Project on Concrete Mix Design for various grades of Concrete
A:- calculate the concrete mix design for M35 grade concrete with fly ash ?
ans:- concrete mix proportion
1) stipulation for proportioning
a) grade designation : M35
b) types of cement : OPC 43 grade confirming to IS 8112
c) maximum nominal size of aggregate : 20mm
d) minimum cement content : 320 kg/m^3 ( from table 5 of IS 456:2000- exposure condition )
e) maximum water-cement ratio : 0.45( from table 5 of IS 456:2000- exposure condition )
f) workability : 100mm ( slump value for pumpable concrete )
g) exposure condition : severe ( for reinforced concrete )
h) method of concrete placing : pumping
i) degree of supervision : good
j) types of aggregate : crushed angular aggregate
k) maximum cement content : 450 kg/m^m
l) chemical admixture type : superplasticizer
2) test data for material :
a) cement used : OPC 43 grade confirming to IS 8112
b) specific gravity of cement : 3.15
c) chemical admixture : superplasticizer conforming to IS 9103
d) specific gravity of
- coarse aggregate : 2.74
- fine aggeragte : 2.74
e) water absorption
- coarse aggregate : 0.5%
- fine agregate : 1.0%
f) free surface moisture
- coarse aggregate : nil
- fine aggregate : nil
d) sieve analysis
- coarse aggregate :
- fine aggregate : confirming to grading zone I of table 4 of IS 383
3) target strength for mix proportioning
f'ck = fck + 1.65 S
where f'ck = target average compressive strength at 28 days
fck = characteristic compressive strength at 28 days
S = standard deviation
from table 1 of 10262 : 2009 , standard deviation , S= 5 N/mm^2
therefore, target strength = 35+ 1.65 * 5 = 43.25 N/mm^2
4) selection of water-cement ratio :
from table 5 of IS 456:2000 for severe exposure , maximum water-cement ratio=0.45
based on experience , adopted water cement ratio is 0.40
0.40<0.45 hence ok
5) selection of water content :
from table 2 of 10262:2009 , maximum water content for 20 mm aggregate = 186 litre ( for 25mm to 50mm slump
range)
estimated water content for 100 mm slump = 186 + 6/100*186 = 197 litre
as superplasticizer is used the water content can be reduced up to 30 percent
based on trial with superplasticizer water content reduction of 29 percent has been achieved the arrived water content =
197*0.71= 140 litre
6) calculation of cement and fly ash content :
water-cement ratio = 0.40
cementatious material ( cement + fly ash ) content = 140/0.40= 350 kg/m^3
from table 5 of IS 446, minimum cement content for severe exposure condition = 320 kg/m^3
350 kg/m^3 > 320 kg/m^3 hence ok
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 material
b) in certain situations increase in cementitions material content may be warrented . the decision on increasing in cementitious material content and its percentage may be used on experience and trial
note :- this illustrative exampleis with increase as 10 percent cementitious material content
cementitious material content = 350*1.10=385 kg/m^3
water content = 140 kg/m^3
so water -cement ratio = 140/385= 0.364
fly ash @ 30%of total cementitious material content = 385*30% =115 kg/m^3
cement (OPC) = 385-115= 270kg/m^3
saving of cement while using fly ash = 350-270=80 kg/m^3
fly ash being utilized = 115 kg/m^3
7) proportion of volume of coarse aggregate and fine aggregate content
from table 3 volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate ( zone 1)
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 to be increased to decrease the fine aggregate content . as the water-cement ratio is lower by 0.10 proportion of volume of coarse aggregate is increased by 0.02 ( at the rate of -/+ 0.01 for every -+ 0.05 chamge 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 that also volume of coarse aggregate may be rquired to be increased suitably based on experience
for pumpable concrete these value should be reduced by 10 percent
therefore , volume of coarse aggregate = 0.62*0.9= 0.56
volume of fine aggregate content = 1-0.56 = 0.44
8) mix calculations :
the mix calculation per unit volume of concrete shall be follows
a) vaolume of concrete = 1m^3
b) volume of cement = mass of cement /specific gravity of cement *1/1000
= 270/3.15*1/1000
= 0.086 m^3
c) volume of fly ash = mass of fly ash / specific gravity of fly ash *1/1000
= 115/1*1/1000
= 0.052 m^3
d) volume water = mass of water/ specific gravity of water *1/1000
= 140/1*1/1000
= 0.140 m^3
e) volume of chemical admixture
(superplasticizer)(@2.0 percent
by mass of cementitious material ) = mass of chemical admixture /specific gravity of admixture*1/1000
= 7/1.145*1/1000
= 0.007 m^3
f) volume of all in aggregate = [a-(b+c+d + e)]
= 1-(0.086+0.052+0.140+0.007)
= 0.715 m^3
g) mass of coarse aggregate = f*volume of coarse aggregate * specific gravity of coarse aggregate *1000
= 0.715 * 0.56 * 2.74 * 1000
= 1097 kg
h) mass of fine aggregate = f*volume of fine aggregate * specific gravity of fine aggregate * 1000
= 0.715 * 0.44 * 2.74 *1000
= 862 kg
9) mix proporation for trial
cement = 270 kg/m^3
fly ash = 115 kg/m^3
water = 140 kg/m^3
fine aggregate = 862 kg/M^3
coarse aggregate = 1097 kg/m^3
chemical admixture = 7.7 kg/m^3
water cement ratio = 0.364
10) the slump shall be measured and water content and dosage admixture shall be adjusted for achieving the required slump based on trial if required . the proporation shall be reworked for the actual water content and checked for durability requirement .
