QA QC_green conc

1. Quality Control & Quality Assurance
of concrete
Quality Assurance
It is a method for the
monitoring & evaluation of the
various aspects of concrete
construction to ensure the
guarantee of quality.
Quality Control
A series of analytical
measurements used
to assess the quality of
the analytical data
Quality assurance scheme is a management system , which
increases confidence that a material, product or service will
conform to specified requirements.

2. What are QA and QC?
QA consists of all the activities conducted by the
owner, agency, or its representatives in order to
confirm that the delivered product meets
specifications.
QC refers to various tests, inspections & all activities
conducted by the contractor (such as batching,
placing, and finishing) to ensure that the product will
meet project specifications.

3. The quality assurance system should have the following
basic parameters.
Site documents
Mandatory and optional testing
Availability of field and departmental laboratories
Manufacturing test certificates
Departmental team inspections
Checklist guide for works
Site inspections
Post quality testing of finished works
Quality certification
Monthly reporting and review meetings
QA/QC of concrete

4. IS guidelines for QA/QC of concrete
1. Sampling of concrete: IS 456 stipulates random samples
from fresh concrete as per IS 1199.Three fresh samples of
totaling not less than 0.02 m3 taken directly from mixture or
from placed concrete at time of placing collected for fresh
concrete tests & checking 28 days strength.
2.Three test specimens shall be made for each sample for
testing at 28 days. Additional samples may be required for
various purposes such as to determine the strength of
concrete at 7 days.
3.The specimen shall be tested as described in IS 516.
4.The test results of the sample shall be the average of the
strength of three specimens. The individual variation should
not be more than ±15 percent of the average.

5. IS guidelines for QA/QC of concrete
5. Structural design based on characteristics strength of
concrete, which is the strength of material below which not
more than 5% of the test results are expected to fall.
6. Target strength should be higher than characteristics
strength & calculated as f t = f ck + k s
Where, k= probability factor
S= standard deviation
7. Probability factor for tolerance, where not more than 5% of
test results (1 in 20) are expected to fall below
characteristics strength is 1.65 hence relation is
f t = f ck + 1.65 s

6. IS guidelines for QA/QC of concrete
8. IS 456 specified minimum frequency of sampling

7. IS guidelines for QA/QC of concrete
9. IS 456 demand that the concrete shall be satisfy the
strength requirement for mean strength as follows
M15 grade concrete:
f m mean strength ≥ f ck + 0.825 times standard deviation
or
f ck + 3 Mpa whichever is greater
With individual test sample result ≥ f ck − 3 Mpa
M20 or higher grade concrete:
f m mean strength ≥ f ck + 0.825 times standard deviation
or
f ck + 4 Mpa whichever is greater
With individual test sample result ≥ f ck − 4 MPa

8. IS guidelines for QA/QC of concrete
10. Standard deviation of each grade should be determine from
test strength results of samples-
Total no of test samples required should not be less than 30
When sufficient test sample results are not available then
values of standard deviation taken as follows (ref 456:2000)
Grade of concrete Assumed Standard Deviation in MPa
M15 3.5
M20 to M25 4.0
M30 to M50 5.0

9. Advantages of quality control of concrete
1. QC means a rational use of the available resources after
testing their characteristics & reduction in material costs.
2.In absence of QC there is no guarantee that over dosage of
one will compensate other thing like extra addition of 1 bag of
cement will not compensate for incomplete compaction or
insufficient curing.
3.In absence of QC at site ,the designer is tempted to
overdesign, so as to minimize the risk. This will increase cost.
4.QC assures checks at every stages of the production &
rectification of the faults at right time will reduce delay.
5. Finally QC reduces maintenance cost.

10. Quality control application in concrete construction
Transport of the concrete to the construction site.
Slump test of the concrete.
Pouring of the concrete.
Control of water addition.
Vibration/Compaction of the concrete.
Preparation of areas where different concrete pours are done.
Control of compression test samples
Control of formwork removal.

