2. INTRODUCTION
Concrete is obtained by mixing cement, fine aggregate, coarse
aggregate, water and admixtures in required proportions. The
mixture when placed in forms and allowed to cure becomes
hard like stone.
The hardening is caused by chemical action between water and
the cement due to which concrete grows stronger with age.
It is the most widely-used man-made construction material in
the world.
2CONCRETE MIX DESIGN
4. CEMENT
Cement and water forms the ‘active’ component of concrete, while
the inactive group comprises the fine and coarse aggregates.
The cement and water form a paste that hardens and bonds the
aggregates together.
Types of Cement
Although around 18 types of cements are recognized by BIS, more
commonly used ones are:
• Ordinary Portland Cement 33, 43, & 53 grade OPC,
• Blended Cements (PPC and PSC).
• Sulphate Resisting Cement (SRC),
• Low Heat Portland Cement (LHPC),
• Hydrophobic Portland Cement,
• Colored Cement (White Cement).
4CONCRETE MIX DESIGN
5. AGGREGATES
• They are cheaper than cement and impart greater volume
stability and durability to concrete.
• The main purpose is to provide bulk to the concrete.
• Some of the aggregates may be chemically active.
CLASSIFICATION
• Geological origin – natural and artificial
• Size – fine, coarse and all-in
• Shape – rounded, irregular, angular, flaky and elongated
• Unit weight – normal-weight, heavyweight and lightweight
5CONCRETE MIX DESIGN
6. WATER
• The most important and least expensive ingredient of concrete.
• One part of the water is used in the hydration of cement to form
the binding matrix.
• The remaining water affords lubrication and workability to the
concrete.
• Water-cement ratio depends on the grade of concrete, its
workability, durability, nature and type of aggregates etc.
• Potable water is ideal for concreting.
• Seawater may be used in PCC.
6CONCRETE MIX DESIGN
7. ADMIXTURES
Added to the concrete immediately or during mixing to modify its
properties in the fresh or hardened state.
Types:
• Accelerators - speed up the initial set of concrete.
• Retarders – delay the setting time of concrete mix.
• Plasticizers and Super-plasticizers - water reducers.
• Air entraining admixtures
• Water proofers
• Pigments
• Corrosion-inhibiting chemicals
• Antifungal admixtures
7CONCRETE MIX DESIGN
8. TYPES OF CONCRETE MIXES
1. NOMINAL MIX
Mixes of fixed proportions, IS:456-2000 permits nominal
mixes for concretes of strength M20 or lower
2. DESIGN MIX
Designed on the basis of requirements of the concrete in
fresh and hardened states.
8CONCRETE MIX DESIGN
9. TRIAL MIXES
Prepared to verify whether the Design Mix would perform as
per the assumptions. If appreciable variation exists, the
available alternatives are:
1. directly employ the trial mix proportions at the site
2. modify the trial mix proportions on the basis of intuition and
employ the revised proportions at the site
3. prepare further trial mixes incorporating changes in the
proportions based on the feedback generated from the
previous mix.
9CONCRETE MIX DESIGN
10. CONCRETE MIX DESIGN
DEFINITION
“ Mix Design is the science of determining the relative
proportions of the ingredients of concrete to achieve the
desired properties in the most economical way.”
CONCRETE MIX DESIGN 10
11. PRINCIPLES OF MIX DESIGN
1 The environment exposure condition for the structure
2 The grade of concrete, their characteristic strength’s and
standard deviations
3 The type of cement
4 The types and sizes of aggregates and their sources of supply
5 The nominal maximum sizes of aggregates
6 Maximum and minimum cement content in kg/m3
7 Water cement ratio
8 The degree of workability of concrete based on placing
conditions
CONCRETE MIX DESIGN 11
12. 9 Air content inclusive of entrained air
10 The maximum/minimum density of concrete
11 The maximum/minimum temperature of fresh concrete
12 Type of water available for mixing and curing
13 The source of water and the impurities present in it.
CONCRETE MIX DESIGN 12
16. FACTORS DEFINING THE CHOICE OF MIX
PROPORTIONS
1. Compressive Strength
2. Workability
3. Durability
4. Type, size and grading of aggregates
5. Aggregate-cement ratio
CONCRETE MIX DESIGN 16
17. COMPRESSIVE STRENGTH
Abram’s Law
log F = log A1 – x log B1
where F is the compressive strength
A1, B1 are constants and
x is the w/c ratio by weight
CONCRETE MIX DESIGN 17
18. WORKABILITY
“that property of freshly mixed concrete which determines the
ease and homogeneity with which it can be mixed, placed,
consolidated and finished.”
