workmanship on building sites

8/6/2019 Workmanship on Building Sites

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Materials, Handling, PreparationMaterials, Handling, Preparation

SafetySafety

Cement, when mixed with water, releasesCement, when mixed with water, releases

alkali; take precautions to avoid dry cementalkali; take precautions to avoid dry cement

entering the eyes, mouth and nose when mixingentering the eyes, mouth and nose when mixingconcreteconcrete

Prevent skin contact with wet cement orPrevent skin contact with wet cement or

concrete by wearing suitable protective clothingconcrete by wearing suitable protective clothing

If cement or concrete enters the eyes,If cement or concrete enters the eyes,

immediately wash it out thoroughly with cleanimmediately wash it out thoroughly with clean

water, seek medical treatmentwater, seek medical treatment


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ReadyReady--Mix Concrete DeliveryMix Concrete Delivery

Check Delivery TicketCheck Delivery TicketSerial number and date, truck numberSerial number and date, truck number

Name of the Purchaser, Location of the SiteName of the Purchaser, Location of the Site

Grade of Concrete orMix proportion, SpecifiedGrade of Concrete orMix proportion, Specifiedworkability, Min Cement Content, Cement Typeworkability, Min Cement Content, Cement Type

Nominal max size of AggregateNominal max size of Aggregate

Proportion of FlyProportion of Fly--Ash / GGBS in the MixAsh / GGBS in the MixMax Free w/c Ratio, Type of Admixture, dosageMax Free w/c Ratio, Type of Admixture, dosage

Quantity of Concrete, Time of loadingQuantity of Concrete, Time of loading

Any other items specifiedAny other items specified


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Handling and Site StorageHandling and Site Storage

ReinforcementR

einforcementKeep clean; store reinforcement of ground;Keep clean; store reinforcement of ground;cover with polythene sheet to prevent corrosioncover with polythene sheet to prevent corrosion

Do not permit rusting; if necessary cover theDo not permit rusting; if necessary cover the

steel to exclude rain, but allow good circulationsteel to exclude rain, but allow good circulation

of air all around the steelof air all around the steel

Store different sizes separately from each otherStore different sizes separately from each other

and ensure that they are clearlyand ensure that they are clearly labelledlabelled

Dirt / grease prevents proper bond with theDirt / grease prevents proper bond with the

concreteconcrete


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Storing AccessoriesStoring Accessories

Binding wire, joints sealants, water bars, coverBinding wire, joints sealants, water bars, cover

blocks, spaces, admixtures, release agents etcblocks, spaces, admixtures, release agents etc

in conditions and temperatures such that theyin conditions and temperatures such that they

do not deteriorate, becomes damaged, soiled ordo not deteriorate, becomes damaged, soiled orcontaminatedcontaminated


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InIn--Situ ConcreteSitu Concrete

Weather ConditionsWeather ConditionsHot weather: Take precautions to ensure thatHot weather: Take precautions to ensure thatthe temperature of concrete is not higher thanthe temperature of concrete is not higher than

3030oo C at the time of placingC at the time of placing

Cold weather: The temperature of concreteCold weather: The temperature of concreteshould not fall below 5should not fall below 5oo C at any time duringC at any time during

placing and compacting; place the concreteplacing and compacting; place the concrete

quickly; do not place concrete against frozen orquickly; do not place concrete against frozen orice and snow covered surfacesice and snow covered surfaces

Ensure that the concrete temperature is at leastEnsure that the concrete temperature is at least

1010oo C, insulate the concrete surfaceC, insulate the concrete surface


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Preparation for ConcretingPreparation for ConcretingClean all rubbish, debris, free water from allClean all rubbish, debris, free water from all

surfaces on to which the concrete is to besurfaces on to which the concrete is to be

poured; remove wire nails, screws etc in thepoured; remove wire nails, screws etc in thecase of formworkcase of formwork

General inspection: Check availability ofGeneral inspection: Check availability of

Materials including RMC, Labor, Plant andMaterials including RMC, Labor, Plant and

Equipment, Power and Water Supply, StandbyEquipment, Power and Water Supply, StandbyEquipment and SparesEquipment and Spares