11. 1) To increase the slump & workability.
2) To increase or decrease initial setting time.
3) To increase strength of concrete
4) To reduce heat of hydration
5) To reduce shrinkage rate
6) To accelerate rate of strength gain in early age
7) To improve resistance to impact & abrasion.
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Functions of Admixtures
In concrete

12. 8) To increase resistance to chemical attack,
corrosion of steel
9) To reduce segregation and improve pump
ability, finish.
10) To increase bonding between steel & concrete
11) To produce colour concrete
12) To increase bonding between old & new
concrete
13) To reduced cost of concrete
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Functions of Admixtures
In concrete

13. Classification of Admixtures
• Mineral Admixture-
A)Natural pozzolana-
Clay & shale
Opalinc cherts
Diatomaceous earth
Volcanic tuffs &
Pumicites
B)Artificial pozzolana-
Fly ash
Blast furnace slag
Silica Fumes
Rice husk ash
Metakaoline
surkhi
• Chemical Admixture
Plasticizers
Super plasticizers
Accelerators
Retarders
Air entraining agents
Grouting
Waterproofing agents
Corrosion resisting
Bonding agents
Colouring admixtures
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14. Mineral Admixtures and Properties

15. Fly Ash: How it work in concrete?
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16. Advantages of fly ash
1) To reduce heat of hydration & thus reduce thermal cracks &
improve soundness of concrete.
2) To improve workability & pump ability
3) It convert released lime from hydration of OPC into additional
cementations material-contribute strength improvement.
4) Due to reaction between fly ash & liberated lime improves
permeability (pore refinement)
5) To reduce requirement of cement for same strength & reduce
cost of concrete.
6) Concrete using fly ash is generally show reduced segregation
and bleeding

17. Silica Fume
Properties
1. It is also referred as “microsilica”. It is an artificial pozzolanic
admixture.It is a by-product during the manufacture of silicon or
Ferro silicon alloy.
2. Spherical shape. Extremely fine ( particle size < 1 micron)
3. 100 times smaller than avg. cement particles.
4. Specific surface area 20000 m2/kg. Silica fume, is a highly active
pozzolan and has cement properties because of fine nature.
5. Water demand increase, workability reduce. Concrete with micro
silica causes produce more heat of hydration & initial plastic
shrinkage.
6. Reduce bleeding & no segregation.
7. With silica fume concrete become resistant to corrosion,
increase in strength & durability, control permeability.
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18. Plasticizers-(water reducers)
 Plasticizes is an admixtures used in concrete to improve
workability by reducing water content.
 They gives-
1. Better workability without increasing water
2. Which gives easy placement of concrete in poor locations
without vibrations.
3. True shutter finish for highly reinforced member.
4. Reduction in cement content
Typical water reducers reduce the water content by
approximately 5% to 15%.

19. Plasticizers-(water reducers)
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Cement particles are deflocculated & dispersed.
When they deflocculated water trapped in flocs get released.

20. Super plasticizers :(High-Range Water
Reducers HRWR)
• These admixtures are added to concrete for
production of flowing, self levelling, self
compacting and for production of high strength,
high performance concrete.
• They reduce water content upto 30%
• Dosage -1 to 2% by weight of cement
• workable concrete that can be placed with little
or no vibration or compaction while still free of
excessive bleeding or segregation.

21. Flow of mortar-workability
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22. Retarding Admixtures
1. Retarder is an admixture that slows down the
chemical process of hydration(rate of hydration)
2. Concrete remain in plastic & workable for long time.
We can place it without structural discontinuities.
3. They use to overcome the accelerating effect of high
temperature ,high humidity on concrete in hot
weather. ex. grouting oil wells.
4. Retarders do not decrease the initial temperature of
concrete.
5. They delay initial setting by forming a thin coating on
the cement particles & slow down their reaction with
water .

23. Accelerating Admixtures
 They added to concrete to accelerate or increase
the rate of early strength development in concrete
and shorten the setting time-
1.For earlier removal of formwork
2.Reduce period of curing
3.Structure can be place in service in advance
4.Compensate retarding effect of low temperature
during cold weather concreting-add calcium
chloride.
5.In emergency repair work- highway, bridge
6.Plugging leakage

24. Air-Entraining Admixtures
Increased resistance to freezing and thawing.
Improvement in workability.
Reduction in strength.
Reduces the tendencies of segregation.
Reduces the bleeding and laitance.
 Decreases the permeability.
Increases the resistance to chemical attack.
Permits reduction in sand content.
Improves place ability, and early finishing.
Reduces the cement content, cost, and heat of hydration.
Reduces the unit weight.
Permits reduction in water content.
Reduces the modulus of elasticity.

25. Corrosion resistancing
• The chlorides can cause corrosion of steel
reinforcement in concrete.
• Ferrous oxide and ferric oxide form on the
surface of reinforcing steel in concrete.
• Ferrous oxide reacts with chlorides to form
complexes that move away from the steel to
form rust. The chloride ions continue to
attack the steel until the passivating oxide
layer is destroyed.

26. Shrinkage-Reducing
Admixtures
• Shrinkage cracks,
such as shown on this
bridge deck, can be
reduced with the use
of good concreting
practices and
shrinkage reducing
admixtures.

27. Coloring admixtures
(Pigments)
• Red and blue
pigments were
used to color this
floor