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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

First Edition : May 2007

L–C O N C R E T E W O R K

1.0 CONCRETE

1.1 Scope

This section covers the supply of materials for concrete, design of concrete mixes,

quality control of concrete, mixing, transporting, placing and curing of concrete,

and testing of concrete.

The standard of materials and workmanship shall not be inferior to the

recommendations of the current:

British Standard 8110 : Structural Use of Concrete

British Standard Code of Practice BS 8007 1987: Design of Concrete Structures for Retaining Aqueous liquids.

Appropriate Malaysian Standards approved by the S.O.

Unless otherwise specified, all reinforced concrete for retaining aqueous liquids

shall comply with BS 8007 and shall be of Grade C35A designed to resist Class 2

Sulphate Conditions as defined in BS 5238: Part 1 Table 7.

1.2 Concrete Production at the Site

At the commencement of the Contract the Contractor shall submit for the approval

of the S.O. a method statement detailing with regard to the requirements of this

Specification his proposal for the organization of concreting activities at the site.

The method statement shall include the following items :-

(a) Plant proposed;

(b) Laying of concrete production facility;

(c) Proposed method of organisation of the concrete production facility;

(d) Quality control procedures for concrete and concrete materials;

(e) Method of transport and placing of concrete;

(f) Striking times for formwork and procedure for temporary support of beams

and slabs.

Certificates

1.3 Test

Unless otherwise directed by the S.O., manufacturer's test sheets shall be supplied

with each consignment of cement and admixture certifying compliance with the

relevant standard.

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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

First Edition : May 2007

The Contractor shall also submit to the S.O. certificates of calibration for the

weighing and dispensing equipment on the concrete batch mixing plant, certified

test results for all tests carried out on aggregate, water, fresh concrete and hardened

concrete, all as specified.

Samples

1.4 Aggregate

Prior to the commencement of the trial mixes of concrete the Contractor shall

submit for approval samples 50 kg in weight of each aggregate which he proposes

to use.

The source of each aggregate shall be clearly marked on the container of each

sample.

Certified test results demonstrating compliance with the relevant quality standard

shall be submitted at the same time. Samples approved by the S.O. shall remain

preserved at site for reference.

1.5 Records of Concreting

An accurate and up to date record showing dates, times, weather and temperature

conditions when various sections of the works are concreted shall be kept by the

Contractor and shall be available for inspection by the S.O. The Contractor shall

also record the results of all tests of concrete and shall identify these results with the

parts of the works of which the samples material is representative.

For each grade of concrete, the Contractor shall submit to the S.O., not later than

twenty-four hours after concreting, a daily return of the number of batches mixed,

the number of batches and total volume of concrete placed, the number of batches

wasted or rejected and the weight of cement used.

The return shall also include specific details of each location in the works where

concrete is placed, together with the grade of concrete, total volume of concrete

placed and the number of batches used for each location.

Mixes

1.6 Concrete

At the commencement of the works the Contractor shall design a mix for each grade

of concrete which will be required for use in the works and shall submit full details

of the mix designs to the S.O. for his approval. Each mix design shall be according

to the requirements of BS 5328.

1.7 Construction Joints and Lifts

The Contractor shall submit to the S.O. for his approval, as soon as is practicable

after the acceptance of his tender and not less than three weeks before the

commencement of concreting, drawings showing his proposals for placing concrete

on which the position of all construction joints and lifts shall be shown. No

concreting shall be started until the S.O. has approved the method of placing, the

positions and form of the construction joints and the lifts. The construction joints

shall be located so as to impair the strength of the structure.

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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

First Edition : May 2007

Rebates, keys or notches shall be formed and waterstops inserted as the S.O. may

require. The position of construction joints and the size of formwork panels shall be

so coordinated that where possible the line of any construction joint coincides with

the line of a formwork joint and that in any case all construction joint lines and

formwork joint lines appear as a regular and uniform series.

For all exposed horizontal joints and purposely inclined joints, a uniform joint shall

be formed with a batten of approved dimensions to give a straight and neat joint

line.

1.8 Cement

The cement used for any particular mix shall comply with whichever of the

following standards is relevant :-

cement

12

BS

Ordinary

Portland

Sulphate-resisting Portland cement BS 4027

Portland Pulverised-Fuel Ash cement MS 1227

Portland Blastfurnace Cement MS 1389

For water retaining structures, the cement used shall be a blended cement

comprising ordinary portland cement from an approved source and conforming to

BS12 and containing 25%, by mass, of pulverised fly ash (PFA) to the requirement of

MS 1227, or containing 50%, by mass, of ground granulated blast furnaced slag

(GGBS) to the requirement of MS 1389. The cement used shall be an approved

brand of Malaysian manufacture unless otherwise approved.

In addition to the requirements for soundness of cement given in the relevant British

Standard for the type of cement being used, the cement shall also be tested for

soundness in accordance with ASTM C151-77 `Standard Test Method for Autoclave

Expansion of Portland Cement'. The expansion of the cement bar resulting from this

test shall not exceed 0.8 percent.

The Contractor shall provide from each consignment of cement delivered to the site

such samples as the S.O. may require for testing. Any cement which is, in the

opinion of the S.O., lumpy and partially set shall be rejected and the contractor

shall promptly remove such cement from the site. Cement which has been stored

on the site for more than forth days and cement which in the opinion of the S.O. is

of doubtful quality shall not be used in the works unless it is retested and the test

results show that it complies in all respects with the relevant standard.

