IS3370(PART1)-1965 Concrete Structures for the Storage of Liquids(Genaral Requirements)

IS: 3370(Part I)-1965

Indian Standard

CONCRETESTORAGE

C DE OF PRACTICE FORSTRUCTURESFOR THE

OF LIQUIDSPART I GENERAL REQUIREMENTS

CementandConcreteS~ectiona1Committee,BDC 2

ChairmanSiraxL’~. K. NAsiBIAR

RepresentingTbe ConcreteAssociationof India, Bombay

MembersSEasN. H. MOHILE (Alternate to

Shri K. K. Nambiar)Ssrus K. F. ANTIA M. N. Dastur & Co (Pvt) Ltd, CalcuttaCOL G. BENJAMIN Engineer-in-Chief’sBranch, Army Headquarters

SEas R. S. MErsANDssU (Alternate)SERT P. S. BEATNAGAR Bhakra & BeasDesignsOrganization,New DelhiDR I. C. Dos M. PAls CUDDoU Central Water & Power Comnsission (Ministry of

Irrigation & Powcr)SmsiV. K. MUssTNY (Alternate

SssaiN. D. D~TARY

Snax N. G. DEWANSUPEsuNTENDING ENGINEER,

2ND CIRcLE (Alternate)Da R. R. HA~s,rsANoADI

SnasV. N. PAl (Alternate)SEar P. C. HAzssAJOINT DzaEc~roR STANDARDS

(B&S)DRPxrrY DIRECTOR STANDARDS

(B&S) (Alternate)SaRI S. B. JOSEXSEEsM. M. LALPRoFS. R. MERRA

In personal capacity ( Dutt Niwas, 27 LahurnamRoad,Bombay-7)

Central Public Works Department,NewDelhi

The AssociatedCementCompaniesLtd, Bombay

Geological Surveyof India, CalcuttaResearch,Designs& StandardsOrganisation(Minis-

try of Railways)

S. B. Joshi& Co Ltd, BombayU. P. GovernmentCementFactory,ChurkCentral Road ResearchInstitute (CSIR),

DelhiNew

DR R. K. GEosa(Alternate)SaRI S. N. MuxaajI NationalTestHouse,Calcutta

SHE! N. C. SENGUPTA (Alternate)Saxi ERAcssA. NADIEsHAR Institution of Engineers(India), CalcuttaSam C. B. PATEL National Buildings Organization(Ministry of Works

& Housing)Saas RABneDER SINost (Alternate)

PRoF G. S. RAaAswAaY Central Building Research Institute (CSIR),Roorkee

SaRI M. C. TAMEANKAR (Alternate)(Continued on page 2)

BUREAU OF INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

IS: 3370 (Part I) - 1965

(Continuedfrompage 1)Members Representing

Sst~TT. N. S. RAo GammonIndia Ltd, BombaySUET S. R. PsNHEI.~O (Alternate)

REPRESENTATIVE Martin Burn Ltd, CalcuttaSIRI NhssAR CUANDRA Rn”’ Dalmia Cement(Bharat) Ltd, CalcutiaSECRETARY Central Board or Irrigation & Power,New DelhiDR BE. SURHARAJtT Indian RoadsCongress,New DelhiSHRI J.M. TaRsiAss RoadsWing, Ministry of Transport

SsssssN. H. KESWANI (Alternate)DR H. C. VrsvzevARvA, Director,BIS (&-officw Member)

DeputyDirector (Civil Engg)Secretasy

SnaxY. R. TANEJAExtra AssistantDirector (Civil Engg),BIS

ConcreteSubcommittee,BDC 2 2Convener

SHUT S. B. Jossir S. B. Joshi & Co Ltd, BombayMembers

SEaTN. H. BssAowAseA~x Engineer-in.ChieE’sBranch,Army HeadquartersDR I. C. Dos M. PATS CuDnou Central Water & Power Commission (Ministry of

Irrigation & Power)SEaTY. K. MURTHY (Alternate)

DEPUTY DIRECTOR STANDARDS Research, Designs & Standards Organization(B & S) (Ministry of Railways)

DutEcTost EngineeringResearchDepartment,HyderabadSiIRI V. N. GuseAJT MaharashtraPublic Works DepartmentSssrnM. A. H,.muz National Buildings Organization (Ministry of Works

& Housing)SERT B. S.SEsYAMuu11~ssy (Alternate)

Sisai C. L. HANDA Central Water & Power Commission(Ministry orIrrigation & Power)

SHRI P. C. HAzRA GeologicalSurveyof India, CalcuttaSItRI K. K. NAMHTAR The ConcreteAssociationof India, Bombay

SstasC. L. N. IYENG.&a (Alternate)Da M. L. PuRr Central Road Research Institute (OSIR), New

DelhiPROFG. S. RAMA5wAMY Central Building Research Institute (CSIR)

RoorkeeSeaTM. G. TAssUANKAss (Alternate)

SERST. N. S. RAo GammonIndia Ltd, BombaySUET S. R. Pxssssaao(Alternate)

Sm’EstINTENDTIeQENosisEErs,2ND CentralPublic WorksDepartment,New DelhiCIRCLESuits 0. P. GoEL (Aurrnate)

SlsaIJ. M. TstERAN RoadsWing, Ministry of TransportSEal R. P. SutKA (Alternate)

Dit H. C. VIsYESVARAYA Indian StandardsInstitutionSUET H. T. YAN Braiihwaite Burn & Jessop ConstructionCo Ltd,

Calcutta

Panelfor ConcreteCodes, BDC z: 2:SHE! S. B. JOSHI S. B.Joshi& Co Ltd, BombaySisatK. K. NAsaBlAB The ConcreteAssociationof India, BombayDR H. C. VIaVESX AEAYA Indian StandardsInstitution

2

AMENDMENTNO. I COTOBER198a

IS:3370(Part I)—1965 CODE OF PRACTICE FOR CONCRETESTRUCTURESFOR THE STORAGEOF LIQUIDS

PART I GENERAL REQUIREMENTS

Alterations

(Paqe 3. oZmis, 03) - S~ibstttute the followingfor the existing c2.ause:

‘0.3 Although the provisions of this code cover main]jstructuresfor the storageof liquids, the generalrequirementsgiven in Part I of this code may generel2,yapp3~y to the design of reinforced concreteandprestressed concrete structures for the conveyazceof liquids, such as aqueducts and superpass ages; theother requirements given in the code ma~r also be appliedwith applopriate modifications.’

(fiuqe a, oLa~e. Li, Zaet Zin)‘impermeability’ foi’ ‘permeability’.

(P46.7, cLaus. Li, Un. ii) —

‘impermeability’ for ‘permeubllity’.

