1.0 CONCRETE

1.1 Scope

This. section covers the supply of materials for concrete, design of concrete mrxes,qualrty- control of concrete, mixing, nansporting, placing and Curing ofconcrete, andtesting of concrete

The stand-ar{ of materials and workmanship shall not be inferior to therecommendations of the current:

o British Standard 8110 : Structural Use of Concrete

o British Standard Code of Practice BS 8007 1987: Design of Concrete Skucturesfor Retaining Aqueous liquids.

. Appropriate Malaysian Standards approved by the S.O.'*-r!

Unless otherwise specified, all reinforced concrete for retaining aqueous liquids shall1o-qll with BS 8007 and shall be of Grade C40 designed to iesist Class j SulphateConditions as defined in BS 5238: Part I Table 7.

1,2 Concrete Production at the Site

At the colnmencement of the Contract the Contractor shall submit for the approval ofthe S.O. a method statement detailing with regard to the requirementi of thisSpecification his proposal for the organiiation of concreting activit-ies at the site.

The method statement shall,include the following items:-

(a) Plantproposed;'.=J O) 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;(0 Striking times for formwork and procedure for temporary support of beams and

slabs.

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1.3 Test Certificates

Unless otherwise directed by the S.O., manufacturer's test sheets shall be suppliedwith each consignment of cement and admixture certifying compli*r. #tt ttt"relevant standard.

Th; Contractor shall also submit to the S.O. certificates of calibration for theweighing and dispensing equipment on the concrete batch mixing plant, certified testresults for all tests carried out on aggregate, water, fresh conciete and hardenedconcrete, all as specified.

Aggregate Samples

Prior to the commencement of the frial mixes of concrete the Contractor shall submitfor 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 eachsample.

. Certified test results demonstrating compliance with the relevant quality standardshall be submitted at the same time. Samples approved by the S.O. stratt remainpreserved at site for reference.

Records of Concreting

An accurate and up to date record showing dates, times, weather and temperatureconditions when various sections of the works are concreted sha-ll be kept by theContractor and shall be available for inspeclio1

-b_V ltre S.O. The Contractor ihali alsorecord the results of all tests of concrete-and shaliidentifr th;r; *il;r;tlt the parrsof the works of which the samples material is representative.

For each grade of concrete, the Contractor shall submit to the S.O.o not later thantwenty-four hours after concreting, a daily return of the number of barches mixed, thenumber of batches and total volume of concrete placed, the number of batches wastedor rejected and the weight of cement used.The return shall also include specific details of each location in the works whereconcrete is placed, together with the grade of concrete, total volume of concreteplaced and the number of batches used for each location.

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1.6 Concrete Mixes

A1th. col4lnertcement of the works the Contractor shall design a mix for each gradeof concrete which will be required for use in the works and shall submit fuIl detalls ofthe mix designs to the S.O. for his approval. Each, mix design shall be according to

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the lequirements ofBS 5328.

Construction Joints and Lifts

The Conhactor shall submit to the S.O. for his approval, as soon as is practicableafter the acceptance of his tender and not tess tfran- three weeks fefore thecommencement of concreting, drawings showing his proposals for placing concreteon which the_position of all construction joints and -lifts shall be stown. Noconcreting shall be started until the S.O. has approved the method of placing, then_os-tti,ong and form of the construction joints and the lifts. The construction jointsshall be located so as to impair the strength of the structure.

Rebates,_keys ol notches shall be formed and waterstops inserted as the S.O. mayrequire. The position of construction joints and the size bf formwork panels shall beso coordinated that where possible the line of any construction joint ioincides withthe line of a formwork joint and that in 4ny case all construction joint lines andformwork joint lines uppeu, as a regular ana uniform ,.ri"r.For all exposed horizontal joints and purposely inclined joints, a uniform joint shallbe formed with a batten of approved dimensions to give a straight and neat joint line.

Cement

The cement used for any pafticular mix shall comply with whichever of the followingstandards is relevant :-

Ordinary Portland cement BS 12Sulphate-Resisting Portland cement BS 4027Portland Pulverised-Fuel Ash cement MS lZ27Portland Blastfurnace Cement MS 1389

For.water retaining structureso the cement used shall be a blended cement comprisingordinary portland cement from an approved source and conforming to ss iz anocontaining 25Y2,by mass, of pulverised fly ash (PFA) to the requiremint of MS 1227,or containing 50Yo, by mass, of ground granulated blast fumaced slag (GGBS) to therequirement of MS 1389. The cement used shall be an approved Urand'of Malaysianmanufacfure unless otherwise approved.

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In addition to the requirements for soundness of cement given in the relevant BritishStandard for the type of cement being used, the cement shall also be tested forsoundness in accordance with ASTM Cl5l-77'standard Test Method for AutoclaveExpansion of Portland Cement'. The expansion of the cement bar resulting from thistest shall not exceed 0.8 percent.

ttte Co"ttactor shall provide from each consignment of cement delivered to the sitesuch samples as the S.O. may require for testing. Any cement which is, in the opinionof the S.O., lumpy and partially set shall be rejected and the contractor shall promptlyremove such cement from the site. Cement which has been stored on the site for morethan forth days and cement which in the opinion of the S.O. is of doubtful qualityshall not be used in the y:rfr unless it is ietested and the test results show that itcomplies in all respects with the relevant standard.

Storage of Cement

Immediately upon arrival al the site, cement shall be stored in silos designed for thepurpose or in dry weather-tight and properly ventilated structures with ioorc raised500 mm above ground level with adequate provision to prevent absorption ofmoisture. All storage facilities shall be subject io upproroul by the S.O. and shall besuch as to permit each access for inspection and identification. Each consignment ofcement shall be kept separately and the Contactor shall use the consignmJnts in theorder in which they are received.

Cement of different types and from different sources shall be kept in clearly markedseparate storage facilities. Cement delivered to the site in drums or bags provided bythe supplier or manufacturer shall be stored in the unopened drums or bags until usedin the works.

Any cement in drums or bags which have been opened on the site shall be usedimmediatety or shall be disposed of,

Aggregates

Aggregates for concrete shall be obtained from an approved soluce and shall conformwith the requirements of BS 882.

Sampling and testing of aggregates shall be carried out asaccordance with the requirements of the appropriate clausesabsorption of aggregates when tested in accordance with theprescribed in Part 2 of BS 812, shall not exceed 3ol0.

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required by S.O inof BS 812. Waterstandard procedure

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The aggregates to be supplied shall not give rise to any alkali reaction with thecement, whether silica or carbonate. Potential reactivity or otherwise of aggregatesshall be determined in accordance with ASTM C2Bg.

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In addition, the soluble chlorid"s .a1d sulphates cgntent of the aggrqgates shall be

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suctr that the concrete mix as a qhole gomplies with the qpgc!fied limits of,saltcontent.

Tests for chlorides-and sulphates and for potential alkali reaction shall be carried outwhen required by the S.O. :

Notwithstanding any provisions contained herein, limestone aggregates shall not beused in underground and water retaining structures.

Storage of Aggregates

The Contractor shall provide means of storing the aggregates at each point whereconcrete is made such that :

(i) Each nominal- size of coarse aggregate and fine aggregate shall be keptseparated at all times;

(iD Contamination of the aggregates by the ground or other foreign matter shallbe effectively prevented at all times;

(iii) Each heap of aggregate shall be capable of draining freely.The Contractor shall ensure that graded coarse aggregates are tipped, stored andremoved fi"om 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 toa constant and uniform moisture content of thJ fine aggregate continuously andadjusts the amounts of fine aggregate and added water ln *"tr batch of concretemixed to allow for the water contained in the fine aggregate. If necessary to meet therequirements of this clause, the

Contractor shall protect the heaps of fine aggregate against inclement weather.

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I . t2 'Water

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rWater for washing aggegates and for mixing concrete and curing shall be clean andfree from harmful matter and shall satisfy the recommendations in the Appendix toBS 3148. When required by the S.O. the Contractor shall take samples oi th" waterbeing used for which it is proposed to use for mixing concrete and test them forquality, including determining the concentration of sulphates and chlorides, whichshall be such that the concrete mix as a whole complies with the specified limit forsalt content

1.13 Admixtures

Admixtures shall mean material added to the concrete materials during mixing for thepurpose 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 writingtor each instance. Both the amount added and the method of use shall be to theapproval of the S.O. who shall aiso be provided with tfre fofio*i"girf"r."tir; ;

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(i) The typical- ?moqnt added and the detrimental effects if any, due to anincrease 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 isappropriate:-

- Air entraining admixtures BS S075partz

- Water reducing admixtures BS 5075 part I

- Retarding admixtures BS 5075 part 1

- Fly ash and raw or calcined natural pozzolans for use as a mineral admixture ASTMc 618

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1.15

Test Equipment

The contractor shall furnish all equipment and materials necessary for collectingsamples.andcarrying out field laboratory tests on materials for concrete and on freshand hardened concrete. Laboratory equipment shall'be housed in a suitable laboratorybuiltling on the site, vvhich shall alSo'incbryoiate spaCe for storage' of 'fibld testequipment, and for curing of concrete test cubes in an orderly manner so that they arereadily accessible for testing on the due date. The contractor shall also furnistr allweights, containers and other equipment necessary for testing the weight-batchingequipment for concrete materials and the dispensers for admixtures.