1.9 Storage of Cement

Immediately upon arrival at the site, cement shall be stored in silos designed for the

purpose or in dry weather-tight and properly ventilated structures with floors raised

500 mm above ground level with adequate provision to prevent absorption of

moisture. All storage facilities shall be subject to approval by the S.O. and shall be

such as to permit each access for inspection and identification. Each consignment of D:\TECHNICAL DEPARTMENT\SPECIFICATION\SPEC FINAL PDF\PDF New Folder Final\L-Concretework 1-new1.doc L.3

SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

First Edition : May 2007

cement shall be kept separately and the Contractor shall use the consignments in the

order in which they are received.

Cement of different types and from different sources shall be kept in clearly marked

separate storage facilities. Cement delivered to the site in drums or bags provided

by the supplier or manufacturer shall be stored in the unopened drums or bags until

used in the works.

Any cement in drums or bags which have been opened on the site shall be used

immediately or shall be disposed of.

1.10 Aggregates

Aggregates for concrete shall be obtained from an approved source and shall

conform with the requirements of BS 882.

Sampling and testing of aggregates shall be carried out as required by S.O in

accordance with the requirements of the appropriate clauses of BS 812. Water

absorption of aggregates when tested in accordance with the standard procedure

prescribed in Part 2 of BS 812, shall not exceed 3%.

The aggregates to be supplied shall not give rise to any alkali reaction with the

cement, whether silica or carbonate. Potential reactivity or otherwise of aggregates

shall be determined in accordance with ASTM C 289.

In addition, the soluble chlorides and sulphates content of the aggregates shall be

such that the concrete mix as a whole complies with the specified limits of salt

content.

Tests for chlorides and sulphates and for potential alkali reaction shall be carried out

when required by the S.O.

Notwithstanding any provisions contained herein, limestone aggregates shall not be

used in underground and water retaining structures.

1.11 Storage of Aggregates

The Contractor shall provide means of storing the aggregates at each point where

concrete is made such that :

(i) Each nominal size of coarse aggregate and fine aggregate shall be kept

separated at all times;

(ii) Contamination of the aggregates by the ground or other foreign matter shall be effectively prevented at all times;

(iii) Each heap of aggregate shall be capable of draining freely.

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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

First Edition : May 2007

The Contractor shall ensure that graded coarse aggregates are tipped, stored and

removed from store in a manner that does not cause segregation.

Wet fine aggregate shall not be used until, in the opinion of the S.O., it has drained

to a constant and uniform moisture content of the fine aggregate continuously and

adjusts the amounts of fine aggregate and added water in each batch of concrete

mixed to allow for the water contained in the fine aggregate. If necessary to meet

the requirements of this clause, the Contractor shall protect the heaps of fine

aggregate against inclement weather.

1.12 Water

Water for washing aggregates and for mixing concrete and curing shall be clean and

free from harmful matter and shall satisfy the recommendations in the Appendix to

BS 3148. When required by the S.O. the Contractor shall take samples of the water

being used for which it is proposed to use for mixing concrete and test them for

quality, including determining the concentration of sulphates and chlorides, which

shall be such that the concrete mix as a whole complies with the specified limit for

salt content.

1.13 Admixtures

Admixtures shall mean material added to the concrete materials during mixing for

the purpose of altering the properties of the concrete mix.

Admixture containing calcium chloride shall not be used.

Admixtures shall not be used unless the S.O. has given his prior approval in writing

for each instance. Both the amount added and the method of use shall be to the

approval of the S.O. who shall also be provided with the following information :-

(i) The typical amount added and the detrimental effects if any, due to an

increase or decrease in this amount;

(ii) The chemical name(s) of the main active ingredient(s) in the admixture;

(iii) Whether or not the admixture leads to the entrainment of air when used at the amount the manufacturer recommends.

Any approved admixture shall conform to whichever of the following standards is

appropriate :-

- Air entraining admixtures BS 5075 Part 2

- Water reducing admixtures BS 5075 Part 1

- Retarding admixtures BS 5075 Part 1

- Fly ash and raw or calcined natural

pozzolans for use as a mineral admixture ASTM C 618

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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

First Edition : May 2007

1.14 Test

Equipment

The contractor shall furnish all equipment and materials necessary for collecting

samples and carrying out field laboratory tests on materials for concrete and on fresh

and hardened concrete. Laboratory equipment shall be housed in a suitable

laboratory building on the site, which shall also incorporate space for storage of

field test equipment, and for curing of concrete test cubes in an orderly manner so

that they are readily accessible for testing on the due date. The contractor shall also

furnish all weights, containers and other equipment necessary for testing the weight-

batching equipment for concrete materials and the dispensers for admixtures.

1.15 Grades of Concrete

Grades of concrete for use in the work shall be as shown in the table below:-

Concrete grade Maximum

aggregate

size (mm)

Characteristic

strength at 28 days

(N/sq.mm)

Minimum

cement

content (kg/cu.m)

Maximum

Cement

content

(kg/cu.m)

Maximum

free

water/cement

ratio

C40 C35A** C35A** C30 C25 C20 C15 20

20

40

20

20

20

20

40

35

35

30

25

20

15

325

325

300

275

250

225

205

550

400*

550

550

550

550

550

0.55

0.55**

0.60

0.65

0.70

-

-

* Maximum cement content 400 kg/m3 where OPC or cement containing GGBS is used. Maximum cement content 450 kg/m3 where cement

containing PFA is used.