— Substitute

Substitute

(DDC 2)

Printed at Slmco Printing Press, Oe~1di

1ST 3370 (Part Ip~ 1965

Indian Standard

CODE OF PRACTICE FOR CONCRETESTRUCTURESFOR TFIE STORAGE

OF LIQUIDSPART I GENERAL REQUIREMENTS

0. FOREWORD

0.1 This Indian Standard(Part I) wasadoptedby the Indian StandardsInstitution on 19 November 1965, after the draft finalized by theCement and ConcreteSectional Committee had been approved by theCivil EngineeringDivision Council.

0.2 The needfor a codecoveringthe designandconstructionof reinforcedconcreteandprestressedconcretestructuresfor the storageof liquids hasbeenlong felt in this country. So far, such structureshave beendesignedto varyingstandardsadapted from the recommendationsof the Institutionof Civil Engineersandof the PortlandCementAssociationwith the resultthat the resultant structurescannot be guaranteedto possessa uniformsafetymarginand dependability. Moreover,the design and constructionmethodsin reinforcedconcreteandprestressedconcrete are influenced bythe prevailing construction practices, the physical properties of thematerialsand theclimatic conditions. The needwas, therefore,felt to laydown uniform requirementsof structuresfor the storageof liquids givingdueconsiderationto thesefactors. In order to fulfil this need, formulationof this Indian Standardcode of practice for concretestructuresfor thestorage of liquids [IS:3370-1965] was undertaken. This part dealswith general requirements. Three other parts of the code are thefollowing:

Part II ReinforcedconcretestructuresPart III PrestressedconcretestructuresPart IV Designtables

0.3 Although the provisionsof this code cover mainly structuresfor thestorageof liquids thegeneralprovisions of this code may also be appliedwith suchmodificationsas foun~I necessary,to suit thespecialconditionsinthe design of reinforced concreteand prestressedconcretestructuresforthe conveyanceof liquids, such asaqueductsandsuperpassages.

0.4 While the common methods of design and construction have-beencovered in this code, design of structures of special forms or in unusualcircumstancesshould be left to thejudgementof theengineerand in such

3

IS: 3370 (Part1) - 1965

casesspecialsystemsof designandconstructionmay be permittedon pro-duction of satisfactoryevidence regarding their adequacyand safety byanalysisor testor by both.

0.5 In this standardit hasbeenassumedthat thedesignof liquid retainingstructures,whetherof plain, reinforced or prestressedconcreteis entrustedto a qualified engineerand that the executionof the work is carried outunderthe directionof an experiencedsupervisor.

0.6 All requirementsof IS: 456~l964* and IS: 1343-1960t, in so far asthey apply,shall be deemedto form partof this code exceptwhere other-wise laid down in thiscode.

0.7 Thefigures 1 to 7 given in this code are only diagramatic and areintendedmerelyto illustrate the definitionsandprinciplesgiven in thecodeandneednot be treatedaspreferreddesigns.

0.8 The Sectional Committee responsible for the preparation of thisstandardhas takeninto considerationthe views of engineersandtechnolo-gists andhasrelatedthestandardto the practicesfollowed in the countryin this field. Due weightagehas alsobeengiven to the needfor interna-tional co-ordinationbetweenthe standardsprevailingin differentcountriesof the world. Theseconsiderationsled the SectionalCommitteeto deriveassistancefrom publishedmaterialsof the following organizations:

British StandardsInstitution,PortlandCementAssociation,Chicago,USA, andInstitution of Civil Engineers,London.

0.9 For the purposeof decidingwhethera particular requirementof thisstandardis compliedwith, the final value,observedor calculated,expres-singthe result of a test or analysis, shall be rounded off in accordancewith IS : 2-1960t. The number of significat¶t places retained in theroundedoff valueshouldbe the sameas that of the specified value in thisstandard.

1. SCOPE

1.1 This standard (Part I) lays down the general requirementsfor thedesignandconstructionof concretestructures,plain, reinforced or pre~-tressedconcrete,intendedfor storageof liquids, mainly water.

The requirementsapplicablespecifically to reinforcedconcreteliquidretainingstructuresarecoveredin Part II.

*Codeof practicefor plain andreinforcedconcrete(secondrevision).

~Codeof practicefor prestressedconcrete.~Rulesfor roundingoff numericalvalues(revised).

4

1ST 3370 (Part I)-1965

1.2 This codedoesnot cover the requirementsfor reinforced and pies-tressedconcretestructuresfor storage of hot liquids and liquids of lowviscosity andhigh penetrating power like petrol, diesel oil etc. Specialproblemsof shrinkagearisingin thestorageof non-aqueousliquids andshemeasuresnecessarywherechemical attack is possible, are also not dealtwith. The recommendations,however, may generally be applicable tothestorageat normal temperaturesof aqueousliquids andsolutions whichhave no deterimental action on concrete and steel or where sufficientprecautions are taken to ensureprotection of concrete and steel fromdamagedue to actionof suchliquids as in thecaseof sewage.

2. MATERIALS

2.1 The requirements for materials shall be governed by 4 ofIS: 456~l964*and4 of IS: 1343-1960tfor reinforced concrete and pres-tressedconcrete members, respectively, with the following additionalrequirements:

a) Porous aggregates— Under no circumstancesshall the useof porousaggregates,such as burnt clay and broken brick or tile, beallowed for partsof structure either in contact with the liquidson any faceor enclosingthespaceabove sheliquid.

b) Prestressingsteel— The prestressingsteel for prestressedconcretemembersof the structureshall comply with the requirementsofeither IS: 1785-1964or IS: 2090-1962§.

2.2 Jointing Materials —Joint, fillers, joint sealing compounds,waterbarsandjoint cover platesshall conform to the requirementsof relevantIndian Standards.

3. i~ONCRETE MIX

3.1 Provisionsin 5 of IS : 456~l964* and 4.2.5 of IS: 1343-1960tshallappiy for reinforcedconcreteandprestressedconcrete members,respecti-vely, subject to the following further requirements:

a) Except in caseof thick sections as described in 7 and parts ofstructure neither in contact with the liquid on any fice norenclosingthe spaceabove theliquid, concrete mix weaker thanM 200’shall not be used.

Codeof practice for plain and reinforcedconcrete (secondrevision).

tCode of practicefor prestressedconcrete.~Specification for plain hard drawnsteelwire for prestressedconcrete. (Sincerevised

andsplit into two parts).

SSpecilicaiionfor higb tensilesteelbarsusedin prestressedconcrete.

5

IS: 3370 ( Part I) - 1965

b) The minimum quantityof cementin the concrete mix shallbenot less than 330 kglm3 in reinforced concretework, 360 kg/in3in posttensionedprestressedwork and380 kg/in5 in pretensionedprestressedwork. The maximum quantity of cement in theconcretemix shallpreferablynot exceed530 kg/in3 of concrete.

c) The designof the mix shall be such that the resultantconcreteis sufficiently impervious. The mix obtainedin accordancewiththe above, if fully compacted,will generally give a degreeofimpermeability adequatefor all ordinary purposes. In specialcircumstances,the engineer-in-chargeshould satisfy himself thatan adequatepermeabilityis obtainedby percolationtests.

