Indian standard method for mix design M45

Mix Design for M45, Indian Standard method of mix design, Mix design for Pumpable Concrete, Mix design by IS456-2000

2. Design a concrete mix for M45 grade of concrete with the following data. (by IS Method)
Type of Cement OPC 43 Grade
Maximum Size Of Aggregate 20 mm
Type of Exposure Sever (RCC)
Workability 125 mm slump
Minimum Cement Content 320kg/cum
Specific gravity of cement 3.15
Specific gravity of coarse aggregates 2.80
Specific gravity of fine aggregates 2.70
w/c ratio 0.42
Method of placing of concrete Pumping
Degree of Supervision Good
Type of aggregate Crushed angular Agg.
Super plasticizer will be used 20%
Water Absorption
Coarse Aggregate
Fine Aggregate
0.5%
1%
Free Surface Moisture
Coarse Aggregate
Fine Aggregate
Nil
Nil
Grading of Coarse agg. Conforming to Table 2 of IS 383
(p) Grading of Fine agg. Conforming to grading zone II

3. 9.2.4.2 (IS 456-2000) Assumed standard
deviationWheresufficienttestresultsfora
particulargradeofconcretearenot
available.thevalueofstandard
deviationgiveninTable8maybe
assumedfordesignofmixinthe
firstinstance.Assoonastheresults
ofsamplesareavailable,actual
calculatedstandarddeviationshall
beusedandthemixdesigned
properly
.

4. Step-1 Target Mean Strength
• F’ck= fck+ 1.65 s
= 45 + 1.65 X 5 = 53.33 N/SQM
Where F’ck-Target mean compressive strength at 28 days.
fck-Characteristic Compressive strength at 28 days.
s-Standard Deviation. ( Table 8, page no 23, IS 456)

5. Step-2 Selection Of Water Cement Ratio
Clause 8.2.4.1 (IS 456-2000) Thefreewater-cementratioisan
importantfactoringoverningthedurabilityofconcreteand
shouldalwaysbethelowestvalue.Appropriatevaluesfor
minimumcementcontentandthemaximumfreewater-cement
ratioaregiveninTable5fordifferentexposureconditions.The
minimumcementcontentandmaximumwater-cementratio
applyto20mmnominalmaximumsizeaggregate.Forothersizes
ofaggregatetheyshouldbechangedgiveninTable6.(IS456)

7. •For Severe Exposure (RCC) and maximum nominal size of aggregate 20 mm.
As per IS Water Cement ratio is 0.45
Adopted W/c Ratio is 0.42 < 0.45
Hence, Its Ok.

8. Step-3 Selection of Water Content
•Clause 4.2 (IS 10262-2009) Thewatercontentofconcreteis
influencedbyanumberoffactors,suchasaggregatesize,
aggregateshape,aggregatetexture,workability,water-cement
ratio,cementandothersupplementarycementitiousmaterial
typeandcontent,chemicaladmixtureandenvironmental
conditions.Anincreaseinaggregatessize,areductioninwater-
cementratioandslump,anduseofroundedaggregateand
waterreducingadmixtureswillreducethewaterdemand.On
theotherhandincreasedtemperature,cementcontent,slump,
water-cementratio,aggregateangularityandadecreaseinthe
proportionofthecoarseaggregatetofineaggregatewill
increasewaterdemand

9. Clause 4.2 (IS 10262-2009)-Thequantityofmaximummixingwaterperunit
volumeofconcretemaybedeterminedfromTable2.(IS 10262-2009) The
watercontentinTable2isforangularcoarseaggregateandfor25to50mm
slumprange.ThewaterestimateinTable2canbereducedbyapproximately
10kgforsub-angularaggregates,20kgforgravelwithsomecrushedparticles
and25kgforroundedgraveltoproducesameworkability.Forthedesired
workability(other than 25 to 50 mm slump range),the required water content
may be established by trial or an increase by about 3 percent for every
additional 25 mm slump oralternativelybyuseofchemicaladmixtures
conformingtoIS9103.Thisillustratestheneedfortrialbatchtestingoflocal
materialsaseachaggregatesourceisdifferentandcaninfluenceconcrete
propertiesdifferently.Water reducing admixtures or super plasticizing
admixtures usually decrease water content by 5 to 10 percent and 20 percent
and above respectively at appropriate dosages.