** Maximum free water cement ratio is 0.55 where OPC or cement containing GGBS is used. Maximum free water cement ratio is 0.50 where cement

containing PFA is used.

*** Blended cement comprising Portland cement and PFA or PFA as specified

Concrete grade is that number which represents its 28 day characteristic strength

expressed in N/sq.mm.

Characteristic strength is that value of cube crushing strength below which none of

all test results fail. This condition shall be deemed to be satisfied when test results

comply with the specified test requirements.

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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

First Edition : May 2007

Maximum free water/cement ratios shall be based on aggregates being in a surface-

dry condition.

1.16 Free Water/Cement Ratio

In designing and establishing approved mixes of concrete for any part of the works

the contractor shall keep strictly within the limitations on free water/cement ratios

which may be shown on the drawings or expressly stated elsewhere as applying to

concrete for particular parts of the works.

1.17 Limits of Salt Content

No concrete shall contain more than the following total quantities of substances

expressed as percentages by weight of cement :-

(a) For mixes containing ordinary Portland cement to BS 12 :

Total water soluble chlorides 0.4% (as chloride ions)

b) For mixes containing cements complying with BS 4027 :

Total chlorides 0.2% (as chloride ions)

c) For mixes used for pre-stressed concrete (all cement types) :

Total chlorides 0.1% (as chloride ions)

d) For all mixes :

Total acid soluble sulphates 4.0% (as SO3 ions)

Tests shall be carried out in accordance with the following standards :-

Chlorides in aggregates ASTM D 1411

Sulphates in aggregates BS 1377 Test 9

Chloride ion in mixing water ASTM D 512

Sulphates in mixing water ASTM D 516

Workability

1.18

The workability of each grade of concrete shall be such that satisfactory compaction

can be obtained when the concrete is placed and vibrated and that there is no

tendency to segregate when it is handled, transported and compacted by the

methods which the contractor proposes to use in the works.

For reinforced concrete, the compacting factor, determined by the method

described in BS 1881, shall not be less than 0.85 nor greater than 0.92. For

unreinforced concrete the compacting factor shall be not greater than 0.85. Where D:\TECHNICAL DEPARTMENT\SPECIFICATION\SPEC FINAL PDF\PDF New Folder Final\L-Concretework 1-new1.doc L.7

SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

First Edition : May 2007

pumping of concrete is permitted, the compacting factor may be increased to 0.95,

provided that the conditions are not varied. In any case no pumped concrete shall

be used for all water retaining structures.

1.19 Design of Concrete Mixes

Each mix design shall be such that :

(i) The aggregate shall comprise both fine aggregate and coarse aggregate. The

maximum size of coarse aggregate shall be 20 mm or 40 mm as approved by

the S.O.

(ii) The cement content shall not be below the minimum specified for the grade of concrete.

(iii) The maximum free water/cement ratio shall be the maximum water/cement ratio when the aggregate is saturated but surface dry.

(iv) The mixes shall be designed to produce a targeted mean concrete cube strength at 28 days after manufacture and shall be greater than the

characteristic strength at 28 days by a margin of at least 10 N/sq.mm for Grade

15 and 15 N/sq.mm for Grade 20, 25, 30, 35A and 40.

(v) Where sufficient data can be produced by the contractor to show that the standard of acceptance for characteristic strength can be maintained using a

lower margin, the mix may be redesigned to have such reduced margin.

Sufficient data shall consist of cube test results from at least 40 separate

batches of concrete produced over a same plant under similar supervision.

The reduced margin shall be 1.64 times the standard deviation of the test

results considered, but not less than 5 N/sq.mm for Grade 15 and 7.5

M/sq.mm for Grades 20, 25, 30, 35A and 40.

For any concrete containing admixtures, the strengths shall not be less than those

specified but the mixes for the grade of concrete shall be separately designed to take

account of the effects of the admixtures, and shall have separate trial mixes made

and tested.

Mixes

1.20 Trial

As soon as the S.O. has approved each of the concrete mix designs, two batches

from a trial mix for each grade shall be produced in laboratory using cement and

surface dry aggregates known to be typical of the proposed source of supply. The

proposed mix proportions of each grade shall be approved only if both batches have

the correct cement content and free water cement ratio at or below the maximum

value for the proposed degree of workability.

When mix proportions have been approved by the S.O., three further batches of

concrete for each grade shall be made at site under full scale production conditions

using the same mixing time and handles by means of the same plant which the

Contractor proposes to use in the works.

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First Edition : May 2007

The proportions of cement, aggregates and water, shall be carefully determined by

weight in accordance with the contractor's approved mix design, and sieve analyses

shall be made, by the method described in BS 812, of fine aggregate and each

nominal size of coarse aggregate used.

The compacting factor of each batch of each trial mix shall be determined

immediately after mixing by the method described in BS 1881 and shall not be

outside the limits specified in clause 2.3.18.

Three 150 mm compression test cubes from each of the three batches shall be made

by the Contractor in the presence of the S.O. from each trial mix. The cubes shall be

made, cured, stored and tested at 28 days after manufacture in accordance with the

method described in BS 1881. If the average value of the compressive strength of

the nine cubes taken from any trial mix is less than the target mean strength used in

the mix design or if any inpidual cube test result falls below 85% of the target

mean strength, the Contractor shall redesign that mix and make a further trial mix

and set of test cubes.