Confirm setting out checkingConfirm setting out checking


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Preparation for ConcretingPreparation for ConcretingConfirm inspection earlier permanent workConfirm inspection earlier permanent work

If appropriate, obtain weather forecastIf appropriate, obtain weather forecast

Check adequacies of access to points ofCheck adequacies of access to points ofdischarge and access platformsdischarge and access platforms

Check readiness of the batching plantCheck readiness of the batching plant

Check the communication systemCheck the communication systemConfirm arrangements for transporting, placing,Confirm arrangements for transporting, placing,

compacting, finishing, curing and testingcompacting, finishing, curing and testing


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Preparation for ConcretingPreparation for Concreting--Earth FacesEarth Faces

When concreting against earth surfaces, check:When concreting against earth surfaces, check:

Stability of earth slopesStability of earth slopes

Safety of earth faces when construction plantSafety of earth faces when construction plantis in operationis in operation

Arrangements for removal of waterArrangements for removal of water


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InIn--Situ ConcreteSitu ConcretePreparation for ConcretingPreparation for Concreting--Joints etcJoints etc -- CheckCheck

Construction of joints, dowels, water bars etcConstruction of joints, dowels, water bars etc

Inserts and boxInserts and box--outs for accuracy and securityouts for accuracy and security

Fixing of stop endsFixing of stop endsArrangement for forming kickersArrangement for forming kickers

Preparation of hardened surfacesPreparation of hardened surfaces


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Reinforcement CheckR

einforcement CheckSize, type, markings, location and cover areSize, type, markings, location and cover are

correctcorrect

Anchorages and laps are correctAnchorages and laps are correctThat it is rigidly securedThat it is rigidly secured

Surface conditionSurface condition

Use of spacers including type and sizeUse of spacers including type and sizeThe aim of preThe aim of pre--concreting check is to ensureconcreting check is to ensure

that concreting proceeds without delay / defectsthat concreting proceeds without delay / defects


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Sampling and TestingSampling and TestingFollow appropriate procedures, usingFollow appropriate procedures, using

equipment in good working orderequipment in good working order

Complete certificates of sampling, cube making,Complete certificates of sampling, cube making,curing and testing to confirm compliance withcuring and testing to confirm compliance with

SpecificationsSpecifications

Transport concrete cubes to the lab ensuringTransport concrete cubes to the lab ensuring

that they are kept moist, are not damaged andthat they are kept moist, are not damaged and

spend the minimum time in transitspend the minimum time in transit


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Sampling and TestingSampling and TestingThe procedures for sampling, specimenThe procedures for sampling, specimen

making, curing and testing given in IS:516 &making, curing and testing given in IS:516 &

IS:1199 are very detailed and involve the use ofIS:1199 are very detailed and involve the use of

well maintained standard equipment confirmedwell maintained standard equipment confirmed

at regular intervals to comply with theat regular intervals to comply with the

appropriate Standardsappropriate Standards

Cubes should be stored and tested at anCubes should be stored and tested at anaccredited laboratory; store specimens underaccredited laboratory; store specimens under

controlled temperature (27controlled temperature (27oo C inC in 33oo C)C)


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Sampling and TestingSampling and TestingDeviations from standard requirements canDeviations from standard requirements can

affect results significantly and may lead toaffect results significantly and may lead to

errors in judgment concerning the quality of theerrors in judgment concerning the quality of the

concreteconcrete

Supervision of personnel trained in theSupervision of personnel trained in the

procedures is essentialprocedures is essential

The use of a laboratory accredited for siteThe use of a laboratory accredited for site

sampling and specimen making issampling and specimen making is

recommendedrecommended


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Placing ConcretePlacing ConcretePlace concrete in one continuous operationPlace concrete in one continuous operation

between and up to the construction joints orbetween and up to the construction joints or

other limiting featuresother limiting features

Discharge concrete through the reinforcementDischarge concrete through the reinforcement

or other obstructions with care; avoid dispersal,or other obstructions with care; avoid dispersal,

segregation or loss of ingredientssegregation or loss of ingredients

Where reinforcement is congested use chutesWhere reinforcement is congested use chutes

or trunking to direct the concrete into positionor trunking to direct the concrete into position

