concrete ppt

8/3/2019 Concrete Ppt

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PROJECT PRESENTATIONPROJECT PRESENTATION

QUALITY CONTROQUALITY CONTROININ

MANUFACTURING OF MANUFACTURING OF

SLABSSLABS

UNDER THE GUIDANCE OFUNDER THE GUIDANCE OF

Sh. S.GUPTA DEAN IRICESh. S.GUPTA DEAN IRICEN

SUNIL MSUNIL MCHARANCHARAN

AGYAPAAGYAPA

Why PSC ?

RCC has certain disadvantage

– Large deflection

– Inevitable Cracks– Reduced stiffness

– Unsuitable for large spans as DL b

ADVANTAGES OF PS

1. Better utilization of section henc

saving in material.

2. Better shear resistance

3. Lighter & slender members du

concrete strength & steel

4. Crack-free structure

5. Improved durability

ADVANTAGES CON

1. Economical for high spans

2. Better fatigue strength for dynamic

loaded structures.

3. Lower maintenance vis-à-vis steelvery suitable for structures in the vi

of OHE

4. Very suitable for pre-cast constru

hence faster

Prestressing BedPrestressing Bed

The bed should be strong enough to strand force after stressing without abuckling or bending(specially ancho

The C.G of stressing bed and the C.Gstrand profile should match perfectlyotherwise there is maximum chancesdeformation.

The base alignment should be parallstrand in PSC slabs. Uneven in level

the moulds or press the mould end por after stressing.

. Suppose there are five moulds in a stressing b

mould’s level is 5mm below the required lev

mould is 8mm above the required level, in th

below level mould will get lifted after stressi

This will not only increase the depth of slab b

also affect the perfect bonding of pre-stressedafter concreting.

The quality of that particular slab will be poo

poor bonding property, even though the qual

concrete is excellent. In case of lifted base lefriction will take place during stressing.

Due to this friction force, the pressure gau

false reading. Suppose 100 ton load is app

show 105 tons. In other words, if 100 ton

be applied, but in case of friction, it may s

ton at 95 tons applied load. Friction may r

under-stressing.

The wire position should be perfect adrawing. The inspecting engineer sh

each and every mould and plates for

dimension and cable position.

All PSC slabs moulds should be made of

quality, suitable thickness plate (min. 6mm

should have smooth surface finish

The bottom base should be locked with nu

provision and a top tie rod should be prov

every 1.5 meter to avoid bulging of mould

concreting.

Only good quality mould oil should be us

excess oil at the bottom of mould base sho

wiped out with cloth.

SteelSteel

Procure HSYD steel from ISI approved

manufacturers

Test it from govt approved labs and do vi

e.g. rust,blowholes,pits etc.

After receiving satisfactory test results fro

laboratory, steel should be used for reinfo

purpose.

HTS StrandHTS Strand

HTS wire should be procured from BISmanufacturers. Each and every consignm

have manufacturers test certificate. Onc

material is received, test sample should

laboratory for testing.

The following are the important tests of

1. Elongation percentage

2. Cross-section area

3. Lay length4. Yield stress

5. Breaking load

The most important is yield stress. This pla

role in the quality of pre-stressed concrete.strands after stressing should be in elastic l

stress is not upto the mark, it may go into p

that case, pre-stress losses will be more. Th

care should be given on this account. The manufacturer test result should be com

lab test reports. If variation in results if bey

permissible limits, the consignment should(

: The first consignment of HTS wire should

relaxation test certificate.

HTS StrandHTS Strand

The wedges and barrels should be procurereputed manufacturer.

It should be ensured that the barrels wont

after stressing. This can be verified by che

slipping.

The jack should be good quality and sho

free from oil leakage. A spare jack must

available at site in case of failure. This i

Necessary spares should be available, ie

Two pressure gauge should be calibrreputed laboratory. Both the gauges fixed to the hydraulic machine durinstressing operation. The reading of b

pressure gauge should be same after correction factor as per calibration c

One gauge to be removed from machshould be kept in safe custody of as

gauge. The master gauge can be usedof any doubt.

Stressing OperationStressing Operation

This should be done very carefully. Alwa

should be applied gradually. First, 5 or 10

required load should be applied and elong

should be measured. This is being done to

any sags in the strand, as practically it is n

to fix a sag free wire.

The first reading should be noted as initia

Then strand should be stressed to be requ

maximum load. Then note down the finalBy deducting initial reading from the fina

we get elongation of a strand.

This can be cross checked with test certificby following formula:

L=PL/AE

P= load applied

L= length of HTS strand form wedge end tend.

A= actual cross-section area of the strand.

E= modulus elasticity of steel.

1. Stressing record of each and every strand s

2. The elongation should be within permissiblper I.S specification.

Ingredients of concreIngredients of concre Cement

Aggregates

– Fine

– CoarseTogether these occupy 70-75% of total vo

Water – Though indispensable- its be controlled

Admixture – optional but desirablestrength concrete.