DURABILITY
“the resistance to weathering action due to environmental
conditions such as changes in temperature and humidity,
chemical attack, abrasion, frost and fire.”
CONCRETE MIX DESIGN 18
19. REQUIREMENTS AND TESTS OF MATERIALS
REQUIRED FOR MIX DESIGN
ASSIGNMENT # 1 TO BE SUBMITTED BY 07-02-2011
Roll #s 01-21 – Cement
Roll #s 22-42 – Aggregates
Roll #s 43-63 – Water and Admixtures
CONCRETE MIX DESIGN 19
20. METHODS OF CONCRETE MIX DESIGN
1. American Concrete Institute Committee 211 method
2. Bureau of Indian Standards Recommended method IS 10262-82
3. Road note No. 4 (Grading Curve) method
4. Department Of Environment (DOE - British) method
5. Trial and Adjustment Method
6. Fineness modulus method
7. Maximum density method
8. Indian Road Congress, IRC 44 method
CONCRETE MIX DESIGN 20
21. American Concrete Institute Method of Mix Design
(a) Data to be collected :
(i ) Fineness modulus of selected F.A.
(ii ) Unit weight of dry rodded coarse aggregate.
(iii ) Sp. gravity of coarse and fine aggregates in SSD condition
(iv ) Absorption characteristics of both coarse and fine
aggregates.
(v ) Specific gravity of cement.
(b) From the minimum strength specified, estimate the average
design strength by using standard deviation.
(c) Find the water/cement ratio from the strength and durability
points of view. Adopt the lower value.
CONCRETE MIX DESIGN 21
22. (d) Decide the maximum size of aggregate to be used. Generally
for RCC work 20 mm and pre-stressed concrete 10 mm size are
used.
(e) Decide workability in terms of slump for the given job.
(f ) The total water in kg/m3
of concrete is determined,
corresponding to the selected slump and selected maximum
size of aggregate.
(g ) Cement content is computed by dividing the total water
content by the water/cement ratio.
(h) Select the bulk volume of dry rodded coarse aggregate per unit
volume of concrete, for the particular maximum size of coarse
aggregate and fineness modulus of fine aggregate.
CONCRETE MIX DESIGN 22
23. ( j ) The weight of C.A. per cubic meter of concrete is calculated by
multiplying the bulk volume with bulk density.
(k ) The solid volume of coarse aggregate in one cubic meter of
concrete is calculated by knowing the specific gravity of C.A.
(l ) Similarly the solid volume of cement, water and volume of air is
calculated in one cubic meter of concrete.
(m) The solid volume of FA is computed by subtracting from the
total volume of concrete the solid volume of cement, CA, water
and entrapped air.
(n) Weight of fine aggregate is calculated by multiplying the solid
volume of fine aggregate by specific gravity of F.A.
CONCRETE MIX DESIGN 23
24. ACI METHOD: DESIGN EXAMPLE
1 Design a concrete mix for the construction of an elevated water
tank. The specified design strength of concrete (characteristic
strength) is 30 MPa at 28 days measured on standard cylinders.
Standard deviation can be taken as 4 MPa. The specific gravity
of FA and C.A. are 2.65 and 2.7 respectively. The dry rodded
bulk density of C.A. is 1600 kg/m3, and fineness modulus of FA
is 2.80. Ordinary Portland cement (Type I) will be used. A slump
of 50 mm is necessary. C.A. is found to be absorptive to the
extent of 1% and free surface moisture in sand is found to be 2
per cent. Assume any other essential data.
CONCRETE MIX DESIGN 24
25. 1 Mean Cylinder Compressive Strength
Assuming 5 per cent of results are allowed to fall below
specified design strength,
The mean strength,
fm= fmin + ks
= 30 + 1.64 x 4
= 36.5 MPa
2 Water/cement ratio
Strength criteria
Durability criteria
CONCRETE MIX DESIGN 25
30. CONCRETE MIX DESIGN 30
The mixing water content is 185 kg/m3
of concrete
The approximate entrapped air content is 2%.