3.2 Pneumatic Mortar

3.2.1 The grading of fine aggregatesfor pneumatic mortar should con-form in general to grading zone I or II specified in Table 3 ofIS: 383.1963*.

NOTE — Pneumatic mortar is mortar applied pneumatically through a suitablenozzle;i(is used,for example,as cover to external prestressingsteel. ~ internalrendering.

3.2.2 The proportions of pneumatic mortar should be such that useratio (by weight) of cementcontentto fine aggregateis neither less than0~3 nor more than 0~5.

3.2.3 A suitablemix for final cover coat of pneumaticmortar is 50 kgcement, 45 kg hydratedlime and 140 kg of dry sand of such sizethat itwill pass through 236 mmIS Sieve.

3.3 Imperviousnessof ConcreteMix — In theconstructionof concretestructuresfor the storageof liquids, the imperviousnessof concreteis animportant basic requirement. The permeability of any uniform andthoroughly compacted concrete of given mix proportions is very largelydependent on the water-cement ratio. While an increase in this ratioleads to an increase in the inherent permeability, a very much reducedwater-cement ratio of a mix with a given cement content may cause compac-tion difficulties and thus may prove equally harmful. For a given mixmade with particular materials, there is a lower limit to the water-cementratio which can be used economically on any job. It is essential to selecta richness of mix compatible with available aggregates, whose particleshape and grading have an important bearing on workability which mustbe suited to the means of compaction selected. Efficient compactionpreferably by vibratioi is essential. In practice, it is usually convenient,particularly when dealing with thin congested reinforced sections, to specifya cement content sufficiently high to ensure that thorough compaction isobtainable while maintaining a sufficiently low water-cement ratio. In

eSpecification for coarseandfine aggregatefrom naturalsouree~’for concrete (revised).

Sincerevised).6

IS: 3370 (Part I ) - 1965

thicker sections,wherea reductionin cementcontentmight be desirable torestrictthe temperaturerise due to cementhydration, a lower cementcontentis usuallypermissible,partly becausethe overall permeabilityofthesection is reduced by the greaterthickness and partly becauselesscongestedconditions may permit thorough compactionof a somewhatdrier mix.

While properattentionmustbe paid in achievinga mix of inherentlylow permeability,it should berecognizedthat common and more seriouscausesof leakage in practice, other than cracking,are defectssuch assegregationand honeycombingand in particular all joints are potentialsotirceof leakage.

The mixesas specified in 3, if fully compacted,will give a degreeofpermeabilityadequatefor all ordinarypurposes. In specialcircumstances,wherenecessary,theengineershouldsatisfyhimself by a percolationtest,that an adequatedegreeof impermeabilityis obtained.

4. SiTE CONDITIONS

~.1The following conditionsof thesite in relation to the functional andstructuralrequirementsof the liquid retaining (storage)structure materi-ally influencethe methodsof designand thecost of the structure:

a) Physical characteristicsof soil in which the liquid retainingstructuremaybe partly or wholly enclosedand also the physicalandgeologicalfeaturesof the supportingfoundations,

b) Extent of water-loggingat the site, andc) Chemicalpropertiesof the soil andof the groundwater.

4.2 In making the choiceof the siteand in the preparationof the designthefactors mentionedin 4.1 should be taken into accountgenerally asndicatedbelow:

a) External eaTtk pressure — Relieffrom externalearthpressureseitherwholly or partially should not generally be relied upon, unlessthe operation of such pressures throughout the service life of theliquid retaining structure is ensured. On the other hand, walls ofthe liquid retaining structure shall be checked for externalpressuresunderemptyor partially-emptyconditions.

b) Water-loggedground— If in the sitting of a liquid retainingstructure,water-loggedground cannot be avoided, the dangersof the externalwater pressureshall be carefully guardedagainstby the following:1) Designing thestructureto resistsuchpressureunderempty or

partially-emptyconditionsandtaking precautionsto preventfloating andensuringstable equilibrium underall conditionsof internalandexternal loads. It is advisableto make the

7

lS:3370(Part I)- 1965

design such that the minimum gravity weight exceeds theuplift pressure by at least 20 percent.

2) Providing under floor drainage to reduce the level of theexternal water as far as local conditions permit.

3) Providing relief valves discharging into the liquid retainingstructure when the external pressure exceeds the internalpressure; this arrangement is feasible only in cases when theliquid retaining structure is not required for the storageofliquids which shouldnotbe contaminated.

4) Designing both internal and external facesof the walls andfloor as water retaining faces, where the walls and floors ofthe liquid retaining structure are submergedin water orwaterbearingsoils.

c) Stabili~y— The equilibrium and safety of structureand parts ofit againstsliding and overturning especiallywhen the structureis founded on a side long or sloping ground.,shall alsobechecked.

d) Settlementandsubsidence— Geologicalfaults, mining, earthquakes,existence of subsoils of varying bearing capacities may give riseto movement or subsidenceof supporting strata which may resultin serious cracking of structure. Special considerationsshouldbe givenin the preparationof the design, to the possibleeffectof subsidence or movement of the foundationstrata.

e) Injurious soils— Chemical analysis of the soil anu ground water isessentialin caseswhere injurious soils are expected to exist, asconcretestructure may stTffer severedamage in contact with suchsoils. The use of sulphate resisting cement will increase theresistance to the action of certain injurious soils but may notafford complete safeguard. An isolating coat of bituminous orother suitable material may improve the protective measures.

5. PROTECTIONAGAINST CORROSION

5.1 The type of liquid to beretainedshould be consideredin relation tothe possibility of corrosion of steel or attack on concrete with corrosionwaters (as in the case with certain natural waters), it is desirable to usericher anddenserconcrete and provide increasedcover to steel. Consi-derations may also be given to the use of specialcements, such as,sulphate-resistingcementor high aluminacement. Whereattack is likelyto beappreciablethe provisionof an impervious protective lining shouldbe considered.

6. CONTROL OF CRACKING

6.1 Designof liquid retainingstructureshasto bebasedon the avoidanceof crackingin the concretehaving regardto its tensilestrength.Important

8

IS: 3370(Part I). 1965

causesof crackingin concreteand measuresto be adopted for avoidingthem aregiven below.

6.1.1 Designof reinforcedconcretemembersshould be made in accor-dancewith the usual principle of ignoringthetensileresistanceof concrete.Additionally, it shouldalso be ensuredthat thecalculatedtensilestressonthe liquid retainingfaceof the equivalentconcretesection (after allowingfor thesteel area in equivalentconcreteunits) does not exceedthe limitsprescribedby this standard [see Table 1 of IS: 3370 (Part II) - 1965*]assumingin the calculationsthat the entiresectionof theconcrete(includ-ing cover) participates in resisting the direct and flexural loads. Thepermissiblelimits of tensilestressin theconcretefdr calculationsrelatingtoresistanceto cracking will naturally provide a much smaller margin ofsafetyagainstultimatetensilestrengthof concretebecausethe consequencesof crackingareusuallymuchless seriousthan thoseof structuralfailure.