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Grades of Concrete

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

t Maximum cemeni content 400 kg/m3 where OPC or cement containing GGBSis used. Maximum cement content 450 kgim3 where cement containin!'pFA isused.

t{< Maximum free water cement ratio is 0.55 where OPC or cement containingGGBS is used. Maximum free water cement ratio is 0.50 where ,.*"nicontaining PFA is used.

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Concrete glade is that number which represenls its 28 day Characte i- ic streiethexpressedin N/sq.mm

Characteristic strength is that value of cube crushing strength below which none of alltest results fail. This condition shall be deemed to be satisfied when test resultscomply with the'specified teit igquirements.

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 4pproved mixes of concrete for any part of the worksthe contractor shall keep shictly within the limitations on free water/cement ratioswhich may be shown on the drawings or expressly stated elsewhere as applying toconcrete for particular parts of the works.

l.l7 Limits of Salt Content

No concrete shall contain more than the following total quantities of substancesexpressed as percentages by weight of cement :-

(a) For mixes containing ordinary Portland cement to BS 12 :Total water soluble chlorides 0.4% (aschloride 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) i:ffitffi::luble sulphat es 4.vyo(as so3 ions)Tests shall be carried out in accordance with the following standards :-

o Chlorides in aggregates ASTM D l4l Io Sulphates in aggregates BS 1377 Testgo Chloride ion in mixing water ASTM D Sl2r Sulphates in mixing water ASTM D 516

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The worl5ability of each gr-ade Of cAncrete shatl be such'thbt,ratirft ;compagtioncan be obtained when the concrete is placed and vibrated and that there is notendency to segregate when it is handled, transportea *d

"ornpurt.a tt td;rtil;;

For reinforced concrete,_the compacting factor, detennined by the method describedin BS 1881, shall not be less than 0.85 nor greater than 0.92. For unreinforcedconcrete the compacting factor shall be not greater than 0.85. Where pumping ofconcrete is permitted, the compacting factor may be increased to 0.95, provided thatthe conditions

i:*-:Ted. In any case no pumped concrete shall be used for allwater retaining strucfures.

1.19 Design of Concrete Mixes

Each mix design shall be such that :

The aggregate shall comprise both fine aggregate and coarse aggregate. TheT*;1* size of coarse aggegate shall be 20 mm or 40 mrn as approved bythe S.O.

The cement content shall not be below the minimum specified for the grade ofconcrete.

The ma;cimum free water/cement ratio shall be the maximum water/cementratio when the aggregate is saturated but surface dry.

The mixes shall be designed to produce a targeted mean concrete cubestrength at 28 days after manufacture and shail be greater than thecharacteristic strength at 28 days by a margin of at leasil0 N/sq.mm forGrade 15 and 15 N/sq.mm for Grade 20,25,30, 35A, 40and 45.

Where sufficient data can be produced by the contractor to show that thestandard of acceptance for characteristic shength can be maintained using alower margin, the mix may be redesigned to have such reduced margin.Sufficient data shall consist of cube test results from at least 40 ,.ouLt.batches of concrete produced over a same plant under similarcupr*irion.The reduced margin shall be 1.64 times the standard deviation oi the testrezults considered, but not less than 5 N/sq.mm for Grade 15 and 7.5IWsq.mm for Grades 20,25,30, 35A 40and45.

(D

which the contractorproposes to use infie ryorks

(ii)

(iii)

(iv)

(v)

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For any concrete containing admixtures, the strengths shall not be less than thosespecified but the mixes for the grade of concrete shall be separately designed to takeaccount of the effects of the admixtures, and shall have separate tial mixes maae and

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tested.

Trial Mixes

As soon as the S.O. has approved each of the concrete mix designs, two batches froma trial mix for each grade shall be produced in latoratory using cement and surfacedry aggregates known to be typical of the proposed source of supply. The proposedmix proportions of each grade shall be approved only if both batches have the correctcement content an$ frry Yll"t cement ratio at or below the maximum value for theproposed degree of workability.When mix proportions have been aBproved by the S.O., three further batches ofconcrete for each grade shall be made at site under firll scale production conditionsTitg the sarne mixing time and handles by means of the same plant which theContractor proposes to use in the works.

The proportions-of cemgnt, aggregates and water, shall be carefully determined byY.tqhl in accordance with the contractor's approved mix design, and sieve analysesshall be pade, by the method described in BS 812, of fine aggregate and eachnominal size of coarse aggregate used.

The compacting factor of 'each batch of each trial mix shall be determinedimmediately after mixing by the method desqibed in BS 1881 and shall not beoutside the limits specified in clause 2.3.18.

Jhg. 1j0 * compression test cubes from each of the three batches shall be madeby the Conkactor in the presence of the S.O. from each trial mix. The cubes shall bemade, cured, stored and tested at 28 days after manufacture in accordance with themethod described in BS 1881. If the average value of the compressive strength of thenine cubes t*:1 from any tria! mix is less than lhe target mean strength uid in th.mix design or if any individual cube test result faUs betow 85% of the target meanstrength, the Contractor shall redesign that mix and make a further trial mix ind set oftest cubes.

A full scale test of the workability of each trial mix of each grade of concrete shall bemade by the contractor in the presence of the S.O. The trial mix of each grade ofconcrete shall be batched, mixed and then transported a representative distanJe in themanner that the contractor proposes to batch, mix ana tr;rp;; th. .""*.*.;;;;placed in the works. After discarding tnr ntri uiirh;;;;;;'ril;r..t. iiol ru*,batches shall be.placed and

"o-puoLd in trial moulds both ior reinforced Jal massconcrete with dimensions typical of the works in accordance with the proceduresdescribed in later clauses, the sided of the moulds being capable of being stripped

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without undue disturbance of the concrete placed therein, The sides of the mouldsshall be stripped after the concrete has set and the workability judged by the surfaceappearance and compaction obtained. If the workability test shows that theworkability required is not attained for any trial mix for any grade of concrete, thetrial mix shall be re-designed by the Contractor aqd a further full scale workabilitytest undertaken for that trial mix.

The re-design of the concrete mixes and the making and testing of trial mixes ofconcrete shall be repeated for each grade of concrete until trial mixes of concretehave been established which meet thi specified requirements and have the requiredworkabitity as demonstrated in the full rrut. *ottuUifity t.rGrcttU.i

"U"r.:If at any time during the construction of the works the S.O. approves a change in thesource of cement or aggregate or if the grading of the aggregate alters to such anextent that the fraction of aggregate retained on any sieve cannot be maintainedwithin two percent of the tgd g*ity of fine and coarse aggregate when adjusted asspecified for sampling and testing of aggregates, then further trial mixes of concreteshall be made, tested and approved for use.

Material Batching

All cement used in the manufacture of concrete shall be measured by weight eitherwith an approved weighing machine or by making the size of each batch of concretesuch as to require an integral number of complete bags or drums ofcement.

For concrete of Grades20,25,30, 35A 40 and 45, the fine aggregate and the severalnominal sizes of coarse aggregates shall be measured singly or cumulatively byweight using weight-batching machines.

For concrete of Grade 15,-the fine and coarse aggregate shall be measured separatelyeither by weight using weight-batching machines or6y volume in gauge boxes.

Weight-batching machines shall provide facilities for the accurate conhol andmeasurement of the aggregates eithlr singly or cumulatively and shall be capable ofimmediate adjustment b.V-se-r.nlskilled operators in order to permit variations to bemade to the mix. All_weigh dials shall be easily visible from the place at which fillingand emptying of the hoppers is controlled.

Every concrete mixing machine shall be fitted with a device to measure added waterby weight_ and shall be so construcled that the water inlet and outlet valves areinterlocked so that either one of thpm cannot be opened unless the other is fullyclosed. 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 pointclear of the mixing plant. The entire water system shall be maintained free of leaks atall times and'the measuring device shall be fitted with a drain pipe which allows the

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full quantity of water being measured to be drained off for checking themeasurement. The outlet arrangement of the measuring device shall be such thatbetween five and ten percent of the water enters the mixer before the other materialsand 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-shalt Ue ieaAiti aa3uitaUte-ss ttrat Aa:quantit)' oi*"i.r.added to the mixer can, if necessary, be varied for each batch.

Where volume batching is permitted by the Specification, gauge boxes shall besoundly constructed of timber or steel to contain exactly the volume of the variousaggregates required for one'batch of each mix. They shall have closed bottoms andshall be clearly m#ked with the mix and aggregate for which they are intended.

When calculating theisize of the gauge:box for fine aggregate, an allowance shall bemade.folthe-Uutting gf ft" fine aggregale due to th-e-arierage amount of moisturecontained in the stockpiles on the site. Before the contractor puts any gauge box intouse on the site he shall obtain the approval of the S.O. of the size and construction ofsuch gauge box.

Any admixtures which may be used shall be measured separately in calibrateddispenseis.

All mixing and batching plants shall be maintained free of set concrete or cement andshall- be clean before commencing mixing. The accuracy of calibration of anyweighing plant, water measuring plant and admixture dispenser, shall be checkedbefore carrying out trial mixes, before mixing concrete for inclusion in the work, aftereach service or adjustment to the mixing plant, and in any case at least once permonth.

