1. Cement Concrete Mix Design and Quality ControlBy
Dr. Sunil Kumar
Professor
Department of Civil Engineering
Harcourt Butler Technological Institute
Kanpur

2. Major Advantages of Concrete Roads
Long life (30-40 yrs.)
Low maintenance cost
Fuel 14% for load carriers
Utilise up to 30% of fly ash – disposal of which is a great problem
Economical when life cycle cost is compared
Pollution free construction
Inconvenience to users due to less frequent repair
Good riding quality throughout life
No effect of spillage of oil

3. Conti….. Roads can withstand extremes of weather
Better performance over poor soil sub grade
Better light reflectivity
Safer night driving due to visibility
Fuel saving in road construction
Skid resistance
Good noise record
Conservation of material

4. Roads Through Villages
A common feature of village roads in the absence of any drainage arrangement
In most cases, the road level is low & water accumulate on them during rains, the road itself acting as a longitudinal drain
Such roads are frequently damaged after rains
If they are concreted, the damage can be minimise

5. What is concrete?
In very simple terms concrete can be looked upon as a conglomerate rock consisting of large aggregate particles embedded in the matrix of “paste”.
Paste is the mixture of water and cement.

6. Ingredients
Cement
Aggregates
Water
Admixtures

7. Basic Concrete Engineering
Good concrete
Proportioning of concrete mixes
Permeability and porosity of concrete

8. Good Concrete Method exist to determine only workability and strength
How do we work with other properties such as segregation resistance, durability etc ?

9. Expectation from Good Concrete
fresh state
Homogeneity
Workability
Segregation resistance
hardened state
Strength
Durability

10. Workability of Concrete

11. Strength of Concrete Ultimate Strength Strength of aggregates
Strength of mortar
Ultimate Strength
Inversely proportional to water cement ratio
Curing condition
Compaction
Quality of binder ( including use of admixture)

12. Durability of Concrete
Concrete is not a maintenance free material and required periodic inspection
Durability of concrete is determined through a complex interaction between parameters related to
Design of structures, such as permissible crack width, grade of concrete used and design cover to the reinforcement
Choice of appropriate material in construction
Quality control during construction maintaining good construction materials such as curing etc.
Environment in which structure is placed

13. Principles of Concrete Mix Design
Design involves proportion of the given constituents which would produce concrete possessing specifies properties on both in fresh and hardened state with the maximum overall economy.

14. Factors in the choice of mix designing
Grade designation
Type of cement
Maximum nominal size of aggregates
Minimum water cement ratio
Workability
Minimum cement content

15. Concrete Mix Proportion
proportion of nominal mix concrete
grade
Total quantity of dry agg. per 50 kg of cement
Proportion of fine agg. To coarse agg. (by mass)
Quantity of water per bag of cement (max)
M 5
800
Generally 1:2
But subjected to an upper limit of 1:1.5 and lower limit 1:2.5 60
M 7.5
625 45
M 10
480 34
M 15
330 32
M 20
250 30

16. Variability of Concrete Strength
Variation in the quality of constituent materials
Variation in mixed proportion
Quality of supervision and workmanship
Variation due to sampling and testing of concrete specimen.

17. Target mean strength
Considering the inherent variability of concrete strength during production, it is necessary to design the mix to have a target mean strength which is greater than the characteristic strength by a suitable margin.
f¹ = fck + k*s
f¹ = target mean strength
fck = characteristic strength
s = standard deviation
k = 1.65
Not more than 5% of the test results are expected to fall below fck.

18. Procedure for proportioning design concrete mixes
Step 1
Arrive at the mean target strength from characteristic compressive strength and level of quality control

19. Suggested values of standard deviation
Grade of concrete
s.d. for diff. degree of control (N/mm²)
Very good
Good
fair
M 10
2.0
2.3
3.3
M 15
2.5
3.5
4.5
M 20
3.6
4.6
5.6
M 25
4.3
5.3
6.3
M 30
5.0
6.0
7.0

20. Degree of quality control
Very good –
Fresh cement from single source and regular test weigh batching
Aggregates in single sizes, controlled grading and moisture content
Controlled water addition
Frequent supervision
Regular workability and strength tests
Field lab facility

21. Step 2 Nominal maximum size of aggregate (mm)
Assume an air content
depends on size of aggregate
Nominal maximum size of aggregate (mm)
Entrapped air as % of volume of concrete 10
3.0 20
2.0 40
1.0

22. Step 3
Choose a water cement ratio for mean target strength from Fig. 46 given in SP:
Water cement ratio satisfy maximum value prescribed for exposure condition in IS: 456

23. Step 4
Calculate approximate sand and water content per cubic meter of concrete
water cement ratio=0.35
Max. size of agg. (mm)
Water content per cubic meter of concrete
Sand as % of total agg. by absolute volume 10
208 62 20
186 45 40
165