A full scale test of the workability of each trial mix of each grade of concrete shall

be made by the contractor in the presence of the S.O. The trial mix of each grade of

concrete shall be batched, mixed and then transported a representative distance in

the manner that the contractor proposes to batch, mix and transport the concrete to

be placed in the works. After discarding the first batch so made, the concrete from

later batches shall be placed and compacted in trial moulds both for reinforced and

mass concrete with dimensions typical of the works in accordance with the

procedures described in later clauses, the sided of the moulds being capable of

being stripped without undue disturbance of the concrete placed therein. The sides

of the moulds shall be stripped after the concrete has set and the workability judged

by the surface appearance and compaction obtained. If the workability test shows

that the workability required is not attained for any trial mix for any grade of

concrete, the trial mix shall be re-designed by the Contractor and a further full scale

workability test undertaken for that trial mix.

The re-design of the concrete mixes and the making and testing of trial mixes of

concrete shall be repeated for each grade of concrete until trial mixes of concrete

have been established which meet the specified requirements and have the required

workability as demonstrated in the full scale workability test described above.

If at any time during the construction of the works the S.O. approves a change in the

source of cement or aggregate or if the grading of the aggregate alters to such an

extent that the fraction of aggregate retained on any sieve cannot be maintained

within two percent of the total quantity of fine and coarse aggregate when adjusted

as specified for sampling and testing of aggregates, then further trial mixes of

concrete shall be made, tested and approved for use.

Batching

1.21 Material

All cement used in the manufacture of concrete shall be measured by weight either

with an approved weighing machine or by making the size of each batch of

concrete such as to require an integral number of complete bags or drums of

cement.

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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

First Edition : May 2007

For concrete of Grades 20, 25, 30, 35A and 40, the fine aggregate and the several

nominal sizes of coarse aggregates shall be measured singly or cumulatively by

weight using weight-batching machines.

For concrete of Grade 15, the fine and coarse aggregate shall be measured

separately either by weight using weight-batching machines or by volume in gauge

boxes.

Weight-batching machines shall provide facilities for the accurate control and

measurement of the aggregates either singly or cumulatively and shall be capable of

immediate adjustment by semi-skilled operators in order to permit variations to be

made to the mix. All weigh dials shall be easily visible from the place at which

filling and emptying of the hoppers is controlled.

Every concrete mixing machine shall be fitted with a device to measure added water

by weight and shall be so constructed that the water inlet and outlet valves are

interlocked so that either one of them cannot be opened unless the other is fully

closed. The weighing device shall be provided with an overflow with a cross-

sectional area at least four times that of the inlet pipe and with its discharge point

clear of the mixing plant. The entire water system shall be maintained free of leaks

at all times and the measuring device shall be fitted with a drain pipe which allows

the full quantity of water being measured to be drained off for checking the

measurement. The outlet arrangement of the measuring device shall be such that

between five and ten percent of the water enters the mixer before the other

materials and further five to ten percent of the water enters the mixer after the other

materials. The remainder of the water shall be added at a uniform rate with the

other materials. The water measuring device shall be readily adjustable so that the

quantity of water added to the mixer can, if necessary, be varied for each batch.

Where volume batching is permitted by the Specification, gauge boxes shall be

soundly constructed of timber or steel to contain exactly the volume of the various

aggregates required for one batch of each mix. They shall have closed bottoms and

shall be clearly marked with the mix and aggregate for which they are intended.

When calculating the size of the gauge box for fine aggregate, an allowance shall be

made for the bulking of the fine aggregate due to the average amount of moisture

contained in the stockpiles on the site. Before the contractor puts any gauge box

into use on the site he shall obtain the approval of the S.O. of the size and

construction of such gauge box.

Any admixtures which may be used shall be measured separately in calibrated

dispensers.

All mixing and batching plants shall be maintained free of set concrete or cement

and shall be clean before commencing mixing. The accuracy of calibration of any

weighing plant, water measuring plant and admixture dispenser, shall be checked

before carrying out trial mixes, before mixing concrete for inclusion in the work,

after each service or adjustment to the mixing plant, and in any case at least once

per month.

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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

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Concrete

1.22 Mixing

Concrete shall be mixed in batches in plant capable of combining the aggregates,

cement and water (including admixtures, if any) into a mixture uniform in colour

and consistency, and of discharging the mixture without segregation.

On commencing work with a clean mixer, the first batch shall contain only half the

normal quantity of coarse aggregate to compensate for the adhesion of the other

materials to the drum.

The moisture contents of the aggregates shall be determined before the

commencement of each day's concreting and at such intervals during each day as

may be necessary. The Contractor shall make due allowance for the water

contained in the aggregates when determining the quantity of water to be added to

each mix, and shall adjust the amount of water added to each mix to maintain

constant the approved free water/cement ratio of the mixed concrete.

Concrete

1.23 Ready-Mixed

Ready-mixed concrete shall not be used in any part of the works without the S.O.'s

written approval, which may be withdrawn at any time.

The Contractor shall satisfy the S.O. that ready-mixed concrete complies with the

Specification in all respects, add that the manufacturing and delivery resources of

the proposed supplier are adequate to ensure proper and timely completion of each

concreting operation.