Mixing Concrete

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 andconsistency, and of discharging the mixture without segregation.

On commencing work with a clean mixer, the first batch shall contain only half thenormal quantity of coarse aggregate to compensate for the adhesion of the othermaterials to the drum.

The moisture contents of the aggregates shall be determined before thecommencement of each day's c-oqc-reting aid at such intervals during each day * *uVbe necessary. The Conhactor shall make due allowance for the watelr containld in theaggregates when determining the quanlity of water to be added to each mix, and shalladjust the amount of water added to each mix to maintain constant the approved freewater/cement ratio of the mixed concrete.

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Ready-Mixed Conc(ete-

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. : ' , :Ready-mixed concrete. shall 1ot b-e used in any part of the works without the S.O.'swritten approval, which may be withdrawn at any time.

The Contactor shall satis$ the S.O. that ready-mixed concrete complies with theSpecification in all respects, add that the manufacturing and delivery reiources of,theproposed supplier are adequate to ensure proper and timely completion of eachconcreting operation.

The specified requirements as to the sampling, trial-mixing testing and quality ofconcrete of various gradel shall apply equally to ready-miied concrete wtrich shdtfurthermore be made and delivered in accordance with BS 532g :'l9gl.

Any additional facility, whi-ch the S.O. may require for the supervision and inspectionof the batching, mixing and transporting of ready-mixed conirete shall be allowed tobe used after 45 minutes of initial rnixing.

High Alumina Cement

The composition of high alumina cement shall comply with B.S. 915 part Two. Itshall consist of a minimum of 32% of alumina *i ttr. minimum compressivestrengths of mortar cubes at one and three days shall be 4}N/sq.mm and 48 f.ilrq.-*respectively.

High alumina cement shall be refrained from being used in structural concreteincludi-Ilq foundations as a substantial reductions in strengths is observed under thevulnerable tropical conditions.

Preparing for Concreting

lefory placing concrete the contractor shall remove from the surface of thefoundations or previously placed concrete, all oil, loose fragments of rock, earth,mud, timber and other debris, and standing water, to the satisfaition of the S.O.

Where specified and elsewhere as ordered by the S.O., the excavated surfaces shallbe prepared as specified under concrete protection.

Transporting Concrete

Concrete shall be conveyed from the mixer to its place in the works as rapidly aspossible by methods which will prevent segregation or drying out and.nr*. thut th.

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concrete- is of the required workability at the time of placing. If segregation hasnevertheless occurred in any instance, the materials shall be re'mixed or rejected.

PlacingConcrete : , ' ' ,. :

Concrete s.hall b-e plu:-.d and compacted before the initial set has orrurr"a *d, io *yevent, 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 withan energy absorbing device, it shall be kept as close to-the work as'piacticaUte.Mortar or water used at the beginning or end of a run shall be discharged outside theformwork..

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Y::fyf,]I,:,|:.d,,th".19 of the:upply,pipe shalt be kept immersed in theconcrete dunng Pt?91n9 to assist compaction. Mortar and water used at the beginningor end or a run shall be discharged outside the formwork.

Concreting in Hot Weather

In hot weathero the contractor shall take steps to ensure that the temperature of ,the::Ti"r: as gfaged. shall not exceed 32 deg. c and that the

-*i*"--irt;*;temperature attained during setting does not exceed 70 deg. c.

l"_-":T"Y. this, the contractor. shall provide sun shades over stockpiles of aggregate,cement silos, mixing water jank-s and pipelines and in addition shalicarry ouiifrr-f"riand as necessary other of the following procedures which shall be submitted to theS.O. forapprov-al:

(D Cool the mixing water and replace part of the water by chipped ice. The iceshall be completely melted by the time mixing is completro. -'

(ii) Spray clean cool water over the aggregate stockpiles. The Contractor shallcarry out regular tests on the aggregates to rnoo. that concenhations ofTlp,Pr:_r :i.:ht:liqes d.o not rise-io unaccepable tevels, *d;;;;;;th;;morsture content determinations allow for such spiaying.

(iii) Shade or wet outside of the formwork.(iv) Apply a fine moisture (fog) spray of clean cool water to shaded areasimmediately prior to placing concrete.(v) Pourconcreteatnight.

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Compaction

All concrete placed in-situ shall be compacted with power driven internal typevibrators supplemented by hand spading and tamping eicept as otherwis. upprou.aby the S.O. The vibrators shall at all times be adequate in number, amplitide andpoyer to compact the concrste properly and quictiy throughout the wilole of thevolume being compacted. Spare vibrators shall be readily on hand in case ofbreakdown

Vibrators shall be inserted into the uncompacted concrete vertically and at resularintervals.

.Wh:1. the Tc-gTpacted concrete is in a layer above freshly compicted.concrete the vibrator shall be allowed to penetrate vertically for about i00 tn- iotothe previous layer. In no circumstances shall vibrators be allowed to come intocontact with the reinforcement or formwork nor shall they be withdrawn quicklyfrom the mass of concrete but shall be drawn back slowly ,o u, not to leave voids.Intemal type.vibrators shall not be placed h ft9 concrete in a random or haphazardm.SITer nor shall concrete be moved from part of the work to another by means ofthevibrators.

The duration of vibration shall be limited.to that required to produce satisfactorycompaction without causing segregation. vibration rhujl ;;;Jr;;;i;lontinuedatter water or excess grout has appeared on the surface.

Attendance of Steel f ixer and Carpenter

During the concreting of all reinforced concrete, including prestressed concrete, acompetent steel fixer and carpenter shall be in attendance otieactr concreting g*g,'toensure that the reinforcement, formwork and embedded fittings are kept in p"oiitioli aswork proceeds.

Curing of Concrete

Concrete shall be cured.by protecting the surface from the effects of sunshine, dryingwinds, fros! rain, rynning watgr oimechanical damage for a;;i"** p;;ll-;?four days when the cement used in the concrete is sulpliate-resisting portland r.;;;Portland Pulverised-Fuel Ash cement or Portland gt*t nr*ir. C.*mt. Th;protection tldl !-" applied as soon as practicable after completion of placing Uy on.or more of the following methods as approved by the S.O.:

qa) By water sprays in continuous operation;(b) By covering with hessian or- similar absorbent material, or sand, keptconstantlv wet:

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(c) After tholo_u8h wetting, by covering with a layer of waterproof fabric kept incontact with the concrete surface.

t r : . , , . , . , , . . .(d) By the application of an approved non-staining liquid curing membrane whichis either self-removing or easily removed following curing period and whichhas a 75o/o moisture retention standard. The'liquid shall be ipplied to formedsurfaces immediately after stripping the formwork.

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Liquid curing membrane (d) shall not be used on Class Ul surfaces where laitance islo P. removed and aggregate exposed to provide a satisfactory bond for placingnrnner concrete ormortar soreeds or on surfaces where the S.O. is of the opinion thatthe appearance of the concrete surface will be affected.

Construction Jointi

A construction joint is defined as ajoint in the concrete introduced for convenience inconstruction at wh]ch^spgcial measures are taken to achieve subsequent continuitywithout provision for further relative movement.

Concrete pll9d-to form the face of a construction joint shall have all laitanceremoved 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 nothardened bf ;ntu|1tq the concrete surface with water under pressure or brushing with1 wire ,b*tl, sufficient to remove_the outer mortar skin and expose the largeaggregate without being disturbed. Where the laitance cannot be removed due io|*9"TTU 9{qt concrete, the whole of the concrete surface forming the joint shall betreated by high pressure rlatel jet, sand blasting, use of a needle gun or a scalinghammer to remove the surface laitance.Before concreting is resumed, all loose matter on the existing concrete surface shallbe removed and the surface slightly wetted.

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Dimensions and Surfaces of Finished Concrete

Workmanship in formwork and concreting shall be such that concrete shall require nomaking good, surfaces leing gerfectly compacted, smooth *J;th;;;;;ffi;;;.Concrete.surfaces fo1 the various classes of *for-.d and formed i*irftli .rrall inany event not exceed the maximum permitted tolerance which shall be as shown inthe table below except where expr-ssly stated otherwise i" ir,, sfiif;;;;;Drawings.

In the table "line and level" and "dimension" shall mean the lines, levels and cross-sectional dimgnsions shown on the Drawings.

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Surface irregularities shall be classified as "abrupt" or "gradual". Abrupt irregularitiesinclude, but shall not be limited to offsets and fins caused by displaced or misplacedformwork, loose knots and other defects in formwork materials, and shall be tested bydirect measurement. Gradual inegularities shall be tested by means of a straight,template for'plane surfaces or its suitable equivalent for curved surfaces, the templatebeing 3.0 m long for unfonned surfaces and 1.5 m long for formed surfaces.