FIELD TESTINGFIELD TESTING

of cementof cement

Date of manufacture –

Because aging reduces the strengt

Open the bags – No lumps shouldpresent (Mean no setting)

Thrust your hand into the cementshould be cool feeling (means no hydration no setting)

Pinch of cement between fingers-give smooth feeling (means no se

Period of storage %age of 28

streng

Fresh 100%

3 months 80%6 months 70%

12 months 60%

24 months 50%

FIELD TESTINGFIELD TESTING ContdContd

Handful of cement thrown on wshould float initially before fina

settling

Take 100 gm of cement, make paste, prepare cake with sharp e

on glass plate and Immerse in w

– Shape shouldn’t be disturbed– It should set and attain strength.

LABORATORY TESTLABORATORY TEST --ii

Fineness of cement

100 gm cement taken

Hand sieving for 15 minutes on 90 µ IS

Residue on sieve weighed

• For OPC - limit of residue = 10%

• PPC,HSOPC, SGC- residue = 5%

More fineness increases only the early stre

the ultimate strength.

QUALITY CONTROL IN CEMQUALITY CONTROL IN CEM

Obtain test certificate from company

Every bag should carry these markin

– Ref. to IS : specification

– Wt. of bag in Kg or other method

– Week/year of packing i.e. 33/2002

– Type of cement

Record of daily variation in cement s

tested in plant

Good plants will not hesitate in providing

AGGREGATESAGGREGATES

FINE AGGFINE AGG Which passes through 4.75 mm IS

(5-10% oversize permitted by IS : 3

1970) Coarse Agg : Which are retained o

mm IS : sieve

(5-20% passing the sieve are permi

PHYSICAL PROPERTIES OFPHYSICAL PROPERTIES OF

contdcontd

Texture

– It defines the surface of aggregates

Smooth – Requires less cement– Permits denser packing

– Permits better workabil

Rough – High bond strength in tens

• Requires more cement

PHYSICAL PROPERTIPHYSICAL PROPERTI

ABSORPTION– Bone dry aggregates absorbs certain a

water. It affects

Workability

W/C ratio Durability

– Porosity affects durability as it is harm

conditions of alternate freezing and th

(But the rate and amount of absorption i

only up to final setting time.)

PHYSICAL PROPERTIPHYSICAL PROPERTI

ABSORPTION– Bone dry aggregates absorbs certain a

water. It affects

Workability

W/C ratio Durability

– Porosity affects durability as it is harm

conditions of alternate freezing and th

(But the rate and amount of absorption i

only up to final setting time.)

Agg drynessAgg dryness Bone Dry- When internal pores are

Air Dry- When some of the pores a

Saturated Surface Dry (SSD)- Whepores are filled.

Moist - When all the pores are fillewater is also sticking on surface

SALT CONTAMINATSALT CONTAMINAT

Sea dredged aggregates have problem contamination

These shouldn’t be used for PSC work

If permission granted in spl. case, th

washed &i) Chloride content shouldn’t be more t

0.04% (by wt. of FA)

0.02%(by wt. of CA)

ii)Sulphate content shouldn’t be more 0.4% (by total wt. of FA & CA )

WATERWATER

It should be clean &free fromoils,acids,alkalis,salts,sugar,org

materials etc.The pH value not less than 6.

If water is satisfactory for mixisafe for curing.

No strain on curing

LimitsLimits

Chlorides shouldn’t be more than 10,00Sulphates shouldn’t be more than 3,00

Turbidity shouldn’t be more than 2,00

Carbonate & bi Carbonate if more

2,000 ppm tests for setting time

strength be conducted

MIXINGMIXING

MIXING TIME

25 to 30 revolution @ 15

minimum required for prope

Therefore 2 minute mixing i

Mixing is faster in natural a

WorkabilityWorkability

Compactibility- or ease withconcrete can be compacted

Mobility- or ease with which

can flow into formwork & arreinforcement.

Stability- or ability of concreremain stable, cohesive and

homogeneous mass while havibrating without segregation

SLUMP TESTSLUMP TEST

Vessel shape – frustum of cone of 30

10 cm. dia at top & 20 cm at bottom

Concrete filled in four layers eachcompacted with 25 strokes of bullet p

16 mm dia, 60 cm long, steel rod.

Cone is removed & concrete allowed

settle vertical settlement is ‘SLUMP.

FACTORS AFFECTING WORKAFACTORS AFFECTING WORKA

Size of particles

CA/FA ratio

Particle interference – gap grading

Shape of aggregates

Admixtures – Air entraining agentspozzolanas.

Effect of inadequaEffect of inadequat

workabilityworkabilityHoney combing

Less strength

Less durability

Spacing tipsSpacing tips

Overlapping field of action

Watch the concrete

High powered vibrators

High slump concrete

Field of action 8 times vibrahead diameter

Stop vibrationStop vibration -- whenwhen

Concrete surface- shiningappearance

Large air bubbles no longer

Vibration change pitch or to

Over vibration is preferable

under vibration

CURING OF CONCRECURING OF CONCRE

Curing is a procedure used for

– Promoting the hydration of cement

– Control of temp and humidity As a result of curing

– Strength is improved

– Durability is improved and permeabil

concrete is reduced.

PERIOD OF CURINGPERIOD OF CURING

As per IS : 456 for OPC –

As per IRS : CBC for OPC –

Curing mainly depends upon

– Type of cement

– Ambient atmospheric condition

– Mass to surface area ratio

concrete ppt

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