In memberslessthan 225 mm thick, the requirement of limiting thetensile stressasgiven in 6.1.1 shall also be appliedto the faceremotefromthe water retaining face.

6.1.2 Plain concrete liquid retaining structuresor membersmay bedesigned againststructural failure by allowing tension in plain concrete asper the permissible limits for tension in bending specifiedin IS : 456-19641.This will automatically take care of failure due to cracking. However,nominal reinforcement in accordance with the requirements ofIS: 456-19641shall be providedfor plain concretestructuralmembers.

6.1.3 The design of prestressedconcretemembersis basedupon ‘notension ‘ being developedin the concretesection underserviceconditions.The designof prestressedconcreteshall howeverbe furthercheckedagainstcrackingof the liquid retaining face with a load factor against crackingof 1.2.

6.1.4 Cracking may also result from the restraint to shrinkage,free~xpansionand contractionof concretedue to temperatureand shrinkingsndswellingdueto moistureeffects. Suchrestraintmay arisefrom:

.4) the interactionbetweenreinforcementandconcreteduringdryingshrinkage,

b) the boundaryconditionsat thefoundationsor other parts of thestructt:re,and

c) the differential conditionsthroughthe large thicknessof massiveconcrete. Someof themethodsemployed to control or preventsuchcrackingaregiven in 6.1.4.1to 6.1.4.6.

*Codeofpracticefor concretestructuresfor thestorageof liquids Part II Reinforcedconcretestructures.

iCodeof practicefor plain and reinforcedconcrete (secondrevi~ion ).

9

IS: 3370 (Part I) - 1965

6.1.4.1 Correctplacingof reinforcement,useof small sized bars anduseof deformedbarslead to a difuseddistribution of cracks.

6.1.4.2The risk of crackingdueto overall temperatureandshrinkageeffectsmay be minimized by limiting thechangesin moisture content andtemperatureto which thestructureas a wholeis subjected. Undergroundreservoirscanremainpermanentlywet. It will be advantageousif duringconstructionof such reservoirsthin sectionsbelow final water level couldbe kept permanentlydamp. It will, however,be impracticableto main-tain permanentwetnessin elevatedstructureswhich unavoidablymay beleft empty for a period.

6.1.4.3 Crackscanbe preventedin thick walls (or even in thinnersections)by avoiding the useof thick timber shutteringwhich preventtheeasyescapeof the heatof hydrationfrom the concretemass. Due to suchheatof hydration, the concretewall is raisedto arelatively high tempera-ture which will be retainedduring the period the concretehardens. Orremovalof the form work, as the temperatureof concretefalls to thatof thesurrounding air, the concretecontracts.Such contractionwill takeplacewithout crackingif the free movementof the wall is unrestricted,but cracksmay subsequentlydevelopwhereoneor moreof the edgesare restrained.

6.1.4.4The risk of crackingcan also be minimized by reducing therestraintson the free expansionor contractionof the structure. With longwalls or slab; founded at or below ground level, restraints can beminimized by the provisionof a sliding layer. This can be provid~8 hi’founding the structureon a flat layer of concrete (see Note ) with inter-position of some material to break the bond and facilitate movement.However, the lengthof thewall that can be kept free of cracksby th~ useof a sliding layer in its foundationis strictly limited and is related to thetensilestrengthof the wall section. In approximate terms, the tensilestrengthhas to be sufficient to overcome the resistance to sliding of onehalf of the length of the wall. Control of cracking thus requires sub-division of the structureinto suitablelengthsseparatedby movementjoints.The maximumlength desirablebetweenjoints will dependon the tensilestrengthof tlse wall andmay be increasedby suitablereinforcement. Theeffectivenessof movementjoints in controlling cracking will dependnotonly on their spacingbutoften on their preciselocation. This is a matterof experienceandmay be characterizedas the place where crackswouldotherwisedevelop,for example,at changesof section. The location of allmovementjoints shouldbe indicatedon the drawings.

NOTE — In normalcircumstancesthis flat layerof concretemay beweakerthan thatused in other parts of the structure, but not weaker than M 100 specified inIS 456.1964*. Where,howeverinlurious soilsor agressivegroundwaterare expected,the concrete should not be weaker than M 150 specified in IS 456-1964, and ifnecessarya sulphateresistingor other specialcementshould be used.

*Codeof practicefor plain aid reinforcedconcrete(secondrerision ).

10

1St 3370 ( Part I) - 1965

6.1.4.5 Where reservoirsare usedfor reception or storageof hotliquids, allowanceshouldbe madefor the additional stressesproducedbydifference in temperature between inside and outside of the reservoir. Theseverity of the temperature gradient through the concrete can sometimes bereduced by internal insulation.

6.1.4.6Whenever development of cracks or overstressing of theconcrete in tension cannot be avoided, the concrete section should besuitably strengthened. In making the calculations either for ascertainingthe expected expansion or contractionor for strengtheningthe concretesection, the following values of the coefficient of expansion due to tempera-ture and coefficient of shrinkage may be adopted:

Coefficient of expansion 11 x 10’/0C

Coefficient of shrinkage initial shrinkage on first drying450 x 10-’ of the original length;drying shrinkage 200 x l0 of theoriginal length

6.2 Sustainedstressesdue to temperatureand shrinkageeffects may bemodified by .the occurrence of creep. This is often advantageous, forinstance, if the reservoir is filled at a slow rate (a procedurewhich isusually adopted) the margin of safety against cracking may be increasedby the occus rence of creep. This procedure also has the advantage thatresatur~atson of the concrete before it is fully loaded will reduce the contri-bution which drying shrinkagemight maketo theformationof cracks.

6S-~Wherereservoirs are protected with an internal impermeable lining,tbe requirement that all cracking of the concrete be avoided should beretained unless it is established on the basis of tests or experience that thelining has adequate crack bridging properties.

7. THICK SECTIONS

7.1 Thick sectionsshall be those parts of structurewhich have thicknessgreaterthan450mm.Thereis alikelihoodofcrackingin suchsectionsas aconsequenceof temperaturerise during hydration of the cementandsubsequentcooling. Suchcrackingis not easyto controlby reinforcement.Thefollowing aresomeof themeasuresthat may beadoptedfor reducingthelikelihood of cracking:

a) Magnitude of the temperature rise should be restricted by limitingthe cement content, or by using a type of cement with a low rateof heat of evolution or adopting suitable construction methods~Portland cements with lower rates or strength developmentgenerally give lower rates of heat evolution. In such cases thepennissible stresses shall conform to requirements of 3.3. Tem-peraturerise may also be restricted by casting the concretein

II

IS: 3370( Part I) - 1965

shallowlifts at intervalsof a few days so as to allow the escapeofpart of heatfrom theexposeduppersurface.

b) Steeptemperaturegrading will occur by suddenchilling of theconcrete surface. This should be avoided, for instance,someprotectionmay be requiredwhenremovalof heavy timber form-work coincideswith on setof cold weather.

c) Restraintto overallcontractionmay be limited by provision ofmovement joints and by provision of suitable sliding layer(see6.1.4.3and6.1.4.4). Anothercauseof restraintwhichmayleadto crackingoccurs whenasubstantiallift of concreteis castupon a cold foundation. A betterprocedureis to avoidexcessivedisparity in temperature between successive lifts andwhere prac-ticableto introduceshallow lifts whenstarting from or resumingwork on a cold foundation.