The specified requirements as to the sampling, trial-mixing, testing and quality of

concrete of various grades shall apply equally to ready-mixed concrete which shall

furthermore be made and delivered in accordance with BS 5328 : 1981.

Any additional facility, which the S.O. may require for the supervision and

inspection of the batching, mixing and transporting of ready-mixed concrete shall be

allowed to be used after 45 minutes of initial mixing.

1.24 High Alumina Cement

The composition of high alumina cement shall comply with B.S. 915 Part Two. It

shall consist of a minimum of 32% of alumina and the minimum compressive

strengths of mortar cubes at one and three days shall be 42 N/sq.mm and 48

N/sq.mm respectively.

High alumina cement shall be refrained from being used in structural concrete

including foundations as a substantial reductions in strengths is observed under the

vulnerable tropical conditions.

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1.25 Preparing for Concreting

Before placing concrete the contractor shall remove from the surface of the

foundations or previously placed concrete, all oil, loose fragments of rock, earth,

mud, timber and other debris, and standing water, to the satisfaction of the S.O.

Where specified and elsewhere as ordered by the S.O., the excavated surfaces shall

be prepared as specified under concrete protection.

Concrete

1.26 Transporting

Concrete shall be conveyed from the mixer to its place in the works as rapidly as

possible by methods which will prevent segregation or drying out and ensure that

the concrete is of the required workability at the time of placing. If segregation has

nevertheless occurred in any instance, the materials shall be remixed or rejected.

Concrete

1.27 Placing

Concrete shall be placed and compacted before the initial set has occurred and, in

any event, not later than 45 minutes from the time of mixing.

When pneumatic placers are used, if the end of the placer pipe is not equipped with

an energy absorbing device, it shall be kept as close to the work as practicable.

Mortar or water used at the beginning or end of a run shall be discharged outside

the formwork..

When pumps are used, the end of the supply pipe shall be kept immersed in the

concrete during placing to assist compaction. Mortar and water used at the

beginning or end or a run shall be discharged outside the formwork.

1.28 Concreting in Hot Weather

In hot weather, the contractor shall take steps to ensure that the temperature of the

concrete as placed shall not exceed 32 deg. C and that the maximum internal

temperature attained during setting does not exceed 70 deg. C.

To achieve this, the contractor shall provide sun shades over stockpiles of aggregate,

cement silos, mixing water tanks and pipelines and in addition shall carry out the

first and as necessary other of the following procedures which shall be submitted to

the S.O. for approval :

(i) Cool the mixing water and replace part of the water by chipped ice. The ice

shall be completely melted by the time mixing is completed.

(ii) Spray clean cool water over the aggregate stockpiles. The Contractor shall carry out regular tests on the aggregates to ensure that concentrations of

sulphates or chlorides do not rise to unacceptable levels, and to ensure that

moisture content determinations allow for such spraying.

(iii) Shade or wet outside of the formwork.

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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

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(iv) Apply a fine moisture (fog) spray of clean cool water to shaded areas immediately prior to placing concrete.

(v) Pour concrete at night.

1.29 Compaction

All concrete placed in-situ shall be compacted with power driven internal type

vibrators supplemented by hand spading and tamping except as otherwise approved

by the S.O. The vibrators shall at all times be adequate in number, amplitude and

power to compact the concrete properly and quickly throughout the whole of the

volume being compacted. Spare vibrators shall be readily on hand in case of

breakdown.

Vibrators shall be inserted into the uncompacted concrete vertically and at regular

intervals. Where the uncompacted concrete is in a layer above freshly compacted

concrete the vibrator shall be allowed to penetrate vertically for about 100 mm into

the previous layer. In no circumstances shall vibrators be allowed to come into

contact with the reinforcement or formwork nor shall they be withdrawn quickly

from the mass of concrete but shall be drawn back slowly so as not to leave voids.

Internal type vibrators shall not be placed in the concrete in a random or haphazard

manner nor shall concrete be moved from part of the work to another by means of

the vibrators.

The duration of vibration shall be limited to that required to produce satisfactory

compaction without causing segregation. Vibration shall on no account be

continued after water or excess grout has appeared on the surface.

1.30 Attendance of Steel Fixer and Carpenter

During the concreting of all reinforced concrete, including prestressed concrete, a

competent steel fixer and carpenter shall be in attendance on each concreting gang,

to ensure that the reinforcement, formwork and embedded fittings are kept in

position as work proceeds.

1.31 Curing of Concrete

Concrete shall be cured by protecting the surface from the effects of sunshine,

drying winds, frost, rain, running water or mechanical damage for a continuous

period of four days when the cement used in the concrete is sulphate-resisting

Portland cement, Portland Pulverised-Fuel Ash cement or Portland Blastfurnace

Cement. The protection shall be applied as soon as practicable after completion of

placing by one or more of the following methods as approved by the S.O.:

(a) By water sprays in continuous operation;

(b) By covering with hessian or similar absorbent material, or sand, kept

constantly wet;

(c) After thorough wetting, by covering with a layer of waterproof fabric kept in

contact with the concrete surface.

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(d) By the application of an approved non-staining liquid curing membrane which

is either self-removing or easily removed following curing period and which

has a 75% moisture retention standard. The liquid shall be applied to formed

surfaces immediately after stripping the formwork.