Maximum tolerance (mm) in:

Class,offinish

Line andlevol

Abifupt,irieEularitv

Gradual.lirresularitv

U1U2U3F1F2F3

+/.12+/

-6+l :6+/.12+/

-6+l

-3

6 +1.-6+/

-3+l

-3+l

-6+l

-6+l

-3

+12, -6

+1) ' -6

+6/ -6

1.33 Unformed Surfaces

Finishes to unformed surfaces of concrete shall be classified as Ul, rJz,rJ3,spaded,or 'bonded concrete'or such other special finish as may be particularly specified.]frere the glqg of finish is not specified, the concrete stratt Ue fi;i.il;;-'cf-.tir uf .Class Ul finish is the first stage for Class U2 and U3 finishes and for a bonded"g."r,:T :.tf"r?. 91Tr,u2 lnish shall be a leveled and screeded, uniform plain orridged finish, which (unless it is being cgnv:{qd_to Class Y21U3 or bonded concrele)shall not be disturbe'd in any way after the initial set and during the period of cunng,surplus concrete being struck off immediately after compaction. Where a bondedconcrete surface is specified, the laitance shall be removed from the Class Ul finishsurface and the aggregate exposed while the concrete is still green. A spaded finishshall be u^tyfrtt freg {ro1 voids and brought to a reasonably uniform appearance bythe use of shovels as it is placed in the works.Class U2 finish shall be produced by manual or mechanical floating of the concretesurface after the initial set has taken place and the surface has hardened suffrciently.The concrgtg $alt be worked no more than is necessaxy to produce u'*ifot*'sandpaper' finish free from screed marks.

Class U3 finish shall be a hard smooth steel-trowelled finish. Trowellins shall notcommence until the moisture film has disappeared and the concrete h; tt*J.orJsufficiently to prevent oxcess laitance from being worked into the surface. Thesurface 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 theabove operations.

- t7/37

-

1.34

1.35

The Contractor shall prepare sample panels 1000 mm x 500mm of-concrete with anexposed aggregate finish for inspection and approval by the S.O. at the site.

Building in Plant and Grouting- in

Wherever possible, pipes and other items of plant passing through concrete structuresshall be installed and connected to the remainder of the pipework system to ensureproper nt, ana $Ut te boilt'into the structure as *orii pror^.rdr. ' :

Where this procedure is impracticable due to programme o, otfrer requirementsn holesshall be formed for the items of plant to allow them to be built:in later after completeinstallation of the plant,

, ,

In no cas-e shatl individual pipes of a complicated pipework system including,flangedj?itt. be built into concrete structures before accurate fit of the whole system canbechecked after the complete installation.

Where holes are formed these shall be of size arid shape suffrcient to permit ploperplacing and compaction of concrete o, grout. rt;;i"*r ;iil;-f"l;fti.ll"b"treated to produce a'bonded' surface before installation of plant.

Before grouting-in commences the plant shall be adequately supported in position toprevent movement or d4mage during grouting-in

Concrete yse-d fo1 buildinglil shall be qf the s44e grade as concrete of the memberinto which the plant is being built, except that the mix shall also incorporateranapproved e*p*iing additiveis-ud inaccoii gr *itft tttr'**u-Lit".ilutt4ri{,fii;:Concrete used for water retaining structufes shall be non shrink in nature to enswewater tightness. Concrete, mortar and grout shall be carefully placed and compactedaround the plant to avoid damaging or moving the plant.

Structural Pre-Cast Concrete

Structural units of pre-cast concrete shatl be manufactured in the grade of concreteand to the sizes and details shown on the Drawings. The concrete- shall comply inevery aspect with the provisions of the Contract whether such units are manufaituredon the site or obtained from other manufacturers.

- L8/37

-

All cement, aggregate and other materials for pre-cast concrete units with faces whichare 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 conprete units shall comply wittr ttrerequirements for F3 formed surfaces and U3 unformed surfaces except that thedimensional variations shall not exceed the values listed below, unless otherwisedetailed on the Drawings.

Length +/-6 mmCross-secti on +/ 6 mm each directionStraightness 6 ryqr (deviation from intendedline)Flatress, 3 mm (deviation from a 1.5 m straight edge placed in any position on anominally plane surface)Squareness when considering the squareness of a corner, the longer of the twoadjacent sides being checked shall be taken as the baseline, and the shorter side shallnot vary in its distance from the normal so that the differences between the greatestand the shortest dimensionexceeds 6 mm. When the nominal angle is other lhan 90degrees, the included angle between the check line shall be varied accordingly.

T*itl any corner. on any nominally plane surface shall not be more than 6 mm fromthe plane containing the other three corners.

The positions of individual connecting bolts, bolt holes, projecting steel and otherdevices in any associated group (eg. the joint of two pre-cast units) shall be within 3mm of their true position in the $oup in which they are cast. The location of anysuch group shall be within 6 mm-of iis true positio; in tfre uniri" *hi;il;i;-;iprovided that such deviation does not adversely affect the proper assembly of thewhole structure.

The Contractor shall submit to the S.O. for approval, full details of his proposedmethod of carrying out all operations connected wittr tile manufacture ana assemUtyof precast concrete strucfural members, including :

o A description of the types of casting bed, mould and formwork for the varioustypes of members;

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

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

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

- L9/37

-

1.36 Installation of Pre-Cast Concrete Units ., ,: ,,' ,

At all stages and until completion of the work, pre-cast members shall be adequatelyprotected to preserve all permanently exposed surfaces, arises and architecturalfeatures. The protection shall not mark or otherwise disfigure the concrete.

1.37

A11 units shall be laid, bedded, jointed and fixed in accordance with the lines, levelsand other details shown on the Drawings.

Pty:pu.-k mortar jointing for packing shall consist of one part of volume ordinaryPortland cement and two and half parts by volume of fine aggregate passing a I mmsieve. The mortar shall be mixed with ottty sufncient watJr-to"-uffu theiraterialsstick together when being moulded in the hands. The mortar is thoroughlycompacted

Any pre-cast concrete structural member which is found to be cracked, damaged orotherwise inferior in quality,either before or after erection shall be rejected andreplaced by the Contractor.

Prestressed Concrete

The Contractor shall submit to the S.O. for approval his proposed method of carryingout all operations connected with pre-stressed concrete work and his proposals'forhandling, hoisting and placing a position any pre-cast pre-stressed concrete *ritr.

Pre-stressed concrete work whether pre-cast or cast in-situ shall be as detailed on theDrawings and the Contractor shall provide full details of his proposed method ofcarrying 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 ductsAll tendons, duct forming devices, anchorages and other components shall be keptfree of mud, oil (except water soluble oil applied for protection), paint, retarderi,loose rust, or other foreign matter. They shall be placed with a tolerance of +/-3 mmin concrete dimensions of 300 mm of less or * 6 mm in concrete dimenlions over 300mm. I

-20/37 -

. Not less than 95%by weight passing a 19 mm BS sieve;o Not more than 5%by weight passing a l0 norn BS sieve.

.

t ' : '

The proportion of aqglegate, cement and water shall be determined by trial mixes bythe Contractor starting with a cement: aggregate particles ratio.of one to eight byvolume. :

The trial mix shall be considered suitable when all the aggregate particles are coatedwith a film of cement grout. The water content shall be just adequate. ihe concretewhen placed shall contain no layers of laitance.

\r No-fines concrete shall not be mixed bv hand.

Vibration shall not be used to compact the concrete. Three test cubes of no-finesconcrete shall be made of each hial mix. The minimum crushing strength of thechosen mix shall be 3 N/sq,mm at 28 days.

1.40 Pre-Cast Concrete Products

(a) Pre-ca$ concrete products shall where appropriate be conskucted in aocordancewith British Standards as follows, being hydraulically pressed where possible :

Type of Ilnit StandardConcrete blocks BS 6073 : pt I : 1981

Concrete kerbs, etc. BS 7261 :part I : 1990

Concrete flags BS 7263 : pt 1 : 1990

Concrete sils gS SO+Z

Concrete lintels BS 5977

The concrete shall comply in every aspect with the provisions of theSpecification whethe, ,u.h products *

^*iuzutr.a on *e rf" "r "b"f;from other manufacturers.

- 2r/37 -

(b) Interlocking concrete paving shall include supply and laying of pavers,preparation of surface, supply of sand and casting of edge reshaint beams.

The pavers shall comply with the requirement of MA 20, Specification forconcrele. seeln3ntal

.faving Units, published by the Concrete MasonryAssociation of Australia.

1.41 Sampling and Testing of Aggregate: .

The Contractor shall sample and carry out a mechanical analysis of the fure aggregateand each nominal size of coarse aggregate in use employing the methods described inBS 1881 at least once in ,u.t *rrk *h.r, concreting is inlrogress and at such morefrequent intervals as the S.O. may require.

The grading of all aggregates:shall be within specified limits and should ttre fractionof aggregate retained ol *t sieve.difflg"T

t" corre-spondiy frali-on of aggregatein the approved mix by more than 2Yo of the total quantity of fine *J-ro*r"aggregate, S.O may instruct the ,contractor to alter the relative proportions of theaggregates in the mix to allow for such difference.

r.42 Sampling and Testing of Concrete

The Contractor shall provide the equipment necessary to determine the compactingfactor of freshly mixed concrete at each place where concrete is being made and shaiidetermine the compacting factor of the freshly mixed concrete by the methoddescribed 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 theS.O. but not less frequently than as follows unless otherwise particularly specified:-

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

Grades 25,30,354, 40 or part thereof concreted per day;

for concrete ofone set ofcubes per 50 cu.m

Grades 15 or 20 or part thereofconcreted per day

Each set of cubes (six cubes per set) shall be made from a single sample taken from arandomly selected batch of concrete. Three cubes shall be tested 7 days aftermanufacture and three cubes 28 days after manufacture.

i

-22/37 -

1.43

1.44

Compliance wit^

:h Specilied Requirements

The concrete shall be deemed satisfactory provided that .

