Project on Concrete Mix Design for various grades of Concrete
Part 1 : Calculate the Concrete Mix Design for M35 grade concrete with fly ash
1 STIPULATIONS FOR PROPORTIONING
a) Grade designation : M35
b) Type of cement : OPC 43 Grade conforming IS 12269
c) Maximum nominal size of aggregate : 20mm
d) Minimum cement content : 320 kg/m3 (IS 456:2000)
e) Maximum water-cement ratio : 0.45 (Table 5 of IS 456:2000)
f) Workability : 100-120mm slump
g) Exposure condition : Moderate (For Reinforced Concrete)
h) Method of concrete placing : Pumping
j) Degree of supervision : Good
k) Type of aggregate : Crushed Angular Aggregates
m) Maximum cement content : 450 kg/m3
n) Chemical admixture type : Super Plasticizer
2.TEST DATA FOR MATERIALS
a) Cement used : OPC 43 Grade conforming IS 12269
b) Specific gravity of cement : 3.15
c) Chemical admixture : Super Plasticizer
d) Specific gravity of
- Coarse aggregate 20mm : 2.74
Fine aggregate : 2.74
e) Water absorption:
- Coarse aggregate : 0.5 %
Fine aggregate (M.sand) : 2.5 %
f) Free (surface) moisture:
- Coarse aggregate : Nil (Absorbed Moisture also Nil)
Fine aggregate : Nil
g) Sieve analysis:
- Coarse aggregate: Conforming to all in aggregates of Table 2 of IS 383
Fine aggregate : Conforming to Grading Zone II of Table 4 of IS 383
h) Sp.gravity of fly ash : 2.2
3.Target mean strength :
F'ck = Fck+1.65S
where ,Fck = 35N/mm^2
and S = 5 (as per IS 10262 2009 table 1)
F'ck = 35+(1.65*5)
F'ck =43.25N/mm^2
4.Selection of w/c ratio :
For M35 concrete ,
assume the exposure condition is extreme
From table 5 of IS 456 2000
Extrem w/c ratio = 0.4
M35 W/c ratio = 0.45
0.45 > 0.40
hence, the w/c = 0.4
Mini cement content = 320Kg /m^3
5.Selection of water content :
Assume the nominal size of aggregate = 20mm
As per Table 2 of IS 10262 2009
Mini water content for 20mm aggregate = 186 litres
slump range 25mm to 50mm.
Estimated water content for 100 mm slump= 186+(6/100)X 186 = 197 litre
As superplasticizer is used. The water content can he reduced up 30% percent.
Based on trials with superplasticizer water content reduction of 29 percent has been achieved.
Hence, the
arrived water content = 197 x 0.71 = 140 litres.
If the admixture used As plastisizers 20% reduction
186 X 80/100 = 140litres
6.Calucation of cementitios material [cement + fly ash]
W/c ratio = 0.40
water content = 140 kg
Cementitious content = 140/0.4= 350kg /m^3
From Table 5 of IS 456, minimum cement content for 'severe' exposure condition
Mini cemet content = 320kg /m^3
320<350 Hance ok
Now, to proportion a mix containing fly ash the following steps are suggested:
- Decide the percentage fly ash to be used based on project requirement and quality of materials.
- In certain situations increase in cernentitious material content may be warranted, The decision on increase in cementitious material content and its percentage may be based on experience and trial
- NOTE - This illustrative example is with increase of 10 percent cement itious material content.
350*1.10= 385 kg/m^3
water = 140 kg/m^3
Now the W/C = 140/385 =0.364
Fly ash 30% at total cementitious taken
then the fly ash content= 385x 0.3 =115 kg/m^3
There fore The cement content = 385-112= 270 kg/m^3.
7: VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT
From Table 3 of (IS 10262:2009) Volume of coarse aggregate
corresponding to 20 mm size aggregate and fine aggregate (Zone II) 0.62.
for water-cement ratio of 0.50 is In the present case water-cement ratio is 0.44.
Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content.
As the water-cement ratio is lower by 0.06. 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).
Therefore, corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.44 0.632 0.632 x 0.9 =0.568. For pumpable concrete these values should be reduced up to 10%.
Therefore, volume of coarse aggregate Volume of fine aggregate content 1 - 0.568 =0.431 Volume of fine aggregate and coarse aggregate is 0.431 and .568
8: MIX CALCULATIONS
The mix calculations per unit volume of concrete shall be as follows:
a) Volume of concrete 1 m3
b) Volume of cement = [Mass of cement] / [specific Gravity of Cement] x 1/1000 = (277/3.15) x (1/1000) =0.087m3
c) Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000 = (158/1) X (1/1000) = 0.158m3
d) Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000 = (7.6/1.145) x (1/1000) =0.006 m3
e) Volume of all in aggregate = [a-(b+c+d)] = [1-(0.114+0.158+0.006)] = 0.722 m^3
f) Mass of coarse aggregate= ex Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000 = 0.722x 0.568 x 2.74 x 1000 = 1123 kg/m3
g) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000 = 0.722x 0.431x 2.64 x 1000 = 821 kg/m3
9:MIX PROPORTOINS :
Cement : 270 kg/m3
Fine aggregate : 862kg/m3
Coarse aggregate : 1079 kg/m3
Water : 140 kg/m3
Admixture : 7.7 kg/m3
fly ash : 115kg/m3
water cement ratio : 0.364
Mix Proportion By weight 1:2.23:2.80
10: The slump shall be measured, the water content and dosage of admixture shall be adjusted for achieving the required slump on trial.