If interrupted, form additional construction jointIf interrupted, form additional construction joint


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Displacement while placing ConcreteDisplacement while placing ConcreteWhile placing, ensure no displacement orWhile placing, ensure no displacement or

damage occurs todamage occurs to

damp proof membranesdamp proof membranesreinforcementreinforcement

formwork orformwork or

embedded fittingsembedded fittingsIf displacement occurs, take corrective actionIf displacement occurs, take corrective action

immediately; necessary labor to be availableimmediately; necessary labor to be available


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Compacting ConcreteCompacting ConcreteCompact the concrete ensuring thatCompact the concrete ensuring that

a) it forms a solid uniform mass free of voidsa) it forms a solid uniform mass free of voids

b) it is packed tight around the reinforcementb) it is packed tight around the reinforcementc) it fills all parts of formwork or excavationc) it fills all parts of formwork or excavation

d) there is no segregation of ingredientsd) there is no segregation of ingredients

e) it is amalgamated with previous batchese) it is amalgamated with previous batchesf) there is no damage to adjacent concretef) there is no damage to adjacent concrete

g) the required finish will be obtainedg) the required finish will be obtained

h) vibrators are operated by trained personnelh) vibrators are operated by trained personnel


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InIn--Situ ConcreteSitu ConcreteDeep Sections, Walls, Columns, BeamsDeep Sections, Walls, Columns, Beams

Place and compact concrete in layers; eachPlace and compact concrete in layers; each

layer should extend over the length and width oflayer should extend over the length and width of

the section; place succeeding layers withoutthe section; place succeeding layers without

delay and merge them, by compaction, with thedelay and merge them, by compaction, with the

layer belowlayer below

Check for plastic settlement cracking and reCheck for plastic settlement cracking and re--

vibrate as necessaryvibrate as necessary


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Surface FinishSurface FinishFill formwork at a steady rate to allow sufficientFill formwork at a steady rate to allow sufficient

time for compaction, but avoid cold jointstime for compaction, but avoid cold joints

between succeeding layersbetween succeeding layers

Do not permit the vibrator to touch any faces ofDo not permit the vibrator to touch any faces of

the formworkthe formwork

Vibrate thoroughlyVibrate thoroughly

Provide uniformed finish as specifiedProvide uniformed finish as specified

Avoid contact between the formwork face andAvoid contact between the formwork face and

the vibratorthe vibrator


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CuringCuringCuring period: 7 days for concrete surfacesCuring period: 7 days for concrete surfaces

subject to direct wear or abrasionsubject to direct wear or abrasion

10 days; cure and insulate10 days; cure and insulatesections 300 mm or less in thickness when thesections 300 mm or less in thickness when the

average air temperature is 7average air temperature is 7oo C or lessC or less

Curing compound: A oneCuring compound: A one--time application oftime application of

curing compound at the earliest is deemed tocuring compound at the earliest is deemed to

satisfy the requirements of this clausesatisfy the requirements of this clause


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FormworkFormwork

Fix all props and struts vertically and whereFix all props and struts vertically and where

necessary brace them; provide sole plates andnecessary brace them; provide sole plates and

seat them firmly throughout their lengthseat them firmly throughout their length

Seat all supports adequately and securely onSeat all supports adequately and securely on

their bearingstheir bearings

Fix stop ends securelyFix stop ends securely

Align forms correctly and ensure their levelAlign forms correctly and ensure their level

Reference:Reference: Formwork: Guide to Good PracticeFormwork: Guide to Good Practice

issued by The Concrete Society, UKissued by The Concrete Society, UK


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FormworkFormwork

ConstructionConstruction

Construct formwork to soffits with any preConstruct formwork to soffits with any pre--

camber necessary to allow for deflection of thecamber necessary to allow for deflection of the

formwork; any specified preformwork; any specified pre--camber is forcamber is for

concrete itself. Any preconcrete itself. Any pre--camber to allow forcamber to allow for

deflections of formwork is in addition to thisdeflections of formwork is in addition to this

