Concrete mix design

A
Presentation
on
Concrete Mix Design
PRESENTED BY:-
DIVYA VISHNOI
(Assistant Professor)

 Scope
 Introduction
 Mix Design
 Differences b/w IS10262:1982 and 10262:2009
 Exercise
2Divya Vishnoi (Assistant Professor)

 This standard provides the guidelines for
proportioning concrete mixes as path requirement
using the concrete making materials including ether
supplementary materials identified for this purpose.
The proportioning is carried out to achieve specified
characteristics at specified age , work ability of fresh
concrete and durability requirements .
 This standard is applicable for ordinary and standard
concrete grades only.

Concrete is the second largest material consumed
by human beings after food and water as per
WHO. It is obtained by mixing cement, fine
aggregate, coarse aggregate and water 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.
Cont….

The strength, durability and other characteristics
of concrete depend upon the properties of its
ingredients, proportion of the mix, the method of
compaction and other controls during placing,
compaction and curing
Concrete possess a high compressive strength and
is usually more economical than steel and is non
corrosive which can be made with locally available
materials.
Cont….

Hence concrete is used widely in all present-day
constructions. The concrete is good in
compression and bad in tension. Hence liable to
be cracked when subjected to tensile load. In
situations where tensile stresses are developed
concrete is strengthened by steel bars forming a
composite construction called Reinforced Cement
Concrete (RCC).

Mix design is defined as process of selecting
suitable ingredients of concrete and determining
their relative proportions with the objective of
producing concrete of certain minimum strength
with respect to requirement of workability at site,
without sacrificing durability of concrete.

• Design of concrete mixes involves determination of the
proportions of the given constituents namely, cement,
water, coarse aggregate and fine aggregate with admixtures
if any.
• Workability is specified as the important property of
concrete in the fresh state. For hardened state compressive
strength and durability will be considered

 Grade of concrete: This gives the characteristic
strength requirements of concrete. Depending
upon the level of quality control available at the
site, the concrete mix has to be designed for a
target mean strength which is higher than the
characteristic strength.
Cont…..

 Type of cement: The type of cement is important
mainly through its influence on the rate of
development of compressive strength of concrete
as well as durability under aggressive
environments ordinary Portland cement(OPC)
and Portland Pozzolana cement (PPC) are
permitted to use in reinforced concrete
construction. Factors to be considered in Mix
design (as per SP23-1982)
Cont…..

Maximum nominal size of aggregate: It is found
that larger the size of aggregate, smaller is the
cement requirement for a particular water cement
ratio. Aggregates having a maximum nominal size
of 20mm or smaller are generally considered
satisfactory.
Minimum water cement ratio: The minimum w/c
ratio for a specified strength depends on the type
of cement.
Workability: The workability of concrete for
satisfactory placing and compaction

 a) Grade designation: M40
 b) Type of cement: OPC 43 grade conforming to IS 8112
 c) Type of mineral admixture Fly ash conforming to IS 38I2
(Part I)
 d) Maximum nominal size of aggregate: 20mm
 e) Minimum cement content : 320 kg/m3
 f) Maximum water-cement ratio : 0.45
 g) Workability: 100mm(slump)
 h) Exposure condition: Severe (for reinforced concrete)

 j) Method of concrete placing : Pumping
 k) Degree of supervision: Good
 m) Type of aggregate: Crushed angular aggregate
 n) Maximum cement (OPC) content : 450 kg/m3
 p) Chemical admixture type : Super plasticizer

 Specific gravity of cement 3.15
 Specific gravity of coarse aggregate 2.74
 Specific gravity of fine aggregate 2.74
 Water absorption of coarse aggregate 0.5 %
 Water absorption of fine aggregate 1.0 %
 Free surface moisture of coarse aggregate 0.00
 Free surface moisture of fine aggregate 0.00

 Sieve analysis
 coarse aggregate :-
 fine aggregate: Conforming to zone I of IS 383:1970.
15
IS Sieve
Sizes(mm) Remark
I II I (60%) II (40%) Combined
20 100 100 60 40 100
10 0 71.2 0 28.5 28.5
4.75 9.4 3.7 3.7
2.36 0
Analysis of Coarse
Aggregate Fraction
Percentage of different
fractions
Confirmi
ng to
table-2
of IS-383
Divya Vishnoi (Assistant Professor)

 Static constant (t) = 1.65
 Standard Deviation (s) = 5 N/mm2 (Table-1)
 Target strength (ft) = fck + 1.65 x s
=48.25 N/mm²

 From table 5 0f IS 456:2000, maximum water cement ratio (see
4.1)=0.45
 Based on experience adopt water-cement ratio as 0.40.
 0.40 < 0.45, hence, O.K.