(D The average 28 days strength determined from any group of four consecutive'sets of three test cubes exceeds thespecified characteristic strength by-not less -than 7.5 */:O:T* 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 that 1007o of thespecifi ed characteristic strength.

If only one set of threq cube results fails to meet the second requirement, those resultsmay be considered to represent only the particular batch of concrete from which thecube.s were taken, provided that the average strength of the group satisfies the firstrequirement; i :If more ft* o-1. set of three cube results in a group fails to meet the secondrequirement or if the average strength of any group of four consecutive sets of threetest cubes fails to meet the first requirement then all the concrete in all the batchesrepresented by all such cubes shall be deemed not to comply with the strengthrequirements.

Non-Compliance

When the average strength of four sets of three consecutive test cubes fails to meetthe first requirement, no further concrete from that mix shall be placed in the workand the contractor shall establish the cause of the failure and apply such remedies asare necessaxy. The Contractor shall demonstrate by trial mixes and test cube resultsthat the revised mix is in accordanee with the specified requirements.

The Contractor shall within 24 hours of the date of test make proposals for aseementwiJh the. 1.9.^*o* action to be

-taken in respect of any .oori.ti represente? by testcyb-gs wh]ch faiJto meet either of the requirements. These proposals may includl, butshall not be limited to, cutting and testing cores.

Concrete which is ultimately found not be comply with any of the requirements oftheSpecification shall be rejected and shall be broken out and replaced oi otherwise dealtwith as agreed with the S.O.

-23t37 -

1.45 Cutting and Testing of Core Samples

I

a

o

a

a

1.46 Inspection Procedures' . ' . '

Before any concrete is placed, the Contractor shall carry out an inspection to en5.urethat all preparations are complete, including the provision of the necessary equipmentand,Personriel, and shall ensure t-hat suf;ficient materials are available to complete,theworkppposed. : I r-

After completion of this inspection the work shall be offered for inspection by theS.O., sufftcient time being allowed for inspection and correction of any defects. noc91c1etg shall be placed-until the S.O.-has inspected and approved the surfaces uponwhich the concrete is to be placed the formwort< and the reinforcing steel.

.

S1.1" required by the S.O. the Contractor shall institute a 'pour card' system in*T*:9ar$ is.-"d-t ouJ for each lift of concrete and is initialed by the ContractorTd q.O. indicating that the inspections have been carried out.The 'pour card' shall include spaces to identifu the concrete being placed and toItftp

completion of the inspeqlions by the Contractor and S.O. oflne followir.rgltems:

o

a

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 andnoted);Curing procedures;Completion of remedial work (if any)

-24137 -

t.47

Where required all structural concrete in conlact with the ground shall be protected

P *." of the methods specified below, Unless otherwise specified or detailed on the

Drawing, in-situ concrete surfaces which are to be.protected shall have either IJ2 orF2 finish as appropriate.

(a) Prefabricated membrane tanking :The membrane shall be preformed consisting of 1.5 mm thick rubber/bitumencompound formulated for use in hot climates, backed with 0.3 mm thick PVCsheet. The membrane shall adhere with watertight joints to itself at overlaps andto con*ete surfaces prepared wjth ;ui l;fi#;;;***4.-The membrane and primer shall be applied in accordance with themanufacfurer's instructions to horizontal, inclined and vertical surfaces.

1l"r \ brinfine concrete .ha1 praene{, th; membrane sha[ ue applied,bitumen face downwards, and shall extend at least 150 mm beyond the outerlimits of the structure. As soon as the membrane has been applied and beforeany reinforcement or structural concrete is placed, the membrane shall becovered by a sand/cement screed 50 mm thick, extending over the whole area ofthe base of the structure. The membrane projection of 150 mm shall betemporarily protected with a layer of board as specified below to preventmechanical damage.

After the concrete structure hal b;en constructed up to ground level and curingis completed, the surfaces which will be in contact with ttre ground, or asdetailed otherwise on'the Drawings, shall be primed with the material suppliedby the membrane manufacturer. The vertical membrane shall be bonded ontothe projection of the ba;e.lembrane and terminated in a chase at the top. Filletsand reinforcing ships shall be used.

Completed areas of vertical membrane shall be protected from mechanicaldamage during backfill operations by 12 mm ttict cardboard, fibre-board orchipboard secured with suitable adhesive or by concrete block-work.

(b) Made-in-place membrane tanking :

As an alternative to prefabricated membrane taking on horizontal surfaces, thecontractor may propose to design, supply and install a made-in-place membraneof bitumen asphalt concrete laid on a tack coat placed on clean original ground.

,25/37 -

The bitumen asphalt concrete shall comprise bifumen or asphalt and coarse andnne aggregares.

The Contractor shall demonstrate to the S.O. by testing, by trial and byexperience that made-in-place membrane tanking exhibits characteristics whichare,in allrespect equal to or better than prefabricated membrane tanking. Thesystem shall be :-. Waterproof during life of protected structure;o Robust during preparation for concreting;o Durable during life of structure;o Flexible in differential settlement;o Incompressible under weight of structure.

' . '

Made-in-place membrane tanking may be used in place of blinding concreteprovided that the conhactor shall also have demonstrated to the S.O. thepructicaUitity of this system by testing, by trial and by exp( '

. )nence.

Vertical or sloping concrete surfaces shall be protected by prefabricatedmembrane ranking as speciflted which shall overlap and adhere to made-in-place membrane tanking over a width of l50mm.

. l

The emulsion shall be a rubber-rich bituminous emulsion suitable for use in hotclimates imd capable of building up a film with minimum dry thickness of 1.0mm, which is impermeable to waterpenetration and possessing a high degree offlexibility.

A priming mixture shall be made by thoroughly mixing I part emulsion with 6parts fresh water. coats other than priming coat shall not be diluted.

- 26/37 -

Application rates shall be as follows or as necessary to build up a minimum dry filmthickness of 1.0mm.:

Over-coating shall take place as soon as the previous coat has dried. Immediately thefinpl coat has been applied to vertical surfaces, bitumenized building paper shall beapplied to the fresh emulsion and pressed into close contact over the whole area of theprotection.

Horizontal and vertical surfaces shall be protected from mechanical damage duringsubsequent construction work by screed or boarding as specified fot *r*Ui*r;."kid.-"

(d) Polyethylene sheet 250 micron polyethylene sheet shall be placed against vertical orsloping surfaces of excavated ground before placing concrete directly against suchsrufaces.

Backfilling with sand against protected surfaces shall be carried out in such a manner thatthe protection is not damaged. Nevertheless, if such damage occurs, the damage sn*t Umade good to the satisfaction of the S.O.

48 Concrete Protection Procedures

Details of concrete^ protection shall be shown by the contractor on the preliminary*olq"g drawings. Such details shall include corners overlaps, brick or board protectionand details for curves faces, etc. Concrete protection systems proposed for use in thewgrks,.sh{l be demonstrated by the Contractor to the S.O. for approval before rot-irri*of preliminary working drawings showing use of such systems il'tttr works.

Coat

'HorizOntalVerticil I :

rst (priming)2nd

.

3rd

Lst (priming))

2nd

3rd

. .h4th

7

L

1.5

7

7

2

2

-27t37 -

Bases to take machinery and associated pipework shall be constructed in fair facedconcrete to the dimensions shown on the upptorreO machinery drawings or as ordered bythe S.O. The mounting surface of the base shall be steel.floated to true and level planes.

The structural concrete on which the bases:are to be erected shall be prepared by hackingand cleaning off.

Bases shall be tied to the structural concrete with vertical reinforcement. Horizontalrginforyement shall also normally be provided at the level of the pockets for the holdingdown bolts.

, '

Bolt pockets and lead-ins for grout shall be formed by a means which shall have theapproval o_f the SrO, P.glys,f:n: formers witl not be permitted, Where expanded metal isused as a former it shall be left in.

When the machinery has been erected the bolt pockets shall on approval of the S.O. becompletely filled using 3 *i"ry: of 2 parts of gemlnt to 3 parts sharp sand by volumewith sufficient watei to form a thick creamy consistency:

The machinery shall be run under the supervision of the contractor and witnessed by theS.O. after the grout has hardened. When so directed the Contractor shall completi theqoyting operatiol by frlling the space between the top of the concrete and the undersideof the machinery base plate.

No separate ppy-""jwi.tt !e ya$e.fol complying-ig,rh"provision of this clause and allcost shall be deemed to be included elsewhere in the Bill of Quantities.

1.50 Measurement of In-Site Concrete

For concrete placed in-site separate measurements shall be made of plain or mass (i..unreinforced) concrete and of reinforced concrete for each of the specified grades ofconcrete.