The mix proportion shall be reworked for the actual water content and checked for durability requirements
11: Two more trials having variation of 10% of water-cement ratio 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 for field trials.
RESULTS: Mix Proportion by weight of M35 grade of concrete with fly ash is 1:2.08:2.72 and its water-cement ratio was found to be 0.4.
PART 2 : Calculate the Concrete Mix Design for M50 grade concrete without Fly ash
Step 1 : STIPULATIONS FOR PROPORTIONING
a) Grade designation : M50
b) Type of cement : OPC 53 Grade conforming IS 12269
c) Maximum nominal size of aggregate : 20mm
d) Minimum cement content : 320 kg/m3 (Table 5 of IS 456:2000)
e) Maximum water-cement ratio : 0.45 (Table 5 of IS 456:2000)
f) Workability : 100-120mm slump
g) Exposure condition : Moderate (For Reinforced Concrete)
h) Method of concrete placing : Pumping
j) Degree of supervision : Good
k) Type of aggregate : Crushed Angular Aggregates
m) Maximum cement content : 450 kg/m3
n) Chemical admixture type : Super Plasticizer
2 TEST DATA FOR MATERIALS
a) Cement used : OPC 53 Grade conforming IS 12269
b) Specific gravity of cement : 3.15
c) Chemical admixture : Super Plasticizer
d) Specific gravity of
- Coarse aggregate 20mm : 2.74
Fine aggregate : 2.64
e) Water absorption:
- Coarse aggregate : 0.5 %
Fine aggregate (M.sand) : 2.5 %
f) Free (surface) moisture:
- Coarse aggregate : Nil (Absorbed Moisture also Nil)
Fine aggregate : Nil
g) Sieve analysis:
- Coarse aggregate: Conforming to all in aggregates of Table 2 of IS 383
Fine aggregate : Conforming to Grading Zone II of Table 4 of IS 383
3.Target mean strength :
F'ck = Fck+1.65S
where ,Fck = 50N/mm^2
and S = 5 (as per IS 10262 2009 table 1)
F'ck = 50+(1.65*5)
F'ck =58.25N/mm^2
4.Selection of w/c ratio :
For M50 grade concrete ,
assume the exposure condition is extreme
From table 5 of IS 456 2000
severe w/c ratio = 0.45
M50 W/c ratio = 0.44
0.45 > 0.44
hence, the w/c = 0.44
Mini cement content = 320Kg /m^3
5.Selection of water content :
Assume the nominal size of aggregate = 20mm
As per Table 2 of IS 10262 2009
Mini water content for 20mm aggregate = 186 litres (slump range 25mm to 50mm)
clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm slump.
so a 6%is to be added to it.
Estimated water content for 100mm slump = 186+(6/100)*186 = 197 litre
(Note: if super plasticizer is used, the water content can redused up to 20%
Based on trials with super plasticizers water content reduction of 20% has been achieved)
Hence the arrived water content : 197*0.8=158 litres
6.Calucation of cement required :
Adopted w/c ratio =0.44
cement content =158/0.44=359kg/m^3
From table 5 of IS 456 2000 , Minimum cement content for severe exposure conditions = 320kg/m^3
359>320
cement required is 359kg/m^3
STEP 7: VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT
From Table 3 of (IS 10262:2009) Volume of coarse aggregate
corresponding to 20 mm size aggregate and fine aggregate (Zone II) 0.62.
for water-cement ratio of 0.50 is In the present case water-cement ratio is 0.44.
Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content.
As the water-cement ratio is lower by 0.06. 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).
Therefore, corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.44 0.632 0.632 x 0.9 =0.568. For pumpable concrete these values should be reduced up to 10%.
Therefore, volume of coarse aggregate Volume of fine aggregate content 1 - 0.568 =0.431 Volume of fine aggregate and coarse aggregate is 0.431 and 0.568
8: MIX CALCULATIONS
The mix calculations per unit volume of concrete shall be as follows:
a) Volume of concrete 1 m3
b) Volume of cement = [Mass of cement] / [specific Gravity of Cement] x 1/1000 = (359/3.15) x (1/1000) =0.114m3
c) Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000 = (158/1) X (1/1000) = 0.158m3
d) Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000 = (7.6/1.145) x (1/1000) =0.006 m3
e) Volume of all in aggregate = [a-(b+c+d)] = [1-(0.114+0.158+0.006)] = 0.722m3
f) Mass of coarse aggregate= ex Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000 = 0.722x 0.568 x 2.74 x 1000 = 1123 kg/m3
g) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000 = 0.722x 0.431x 2.64 x 1000 = 821 kg/m3
9:MIX PROPORTOINS :
Cement : 359 kg/m3
Fine aggregate : 821 kg/m3
Coarse aggregate : 1123 kg/m3
Water : 1581 kg/m3
Admixture : 7.81 kg/m3
water cement ratio : 0.44
Mix Proportion By weight 1:2.28:3.12
10: The slump shall be measured, the water content and dosage of admixture shall be adjusted for achieving the required slump on trial.
The mix proportion shall be reworked for the actual water content and checked for durability requirements
11: Two more trials having variation of 10% of water-cement ratio 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 for field trials.
RESULTS: Mix Proportion by weight of M50 grade of concrete without fly ash is 1:2.28:3.12 and its water-cement ratio was found to be 0.44.