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PROJECT PRESENTATIONPROJECT PRESENTATION
ONON
QUALITY CONTROQUALITY CONTROININ
MANUFACTURING OF MANUFACTURING OF
SLABSSLABS
UNDER THE GUIDANCE OFUNDER THE GUIDANCE OF
Sh. S.GUPTA DEAN IRICESh. S.GUPTA DEAN IRICEN
BYBY
SUNIL MSUNIL MCHARANCHARAN
AGYAPAAGYAPA
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Why PSC ?
RCC has certain disadvantage
– Large deflection
– Inevitable Cracks– Reduced stiffness
– Unsuitable for large spans as DL b
high
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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
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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
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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.
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. 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.
Prestressing BedPrestressing Bed
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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.
Prestressing BedPrestressing Bed
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The wire position should be perfect adrawing. The inspecting engineer sh
each and every mould and plates for
dimension and cable position.
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All PSC slabs moulds should be made of
quality, suitable thickness plate (min. 6mm
should have smooth surface finish
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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.
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Only good quality mould oil should be us
excess oil at the bottom of mould base sho
wiped out with cloth.
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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.
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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
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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(
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: The first consignment of HTS wire should
relaxation test certificate.
HTS StrandHTS Strand
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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.
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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
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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.
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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.
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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.
NOTE:
1. Stressing record of each and every strand s
kept.
2. The elongation should be within permissiblper I.S specification.
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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.
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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
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Period of storage %age of 28
streng
Fresh 100%
3 months 80%6 months 70%
12 months 60%
24 months 50%
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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.
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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.
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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
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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
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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
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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.)
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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.)
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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
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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 )
(C
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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
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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
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MIXINGMIXING
MIXING TIME
25 to 30 revolution @ 15
minimum required for prope
Therefore 2 minute mixing i
Mixing is faster in natural a
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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
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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.
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FACTORS AFFECTING WORKAFACTORS AFFECTING WORKA
Water
Size of particles
CA/FA ratio
Particle interference – gap grading
Shape of aggregates
Admixtures – Air entraining agentspozzolanas.
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Effect of inadequaEffect of inadequat
workabilityworkabilityHoney combing
Less strength
Less durability
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Spacing tipsSpacing tips
Overlapping field of action
Watch the concrete
High powered vibrators
High slump concrete
Field of action 8 times vibrahead diameter
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Stop vibrationStop vibration -- whenwhen
Concrete surface- shiningappearance
Large air bubbles no longer
Vibration change pitch or to
Over vibration is preferable
under vibration
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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.
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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
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