In-situ concrete and all work in connection therewith as specified shall be valued by thelneasurement of only such items as aro set forth in the Bill of Quantities. Except whereexpressly shown to the contrary, forrnwork (excluding formwork for horizontalconstruction joints) and steel reinforcement shall be measured separately from and inaddition to, measurement of concrete placed in-situ. Measurement of formwork and ofsteel reinforcement shall be as provided in clauses 2.4.14 and 2.5.12 respectively.Unformed surface finishes class U1, U2 and U3 and spaded finish shall notUe measuredfor payment.

- 28t37 -

1.51

1.52

(i) Any pu{pose made hole or opening which has an average cross-sectional area lessthan 1600 sq cm or which has a volume of 0.1 cu metre of less;

(ii) Any. Portiot 9f 9.!11r, rebates,-channels, pipes, ducts or the like wJrose'.rorr-sectional area in 1000 sq mm or less;(iii) Any chamfer 100 mm wide or less on the splay;(iv) The space occupied by any steel reinforcement, rails, joints or the tike embedded

in the concrete.

Building paper or other protection of foundation surfaces, where ordered by theS.O. shall be measured as the net area so protected and no measurement shall bemade of laps or joints.

: J Ia

Concrete telting shail be' separately measurement only if and to.thelextent thalitems for tests are provided in the Bill of euantities.

Measurement of Form Opening of Build in plant

Payment for form opening or build in plant shall be made at the rate per openinstendered. The rate shall include the cost of handling, provision of fatse **t *il?b9-ry necessarylo forming opening or building in at the required position. The rateshall be measured according to the opening size.

Measurement of Grouting Back The Opening

Payment for grouting back the opening shall be made at the rate per openingtendered. The rate shall include the cost of handling, provision of falsework, iuUo*]marerlal and equlpment necessary to complete grout the gap. The grout shall be eitherordinary Portland Cement or Non'shrink grout. The rate shall be ireasured accordineP th. ope.1i1e size. The work could only be considered complete after it has passeithe water tightness test.

-29t37 -

1.53

1.54

Measurement'of Pre-Cast Concrete ' l

Items for Pre-11t concrete shall include the manufacture and fixing in the works ofthe pre-cast units and all works in connection therewith as specified.

Pre-cast concrete shall be measured as fixed in the works by numbers of units. bvvolume, by area or by length as indicated in the Bill of Quantities. Measurement(except where by numbers) shall include the space occupied by joints between unitsbut not by bedding. Otherwise all measurement shall be net except that no deductionshall be made in respect of any purpose formed hole, duct or thl Hke which has anaverage cross-sectional area less than 2500 sq.mm.

)o. senarate measuremenl for-payryent shall bemade in respect of formwork, surfacegri",, linrorcemenl, j.oggles, dowets,. jointing, p?ddld_91 the_ like for pre-castconcrete unless separate items are expressly provided in the Bill of Quantities.Pre-cast pre-stressed concrete and all work in connection therewith as specified shallle vclu3d by the measurement of only such items as are provided in the Bill ofQuantities.

Sizes and Sequence of Concrete pours

Before commencing concreting the Contractor shall submit for approval his detailedproposals for the sequence of placing concrete and the positions of vertical andhorizontal construction joints. The proposals shall comply with the following :-Where.limitations in lengths of floor or roof slabs that may be cast without joints inany direction are stated on the Drawings, the slabs shall be subdivided bvconstruction joints into panels of dimensions not exceeding the stated limit on lenetll.The panels shall be separately concreted in one continuois operation and nshall be

"on.rrt"drr'tiithr ;;;; in adj acent panels tr ;i.#;;;r ;,;. "o

paners- - - -J

- - - - -

Yh*: limitations i1 lene{{rs.9f ylil that may be cast without joints are stated on theDrawings tr.1 *fll be divided into segments not exceeding the stated maximum

l.gtt by vertical joints which are continuous with the floor joints and extend the fullfeight of the walls in an unbroken alignment. Each segmentLbove the top of the walll"g:h and the top 9{ the- wall shall be cast in a series of lifts each of a length andheight to be approved by the S.O.Alternate s.eSmentl in a lift shall be concreted and an interval of 7 days shall elapsebefore the intervening segments in the same lift are concreted.At each joint rebates shall be formed to receive sealing compounds as shown on theDrawings.

- 30/37 -

Each segment of the wall footing and haunch defined by the floor and wall jointsshall be concreted in one continuous operation. Segments shall be concreted

*fffit:ltff: * interval of at least days shall elapse before intervening segments

i.sa ci.u"i"g t; wdiltaining Structures

The structure shall be cleared of all debris and shall be brushed down on allintemal faces with a stiff broom while still dry, and all resulting debrisremoved; all associated reservoir pipework shall be cleaned in accordancewith the specification requirements.

The structure shall then be flooded with approximately 75 mm of clean waterand the whole of the intemal faces shall be carefully brushed down with stiffbrooms, using the water continuously until all faces are clean; the water shallthen be drained off, and the walls and floors hosed and flushed with cleanwater until perfectly clean.

1.56 Testing of Water Retaining Structures

As soon as possible after completion of water retaining struotures but not before theconcrete has attained its specified 28 day, strength they shall be tested for watertightness by filling with water up to the designed top water level. The rate of fillineshall be reasonably constant and shall not exceed 2 m ofdepth in 24 hours except inthe case of small structures where a higher rate may be aliowed by the Contractor.After filling the structure shall be allowed to stand full (being topped up as necessary)for at least 72 hours, for absorption of water by the concrete- to tut . pL., at the endof which period the level shall be accurately noted. The structure shall then be testedfor a fi*ther period of at least zz rrours i+s ffi;l"ii;; ;;;;;;;;.h il;;i;;structures as agreed) and shall be accepted as watertight if :-(i) No leaks or damp patches on the backs of walls are discernible dwins period

of the test (if the backs of walls are wetted by rainfall or any other ciuse thetest must be delayed until they are dry for at leastT} hours). In the case ofindividual parts of

,a,structure being tested independently, the division wallsalso must be watertight

(iD The floor under drainage system of the structtre (if any) remains dry, or theflow in it before the test is not increased as a result of frliing the structure withwater:

o)

All water retaining structures shall on completion, be carefully cleaned as follows:-

(a)

-31/37 -

(iiD

During the 72 hour test period referred to above the loss of water by evaporation shaltbe determined by measurement of the loss of water'from a shallow watertight tray of0.4 sq.m in area containing not less than 75 mm depth of water and positioned to floaton the surface of the water in the structure.

The roofs and manhole covers of the closed reservoirs shall be tested for water-tightness before the laying of any roof membrane by general observation from withinthe reservoir for damp patches or leaks over a period of heavy and prolonged rain butshould such a suitable occurrence fail to happen, the roof and fittings shall be hoseddown vigorously and this shall be repeated in such a way as to keep the roof wet for 3successivedays.

T.h" to9.f.*9 fittings.shall be deemed satisfactory for water-tightness if there are nodiscemible leaks or damp patches from inside the reservoir. Remedial measures andretesting shall be carried out at the Contractor's expense until satisfactory.

Shoutd any parts of the structure fail the above tests in any respect, the Contractorshall immediately take steps to ascertain the nature and positionr oi any defects orleakages, shall empty the structure, and remedy the defeits in an approved manner.Note that a damp patch appearing on the outside of the wall must 6e rectified fromtF watgl face, a,r-egair making the outer face only watertight shall not be approved;this applies to bobbin holes also.

JF.t the remedial w.ork !ra1 been completed in an approved manner, the testing andifnecessary rectification shall be repeated until a satisfactory test is achieved.If necessary, in extreme cases of lack of water-tightness, the structure or any memberor section of a member thereof may be rejected.Any expense in materials (including the supply of water), plant labour and all othercosts including overheads and profit involved in the satisfactory water-tiehtnesstesting.of dJ E water retaining structures in the works shall be inciuded in tie ratesentered by the Contractor in the Bill of euantities.

Any costs, incurred by the Contractor in remedial or replacement work necessary toachieve the satisfactory testing shall be entirely at the.*p.n.. of the Contractor.

Disinfection of lYater Retaining Structures

Disinfection of water retaining structures shall be carried out by the Conhactor afterthese skuctures have passed the water-tightness test.

1.57

- 32/37

-

1.58

The structure shall be emptied. The internal surfaces of the walls, the internal surfaceof the roof, the internal and external surfaces of atl pipes and specials inside thestructure, and all other surfaces inside the structure shall be vigorously brushed andflushed with jets of clear, clean water until all foreign materials, dirt and gnt whichmay have accumulated thereon are removed. All water and material accumulated inthe cleaning operation shall be discharged or otherwise removed from the structure.

The Conlractor shall provide evidence to the satisfpction of the S,O. that the chlorinedosage proposed for sterilisation will not adversely affect joint sealant materials.Chlorination shall be carried out by Method 1 or Method 2 as set out below. TheContractor shall submit details of his proposed method of working to the S.O. forapproval before commencing disinfection ot*y structure.