Construct joints in formwork and betweenConstruct joints in formwork and between

formwork and completed work to prevent loss offormwork and completed work to prevent loss ofgrout. Use foam plastics strip seals, if requiredgrout. Use foam plastics strip seals, if required

Do not overstress the tie boltsDo not overstress the tie bolts


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FormworkFormwork

Cleaning and TreatmentCleaning and Treatment

Before each use of formwork:Before each use of formwork:

a) clean the contact surfaces and dry thema) clean the contact surfaces and dry them

before applying a release agentbefore applying a release agentb) ensure the release agent is appropriateb) ensure the release agent is appropriate

to the surface to be coatedto the surface to be coated

c) coat formwork surfaces evenly and thinlyc) coat formwork surfaces evenly and thinlywith release agent; treat vertical surfaceswith release agent; treat vertical surfaces

before horizontal surfaces and wipe off thebefore horizontal surfaces and wipe off the

excessexcess


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FormworkFormwork Striking TimeStriking Time

Remove the formwork only when the concreteR

emove the formwork only when the concretehas developed sufficient strength; the surface ofhas developed sufficient strength; the surface of

the concrete should not be damaged; thethe concrete should not be damaged; the

structure itself is not overloaded in relation tostructure itself is not overloaded in relation to

the strength reached and there is no excessivethe strength reached and there is no excessivedeflection in structural membersdeflection in structural members

Prop as necessary after striking the formworkProp as necessary after striking the formwork

The concrete strength is assessed by testingThe concrete strength is assessed by testingcubes prepared for the purpose or by referencecubes prepared for the purpose or by reference

to Tables ofMinimum Striking Timesto Tables ofMinimum Striking Times


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FormworkFormwork -- Striking TimesStriking TimesType ofType of

FormworkFormwork

Minimum PeriodMinimum Period

Surface Temp ofSurface Temp ofConc above 16Conc above 16oo CC

before Strikingbefore Striking

Surface Temp ofSurface Temp ofConc 7Conc 7oo CC

Vertical formworkVertical formwork

Columns, Walls,Columns, Walls,BeamsBeams

12 hours12 hours 24 hours24 hours

Soffit formwork toSoffit formwork to

slabsslabs

4 days4 days 6 days6 days

Props to slabsProps to slabs 10 days10 days 15 days15 days

Beams soffitBeams soffit 10 days10 days 15 days15 days

Props to beamsProps to beams 14 days14 days 21 days21 days


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FormworkFormwork

Making good after StrikingMaking good after Striking

Remove fins etc from the surfaceRemove fins etc from the surface

Fill in tie holes with 1:3 semiFill in tie holes with 1:3 semi--dry mortar welldry mortar well

rammed in and finished flush with the face oframmed in and finished flush with the face ofthe concrete; fill blow holes exceeding 5 mmthe concrete; fill blow holes exceeding 5 mm

across with 1:1.5 mortar rubbed inacross with 1:1.5 mortar rubbed in

Take care on permanently exposed concreteTake care on permanently exposed concrete

surfaces; if strength and durability cannot besurfaces; if strength and durability cannot be

assured, agree procedures for repair orassured, agree procedures for repair or

replacementreplacement


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ReinforcementReinforcement

While fixing reinforcement, check the type ofWhile fixing reinforcement, check the type of

steel (Fe 415 / Fe 500) is correct for its locationsteel (Fe 415 / Fe 500) is correct for its location

Steel properties vary, use of lower qualitySteel properties vary, use of lower quality

reinforcement could result in structural failurereinforcement could result in structural failure

Bend reinforcement cold on proper bending m/cBend reinforcement cold on proper bending m/c

Cut and bend bars in accordance with the ISCut and bend bars in accordance with the IS

Do not straighten or reDo not straighten or re--bend bars withoutbend bars without

instructions; if reinforcement temperature isinstructions; if reinforcement temperature isbelow 5below 5oo C obtain instructions before bendingC obtain instructions before bending

workmanship on building sites

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