B:- calculate the concrete mix design for M50 grade concrete without fly ash
ans:- concrete mix proporation
1) stipulations for proporatining
a) grade of concrete : M40
b) types of cement : OPC 43 grade conforming to IS 8112
c) maximum nominal size of aggregate : 20mm
d) minimum cement content : 320 kg/m^3
e) maximum water-cement ratio : 0.45
f) workability : 100 mm ( slump )
g) exposure condition : severe ( for reinforced concrete )
h) method of cocrete placing : pumping
j) degree of supervision : good
k) types of aggregate : crushed angular aggregate
m) maximum cement content : 450 kg/m^3
n) chemical admixture type : superplasticizer
2) test data for material
a) cement used : OPC 43 grade conforming to IS 8112
b) specific gravity of cement : 3.15
c) chemical admixture : superplasticizer conforming to IS 9103
d) specific gravity of :
1) coarse aggregate : 2.74
2) fine aggregate : 2.74
e) water absorption :
1) coarse aggregate : 0.5 percent
2) fine aggregate : 1.0 percent
f) free moisture
1) coarse aggregate :Nil ( absorbed moisture also nil )
2) fine aggregate : Nil
g) sieve analysis
1) coarse aggregate : conforming to table
3) Target strength for mix proporation
f'ck= fck + 1.65 s
where
f'ck = target average compressive strength at 28 days ,
fck = characteristics compresssive strength at 28 days and
s = standard deviation
from table 1 standard deviation s= 5 N/ mm^2
therefore target strength = 50+1.65 *5= 58.25 N/mm^2
4) selection of water-cement ratio
from table 5 of IS 456 maximum water cement ratio = 0.45
based on experience adopt water cement ratio as 0.40
0.40<0.45 hence ok
5) selection of water content
from table 2 maximum water content for 20 mm aggregate = 186 litre ( for 25 mm to 50 mm slump range )
estimated water content for 100 m slump = 186 +6/100*186 = 197 litre
as superplsticizer is used the water content can be reduced up 20 percent and above
based on trial with superplasticizer water content reduction of 29 percent has been achieved hence the arrived water
content = 197*0.71 = 140 litre
6) calculation of cement content
water cement ratio = 0.40
cement content 140/0.40 = 350kg/m^3
from table 5 IS 456 minimum cement content for severe exposure condition = 320 kg/m^3
350 kg/m^3 > 320 kg/m^3 hence ok
7) Proporation of volume of coarse aggregate and fine aggregate and fine aggregate content
from table 3 volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate ( zone 1)
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 to be increased
to decrease the fine aggregate content . as the water cement ratio is lower by 0.10 the proporation of volume of coarse
aggregate is increased by 0.02 ( as the rate of -/+ 0.01 for every -+ 0.05 change in water cement ratio )
therefore corrected proporation of volume of corse aggregate for the water cement ratio of 0.40= 0.62
for pumpable concrete these values should be reduced by 10 percent
therefore volume of coarse aggregate = 0.62 * 0.9 = 0.56
volume of line aggregate content = 1-0.56 = 0.44
8) mix calculations
the mix calculation per unit volume of concrete shall be as follows
a) volume of concrete = 1 m^3
b) volume of cement = mass of cement /specific gravity of cement *1/1000
= 350/3.15*1/1000
= 0.1111 m^3
c) volume of water = mass of water / specific gravity of water *1/1000
= 140/1*1/1000
= 0.140 m^3
d) volume of chemical admixture
( superplasticizer )(@2.0 percent
by mass of cementation material ) = mass of chemical admixture / specific gravity of admixture *1/1000
= 7/1.145*1/1000
= 0.006m^3
e) volume of all in aggregate = [ a-(b+c+d)]
= 1-(0.111+0.140+0.006)
= 0.743m^3
f) mass of coarse aggregate = e * volume of coarse aggregate * specific gravity of
coarse aggregate *1000
= 0.743*0.56*2.74*1000
= 1140 kg
g) mass of fine aggregate = e* volume of fine aggregate * specific gravity of fine aggregate
*1000
= 0.743*0.44*2.74*1000
= 896 kg
9) mix proporation for trial number 1
cement = 350 kg/m^3
water = 140 kg/m^3
fine aggregate = 896 kg/ m^3
coarse aggregate = 1140 kg/m^3
chemical admixture = 7 kg/ m^3
water cement ratio = 0.4
10) the slump shall be measured and water content and dosage of admixture shall be adjusted for achieving the required
slump based on trial if required .the mix proporation shall be networked for the actual water content and checked for
durability requirement .