 From Table 2, maximum water content
 for 20 mm aggregate = 186 litres (for 25 to 50 mm slump range)
 Estimated water content for 100 mm slump= 𝟏𝟖𝟔 +
𝟔
𝟏𝟎𝟎
× 𝟏𝟖𝟔 = 𝟏𝟗𝟕 𝒍𝒊𝒕𝒓𝒆
 As super plasticizer is used. the water content can he reduced
up to 30% percent.
 Based on trials with super plasticizer water content reduction of
29% percent has been achieved, Hence, the arrived water
content = 197 x 0.71 = 140 litres .

 water-cement ratio = 0.40.
 Cementitious material = Water content
W / c ratio
 From Table 5 of IS 456, minimum cement content for
‘severe' exposure conditions=
 hence. O.K.

 Now, to proportion a mix containing fly ash the following steps
are suggested:
 a) Decide the percentage fly ash to be used based on project
requirement and quality of materials
 b) In certain situations increase in Cementitious material content
may be warranted, The decision on increase in Cementitious
material content and its percentage may be based on
experience and trial (see Note),
 NOTE - This illustrative example is with increase of 10 percent
Cementitious material content.

 Cementitious material content= 350 x 1.10 =
 Water Content=
 So. water-cement ratio=
 Fly ash @ 30% of total Cementitious material content= 385 x
30% =
 Cement (OPC) = 385 - 115 =
 Saving of cement while using fly ash = 350 - 270 = and
 Fly ash being utilized =

 From Table 3. volume of coarse aggregate corresponding to 20
mm size aggregate and fine aggregate (Zone I) for water-cement
ratio of 0.50 =0.60.
 In the present case water-cement ratio is 0.40. Therefore.
volume of coarse aggregate is required (0 be increased to
decrease the line aggregate content. As the water-cement ratio
is lower by 0.10. the proportion of volume of coarse aggregate is
increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change
in water-cement ratio) ,
 Therefore. corrected proportion of volume of coarse aggregate
for the water-cement ratio of 0.40 = 0.62

 NOTE - In case the coarse aggregate is not angular one. then
also volume: of coarse aggregate may be required to be
increased suitably. based on experience.
 For pumpable concrete these values should be reduced by 10
percent.
 Therefore. volume of coarse aggregate =0.62 x 0.9 =0.56.
 Volume of fine aggregate content = 1 - 0.56 = 0.44.

 The mix calculations per unit volume of concrete shall
be as follows:
 a) Volume of Concrete = 1
 b) Volume of cement=
=
=

 c) Volume of Fly ash=
=
=
25
1000
1
2.2
115
X

 d) Volume of Water=
=
=

 e) Volume of Chemical admixture( Super
plasticizer)@2.0% by mass of Cementitious material
=
=
=
27
𝟕. 𝟕
𝟏. 𝟏𝟒𝟓
×
𝟏
𝟏𝟎𝟎𝟎
𝟎. 𝟎𝟎𝟔𝟕𝟐𝟓 𝒎 𝟑

 f) Volume of Aggregate=[a-( b+ c+ d+ e)]
= [1-(0.086+0.052+0.140+0.006725)]
=
28
𝟎. 𝟕𝟏𝟓𝟐𝟕 𝒎 𝟑

 Mass of coarse aggregate=f x volume of coarse aggregate x
Specific gravity of coarse aggregate x 1000
= 0.715×0.56×2.74×1000
=1097 Kg
Mass of Fine aggregate=f x volume of fine aggregate x Specific
gravity of fine aggregate x 1000
= 0.715×0.44×2.74×1000
=862 Kg

For one cubic m concrete:
 Water = 140 kg
 Cement = 270 kg
 Sand (fa) = 862 kg
 Coarse Aggregate = 1097 kg
 Chemical admixture= 7.7 kg
 Water – cement Ratio = 0.364
30
Recommendations