7.2 While concretingin thick sections,the requirementsof IS : 456-1964shallapply as far as possible.

8. JOINTS

8.1 Jointsshall be categorizedasbelow:

a) MovementJoints— There are three categories of movement joints:

1) Contractionjoint — A movementjoint with a deliberate discon-tinuity but no initial gapbetweenthe concreteon eithersideof thejoint, thejoint beingintendedto accommodatecontrac-tion of the concrete(seeFig. I ).

A distinction should be made between a completecontractionjoint (see Fig. IA) in which both concreteandreinforcing steel are interrupted, and a partial contractionjoint (seeFig. iB) in which only the concrete is interrupted.the reinforcing steelrunning through.

2) Expan.rionjoint — A movementjoint with completediscontinuityin both reinforcementand concreteand intendedto accom-modate either expansionor contraction of the structure(seeFig. 2).

In general,such a joint requires the proviston of aninitial gapbetweenthe adjoiningpartsof astructurewhichbyclosingor openingaccommodatestheexpansionor contractionof the structure. Design of the joint so as to incorporate.sliding surfaces,is not, however, precluded and may sometimesbe advantageous.

eCodeof practice for plain andreinforcedconcrete(secondrevision).

12

IS a 3370( Part I) - 1965

DISCONTINUITY INCONCRETE BUT NO

INITIAL GAP WATER BAR

., V ~

~ S.r.Y

V.. - .V . .

V .7 ~. .p. S

DISCONTINUITY INSTEEL

lA

JOINT SEALINGCOMPOIJND-\ STRIP PANIING

S. .P~

CONTINUITY OFSTEEL

DISCONTINUITY INCONCRETE BUT NO

INITIAL GAP

lBIA CompleteContractionJoint lB Partial ContractionJoint

FTG. 1 TYsTOAL CoNTRAcTIoN JoiNTS

WATER

Fzo. 2 A TYPiCAL ExPANsioN JoTNT

3) Slidingjoint — A movementjoint with completediscontinuityin both reinforcementandconcreteat which special provisionis madeto facilitate relativemovementin place of thejoint.

A typical applicationis betweenwall andfloor in somecylindrical tank designs(seeFig. 3).

b) Construction Joint — A joint in the concrete introduced forconveniencein constructionat wUch specialmeasuresare takento achieve subsequentcontinuity without provision for furtherrelative movement, is called a construction joint. A typicalapplication is between successive lifts in a reservoir wail(seeFig.4).

S .

JOINT FIL’~~

DISCONTINUITY IN BOTHCONCRETE AND STEEL

13

1St 3370 (Part 1) - 1965

• . .‘. STRIP PAINTINGJOINT SEALING

V COMPOUND9

~ •V FV :7 •

‘VV. . p. .

PREPARED SLIDING SURFACEOR RUBBER PAD

?io. 3 A Tyncax. SLwiseo Joner

1 ~ ,.— PREPARED JOINT:.>. SURFACE

pCONTINUITY OF& I STEEL.9. I

24.L LFro. 4 A Txpxo~ CoxsTaucTxoT JoINT

The position and arrangementof all constructionjointsshouldbe predeterminedby theengineer. Considerationshouldbe given to limiting the number of such joints and to keepingthem free from possibility of percolations in a similar manner tocontraction joints.

c) TemporaryOpenJoints— A gap temporariiy left between the con-crete of adjoining parts of a structure which after a suitableinterval and before the structure is put into use, is filled withmortar or concrete either completely (Fig. 5A) or as providedbelow, with the inclusion of suitable jointing materials (Fig. 5Band SC). In the former case the width of the gap should besufficient to allow the sides to be prepared before filling.

Where measures are taken for example, by the inclusion ofsuitable jointing materials to maintain the watertightness of theconcrete subsequent to the filling of the joint, this type of jointmay be regarded as being equivalent to a contractionjoint(partialor complete)as definedabove.

8.2 Design of Joints — Design of a movementjoint shouldaim at thefollowing desirablepropertiesfor its efficient functioning:

a) Thejoint shouldaccommodaterepeatedmovementof the struc-ture without loss of watertightness.

14

IS: 3370 (Part I) - 1965

-INITIAL GAP LATERFILLED WITH CONCRETE

INITIAL GAP ~ STRIP PAINTING

JOINT SEALING COMPOUND

MORTAR FILLING

5C

Fin. 5 TYPIcAL TEMPORARY OPEN JOINTS

b) The designshould providefor exclusionof grit andwould preventthe closing of thejoint.

c) The materialusedin the constructionof movementhavethe following properties:

debris which

joints should

1) it should not suffer permanentdsstortion or extrusion andshould not be displacedby fluid pressurc

2) it should not slump unduly in hot weather or becomebrittlein cold weather.

3) it should be insoluble anddusableandshould not be affectedby exposure to light or by evaporation of solvent orplasticisers.

4) in specialcases,the materialsshould he non-toxic, taintless orresistantto chemicaland biological actionasmaybe specified.

8.3 Spacingof Joints — Unless alternative effective meansare taken toavoid cracksby allowing for theadditional stressesthat may beinducedbytemperatureor shrinkage changesor by unequal settlement,movementjoints should be provided at the following spacings:

a) In reinforcement concrete floors, movementjoints should bespaced at not more than 7’S m apart in two directions at right

STRIP PAINTING~ INITIAL GAP LATERFILLED WITHCONCRETE

IV V%t9V~4~’

tVI~I.J.

b~~V

SURFACES5A

V. JOINT SEALING

COMPOUND

5B

15

15i3370(Part I)-1965

angles. The wall andfloor joints should be in line except wheresliding joints occur at thebaseof the wall in which case corres-pondenceis not so important.

b) For floors with only nominalpercentageof reinforcement(smallerthan the minimumspecified),the concretefloor shouldbe castinpanelswith sidesnot more than 4’S m.

c) In concretewalls, the vertical movementjoints should normallybe placedat a maximumspacingof 7.5 m in reinforcedwalls and6 m in unreinforced walls. The maximum length desirablebetweenverticalmovementjoints will dependupon the tensilestrength of the walls,andmay be increasedby suitablereinforce-ment. Thus whena sliding layer is placedat thefoundationofawall, the length of wall that can be kept free of cracks dependsupon the capacityof wall sectionto resist the friction induced atthe plane of sliding. Approximately the wall has to stand theeffect of a force at the planeof sliding equal to weight of halfthelengthof wall multiplied by thecoefficient of friction.

d) Amongst themovementjoints in floors and walls as mentionedabove, expansion joints should normally be provided at a spacingof not more than 30 m between successiveexpansionjoints orbetweenthe endof thestructureandthe nextexpansionjoint, allotherjoints being of the contractiontype.

e) When, however, the temperaturechangesto be accommodatedareabnormalor occur morefrequentlythan usual as in the caseof storageof warm liquids or in unin~ulatedroof slabs, a smallerspacingthan 30 m shouldbe adopted,(that is a greaterpropor-tion of the movementjoints should be of the expansiontype)Whenthe rangeof temperatureis small, for example, in certaincoveredstructures,or where restraintis small, for example, incertainelevatedstructuresnoneof the movementjoints providedin small structuresupto 45 m length needbe of the expansiontype Where slidingjoints are provided betweenthe walls andeitherthe floor or roof, the provisionof movementjoints in eachelementcanbe consideredindependently.

