Mix design by Indian standard method for M20

M20 mix design, Indian standard Mix Design method, Mix Design by IS 456-2000

2. 9.3 Nominal Mix Concrete
Nominal mix concrete may be used for concrete of
M 20 or lower. The proportions of materialsfor
nominal mix concrete shall be in accordance with
Table No-9 ( Page No-23 IS456)

6. a) Type of mix, that is, design mix concrete Or nominal mix concrete:
h) Grade designation;
c) Type of cement;
d) Maximum nominal size of aggregate;
e) Minimum cement content (for design mix concrete);
f) Maximum water-cement ratio;
g) Workability;
h) Mix proportion (for nominal mix concrete);
j) Exposure conditions as per Tables 4 and 5;
k) Maximum temperature of concrete at the time of placing;
m) Method of placing;
n) Degree of supervision.

7. 1. Indian Standard Method
•Is Codes Required
1) IS 456-2000
2)IS 10262-2009
3) IS 383-2016

10. Step-1 Target Mean Strength
• F’ck= fck+ 1.65 s
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)

12. 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)

14. •For Mild Exposure and maximum nominal size of aggregate 20 mm.
Water Cement ratio is 0.55
Adopted W/c Ratio is 0.47 < 0.55
Hence, Its Ok.

15. 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

16. Clause 4.2 (IS 10262-2009)-Thequantityofmaximummixingwaterperunit
volumeofconcretemaybedeterminedfromTable2.(IS 10262-2009) The
watercontentinTable2isforangularcoarseaggregateandfor25to50mm
slumprange.ThewaterestimateinTable2canbereducedbyapproximately
10kgforsub-angularaggregates,20kgforgravelwithsomecrushedparticles
and25kgforroundedgraveltoproducesameworkability.Forthedesired
workability(otherthan25to50mmslumprange),therequiredwatercontent
maybeestablishedbytrialoranincreasebyabout3percentforevery
additional25mmslumporalternativelybyuseofchemicaladmixtures
conformingtoIS9103.Thisillustratestheneedfortrialbatchtestingoflocal
materialsaseachaggregatesourceisdifferentandcaninfluenceconcrete
propertiesdifferently.Waterreducingadmixturesorsuperplasticizing
admixturesusuallydecreasewatercontentby5to10percentand20percent
andaboverespectivelyatappropriatedosages.

18. From Table-2.(IS 10262-2009)
Maximum water content is 186 liters.

19. Step-4 Calculation Of Cement Content
Water Cement Ratio= Water Content/Cement Content.
Water Cement Ratio –0.47
Water Content -186 liters
Cement Content = Water Content/ Water Cement Ratio
= 186/0.47
= 395.75 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 300 kg/cum for mild
exposure there fore calculated cement content is more, so Its ok.

20. Step-5 Calculation of Coarse and Fine
Aggregates.
•Clause4.4.(IS 10262-2009)
EstimationofCoarseAggregate-ProportionAggregatesofessentiallythesame
nominalmaximumsize,typeandgradingwillproduceconcreteofsatisfactory
workabilitywhenagivenvolumeofcoarseaggregateperunitvolumeoftotal
aggregateisused.Approximatevaluesforthisaggregatevolumearegivenin
Table3forawater-cementratioof0.5,whichmaybesuitablyadjustedforother
watercementratios.Itcanbeseenthatforequalworkability,thevolumeof
coarseaggregateinaunitvolumeofconcreteisdependentonlyonitsnominal
maximumsizeandgradingzoneoffineaggregate.Differencesintheamountof
mortarrequiredforworkabilitywithdifferentaggregates,duetodifferencesin
particleshapeandgrading,arecompensatedforautomaticallybydifferencesin
roaddedvoidcontent.

22. AsperClause 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 0.47 i.e.itislessby0.03. As the w/c
reduced it is desirable to increase the coarse aggregate proportion to
reduce the fine aggregate content.
Thecoarse aggregate is increased at the rate of 0.01 for every decrease in
w/c ratio of 0.05.
:. (0.01/0.05) x 0.03= 0.006
There Forcorrect volume of CA = 0.62+0.006 = 0.626
:. VolumeofFA=1-0.626=0.374

23. Step-6 Calculation Of Mix Proportions.
•Assume Volume of Concrete = 1 CUM -------(A)
Volume Of Cement = = = 0.126 CUM ------(B)
Volumeofwater= = = 0.186 CUM ------(C)
Volume of all Aggregates = A-( B + C) = 1-( 0.126 + 0.186)= 0.688 CUM ----(D)

24. •Mass of Coarse Aggregates = D x Sp. Gravity CA x Volume of CA x 1000
= 0.688 x 2.7 x 0.626 x 1000
=1162.85kg
•Mass of Fine Aggregates = D x Sp. Gravity FA x Volume of FA x 1000
= 0.688 x 2.65 x 0.374 x 1000
= 681.87 kg

25. Step-7 Mix Proportion
•Cement=395.75kg
•Fine Agg.= 681.87 kg
•CoarseAgg=1162.85 kg Therefore Mix Proportion for M20 Concrete
Cement = 1
FA= = 1.73
CA= = 2.94
1 : 1.73 : 2.94
1 Bag of Cement (50 kg) : FA (86.5 kg) : CA (147 kg)

26. Step-8 Site Corrections
•Water Absorption of Fine Aggregate = 1.0 %
=x 681.87 = 6.81 litre
Actual weight of FA to be Used = 681.87 -6.81= 675.06 Kg.
•Water Absorption of Fine Aggregate = 0.5 %
= x 1162.85 = 5.81 litre
Actual weight of FA to be Used = 1162.85-5.81= 1157.04Kg.
•Actual amount water to be used = 186 + 6.81 + 5.81 = 198.62 litre.