Liquid curing membrane (d) shall not be used on Class U1 surfaces where laitance is

to be removed and aggregate exposed to provide a satisfactory bond for placing

further concrete or mortar screeds or on surfaces where the S.O. is of the opinion

that the appearance of the concrete surface will be affected.

Joints

1.32 Construction

A construction joint is defined as a joint in the concrete introduced for convenience

in construction at which special measures are taken to achieve subsequent

continuity without provision for further relative movement.

Concrete placed to form the face of a construction joint shall have all laitance

removed and the large aggregate exposed prior to the placing of fresh concrete.

The laitance shall wherever practicable be removed when the concrete has set but

not hardened by spraying the concrete surface with water under pressure or

brushing with a wire brush sufficient to remove the outer mortar skin and expose

the large aggregate without being disturbed. Where the laitance cannot be removed

due to hardening of the concrete, the whole of the concrete surface forming the

joint shall be treated by high pressure water jet, sand blasting, use of a needle gun

or a scaling hammer to remove the surface laitance.

Before concreting is resumed, all loose matter on the existing concrete surface shall

be removed and the surface slightly wetted.

1.33 Dimensions and Surfaces of Finished Concrete

Workmanship in formwork and concreting shall be such that concrete shall require

no making good, surfaces being perfectly compacted, smooth and with no

irregularities. Concrete surfaces for the various classes of unformed and formed

finishes shall in any event not exceed the maximum permitted tolerance which shall

be as shown in the table below except where expressly stated otherwise in the

Specification or Drawings.

In the table "line and level" and "dimension" shall mean the lines, levels and cross-

sectional dimensions shown on the Drawings.

Surface irregularities shall be classified as "abrupt" or "gradual". Abrupt

irregularities include, but shall not be limited to offsets and fins caused by displaced

or misplaced formwork, loose knots and other defects in formwork materials, and

shall be tested by direct measurement. Gradual irregularities shall be tested by

means of a straight, template for plane surfaces or its suitable equivalent for curved

surfaces, the template being 3.0 m long for unformed surfaces and 1.5 m long for

formed surfaces.

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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS First Edition : May 2007

Maximum tolerance (mm) in :

Class of finish Line and

level

Abrupt

irregularity

Gradual

irregularity

Dimension

U1 U2 U3 F1 F2 F3 +/-12

+/ -6

+/ -6

+/-12

+/ -6

+/ -3

6

3

3

6

6

3

+/ -6

+/ -3

+/ -3

+/ -6

+/ -6

+/ -3

-

-

-

+12, -6

+12, -6

+6/ -6

1.34 Unformed

Surfaces

Finishes to unformed surfaces of concrete shall be classified as U1, U2, U3, spaded'

or `bonded concrete' or such other special finish as may be particularly specified.

Where the class of finish is not specified, the concrete shall be finished to Class U1.

Class U1 finish is the first stage for Class U2 and U3 finishes and for a bonded

concrete surface. Class U2 finish shall be a leveled and screeded, uniform plain or

ridged finish, which (unless it is being converted to Class U2, U3 or bonded

concrete) shall not be disturbed in any way after the initial set and during the period

of curing, surplus concrete being struck off immediately after compaction.

Where a bonded concrete surface is specified, the laitance shall be removed from

the Class U1 finish surface and the aggregate exposed while the concrete is still

green.

A spaded finish shall be a surface free from voids and brought to a reasonably

uniform appearance by the use of shovels as it is placed in the works.

Class U2 finish shall be produced by manual or mechanical floating of the concrete

surface after the initial set has taken place and the surface has hardened sufficiently.

The concrete shall be worked no more than is necessary to produce a uniform

`sandpaper' finish free from screedmarks.

Class U3 finish shall be a hard smooth steel-trowelled finish. Trowelling shall not

commence until the moisture film has disappeared and the concrete has hardened

sufficiently to prevent excess laitance from being worked into the surface. The

surface shall be trowelled under firm pressure and left free from trowel marks.

The addition of dry cement, mortar or water will not be permitted during any of the

above operations.

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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

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Exposed aggregate finish shall be achieved by exposure of the coarse aggregate

using a method approved by S.O. The average depth of exposure shall be 6 mm for

concrete with a maximum aggregate size of 20 mm and between 6 mm and 12 mm

for concrete with a maximum aggregate size of 40 mm.

The Contractor shall prepare sample panels 1000 mm x 500 mm of concrete with

an exposed aggregate finish for inspection and approval by the S.O. at the site.

1.35 Building in Plant and Grouting- in

Wherever possible, pipes and other items of plant passing through concrete

structures shall be installed and connected to the remainder of the pipework system

to ensure proper fit, and shall be built into the structure as work proceeds.

Where this procedure is impracticable due to programme or other requirements,

holes shall be formed for the items of plant to allow them to be built in later after

complete installation of the plant.

In no case shall inpidual pipes of a complicated pipework system including

flanged joints be built into concrete structures before accurate fit of the whole

system can be checked after the complete installation.

Where holes are formed these shall be of size and shape sufficient to permit proper

placing and compaction of concrete or grout. The surfaces of the holes shall be

treated to produce a `bonded' surface before installation of plant.

Before grouting-in commences the plant shall be adequately supported in position

to prevent movement or damage during grouting-in.

Concrete used for building-in shall be of the same grade as concrete of the member

into which the plant is being built, except that the mix shall also incorporate an

approved expanding additive used in accordance with the manufacturer's

instructions. Concrete used for water retaining structures shall be non shrink in

nature to ensure water tightness. Concrete, mortar and grout shall be carefully

placed and compacted around the plant to avoid damaging or moving the plant.

