Project on Concrete Mix Design for various grades of Concrete
Concrete mix design for M35 grade concrete with flyash .
Grade of concrete = M35
characteristics strength (fck)= 35mpa
standard deviation =1.91mpa
target mean strength fck=fck'+1.65xs.d(from is 456-2000)
=35+1.65x1.91=38.15 Mpa.
test data for material:
aggregates tyoe - crushed.
specific gravity : cement -3.15, coarse aggregate- 2.67 , & fine aggregate -2.62.
water absoption: coarse aggeregate =0.5%, fine aggregate =1.0%.
Mix design : Take sand content as % of total aggregates =36%.
select water cement ratio =0.43 for concrete grade M35.
select water conternt=172 kg.9FROM IS 10262 for 20 mm normal size of aggregates max water content =186kg/m3).
hence , w/c ratio= 172/0.43=400kg/m3.
mix propotyion of FA & CA:
1000(1-a0)=((cement content/sp.grof cement)+water content+(fa?sp.gr.xpf)).
1000(1-a0)=((cementcontent/sp.gr.of cement)+water content+ca/sp.gr.Xpc)).
where ca= coarse aggregate, fa= fine aggregate, pf =sand content as percentage of total aggregates=0.36
pc=percentate of air content in concrete (as per IS:10262 for 20mm nominal size of aggregate is 2%)=0.02.
= 100091-0.02)= 400/3.15+1.72+(FA/2.62X0.36)).
FA= 642 kg/cum.. as the sand is of zone -2 no adjustment is required for sand.
sand content =642kg/cum.
=1000(1-0.02)=400/3.15)+1.72+(ca/2.67x0.64)).
ca = 1165kg/cum.
From combined gradation of coarse aggregate it has been found out that the proportion of 53:47 of 20 mm & 10 mm aggregates produced the best gradation as per Is :383.
hence 20mm of aggregate =619kg. & 10 mm aggregate =546 kg.
To obtain slump in the range of 150-190mm water reducing admixture brand sp430 forsco with a dose of 0.3 % by weight of cement shall be used.
hence the mix proportion becomes: cement w/c water sand 20mm 10mm admix
400 0.43 172 635 619 564 1.2
1 0.43 1.6 1.547 1.36 0.003
units are kg/m3.
cement: sand: coarse aggregate = 1:1.6:2.907.
- To calculate M50 Grade of concrete with out fly ash:
Target mean strenght: F'ck=fck+1.5xs
fck=50N/mm2 for M50 grade.
From table 1 of IS10262-2009 S Value can be taken as 5.0N/mm2
f'ck= 50+1.5x5 =58.25N/mm2.
selection of water cement ratio
given grade of concrete = m50.
Assumue : exposure condition:Extreme. ( From table 5 of is456-2000.)
extreme water ratio =0.40 for m50 grade. lower the w/c ratio better the workability.
so minimum cement content in case of extrem econdition is 360kg/m3
selection of water content
assumue normal size of aggregate -20mm.
table 2 of IS 10262-2009
Minimum water content as of table 2 of IS 10262-2009 is 186 litres or 186kgs.
slump ranges from 20-50mm.
As superplaticizer 20% reduced.
186X80/100=148.8=149 Litres.
calculation of cement content
w/c ratio =0.40 water content= 149 litres/kgs.
cement content c=149/0.40=372.5 kg/m3 =373 kg/m3.
min cement content=360kg/m3.
hence 360<373kg/m3 we can consider it.
vol of coarse aggregate and fine aggregate
According to table 3 if IS 10262-2009.
Nominal size of aggregate =20mm .FA can be taken as zone 1. vol of coarse aggregate =0.60
w/c ratio=0.40 .vol of ca=0.62 , therefore vol of fa =1-0.62=0.38.
Mix calculation :
A) vol of concrete =1m3.
B) vol of cememt content= 373/3.15 x 1/1000=0.118m3.
C) vol of water =149/1 x1/1000=0.149m3.
D) vol of admixture =7.6/1.145 x1/1000=0.006.
vol of coarse aggregate and fine aggregate=(a-(b+c+d))=1-(0.118+0.149+0.006))=0.727m3.
mass of fine aggregate= 0.727x0.38x2.74x1000=756.9kg/m3.
mass of coarse aggregate=0.727x0.62x2.74x1000=1235.02kg/m3.
Trail mix :
cement = 373kg/m3
water =149 kgs
coarse aggregate =1235.02 kg/m3
fine aggregate = 756.9 kg/m3
chemical admixture =7.6 kg/m3
water cemet ratio =0.40
Trial mix ratio =373:756.9:1235.02 = 1:2.02:3.31 i.e., cement: FA: CA.
The trail mix ratio should match the workability, durability and minimum strength of M50 Grade concrete.
if it doen not satisfy the above criteria two or more trials ha s to be done for an increse of 10%.