The required cement content =185/0.47
= 394 kg/m3
31. CONCRETE MIX DESIGN 31
4 Bulk Volume of C.A.
Maximum size of C.A = 20mm
Fineness Modulus of F.A. = 2.80
Find the dry rodded bulk volume of C.A.
33. CONCRETE MIX DESIGN 33
The dry rodded bulk volume of C.A. = 0.62 per unit volume of
concrete
The weight of C.A. = 0.62 x 1600
= 992 kg/m3
34. CONCRETE MIX DESIGN 34
5 The first estimate of density of fresh concrete = 2355 kg/m3
35. CONCRETE MIX DESIGN 35
The weight of all the known ingredients of
concrete
Weight of water = 185 kg/m3
Weight of cement = 394 kg/m3
Weight of C.A. = 992 kg/m3
Weight of F.A. = 2355 – (185 + 394 + 992)
= 784 kg/m3
6 Weight of FA
36. CONCRETE MIX DESIGN 36
Alternatively, the weight of F.A. can be determined by the more
accurate absolute volume method
Absolute Volume = weight/(1000ρ) m3
37. CONCRETE MIX DESIGN 37
Total absolute volume = 697 x 103
cm3
Absolute volume of F.A. = (1000 – 697) x 103
= 303 x 103
Weight of FA = 303 x 2.65
= 803 kg/m3
38. CONCRETE MIX DESIGN 38
7 Estimated quantities of materials per cubic meter of
concrete are:
Cement = 394 kg
F.A = 803 kg
C.A = 992 kg
Water = 185 kg
39. CONCRETE MIX DESIGN 39
8 Proportions
C : F.A : C.A : water
394 : 803 : 992 : 185
1 : 2.04 : 2.52 : 0.47
Weight of materials for one bag mix
in kg = 50 : 102 : 126 : 23.5
40. CONCRETE MIX DESIGN 40
9 The above quantities is on the basis that both F.A
and C.A are in saturated and surface dry condition
(SSD conditions).
FA has surface moisture of 2%
Total free surface moisture in FA = (2/100 x 803)
= 16.06 kg/m3
Weight of F.A in field condition = 803 + 16.06 = 819.06 kg/m3
41. CONCRETE MIX DESIGN 41
Quantity of water absorbed by C.A. = (1/100 x 992) = 9.92 kg/m3
Weight of C.A in field condition = 992 – 9.92
= 982 kg/m3
C.A absorbs 1% water
Water contributed by F.A = 16.06 kg
Water absorbed by C.A. = 9.92 kg
Extra water contributed by aggs. = 16.06 – 9.92 = 6.14 kg
Total water content = 185.00 – 6.14
= 179 kg/m3
Change in Water Content
42. CONCRETE MIX DESIGN 42
Cement = 394 kg/m3
F.A. = 819 kg/m3
C.A. = 982 kg/m3
Water = 179 kg/m3
Field density of fresh concrete = 2374
kg/m3
Quantities of materials to be used in field, corrected for
free surface moisture in F.A and absorption characteristic
of C.A
43. 2. A mix with a mean 28-day compressive strength of 35 MPa
and a slump of 50 mm is required, using OPC. The maximum
size of well shaped, angular aggregate is 20mm, its bulk
density is 1600 kg/m3
and its specific gravity is 2.64. The
available fine aggregate has a fineness modulus of 2.60 and a
specific gravity of 2.58. No air-entrainment is required.
CONCRETE MIX DESIGN 43
Water/Cement ratio
As durability criteria is not
mentioned, consider strength alone
48. Composition of concrete (kg/m3
)
Water = 185
Cement = 386
CA = 1020
FA = 738
Density of Concrete = 2329 (kg/m3
)
CONCRETE MIX DESIGN 48
49. ROAD NOTE No. 4 METHOD OF MIX DESIGN
Proposed by the Road Research Laboratory, UK (1950)
Procedure:
1. The average compressive strength of the mix to be designed is
obtained by applying control factors to the minimum
compressive strength
2. Water/cement ratio is read from compressive strength v/s w/c
ratio graph
3. Proportion of combined aggregates to cement is determined
from tables, for maximum size 40 mm and 20 mm
4. If the aggregate available differs from the standard gradings,
combine FA and CA so as to produce one of the standard
gradings CONCRETE MIX DESIGN 49
50. 5. The proportion of cement, water, FA and CA is determined
from knowing the water/cement ratio and the
aggregate/cement ratio.