1.36 Structural Pre-Cast Concrete

Structural units of pre-cast concrete shall be manufactured in the grade of concrete

and to the sizes and details shown on the Drawings. The concrete shall comply in

every aspect with the provisions of the Contract whether such units are

manufactured on the site or obtained from other manufacturers.

All cement, aggregate and other materials for pre-cast concrete units with faces

which are exposed either internally or externally shall be from the same sources

throughout. Exposed surfaces of the units shall be uniform in colour and in texture.

Formwork and unformed surfaces for pre-cast concrete units shall comply with the

requirements for F3 formed surfaces and U3 unformed surfaces except that the

dimensional variations shall not exceed the values listed below, unless otherwise

detailed on the Drawings.

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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

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+/-6

mm

Length

Cross-section +/6 mm each direction

Straightness 6 mm (deviation from intended line)

Flatness 3 mm (deviation from a 1.5 m straight edge placed in any position on a

nominally plane surface)

Squareness when considering the squareness of a corner, the longer of the two

adjacent sides being checked shall be taken as the baseline, and the shorter side

shall not vary in its distance from the normal so that the differences between the

greatest and the shortest dimension exceeds 6 mm. When the nominal angle is

other than 90 degrees, the included angle between the check line shall be varied

accordingly.

Twist any corner on any nominally plane surface shall not be more than 6 mm from

the plane containing the other three corners.

The positions of inpidual connecting bolts, bolt holes, projecting steel and other

devices in any associated group (eg. the joint of two pre-cast units) shall be within 3

mm of their true position in the group in which they are cast. The location of any

such group shall be within 6 mm of its true position in the unit in which it is cast,

provided that such deviation does not adversely affect the proper assembly of the

whole structure.

The Contractor shall submit to the S.O. for approval, full details of his proposed

method of carrying out all operations connected with the manufacture and assembly

of precast concrete structural members, including :

A description of the types of casting bed, mould and formwork for the various

types of members;

The procedure for concrete casting and the method of curing the concrete;

The procedure for transporting, handling, hoisting and placing of each type of pre-cast structural member;

Full details of temporary supports necessary to ensure adequate stability during erection, due account be taken of construction loads, including wind.

1.37 Installation of Pre-Cast Concrete Units

At all stages and until completion of the work, pre-cast members shall be adequately

protected to preserve all permanently exposed surfaces, arises and architectural

features. The protection shall not mark or otherwise disfigure the concrete.

All units shall be laid, bedded, jointed and fixed in accordance with the lines, levels

and other details shown on the Drawings.

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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

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Dry-pack mortar jointing for packing shall consist of one part of volume ordinary

Portland cement and two and half parts by volume of fine aggregate passing a 1 mm

sieve. The mortar shall be mixed with only sufficient water to make the materials

stick together when being moulded in the hands. The mortar is thoroughly

compacted.

Any pre-cast concrete structural member which is found to be cracked, damaged or

otherwise inferior in quality either before or after erection shall be rejected and

replaced by the Contractor.

1.38 Pr-Sstressed

Concrete

The Contractor shall submit to the S.O. for approval his proposed method of carrying

out all operations connected with pre-stressed concrete work and his proposals for

handling, hoisting and placing a position any pre-cast pre-stressed concrete units.

Pre-stressed concrete work whether pre-cast or cast in-situ shall be as detailed on the

Drawings and the Contractor shall provide full details of his proposed method of

carrying out all operations connected with pre-stressing including :-

(a) Design of concrete mix

(b) Description of concrete casting and curing operations

(c) Procedure for pre-stressing and method of checking and recording the pre-

stress, wire extension and anchorage slip.

(d) Procedure for handling, hoisting and placing of any pre-cast units.

(e) Grouting of ducts

All tendons, duct forming devices, anchorages and other components shall be kept

free of mud, oil (except water soluble oil applied for protection), paint, retarders,

loose rust, or other foreign matter. They shall be placed with a tolerance of +/-3

mm in concrete dimensions of 300 mm of less or ± 6 mm in concrete dimensions

over 300 mm.

Concrete

1.39 No-Fines

No-fines concrete shall be made using a coarse natural aggregate conforming with

BS 882 and cement to BS 4027. No fine aggregate shall be used. The grading of

the coarse aggregate shall be;

Not less than 95% by weight passing a 19 mm BS sieve;

Not more than 5% by weight passing a 10 mm BS sieve.

The proportion of aggregate, cement and water shall be determined by trial mixes

by the Contractor starting with a cement : aggregate particles ratio of one to eight by

volume.

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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

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The trial mix shall be considered suitable when all the aggregate particles are coated

with a film of cement grout. The water content shall be just adequate. The concrete

when placed shall contain no layers of laitance.

No-fines concrete shall not be mixed by hand.

Vibration shall not be used to compact the concrete. Three test cubes of no-fines

concrete shall be made of each trial mix. The minimum crushing strength of the

chosen mix shall be 3 N/sq,mm at 28 days.