Method I

The structure. shall then be filled P th: overflow level wi$ potable water to whichenough chlorine is added to provide a free chlorine residual throughout the structureof not less than 10 mg/l at the end of the appropriate retention period. This shall benot less than 6 hours when the water entering the structure has been chlorinateduniformly by gas-feed equipment or chemical pump or not less than 24 hours whenthe structure has been filled with water which has been mixed with calcium1ry..::H"11.-:t.rggiu1hypochlorite within the structure. The procedure set out inAWWA C652 shall be followed.At the end of the retention period the free chlorine residual shatl be reduced to notmore than 2 mgll by draining and refilling or blending with potable water having alow chlorine concentration, after which the water within the structure shall besampled to determine the free chlorine residual and for bacteriolosical analvsis tocheck for the absence of coliform organisms of faecal origin. If th; ;;itr *.unsatisfactory the structure shall be drained and the disinfection procedure shall berepeated. The costs of any rb-testing shall be borne by the contractor.

Mefhod 2

A solution of 200. mg/l available. chlorine shall be applied directly to all surfaces ofthe structure which would come into contact with water by suitabie brushes or sprayequipment. The disinfected surfaces shall remain in contatt with the strong ctrtorinlsolution for at least 30 minutes after which potable water shall be admitti and thestructure shall be filled and tested for bacteriological quality as in Method l.

Chlo rin e B earin g S olution/lVlixture fo r Disinfection

The chlorine bearing solutior:/mixture shall be prepared using clear, clean water andchlorine, either as liquid chlorine, calcium trypoctrtorite or sodlum hypo.hlod;.

----

- 33/37

-

1.59

Calcium hypochlorite granules, broken to a size not exceeding 0.6 mm ma:rimumdimension, may be poured into the structure from an opening or placed inside on drysurfaces prior to the introduction of flowing water. They shall be so positioned that acurrent of water circulating around the structure shall dissolve them during the filling

:n::'"1Sodium hypochlorite shall be applied to the water entering the structure by means ofa chemical feed pump, or shall be applied by hand-pouring into the structure andallowing the inflowing water to provide the desired

-i*irrg.

Sealing C.ompouhds

Sealing compounds for horizontal construction joints shall be hot applied bituminoussealants complying with the requirements of BS 6213. Sealing compounds forvertical and inclined construction joints shall be bituminous putty of a qualityapproved by the S.O.'s Representative. Both sealing compounds shall be capable ofexpandin-g to ll0% of their orisinal thickness between parallel faces , without,.p*ution.

Horizontal floor joints and vertical and inclined joints to be filled with the sealingcompound shall first be thoroughly cleaned and dried and an approved primercompatible with the sealing compound shall be applied. Each primer and sealing:o*poTd- shall be applied in accordance with the manufacturer's recommendationsfor tropical climates.

Sealing compounds for expansion and contraction joints shall be polyuretane orpolysulphide liquid polymer sealants complying with BS 6213 obtuned fromapproved manufacturers. The sealing compound shall be capable of expanding to133% of its original thickness between parallel faces without extruding and ofcontracting to 67%oof its original thickness without separation.

-34t37 -

Expansion and contraction joints to be filled with the sealing compound shall first bethoroughly cleaned and dried and an approved primer compatible with the sealingcompound shall be applie!. Both primer and sealing_compound shall be applied inaccordance with the manufacturer's recommendations for tropical climates.

1.60 Joint Fillers

Jointfilleisha1leithercorkjointfillerorce1lularjointfiller.. : ,

Cork joint filler shall be waterproof and rotproof and shall not extrude as a result ofcompression. Cork joint filler shall compress to less than 50%o of its originalthickness with immediate recovery to 80% or more of its original thickness.

Cellular Soint nU., shall be preformed low-compression joint frllr. *aa, from f"*rubber. Cellular joint filler ihall recover to its original thickness after each loadingand unloading.

1.61 Waterstopst ,

Waterstops shall be1f3bbe1 or PVC and shall_U: o{a type and manufactureapproved by the S.O. The Contractor shall carefully follow the manufacturer'sinskuctions in any work involving the incorporation of waterstops into structures.

Waterstops shall be fully continuous when laid and site joints shall be limited tosimple butt joints which are to be made with the manufacturer's fusing jig. A carefulcheck shall be made on all joints after completion to ensure that no imperfectionsexist.

Waterstops shall be secwely held in position by the formwork or by means to beapproved by the S.O. and the concrete shall be carefully worked around thewaterstops to ensure that they are completely embedded and that no air pockets willexrst.

Movement Joints

Movement joints are definsd as all joints intended to accommodate relativemovement betwe^en udjory"F parts of a structure,

_special provision being madewhere necessary fbr maintaining the water tightness of the joint. The Conhactor shallcomply with the instructions of manufacturers of proprietary jointing materials andshall, if required by the S.O., demonstrate that thJjointing materialslan be appliedsatisfactorily.

1.62

1.63

The Contractor shall submit to the S.O. for his approval, as soon as practicable afterthe acceptance of his Tender and not less than three weeks before the commencementof concreting, details of his proposals for the installation of waterstops. These shallshow where joints are to be located and details of the intersections and changes ofj:::ijl"" to a scale that shows the position of any joint or shape of any moulded

As far as possible jointing on Site shall be confined to the making of butt joints instraight runs of waterstops. Where it is agreed with the S.O. that it is necessqry tomake an intersection or change of direction or any joint. Other than a butt joint in astraight run, on Site, a prefabricated joint intersection or change of direction pieceshall be made and submitted to such tests as the S.O. may require.

. .

Flexible waterstops shall be fully supported in the formwork, free of nails and clearof reinforcement and other fixtures. Damaged waterstops shall be replaced and duringconcreting care shall be taken to place the concrete so that waterstops do not bend ordistort.

:The surface of set concrete in a movement joint shall, where specified on theDrawings, be painted with two costs of bitumin-ous paint and fresh cbncrete shall beplaced against it only when the paint is dry. Expansion joints shall be formed by aseparating stip of approved preformed joint filler.;;; ;;' ;;;;^* .n, Drawings. At ar joints where acaulking groove is formed, immediately prior to caulking, the groove shall be wirebrushed, and.lgo;g T"T."."1 removed Td bl9*t out by compiessed air. After thegroove has dried it shall be primed and caulked with approved jointing compoundapplied in accordance with the manufacturer's instructions. At all caulked ioints. theface of the caulking strip and 25 mm width of concrete on either side shall6e paintedwith two coats of paint having the same base as the caulking compound

Structriral Tests

The S.O. may, if required, call for loading test on the structure, and for floors, roofsand similar structures. The test load shall be up to l%times the design superimposedload- for tlre areas to be tested. The test load shall not be applied within t+ days of tn.casting of the appropriate.concrete, and temporary timber supports, in case of failing,must be immediately available.

The test shall be satisfactoryif upon removal of that load the residual deflection doesnot exceed one quarter of the maximum deflection after 24 hours loadine. If thet-..:d"ul deflection exceeds this amount, the test is to be repeated and iiresidualdeflection is as above, this may be considered satisfactory. ill *"*uremeni ;;levels of the second test are to be entirely independent of the first test.

- 36137

-

The S.O. may deem tests necessary because :-

(a) Site made test cubes failed to attain specified strensths.(b) Shutteringwasp*-uturliy;.;;il:- e!rv'6rrrr'(c) Overloading occurred during stages of construction or while concrete was(d)(e)(D

AConcrete was improperly cured.Any other circumstances attributed to alleged negligence by the contractor.Any other reason.

T ,1" loading test be.Tld" wholly or in part for reason (a), the test shall be at::Tt::1:]_1:y !i$; irfor.reason (b) to (e) inclusive, then if the test be satisfactory11",:ottltuctor shall be reimbursed for the cost of the test; if for reason (f) Contractorsnall make the test and be reimbursed for the cost of same, whatever ttr. irrt result.If the result of the loading test be unsatisfactory the S.O. may instruct that the part of1l: y*$_"oncemed.b" iuk"r, dory. or t.*ou.J ;i-r;;#r*"#,"'r"*or', *,t,this Specification, or that such remedial measures shall u",ur.*

"r r; il;;ii;;;ork;

secure. If the test was made fo1 o1e or more of the reasons (a) to (e) inclusive, asdetailed above, the. contractor shall take down ot ;;;;;i;ffi:il"i1i.'*orr.,or taKe such remedial measures as the s.o. may instruct, all at his own cost.

-J i lJ | -

10.1 GENERAL

SECTION 10. PILING WORKS

10.1.

10.1.1.

10.1.2.

Setting out shall be carried out from the main grid of the proposed structure. Immediately beforeinstallation of the pile, the pile position shall be marked with suitable identifiable pins, pegs ormarkers,

:For a pile cut-offat or above ground level the maximum permitted deviation of the pile cenhefrom the centre point shown in the Drawings shall not exceed 75mm in any direction. For a pile::r:qqtt:*.ground level an increase in the vertically tolerance is permitted up to I in 75 fromthe finished pile.

The Contractor shall, if ordered by the Fngineer extract and reinstall any pile which has deviatedout of position or alignment by more than the specified limit, or alternatively the substructureshall be modified to the approval of the Engineer. The cost of such extraction-and reinstallation"or any exha cost in the design and construction of a modified foundation shall be bome by theContractor, il in the opinion of the Engineer such extra work has been made necessary due tb theincompetency and/or negligence of the Contractor.