6. Calculate the quantities of ingredients required to produce 1
m3
of concrete, by the absolute volume method, using the
specific gravities of cement and aggregates.
CONCRETE MIX DESIGN 50
51. DRAWBACKS OF ROAD NOTE NO. 4 METHOD
1. Cannot be used directly for the design of air - entrained
concrete
2. No recommendations for durability or strength, regarding the
water/cement ratio
3. The design tables refer to mixes in which the FA and CA are of
the same shape
4. In selecting aggregate/cement ratio, only 3 shapes of
aggregates and 4 gradings are recommended.
CONCRETE MIX DESIGN 51
52. DOE METHOD OF MIX DESIGN
Can be used for concrete containing fly ash.
PROCEDURE
1. Target mean strength is calculated
2. Select water/cement ratio, from the type of cement and CA.
Compare this with the ratio from durability conditions.
3. Decide the water content for required workability
4. Compare the cement content with the minimum cement content
value and adopt the higher value
5. Find out the total aggregate content
6. Determine the proportion of FA using the appropriate FA% v/s
CA size graph, and find the weight of CA and FA
7. Work out a trial mix.
CONCRETE MIX DESIGN 52
53. BIS RECOMMENDED MIX DESIGN METHOD
The BIS recommended mix design procedure is covered in IS
10262-82.
In line with IS 456-2000, the first revision IS 10262-2009 was
published, to accommodate some of the following changes:
• Increase in strength of cement
• Express workability in terms of slump, rather than the
compacting factor
• Extend the W/C ratio v/s compressive strength graph
CONCRETE MIX DESIGN 53
55. MIX DESIGN BASED ON IS RECOMMENDATIONS
Based on IS 10262:1982
Procedure:
CONCRETE MIX DESIGN 55
1. Target mean strength for mix design:
fck* = fck + tS
where fck = characteristic compressive strength at 28 days
S = standard deviation
t = a statistical value depending on the risk factor.
62. 5. Calculation of Cement Content:
cement by mass = Water content/Water cement ratio
To be checked against the minimum cement content for the requirement
of durability and the greater of the two values to be adopted.
CONCRETE MIX DESIGN 62
64. 7. Actual quantities required for mix
Adjust the mix for deviations from assumed conditions
CONCRETE MIX DESIGN 64
8. Check the calculated mix proportions
65. DESIGN EXAMPLE: BIS RECOMMENDED METHOD
Grade M20
(a ) Design stipulations
(i ) Characteristic compressive strength
required in the field at 28 days - 20 MPa
(ii ) Maximum size of aggregate - 20 mm (angular)
(iii ) Degree of workability - 0.90 compacting factor
(iv ) Degree of quality control - Good
(v ) Type of Exposure - Mild
66. (b) Test data for Materials
(i ) Specific gravity of cement - 3.15
(ii ) Compressive strength of cement at 7 days - Satisfies the
requirement of IS: 269–1989
(iii ) 1. Specific gravity of coarse aggregates - 2.60
2. Specific gravity of fine aggregates - 2.60
(iv ) Water absorption:
1. Coarse aggregate - 0.50%
2. Fine aggregate - 1.0%
(v ) Free (surface) moisture:
1. Coarse aggregate - Nil
2. Fine aggregate - 2.0%
67. Design Procedure
1. Target mean strength of concrete
fck* = fck + tS
CONCRETE MIX DESIGN 67
fck = 20, t = 1.64 , S = 4
fck* = 26.6 MPa
73. 4. Determination of cement content
Water-cement ratio = 0.50
water = 191.6 kg/m3
CONCRETE MIX DESIGN 73
Cement = 191.6/0.50 = 383 kg/m3
Is this satisfactory for ‘mild’ exposure condition?
74. 5. Determination of coarse and fine aggregate contents
Specified max. size of aggregate = 20 mm
Corresponding entrapped air = 2%
CONCRETE MIX DESIGN 74
fa = 546 kg/m3
,
Ca = 1188 kg/m3