Tentative Quantities of material

Points IS 10262:1982 IS 10262:2009
Title of the Code
Recommended guidelines for concrete
mix design
Concrete Mix proportioning Guidelines
Strength & Durability
The 1982 version considers strength as
the governing criteria for durability and
so also for the mix design process.
according to the revised one strength may be a factor
for acceptance but may not assures durability
Air Content
IS: 10262-1982 considers expected air
content of 1% to 3% in the design
process depending on the nominal
maximum size of aggregates.
IS: 10262-2009 eliminates consideration of air content
in the mix proportion calculation as it’s not of much
significance.
Water Cement Ratio
The old version suggested that selection
of preliminary free w/c ratio may be
adopted from established relationships
presented in form of graph as
generalized w/c ratio curves for
different cement strengths. Accordingly
six ready reference curves were there
namely A to F for a wide range of
cement strengths from 325kg/cm2 to
625kg/cm2. This selected w/c ratio is to
be checked against limiting w/c ratio
for durability.
The revised version encourages establishing the
relationships for actually used material. Otherwise it
suggests to consider it from the specified table (Table-
5) of IS: 456 for desired exposure condition as
preliminary w/c ratio that has to be further checked for
limiting value ensuring durability.

Points IS 10262:1982 IS 10262:2009
Measure of Workability
IS: 10262-1982 considers
compaction factor as the measure
of workability.
In revised one, slump is considered as the
measure of workability. Measurement of
workability as slump is more convenient,
widely used at sites and is better acceptable.
Mineral Additives
--------------------- The revised code provides guidelines for
addition of supplementary cementitious
additives. So additives like fly ash, silica fume,
ground granulated blast furnace slag, rice husk
ash etc. can be used in concrete mix provided
the strength and durability requirement are met
with.
So as per the revised code the concrete is no
longer a four component system (cement, sand,
coarse aggregates & water) as considered in the
previous version, but it is much more.

Calculation of water content
The quantity of water to be used plays a
vital role in concrete mix design.
Agreeing with the old guidelines, values
of water content have been specified in
terms of kg per cubic meter of concrete
depending upon the nominal maximum
size of aggregates which can be
considered as starting selection point of
water content.
IS: 10262-2009 allows use of water reducers/ super
plasticizers and also specifies the alteration in water
content accordingly.
Further water adjustment was specified in terms of
variation of compaction factor in the older version
whereas the same has been remolded in terms of
slump variation (+3% for every 25mm slump over
50mm) in the revised one.
Estimations of Coarse and Fine
Aggregates
The 1982 publication specifies ratio of
fine aggregates to all-in-aggregates
from which coarse aggregates content
can be derived.
In revised one the volume of coarse aggregates per
unit volume of total aggregates for different zones of
fine aggregates and different maximum nominal size of
aggregates has been tabulated from which the fine
aggregates content has to be derived.
Miscellaneous
---------- The standard is applicable for ordinary and standard
grades of concrete.
• Various requirements have been modified in line
with the requirements of IS: 456-2000-Plain and
reinforced concrete-Code of practice.
• Other illustrations like trial mixes, numerical example
etc have been reviewed and modified.
• An example illustrating mix proportioning with
supplementary cementitious additive (fly ash) has
been included

 IS 10262:2009,
 IS 10262:1982,
 IS 456:2000,
 IS 383:1970,
 IS 2386:1963(part-3),
 IS 3812:2013(part-1),
 IS 8112:2013,
 IS 9103:1999.

36
Exercise

 a) Grade designation: M25,M30,M40
 b) Type of cement: OPC 43 grade conforming to IS 8112
 c) Type of mineral admixture Fly ash conforming to IS 38I2
(Part I)
 d) Maximum nominal size of aggregate: 20mm
 e) Minimum cement content : 320 kg/m3
 f) Workability: 100mm(slump)
 g) Exposure condition: Severe (for reinforced concrete)

 j) Method of concrete placing : Pumping
 k) Degree of supervision: Good
 m) Type of aggregate: Crushed angular aggregate
 n) Maximum cement (OPC) content : 450 kg/m3
 p) Chemical admixture type : Super plasticizer

 Specific gravity of cement 3.15
 Specific gravity of coarse aggregate 2.74
 Specific gravity of fine aggregate 2.74
 Water absorption of coarse aggregate 0.5 %
 Water absorption of fine aggregate 1.0 %
 Free surface moisture of coarse aggregate 0.00
 Free surface moisture of fine aggregate 0.00

 Sieve analysis
 coarse aggregate :-
 fine aggregate: Conforming to zone I of IS 383:1970.
40
IS Sieve
Sizes(mm) Remark
I II I (60%) II (40%) Combined
20 100 100 60 40 100
10 0 71.2 0 28.5 28.5
4.75 9.4 3.7 3.7
2.36 0
Analysis of Coarse
Aggregate Fraction
Percentage of different
fractions
Confirmi
ng to
table-2
of IS-383

41
Thank you

Concrete mix design

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