24. water cement ratio=0.35 Max. size of agg. (mm)
Water content per cubic meter of concrete
Sand as % of total agg. by absolute volume 10
200 26 20
190 23

25. Adjustment of values in water content & sand % for other conditions
Change in conditions stipulated
Adjustment required in water content
Adjustment required in % sand in total agg.
Sand conforming to zone I, III, IV
+1.5 for zone I
-1.5 for zone III
-3.0 for zone IV
Increase or decrease in c.f. by 0.1
± 3%
Each 0.05 increase or decrease in water cement ratio
± 1%
For rounded agg.
-15 kg/m³
-7%

26. Step 5 Determination of cement content
On the basis of water cement ratio which in turn is determined from the water cement ratio v/s strength relationship

27. Step 6 Aggregate determination V = [W+C/Sc+1/P*Fa/Sfa]*1/1000
V= gross volume in m³ - volume of entrapped air
Sc= specific gravity of cement (3.15)
W= mass of water in kg/m³ of concrete
C= mass of cement in kg/m³ of concrete
P= ratio of fine agg. to total agg. by absolute volume

28. Step 7 Adjustment in proportions of concrete mixes
Arrive at the concrete mix proportions for the first trial
Conduct trial mixes with suitable adjustments till the final mix composition is arrived at.

29. Relationship with flexural strength
fcr = 0.7 (fck)½ N/mm²
fcr = flexural strength
fck= characteristic compressive strength of concrete in N/mm²

30. IS:456 specifications on workability
Placing condition
Degree of workability
Slump/c.f.
Pavement using pavers
Very low
c.f.= .75 to .80
Hand placed pavements
low
Slump = 25 to 75 mm

31. IS: 456 specifications on minimum cement content and maximum free water cement ratio
For PCC
Min. cement content kg/m³
Max. free water cement ratio
M 15
240
0.60
M 20
250
0.50
M 25
260
0.45
M 30
280
0.40

32. IS: 383-1970 specification for coarse and fine aggregates
Grading zone of fine aggregate
% passing for single sized aggregate of nominal size
Percentage passing for graded aggregate of nominal size

33. Aggregates
Crushing value- should not greater than 30% for concrete for bearing surface
Los angeles abrasion value- should not greater than 30% for aggregate used for bearing surfaces
Agggregate impact value- should not greater than 30% for aggregate used for bearing surfaces
Flakiness index- should not greater than 25%

34. IRC specification on cc pavements
Semi rigid pavements
Proportion of dry lean concrete- design by trial & error method
Compaction is done by rolling, hence keep slump 0-10 mm.
Cement concrete should not less than 150 kg/m³
Average compaction strength of 5 cubes at 28 days should not be less than 10.0 MPa.
Average compaction strength of individual cube at 28 days should not be less than 7.5 MPa.

35. Rigid Pavement CC Pavement
Strength requirements of coarse aggregate for concrete used in pavements
Aggregate impact value- should not be greater than 30%
Los angeles abrasion value- should not be greater than 30%
Roller compacted concrete pavement (RCCP)
Water content may range 4-7% by weight of dry materials including cement.

36. Concrete Pavements
Rigid pavement using pavement quality concrete (PQC)
IRC: 44- tentative guidelines for cc mix design for pavements.
for minimum flexural strength of 40 kg/mm² in the field assuming good degree of quality in the field.
Cement content lies between 350 to 425 kg/m³
Approx mix proportion = 1:1.5:3
Water cement ratio = 0.38
Workability to be considered in lab for test should be preferably 10 mm slump.

37. Concrete compacted by needle vibrators, hand tampers and plate compactors
A slump of 2.5 to 4.5 cm at paving site is acceptable for compaction by hand operated machines

38. Testing of hardened concrete
Core test
Non destructive test

39. Stage Wise Control of Quality
Pre Construction: Quality of materials
During Construction: (Freshly mixed concrete)
Batching
Mixing
Workability
Compaction
Surface finishing
Post Construction: (Quality of hardened concrete)
Check for riding quality
Check for strength
Check for concrete thickness

40. Concluding Remarks Do not over or under design the pavement
Do not use outdated formulae or other parameters when designing the pavement
Do not try to economies by using poorly trained or unqualified supervisors and operators
Do not use sub-standard tools and equipment
Do not use sub-standard material
Do not use dirty water for making concrete
Do not try to economies on testing of materials
Do not allow any traffic till the joints are permanently sealed

41. Continue……… Do not allow drains to get block or choked
Do not cut joints too early or too late
Do not place on the sub grade that is not thoroughly compacted and dampened
Do not drop concrete into place freely from a height exceeding 1.5 m
Do not vibrate concrete excessively to prevent flow of mortar to the top
Do not allow volume batching of concrete
Do not allow concrete to dry
Do not allow any vehicle on the road till it is fully cured

42. Thanks