11. From Table-2.(IS 10262-2009)
Maximum water content is 186 liters. This is for 50 mm slump.
Estimatedwatercontentfor125mmslump(3% increase for every 25
mm slump and above 50 mm slump, There fore total increase in water
content is by 9%)= 186 + ( 186x 9/100) = 203 liter.
It is given that super plasticizer usedas20%. Therefore actual water to
be used = 203 x 0.80 = 162 Liter.

12. Step-4 Calculation Of Cement Content
Water Cement Ratio= Water Content/Cement Content.
Water Cement Ratio –0.42
Water Content -162 liters
Cement Content = Water Content/ Water Cement Ratio
= 162/0.42
= 385.70 kg/cum
This cement content checked against minimum cement content mentioned in
Table No. 5 of IS 456 for Durability requirement.
The minimum cement content mentioned in Table 5 is 320 kg/cum for mild
exposure there fore calculated cement content is more, so Its ok.

14. Step-5 Calculation of Coarse and Fine Aggregates.
•• Clause 4.4.(IS 10262-2009)EstimationofCoarseAggregate-ProportionAggregatesofessentiallythe
samenominalmaximumsize,typeandgradingwillproduceconcreteof
satisfactoryworkabilitywhenagivenvolumeofcoarseaggregateperunitvolume
oftotalaggregateisused.Approximatevaluesforthisaggregatevolumearegiven
inTable3forawater-cementratioof0.5,whichmaybesuitablyadjustedforother
watercementratios.Itcanbeseenthatforequalworkability,thevolumeof
coarseaggregateinaunitvolumeofconcreteisdependentonlyonitsnominal
maximumsizeandgradingzoneoffineaggregate.Differencesintheamountof
mortarrequiredforworkabilitywithdifferentaggregates,duetodifferencesin
particleshapeandgrading,arecompensatedforautomaticallybydifferencesin
roaddedvoidcontent.

16. As per Clause 4.4.(IS 10262-2009) Volume of coarse aggregate corresponding to
20 mm size aggregate and fine aggregate zone II, for w/c ratio found out to be 0.62.
In the present case w/c ratio is 0.42 i.e. it is less by 0.08. As the
w/c reduced it is desirable to increase the coarse aggregate proportion to reduce
the fine aggregate content.
The coarse aggregate is increased at the rate of 0.01 for every decrease
in w/c ratio of 0.05.
:. (0.01/0.05) x 0.08= 0.016
There For correct volume of CA = 0.62+0.016 = 0.636
For Pumpable Concrete coarse aggregate can be reduced by 10%.
:. Volume of CA = 0.636 x 0.90 = 0.57
:. Volume of FA = 1-0.57 = 0.43

17. Step-6 Calculation Of Mix Proportions.
Assume Volume of Concrete = 1 CUM -------(A)
Volume Of Cement = = = 0.122 CUM ------(B)
Volume of water = = = 0.162 CUM ------(C)
Volume of all Aggregates = A-( B + C) = 1-( 0.122 + 0.162)= 0.716 CUM ----(D)

18. Mass of Coarse Aggregates = D x Sp. Gravity CA x Volume of CA x 1000
= 0.716 x 2.7 x 0.57 x 1000
= 1024.5 kg
Mass of Fine Aggregates = D x Sp. Gravity FA x Volume of FA x 1000
= 0.716 x 2.65 x 0.43 x 1000
= 891.77 kg

19. Step-7 Mix Proportion
Cement = 385.75 kg
Fine Agg.= 891.77 kg
Coarse Agg= 1024.5 kg
Cement = 1 Therefore Mix Proportion for M45 Concrete
FA = = 2.31
1 : 2.31 : 2.65
CA = = 2.65

20. Step-8 Site Corrections