structure.
Water stops shall be used for the full length of the joint.
If non-aggressive fluids are used, joints shall be filled with a
soft material (polystyrene or equivalent) up to 25mm below the
concrete surface inside the tank, basin or the like, and shall be
subsequently sealed with either sand-cement mortar or similar
approved.
When aggressive fluids are involved, such as hydrocarbons, etc.
special joints sealers shall be used for sealing tanks, basins,
ducts and the like.
The joint seat shall be properly cleaned, Moltoprene or
equivalent inserted and sealed all in accordance with Manufacturers
recommendations.
All joints shall be 20 x 15mm in section.
9.0 REINFORCED CONCRETE PITS
10.1 Special Requirements
The casting of reinforced concrete pits for surface water,
sanitary water, oily and semi-oily water sewers shall conform to
the requirements of this specification.
Sealing shall be carried out to ensure that the piping inlets
and outlets are watertight.
The covering slab support surfaces shall be levelled with
mortar.
Where expressly required by the Employer, inside walls shall be
rendered with cement mortar.
When rendering is specified, the surface finish and sealing
around pipes shall be such as to ensure compliance with this
specification.
No rendering shall be applied until the Employer has inspected
and approved the structure.
11.0 TIGHTNESS TESTS FOR TANKS AND PITS
11.1 Special Requirements for Tanks
All basins shall be submitted to a water tightness test, if this
is expressly requested by the Employer.
Water-tightness shall be tested by completely filling the basins
with water.
Water level shall remain constant throughout the period required
for completing the test.
-Level checks shall commence 24 hours after filling, to allow
for the saturation of the walls.
-Basins shall be tested after fitting inlet and outlet pipes,
and prior to backfilling.
-Test shall be commenced after the water level has been brought
to the original level to offset soaking.
-All basin walls and piping intersection points shall be
carefully inspected for leaks.
-Water shall not be added to restore the original level until
the test is completed.
All defects that are shown up by tests shall be made good by the
Contractor, even though this may require demolishing, remaking,
replastering or treatment using special materials, all at the
Contractors expense and at no cost to the Employer.
In the case of bottom leakage in basins, either buried or
above-ground, for which correction would be a problem, the
Contractor shall ensure a thorough waterproofing of the bottom
using the most appropriate systems and materials on the basis of
the basin construction and operational requirements.
-Defective basins, if any, shall be re-tested after all defects
have been repaired or removed until completely satisfactory results
are attained.
-All tests shall be attended by the Contractors and Employers
representatives.
-No backfilling shall be allowed unless all specified tests have
been completed in a satisfactory manner.
11.2 Special Requirements for Pits
All the pits for rain water, sanitary, oily and semi-oily water
collection to a sewer system shall be submitted to tightness test,
if this is expressly requested by the Employer.
Aniline-coloured water shall be used for testing pits so that
leaks, if any, may be more easily detected.
-Each pit shall be tested by filling with water and shall not be
classified as acceptable unless the original water level remains
constant for at lest 30minutes.
-Tightness test shall be commenced 12 hours after filling to
allow for the saturation of the walls; should it be required to
offset the saturation, the water level shall be brought to the
original level.
-Pits shall be tested after connecting all inlet and outlet
pipes, and prior to backfilling.
-Pit inlets and outlets shall be sealed by airtight plugs
inserted into inlet and outlet pipes, or by any equivalent
method.
-All pit walls and piping intersection points shall be carefully
checked for leaks.
-Further water shall not be added to restore the original level
until the test is completed.
-All defects found during testing shall be made good by the
Contractor.
-Defective pits, if any, shall be re-tested after all defects
have been repaired or removed until complete satisfactory results
are attained.
-All tests shall be attended by the Contractors and Employers
representatives.
-No backfilling shall be allowed unless all specified tests have
been completed in a satisfactory manner.
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