8.4 Making of Joints —Jointsshallgc±ierallybe madeaccordingto thebroadprinciplesdiscussedin 8.4.1 to 8.4.3.

8.4.1 Construction Joints— Theseshould be set at right angles to thegeneraldirection of the member(seeFig. 4). The position and arrange-ment of constructionjoints should be determinedby the engineerat thedesignstageandindicatedon the drawings.

The surface film of the first-placed concreteshould preferably beremovedwhilst the concreteis still greento exposetheaggregateandleavea sound irregular surface. This maybe effected by sprayingwith water

16

IS~ 3370(Part I)- 1965

or air andwater,assistedby light brushing,where necessary. If the con-cretehasbeenallowed to harden,it will be necessaryto achievethedesiredsurfaceby hackingthe whole of the surface, care being taken to avoiddamagingtheaggregate.

While the remainderof the concreteshouldbekept continuouslywet,curing of thejoint surfacemay be suspendeda few hoursbeforeconcretingis to be resumedso as to permit no more than superficial drying of thejoint surface. Just before concreting is resumed, the roughenedjointsurface should be thoroughly cleanedand freed from loose matter, pre-ferably,without re-wetting,andthen treatedwith a thin layer of cementgrout,workedwell into the surface,or treatedwith cement/sandmortar inwhich water/cementand sand/cementratios do not exceedthose in thenew concrete. Specialcare should be takez~ to avoid segregationof theconcretealongthejoint planeandto obtain thoroughcompaction.

Alternatively, for horizontaljoints thelayer of grout or mortar maybe omitted,providedthat the workability offirsthatchesof concreteplacedin contactwith thejoint is slightly increased.

8.4.2 Movement Joints— These require the incorporation of specialmaterialsin orderto maintainwatertightnesswhilst accommodatingrela-tive movementbetweenthe sidesof the joint. Suitable materialsfor thispurposearereferredto in 8.5.

Movementjoints, particularly those in floor and roof, also requireprotectionagainstthe entry of debriswhich may interferewith the closingof thejoints.

8.4.2.1 Contraction joints — The joints face of the first-cast concreteshould be finished againsta stopping-off board, or vertical end shutter.which, in the caseof a partial contractionjoint, shouldbe notchedto passthe reinforcement.

Stepsshould be takento preventany appreciableadhesionbetweenthe new andthe old concrete.

Thejoint should be suitably treatedso as to maintain watertightnessduring movementof thejoint (seeFig. C and8.5)

8.4.2.2 Expansionjoints— Theserequirethe provisionof an initial gapbetweenthe concretefaces on the two sides of the joint and this can beconvenientlydoneby the use of materials discussedin 8.5. The initialwidth of this gapshould be specifiedby the engineerand should be stsffi-cient to accommodatefreely the maximum expansionof the structure. Indetermining the initial width, regard should be paid to the requirementsof the jointing materials. These will normally require the maintenance ofa certain minimum width of gap during maximum expansion of the

17

18:3370 (Part I) - 1965

METALLIC WATER BAR

• V.U

V

A

V.

ZJoINT SEALING COMPOUND1POLY VINYL CHLORIDE

WATER BAR

6A

TWO COAT STRIPPAINTING MOULDED WATER BAR

- --v• .I~v...Zq w

ZJOINT SEALING COMPOUND

6C 6DFza. 6 TYPICAL DETAma SHowING Usx Os JOINTING MATERIAlS IN

MovEMENT JoINTS (CoNmAc1~IoN Tysx)

structure. Thejoint shouldbesuitably treated so as to maintain water-tightness during movemqnt of the joint (see8.5 and Fig. 7).

8.4.2.3 Slidingjoints — The two concretefacesof aslidingjoint shouldbe planeandsmooth.

Careshouldbetakenby theuseof a rigid screedingboardor othersuitable means to make the top of the lower concreteas flat as possible.Thissurfacecanusefullybe improved by finishing with a steel float andrubbingdown with carborundum.

Bond betweenthe concreteof the two componentsshouldbe preven-ted by paintingor by insertingbuilding paperor othersuitablematerial.

Thejoint shouldbesuitablytreatedso as to maintain watertightnessduring movementof thejoint.

8.4.3 TemporaryOpenJoints— The concreteon both sides of the jointsshouldbe finished againststoppingoff boards.

V II KLLLj~’~ II.-1’ I

V I

S. .vx1sJ

V.

• .u~I‘‘‘.1

18

IS: 3370(Part I ) - 1965

s-METALLIC WATER SAPJOINT SEALING

Li~~4POUND

l~.W4.

.1 W

~=OINT FILLER

7A

JOINT FILLER

METALLIC WATER BARJOINT SEALING COMPOUND

C VV.

p.

1

JOINT FILLER

7B

COPPER JOINT CodER PLATECI CLAMPING

PLATE GASKETPLASTIC POINTING

V ~ ~ p

V V VL±J99’ •V VV pLRUBBER WATER BAR

7C

LEAD CAULKINGSHEET LEAD JOINT

COVER PLATE

V •~• 9’V •. - . -

V...• . . V.

9.9.9’.qV

PAINT JOINT FILLER

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L. 1 PLATE CAST “—JOINT

INTO CONCRETE

70

JOINT SEALING TWO COAT STRIPCOMPOUND- f PAINTING

VVV 57

7

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7F

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PRECAST COVER

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FIG. 7 TY?ICAL DZT.&ua SHOWING Usx Os JoINTING MA~rxxsAlS IN MovzMaw~JOINTS (BxPANsIoN Tyru)

19

jV’ V V

,— RUSTLESSBOLT

iLLER

IS:3370(Part Il- 1965

In order to minimize the extent of subsequentmovementsduetoshrinkagethejoint shouldbe left openuntil shortly beforethe reservoir isput into serviceandthen filled in with mortar or concreteof specifiedproportions. Wherepossible,thejoint shouldbe filled whenthe tempera-tureis low.

Immediatly beforefilling thegap, the joint faces should,if possible,be thoroughlycleanedandpreparedin the sameway as for constructionjoints (see 8.4.1).

