Project on Concrete Mix Design for various grades of Concrete
Result : The mix design for M 35 grade of concrete with flyash is 1: 2.15:2.94
Mix design of M 50 grade concrete
Aim: Mix design of M 50 grade concrete
Procedure :
Step :1
Stipulation for proportioning
a. Grade designation : M50
b. Type of cement : OPC grade 43 conforming to IS 8112
c. Maximum nominal sizeof aggregate: 20mm
d. Minimum cement content : 320 kg/m3
e. Maximum water-cement ratio : 0.45 (Table :5 IS 456-2000,based on exposure condition)
f. Workability :100mm ,slump value of pumpable concrete
g. Exposure condition : Severe ( for reinforced concrete)
h. Method of concrete placing : Pumping
i. Degree of supervision : Good
j. Type of aggregate: Crushed angular aggregate
k. Maximum cement content : 450 kg/m^3.
l. Chemical admixture type : Superplaticizer.
Step:2
Test data for materials
a. Cement used : OPC 43 grade confirming to IS 8112
b. Specific gravity of cement : 3.15
c. Chemical admixture : Superplaticizer conforming to IS 9103
d. Specific gravity of :
Coarse aggregate : 2.74
Fine aggregate : 2.74
e. Water absorption :
Coarse aggregate : 0.5%
Fine aggregate : 1%
f. Free surface moisture
Coarse aggregate : Nil
Fine aggregate : Nil
g. Seive analysis
Coarse aggregates:
IS seive size (mm) Analysis of coarse aggregate fraction % of different fraction Remarks
I II I II Combined
20 100 100 60 40 100 Confirming to
10 0 71.2 0 28.5 28.5 Table 2
4.75 9.4 3.7 3.7 of
2.36 0 IS 383
Fine aggregate : Conforming to grading Zone 1 of table 4 IS 383.
Step:3
To find target mean strength for proportioning
Target mean strength , f'ck =fck +1.65 s
= 50+1.65*5 =58.25 N/mm2
fck = Characteristic strength
s=standard deviation
Step:4
Selection of water cement ratio
From Table :5 of IS 456-2000, by exposure condition
Here severe condition is considered , Maximum water-cement ratio=0.45
Based on experience water- cement ratio =0.4
0.4 <0.45 ,Hence OK.
Step :5
Selection of water content
Maximum water content for 20mm aggregate =186 litres ( Table 2 of IS 1026:2009) for 25mm to 50mm slump range
For 100 mm slump ,= 186+(6/100)*186 =197 litres
As superplaticizer is used, the water content is reduced upto 30%
Based on trials water content reduction of 29% is achieved with plasticizer
Hence arrived water content = 197*0.71 = 140 litres
Step :6
Calculation of cement content
Water - cement ratio = 0.4
Cement content = 140/0.4 =350 kg/m3
In table 5 of IS 456-2000, the cement content for severe exposure =320 kg/m3
350 kg/m3 > 320kg/m3
Hence OK.
Step: 7
Proportion of volume of coarse aggregate and fine aggregate content
From table 3 of IS 1026:2009 ,volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone 1 ) for water- cement ratio =0.6
In present case the water - cement ratio is 0.4
Therefore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content .
As the water- cement ratio is lowered by 0.1 ,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)
Hence the corrected value of coarse aggregate for the water-cemnt ratio = 0.64
( If coarse aggregate is not of angular type, then also the volume of coarse aggregate may be required to be increased suitably ,based on experience)
For pumpable concrete, these are reduced by 10 %
Volume of coarse aggregate = 0.64*0.9 = 0.576
Volume of fine aggregate = 1-0.576 =0.424
Step:8
Mix calculation
For unit volume of concrete
a. Volume of concrete = 1 m3
b. Volume of cement = ( Mass of cement / Specific gravity of cement ) *1/1000
=(350/3.15)*1/1000
=0.111 m3
c. Volume of water = (Mass of water/ Specific gravity of water )*1/1000
= (140/1)*1/1000 =0.140m3
d. Volume of chemical admixture = (Mass of admixture/Specific gravity of admixture)*1/1000
= (7.6/1.145)*1/1000 =0.006m3
e. Volume of agggregate (fine adn coarse) = a-(b+c+d)
=1-(0.111+0.140+0.006) =0.743m3
f. Mass of coarse aggregate = ex Volume of coarse aggregate x Specific gravity of coarse aggregate x 1000
=0.743*0.576*2.74*1000= 1173kg/m3
g. Mass of fine aggregate =e* Volume of fine aggregate* Specific gravity of fine aggregate *1000
= 0.743*0.424*2.74*1000 =863 kgm3
Step :9 Mix proportion
Cement = 350 kg/m3
Water = 140 kg/m^3
Fine aggregate= 863 kg/m3
Coarse aggregate = 1173 kg/m3
Chemical admixture = 7 kg/m3
Water cement ratio =0.4
Mix ratio =1: 2.46: 3.35
Step : 10
The slump shall be measured and the water content and dosage of admixyure shall be adjusted for achieving the required slump on trial . The mix proportion shall be reworked for the actual water content and checkedd for durability requirements.
Step :11
Two or more trials having variation of 10 % of water-cement ratio in Clause 10( Step 10) shall be carried out and a graph between three water -cement ratios and corresponding strengths shall be plotted to work out the mix proportions for the given target strength for feild trials .However durability shall be met.
Result : The mix ratio for M 50 grade concrete is 1:2.46:3.35