1.40 Pre-Cast Concrete Products

(a) Pre-cast concrete products shall where appropriate be constructed in

accordance with British Standards as follows, being hydraulically pressed

where possible :

Type of Unit Standard

Concrete blocks BS 6073 : Pt 1 : 1981

Concrete kerbs, etc. BS 7261 : Part 1 : 1990

Concrete flags BS 7263 : Pt 1 : 1990

Concrete

5642

sills BS

BS

5977

lintels

Concrete

The concrete shall comply in every aspect with the provisions of the

Specification whether such products are manufactured on the site or

obtained from other manufacturers.

(b) Interlocking concrete paving shall include supply and laying of pavers,

preparation of surface, supply of sand and casting of edge restraint beams.

The pavers shall comply with the requirement of MA 20, Specification for

concrete segmental Paving Units, published by the Concrete Masonry

Association of Australia.

1.41 Sampling and Testing of Aggregate

The Contractor shall sample and carry out a mechanical analysis of the fine

aggregate and each nominal size of coarse aggregate in use employing the methods

described in BS 1881 at least once in each week when concreting is in progress and

at such more frequent intervals as the S.O. may require.

The grading of all aggregates shall be within specified limits and should the fraction

of aggregate retained on any sieve differ from the corresponding fraction of

aggregate in the approved mix by more than 2% of the total quantity of fine and

coarse aggregate, S.O may instruct the contractor to alter the relative proportions of

the aggregates in the mix to allow for such difference.

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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

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1.42 Sampling and Testing of Concrete

The Contractor shall provide the equipment necessary to determine the compacting

factor of freshly mixed concrete at each place where concrete is being made and

shall determine the compacting factor of the freshly mixed concrete by the method

described in BS 1881 on each day or as the S.O. may direct.

For each grade concrete, works test cubes shall be made whenever required by the

S.O. but not less frequently than as follows unless otherwise particularly specified :-

for concrete of one set of cubes per 25 cu.m

Grades 25, 30, 35A, 40 or part thereof concreted per day;

for concrete of one set of cubes per 50 cu.m

Grades 15 or 20 or part thereof concreted per day

Each set of cubes (six cubes per set) shall be made from a single sample taken from

a randomly selected batch of concrete. Three cubes shall be tested 7 days after

manufacture and three cubes 28 days after manufacture.

1.43 Compliance with Specified Requirements

The concrete shall be deemed satisfactory provided that :

(i) The average 28 days strength determined from any group of four consecutive

sets of three test cubes exceeds the specified characteristic strength by not less

than 7.5 N/sq.mm for Grade 15 concrete and 10 N/sq.mm for Grades 20, 25,

30, 35A and 40.

(ii) The average of each set of three test cube results is greater than 100% of the specified characteristic strength.

If only one set of three cube results fails to meet the second requirement, those

results may be considered to represent only the particular batch of concrete from

which the cubes were taken, provided that the average strength of the group satisfies

the first requirement.

If more than one set of three cube results in a group fails to meet the second

requirement or if the average strength of any group of four consecutive sets of three

test cubes fails to meet the first requirement then all the concrete in all the batches

represented by all such cubes shall be deemed not to comply with the strength

requirements.

1.44 Non-Compliance

When the average strength of four sets of three consecutive test cubes fails to meet

the first requirement, no further concrete from that mix shall be placed in the work

and the contractor shall establish the cause of the failure and apply such remedies as

are necessary. The Contractor shall demonstrate by trial mixes and test cube results

that the revised mix is in accordance with the specified requirements.

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SYABAS’ STANDARD SPECIFICATION FOR PIPE LAYING WOKS

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The Contractor shall within 24 hours of the date of test make proposals for

agreement with the S.O. about action to be taken in respect of any concrete

represented by test cubes which fail to meet either of the requirements. These

proposals may include, but shall not be limited to, cutting and testing cores.

Concrete which is ultimately found not be comply with any of the requirements of

the Specification shall be rejected and shall be broken out and replaced or

otherwise dealt with as agreed with the S.O.

1.45 Cutting and Testing of Core Samples

As and where discussed by the S.O. cylindrical core specimens of 150 mm nominal

diameter shall be cut normal to the face of the hardened concrete for the purpose of

examination and testing. The procedure for drilling, examination, measurement and

testing for comprehensive strength shall be in accordance with BS 1881. Prior to

preparation for testing, the specimen shall be made available for examination by the

S.O. If the crushing strength of the specimen determined in accordance with

paragraph 114 of BS 1881 is less than the characteristic strength at 28 days for the

grade requirements in other respect, the concrete in that part of the works of which

it is a sample shall be considered not to comply with the specified requirements.

Procedures

1.46 Inspection

Before any concrete is placed, the Contractor shall carry out an inspection to ensure

that all preparations are complete, including the provision of the necessary

equipment and personnel, and shall ensure that sufficient materials are available to

complete the work proposed.

After completion of this inspection the work shall be offered for inspection by the

S.O., sufficient time being allowed for inspection and correction of any defects. no

concrete shall be placed until the S.O. has inspected and approved the surfaces

upon which the concrete is to be placed the formwork and the reinforcing steel.

Where required by the S.O. the Contractor shall institute a `pour card' system in

which a card is made out for each lift of concrete and is initialed by the Contractor

and S.O. indicating that the inspections have been carried out.

The `pour card' shall include spaces to identify the concrete being placed and to

signify completion of the inspections by the Contractor and S.O. of the following

items:

Preparation of surface on which concrete is to be placed;

Formwork;

Reinforcement;

Ready for concrete placing;

Inspection after removal of formwork (any remedial work shall be agreed and noted);

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