Where it is intendedto treat this type of joint as equivalent to acontractionjoint for the purposeof this code, the joint should be suitablysealedso as to maintain watertightnessduring suhn’nuentmovement ofthejoint.

8.5 Jointing Materials —Jointing materials may be classified as follows:a) Jointfillers,b) Waterbarsandjoint cover plates,andc) Joint sealing compounds (including primers where required).

8.5.1 Joint Fillers—Joint fillers are usually compressiblesheetor stripmaterialsused as spacers. They are fixed to the face of the first placedconcreteand againstwhich the secondplaced concreteis cast. With aninitial gapof about 30 mm, the maximum expansionor contractionthatthe filler materialsmay allow may be of the order of 10 mm.

Joint fillers, as at presentavailable, cannotby themselvesfunctionas watertight expansionjoints. They may be used as support for aneffective joint sealing compoundin floor and roof joints. But they canonly be relied uponas spacersto provide the gap in an expansionjoint,the gap beingbridgedby a waterbar (seeFig. 7).

8.5.2 Water Bars — Water bars are preformed strips of impermeablematerialwhich areembededin the concreteduring constructionso as tospanacross the joint and provideapermanentwatertightsealduring thewhole rangeof joint movement. The mostusual forms of water bars arestrip with a central longitudinal corrugation (see Fig. 6A and 7A),Z shapedstrip (seeFig. 7B), and a centrallongitudinal hollow tube (seeFig. 6B and 7C) with thin walls with stiff wingsof about 150mmwidth.The materialused for the water barsare copperbars, sheetlead, naturalor synthetic rubbers (seeFig. 7C) and plasticssuchaspolyvinyl chloride(PVC) (seeFig. 6B). Galvanizediron sheetsmay also beusedwith thespecific permissionof the engineer-in-chargeprovided the liquids storedorthe atmospherearound the liquid retaining structureis not excessivelycorrosive,for example,sewage.

Of the metalsavailablecopperis mostsuitablefor useaswaterbarasregards ductivity and resistance to corrosion in air, water and concrete.

20

IS: 3370 (Part I ) - 1965

It may, however,be attackedby some wastes. If sheet lead is used,itshould be insulated from concrete by a good coatof bituminousor suitablecomposition. Naturalandsynthetic rubbersandplasticshavevery consi-derableadvantagein handling, splicingandin making intersections.

With all water bars, it is importantto ensurepropercompactionoftheconcrete. The barshouldhavesuchshapeand width that the waterpath throughthe concreteround the barshouldnotbe undulyshort.

The holes sometimesprovided on the wingsof copperwater barstoincreasebond shortenthewater pathand may be disadvantageous.Thewater bar should either be placedcentrally in thethicknessof the wall orits distance from either face of the wall shouldnot be less than half thewidth of the bar. The full concretecover to all reinforcementshouldbemaintained.

The stripwater barsat presentavailablein the newer materialsneedto be passedthrough the end shutterof the first-placedconcrete. It canbe appreciated,however,that theuseof the newermaterialsmakepossiblta varietyof shapesor sections. Someof thesedesigns,for example, thosewith several projections (see Fig. 6D), would not needto be passedthrough the end shutter and by occupying a bigger proportion of thethicknessof the joint would also lengthenthe shortestalternative wateipath throughthe concrete.

8.5.3 Joint Cover Plates—Joint cover plates are sometimesused inexpansion joints to avoid the risk of a fault in an embedded water bar.The cover plate may be of copperor sheetlead. If coppercover plate isusedit shouldbe clampedto the concreteface on eachside of thejointusing suitable gasketsto ensurewatertightness(see Fig. 7D). If sheetleadis used,the edgesmay returninto groovesformedin the concreteandbe madecompletelywatertightby leadcaulking (see Fig. 7E). Facesofthe concreteto whichsheetleadis to be fixed shouldbe paintedwith bitu-minousor othersuitablecompositionandthe leadsheetshouldbe similarlycoatedbeforefixing.

8.5.4 Joint Sealing Compounds— Joint sealing compounds are imper-meableductile materialswhich are required to provide a watertight sealby adhesionto the concretethroughoutthe rangeofjoint movement. Thecommonlyusedmaterialsarebasedon asphalt,bitumen,or coal tar pitchwith or without fillers, such as lime stone or- slate dust, asbestosfibre,choppedhemp,rubber or other suitable material. ‘These are usuallyapplied after constructionor just before tbe reservoiris put into servicebypouring in the hotor cold state,by trowelling or gunningor as preformedstripsironed into position. Thesemayalso beappliedduringconstructionsuchas bypackinground the corrugationof a waterbar. A primeris oftenised to assist adhesionandsomelocal drying of the concretesurfacewith:he help of a blow lamp is advisable. The length of the shortestwater

21

IS 3370(Part I) - 1965

path through the concreteshould be extendedby suitabLy painting thesurfaceof theconcreteon eitherside of thejoint.

Themain difficulties experiencedwith this classof material are inobtaining permanentadhesionto the concreteduring movementof thejoint whilst at the sametimeensuringthat the materialdoesnot slump oris not extrudedfrom tlsejoint.

In floor joints, the sealingcompoundis usually applied in achaseformed in the~surfaceof the concrete along the line of the joint (seeFig. 7C). The actualminimumwidth will dependon the known charac-teristics of the material. In the caseof an expansion joint, the lower partof thejoint is occupiedby a joint filler (seeFig. 7F). Thistype ofjoint isgenerally quite successful since retention of the material is assistedbygrayity and, in many cases,sealing can be delayed until just before thereservoiris put into servicesothatthe amountofjoint openingsubsequentlyto he accommodatedis quite small. The chaseshouldnot be too narrowor too deep to hinder completefilling andthe length of the shortestwaterpath through the concreteshould be extendedby suitably painting thesurfaceof the concreteon either side of the joint. Here againa widerjoint demandsa smallerpercentagedistortion in thematerial.

An arrangement incdrporating a cover slab, similar to that shown inFig. 7G, may be advantageousin reducingdependenceon the adhesionofthe sealingcompoundin direct tension.

Using of sealing compoundsfor verticaljoints is not verysuccessful.A stepped-jointinsteadof a straight through-jointwith a water bar incor-poratedin thejoint andsealingcompoundpacked round the corrugationof the waterbar would be muchmoresuccessful.

9. CONSTRUCTION9.0 Unless otherwise specilied in this code, and subject to the followingadditional recommendations, the provisions of IS : 456.1964* andIS: 1343-1960tshall apply to the constructionof reinforcedconcreteandprestressedconcreteliquid retainingstructures,respectively.

9.1 Thick Sections— The precautionsnecessaryin the constructionofthick sectionsshall be observedas perrequirementsof 7.

9.2 Joints —Jointsshall be constructedin accordancewith requirementsof 8.

9.3 Mixing and Placing of PneumaticMortar

9.3.1 Mixing — The aggregate and cement should be mixed in an

approvedmechanicalmixer and delivered from an approvedmechanical*Code of practice for plain and reinforcedconcrete(secondrevision).