The Contractor shall submit to the Engineer his proposed programme for the execution of thepiling work at least seven days before commencement of the work. ln addition, the Confractorshall inform the Engineer daily of the programme of piling for the following working day andshall give adequate loji"1 of his. intention to work outside normal working hours, if this hasalready been approved by the Engineer.The Contractor shall keep records of each pile installed and shall submit two signed copies oflt.:"..t":otds to the Engineer not later than noon of the next working day after the pile wasinstalled.

GENERAL nnquREnnnivrs FoR ToLERANCES

Setting Out

Setting out shall be carried out using the data and reference points as shown on the Drawings.Immediately before installation of the pile position shall be marked with suitable identifiablepins, pegs or markers.

Position

For a pile cut off at or above ground level the morimum permitted deviation of the pile centrefrom the centrp poinls shown on the Drawings shall not exceed 75*T in any directi-on. For apile cut offbelow ground level an increase in this tolerance is permitted in accordance with sub-Section 10.1 .3 and 10.1 .4 hereinbelow

Vertically

The maximum permitted deviation of the finished pile form the vertical is I in 75.

10.L3.

s10- I

10.1.4.

10.1.5.

i0.1.6.

10.r.7.

Rake

The piling rig shall be set and maintained to attain the required rake. The maximum permitteddeviation of the finished pile from the specified rake or the rake shown on the Drawings is 1 in25.

Forcible Corrections

Forcible'conebtions to concrete piles shall not be permitted. ForCible Conectioni may bepermitted in other types of piles if approved by the S.O. However, no forcible corrections shallbe made to piles which have deviated beyond the permissible limits specified in Sub-sections10.1, 10.1.3 and 10.1.4 above.

Ptlcs Out of Alienment orPosition

The Contractor shall, if ordered by the S.O., extract and reinstall any pile which has deviated outof position or alignment by mdre than the specified limit, or alternatively the substructure shallbe modified to the approval of S.O. The cost of such exfraction and reinstallation or any extracost in the design and construction of a modified foundation shall be borne by the Contractor ifin the opinion of the S.O. such extra works have been made necessary due to the error and/ornegligence of the Contractor.

Records

The Contractor shall keep records of the installation of each pile as required by the S.O. and shallsSbmi^t two-signed copies of these records to the S.O. not later than at noon of the next workingday after pile has been installed. The signed records shall form part of the records for the Works.

Any unexpected driving or boring conditions shall be noted in the records.

sl0-2

r0.2.

r0.2.1.

BORED CAST.IN-PLACE PILES

t0.2.2.

10.2.2.r.

t0.2.2.2.

r0.2.2.3.

10.2.3.

t0.2.3.L

r0.2.3.2.

Materials

Concrete and Reinforcement i'i

:The concrete and reinforcement to be used and workmanship for bored cast-in-sifu piles shall beas specified. rlder the relevant sections of this Specification. The grade of concrete and thedetails of reinforcement to be used shall be as shown on the Drawings.

Permanent Casinss

Permanent casings *hich fOr--part ofthe designed pile shall be as specified in the Drawings.'

i

DrillingFlirid , '

Drilling fluid material, bentonite, shall comply with Specification No. DF CPa of the OilCompanies Materials Association or its equivalent. A certificate shall be obtained by theContractor from the manufacturer of the bentonite powder, showing the properties of eachconsignment delivered to the site. This certificate shall be made available to the S.O. on request.

Bentonite shall be mixed thoroughly with clean fresh water to make a suspension which willmaintain the stability of the pile excavation for the period necessary to place concrete andcomplete construction. Preparation of the suspension shall comply with the manufacfurer'sinstniCtions

Where..ylile or chemically contaminated ground water occurs, special precautions shall be takenp 19Aiff the lentgnite suspension 9r plehydrate the bentonite in fresh water to render it suitablein all respects for the consfuction of piles.-

Borins Onerations

Diameter of Piles

lhe djamgtq _of piles shall not be less than the specified desig4ed diameter at any levelthroughout its length.

Boring

Boring shall be carried down to the depth as required and directed by the s.o.

When deem'ed'necessary by the S.O. the Contractor shall takc undisturbed soil samples while thepile is being bored. The samples shall be taken to an approved Laboratory for testing.

Sampling and all subsequent handling and testing shall be carried out in accordance with8.S.5930.

s10-3

t0.2.3.3.

10.2.3.4.

10.2.3.5.

r0.2.3.6.

10.2.3.7.

Piles shall not be bored close to other piles which have recently been cast and which contain

;:::XT fi#rT,l**ete, such that a fiow of concrete could be induced from or damaged

Temporarv "ur,nn,

r vrulrvr qrY v4Jtrr6J

ITl".rt? "i.|".g: of approved quality.or.an.afpfyed alternative method shall be used tomaintain the stability of pile excavation which might'otherwise collapse.Temporary casings shall be free from significant distortion. They shall be of uniform cross-section.throughout each continuous length. During concreting they shall be free from intemalprojections and encrusted concrete which might prevent the proper formation of the piles being

Where the use of drilling fluid or a column of water is approved for maintainine the stabilitv ofboring, the level of fluid or column of waler in the excavation shall be maintain-ed such thaithefluid pressure always exceeds the pressure exerted by the soil and extemal ground water and anaclequate temporary casing shall be used in conjunction with the method to ensure ttre stabiliW ofthe strata near ground level until concrete has been placed. The fluid water level shali bemaintained at a level not less than I metre above the levil of the external ground water.

ln the elent of a rapid loss of bentonite suspension or water from the piling excavation, theexcavation shall be backfilled without delay and the instructions of the S.O. shall be obtainedprior to resuming boring at the location.

:

spirrage a.dbiibodAll reasonable steps shall be taken to prevent the spillage of bentonite suspension or water on thesite in areas outside the immediate vicinity of the boring operations. Discarded bentonite watershall beremoved from the;rle without delay. The disposalof bentonite water shall comply withthe regulations of the Local Conholling Authorities.

Pumping of Boreholes

Pumping from the borehole shall not be permitted unless a casing has been placed into the stable:tt"P. to prevent the further ingress of water in significant quantities from other sfrata into theboring, or, unless it can be shown that pumping will not have a detrimental effect on thesurrounding soil or its properties.

Continuity of Construction

llt: _loytructe{ in stable soil,rruithout the use of temporary casings or other support, shall bebored and concreted without delay to ensure that the soil characteristics are not-significantlyaltered.

Enlarqed of Pile BasesI

T: ..|t**:d pile base shall not be.smaller than the_dimensions specified and shall be concenhicwltf tle pile shaft d]aqeter.

.A -sloping surface of the frustum forming the enlargement shallmake an angle to the horizontal of not less than 550.

10.2.3.8.

I0 '2,3.9,Cleanl iness.ofF. . i le.Bases,. ] .ffiOn completion of boring loose, disturbed or remoulded soil or fragments of rock shall beremoved from the base of the pile.

10.2.3.10. Insnection

For dry boreholes, each hole shall be inspected prior to the placing of concrete in it. Theinspections shall be carried out from the ground surHce in the case where the borehole diarn-eteris less than 750mm. Where the borehole diameter exceeds 750mm, adequate equipmentconforming to B.S. 5930 shall be provided to enable the Contractor and the S.O. to descend intothe borehole for the purpose of inspection.

For wet boreholes, i.e. holes filled with drilling fluid or water, a suitable probe shall be providedto ascertain the evenness and cleanliness of the pile base.

10.2.4. Placine and Reinforc6ment

10.2.4.1. Joints in Loneitudinal Bars: ,Reinforcement shall be such that the full shength of the bar is effective across the joint and thejoint shall be made so that there is no relative displacement of the reinforcement durins the

construction of the pile and the spacing of the reinforcing bars shall be maintained in such i*utthat proper concreting shall not UL impiOea.

!0.2.4.2. Positions ofReinforcembnt

Adequate spacer blocks, guide tubes, and lifting wires shall be provided so as to maintain thereinforcing steel in the positions as specified.

t - '

Where temporary casings are employed, the longitudinal reinforcement shall exend at least 1.0mehe below ltre lo1top of the casings so that movement of the reinforcement during exhactionofthe casing is minimised.

---- ------e

10.2.5. Concreting Operotions \

v 10.2.5.1. Placing Concrete

The method:f p]Tilg.Td the workability of concrete shall be such that a continuous monolithicconcrete shaft of the full cross-section is formed.

10.2.5.2. Workabilitv of Coqorete

The workability of the concrete shall be determincd by the slump test as described in M.S. 26,

The suggested slump details for typical concreting situations shall be as specified in Table l0.lbelow. The slump shall be measured at the time of discharge into the borehbb.

TABI/E 10.1 -

SLUMP RANGE FOR TYPICAL CONCRETING SITUATIONSTypical Conditions

' ofUse :SlumpRange

" (mm)

Placed into water-free unline4 bore. Widely spaced

s10-s

75 to 125

Where pile diameter is less than 600mm. 100 to 175

,

Where concrete is to be placed by tremie under water ordrilling fluid.

-

, 150 to collapse

t0.2.5.3.

10.2.5.4.

10.2.5.5.

Compaction

Internal vibrators .shall not be usef Jo compa{ concrete unless it can be satisfied that they will

not cause segregation