•Codeof practicefor prestressedconcrete.

22

IS: 3370 (Part I) - 1965

digester. The minimum amount of water should be injected into themixture as this will ensure maximumdensity of the mortar.

9.3.2 Placing — The pneumatic mortar should be applied with anapprovednozzleby a skilled operator. The velocity of the material leav-ing the nozzle should be maintained uniform and should be such as toproduceminimum reboundof sand.

9.3.3 Curing — Immediatelyafter pneumaticmortar has beenplaceditshould be protectedagainst premature drying by shadingfrom strongsunshineand shielding from the wind. As soon as it has hardenedjustsufficiently to avoid damageit shouldbe thoroughly wettedandthereafterkept wet continuously for at least seven days. Adequate protectionagainstfluctuations in temperatureby shadingand shielding, shall alsobe given.

9.4 Construction of Floors

9.4.1 Floors Foundedon the Ground

9.4.1.1 The ground should be covered with an at least 75 mmthickplain concretescreedof compositionas describedin 6.1.4.4.Floorscastonthe ground should be in not less than two layers, the bottom layer of whichmay comprise or replace the plain concrete screed. When the screedformsan integral part of the floor slab forming one of the two layersthen themix for screedshall conformto the requirementsof 3.

9.4.1.2 A layerof building paperor othersuitablematerialshould belaid betweensuccessivelayers.

9.4.1.3 The layers, other than the plain concretescreed, if used,shouldbe placed in panels,the sidesof which shouldnot exceed7’S m inthe caseof reinforcedslabsand4’S m in the caseof plain slabs.

The tendencyfor the developmentof cracksin the upper layer ofpavingslabor a reservoirfloor is greatlydiminishedif the reinforcementisdiscontinuousthrough the joints and it is recommendedthat the floorpanelsbe laid in chessboardfashion ( all the ‘black or all the ‘white’squaresfirst). The edgesof the panelsin the bottomlayer may bebutt-jointed andthe panelsin thevarious layers shouldbe arrangedto breakjoint.

9.4.2 SuspendedFloors — Floors which arenot directly supportedon theground shouldbe cast in panels, the sides of which should not exceed7’S m. At joints in suspendedfloors, the surfaceof the panelsfir a widthnot less than the thicknessof the panelon eachside of the joint should beprimed andpaintedwith at leasttwo coatsof bituminousor otherapprovedpaint.

23

IS:3370 (Part I).1965

9.4.3 Junction of Floor and Walls— Where the wall is designedto bemonolithic with the bottomslab,a suitablearrangementof reinforcementand form-work shall be madeto facilitate theform-work to fit tightly andavoid leakageof cementpastefrom newlydepositedconcreteas such leak-ageif allowed to takeplaceis very liable to causeporosityin thefinishedconcrete. One such arrangementis by providing a continuousupstandsectionof the wall castat the sametime, as, andintegrally with, the slab;the height of this upstand must be sufficient to enable the next lift ofform-work to fit tightly and avoid leakageof the cementpastefrom thenewly depositedconcrete.

9.5 Construction of Wails

9.5.1 In all caseswhere the reinforcingsteelis discontinuousat verticalcontraction joints, the walls should be constructed in alternatepanelswithaslong a pauseas practicablebeforethe concreteis placedin theinterven-ing panels.

9.5.2 Where the reinfQrcementis continuousthroughverticaljoints inwalls, construction in alternate panels may result in a greater tendency tothe developmentof cracks in those panels which are cast between twoearlier placed panels, the existenceof which increases restraint of thenaturalshrinkageof the intermediatepanel.

9.5.3 The height of any lift should not exceed 2 m unlessspecialprecautionsare taken to ensure through compaction throughout bymechanicalvibration or by othersuitablemeans.

9.5.4 Ali vertical joints shouldextendthe full height of the wall in un-brokenalignment.

9.6 SurfaceFinish to PrestressedConcreteCylindrical Tanks — Thecircumferentialprestressingwires of a cylindrical tank shouldbecoveredwith a protective coat, which may be pneumaticmortar, having a thick-nessthat will provideaminimumcoverof 40 mm over thewires.

9.7 Formwork

9.7.1 RemovalofFormwork— The requirementsshallconformto 20.2.3of

IS 456~l964*.9.7.2 Bolts passingcompletely through liquid-retaining slabs for the

purposeof securingand aligning the form-work shouldnotbe usedunles~effectiveprecautionsare takento ensurewater-tightnessafter removal.

9.8 LinIng of Tanks — The type of liquid to be stored shouldbe consi-deredin relationto thepossibilityof corrosionof thesteelor attackonthe

•Codeorpracticefbr plain andreinforcedconcrete (secondrevision).

24

IS: 3370(Part I). 1965

concrete. Provisionof an impermeableprotectivelining should be consi-dered for resistanceto the effects of corrosive liquids. Certain naturalwaters exhibit corrosive characteristics and in suchcasesit is important toobtain adenseimpermeableconcreteand with a higher cement content.An increasedcoverto the steelis alsodesirable. Useof sulphate resistingportland cement,pozzolanacement,or blast-furnanceslag cement may incertaincasesbe advantageous.

10. TESTS ON STRUCTURE

10.1 In addition to the structuraltest of the structure,as given in 21.3 ofIS: 456.1964*, the tanks shall also be teste4 for watertightnessat fullsupply level as described in 10.1.1,10.1.2and10.1.3.

10.1.1 In the caseof tanks whose external faces are exposed such aselevatedtanks, therequirementsof the testshall be deemedto be satisfiedif the externalfacesshow no signs of leakageand remain apparentlydryover the periodof observationof sevendays after allowing a sevendayperiod for absorptionafterfilling.

10.1.2 In the caseof tankswhoseexternalfacesare submergedand arenotaccessiblefor inspection,suchas undergroundtanks,the tanksshall befilled with water andafter the expiry of seven days after the filling, thelevel of the surfaceof the water shall be recorded. Thelevel of the watershall be recordedagainat subsequentintervals of 24 hours over a periodof sevendays. The total drop in surfacelevel overa period of sevendaysshall be takenas an indication of the watertightnessof the tank. Theengineer-in-chargeshall decide on the actual permissiblenature of thisdrop in thesurfacelevel, taking into accountwhether the tanks are openor closedandthe correspondingeffect it has on evaporationlosses. Formany purposes,however,undergroundtankswhosetop is coveredmay bedeemedto be water-tightif the total dropin the surfacelevel overaperiodof sevendaysdoesnot exceed40 mm.

10.1.3 If the structuredoesnot satisfy the conditions of test, and thedaily drop in waterlevel is decreasing.the periodof testmay be extendedfor a further sevendaysandif specified limit is then reached,the structuremay be consideredas satisfactory.

Code of practicefor plain and reinforcedconcrete ucondreoiswn).

25