Project on Concrete Mix Design for various grades of Concrete
Mix design for M35 grade concrete with fly ash
Aim: Mix design for M 35 grade concrete with fly ash
Procedure:
Step: 1
Stipulations for proportioning
a. Grade designation: M35
b. Type of cement: OPC 43 grade conforming to IS 8112
c. Type of mineral admixture: Fly ash confirming to IS 3812 ( Part 1)
d. Maximum nominal size of aggregates: 20mm
e. Minimum cement content : 320 kg/m^3 (Table :5 IS 456-2000,based on exposure condition)
f. Maximum water-cement ratio : 0.45 (Table :5 IS 456-2000,based on exposure condition)
g. Workability:100mm slump value of pumpable concrete
h. Exposure condition: Severe ( for reinforced concrete)
i. Method of concrete placing: Pumping
j. Degree of supervision: Good
k. Type of aggregate: Crushed angular aggregate
l. Maximum cement content : 450 kg/m^3.
m. Chemical admixture type: Superplasticizer.
Step:2
Test data for materials
a. Cement used: OPC 43 grade confirming to IS 8112
b. Specific gravity of cement: 3.15
c. Fly ash: Conforming to IS 3812 part 1
d. Specific gravity of fly ash: 2.2
e. Chemical admixture: Superplasticizer conforming to IS 9103
f. Specific gravity of :
Coarse aggregate: 2.74
Fine aggregate: 2.74
g. Water absorption :
Coarse aggregate : 0.5%
Fine aggregate: 1%
h. Free surface moisture
Coarse aggregate: Nil
Fine aggregate: Nil
i. Sieve analysis
Coarse aggregates:
| IS sieve 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 mix proportioning
Target mean strength f'ck = fck +1.65s
= 35 +1.65*5 =43.25 Nmm2">N/mm2
fck- Characteristic compressive strength
s- Standard deviation
Step:4
Selection of water-cement ratio
Maximum water-cement ratio =0.45 (for severe condition ,from table 5 of IS 456-2000)
On experience water- cement ratio =0.4
0.4 <0.45, Hence OK.
Step :5
Calculation of water content
Maximum water content for 20mm aggregate =186 litres ( Table 2 of IS 10262:2009) 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
Cementatious material ( Cement +flyash ) = 140/0.4 =350 kgm3">kg/m3
In table 5 of IS 456-2000, the cement content for severe exposure =320 kgm3">kg/m3
350 kgm3">kg/m3 > 320 kgm3">kg/m3
Hence OK.
To proportion the mix containing fly ash the following steps are suggested :
a. The percentage of fly ash needs to be decided based on project requirements and the quality of materials.
b. In some cases, an increase in cementitious materials can be warned. Increase in cementitious material content and its percentage may be based on experience and trial
In this increase of 10%, cementitious material content is considered.
Cementitious material content = 350*1.1 =385 kgm3">kg/m3
Water content = 140 kgm3">kg/m3
So, water-cement ratio = 140/385 =0.364
Fly ash at 30% total cementitious material content = 35-30% =115 kgm3">kg/m3
Cement (OPC) =385-115 =270 kgm3">kg/m3
Saving of cement while using fly ash = 350-270=80 kgm3">kg/m3
Fly ash being utilized = 115 kgm3">kg/m3
Step: 7
The proportion of 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 1) for water-cement ratio =0.6
In the 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 the 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-cement 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 calculations
Mix calculation per unit volume of concrete:
a. Volume of concrete = 1 m^3.
b. Volume of cement = (Mass of cement / Specific gravity of cement ) *1/1000
= (270/3.15 )*1/1000 =0.086 m3">m3
c. Volume of flyash = (Mass of flyash / Specific gravity of flyash )*1/1000
= (115/2.2) *1/1000 = 0.052 m3">m3
d. Volume of water = ( Mass of water / Specific gravity of water)*1/1000
= (140/1)*1/1000 =0.140 m3">m3
e. Volume of chemical admixture = ( Mass of admixture / specific gravity of admixture)*1/1000
=( 7.6/1.14)*1/1000 =0.006 m3">m3
f. Volume of aggregate ( Fine and coarse) = a- (b+c+d+e)
= 1-(0.086+0.052+0.140+0.006) =0.716 m3">m3
g. Mass of coarse aggregate = f* Volume of coarse aggregate * Specific gravity of coarse aggregate *1000
= 0.716*0.576*2.74*1000 =1130 kgm3">kg/m3
h. Mass of fine aggregate = f* Volume of fine aggregate* Specific gravity of fine aggreate*1000
= 0.716*0.424*2.74*1000= 831 kgm3">kg/m3
Step :9
Mix proportion
Cement = 270 kgm3">kg/m3
Fly ash = 115 kgm3">kg/m3
Water = 140 kgm3">kg/m3
Fine aggregate = 831 kgm3">kg/m3
Coarse aggregate = 1130 kgm3">kg/m3
Chemical admixture = 7 kgm3">kg/m3
Water- cement ratio = 0.364
Mix ratio 1: 2.15: 2.94
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 field trials.However, durability shall be met.
Result : The mix design for M 35 grade of concrete with fly ash is 1: 2.15:2.94
II Mix design of M 50 grade concrete without fly ash
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 size of aggregate: 20mm
d. Minimum cement content: 320 kgm3">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: Superplasticizer.
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: Superplasticizer 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 sieve 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 Nmm2">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 10262:2009) 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 kgm3">kg/m3
In table 5 of IS 456-2000, the cement content for severe exposure =320 kgm3">kg/m3
350 kgm3">kg/m3 > 320kgm3">kg/m3
Hence OK.
Step: 7
The proportion of 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 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-cement ratio = 0.64
( If the 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">m3
b. Volume of cement = ( Mass of cement / Specific gravity of cement ) *1/1000
= (350/3.15)*1/1000 =0.111 m3">m3
c. Volume of water = (Mass of water/ Specific gravity of water )*1/1000
= (140/1)*1/1000 =0.140 m3">m3
d. Volume of chemical admixture = (Mass of admixture/Specific gravity of admixture)*1/1000
= (7.6/1.145)*1/1000 =0.006 m3">m3
e. Volume of agggregate (fine and coarse) = a-(b+c+d)
=1-( 0.111+0.140+0.006) =0.743 m3">m3
f. Mass of coarse aggregate = e* Volume of coarse aggregate x Specific gravity of coarse aggregate *1000
= 0.743*0.576*2.74*1000= 1173 kgm3">kg/m3
g. Mass of fine aggregate = e* Volume of fine aggregate x Specific gravity of fine aggregate *1000
= 0.743*0.424*2.74*1000 =863 kgm3">kg/m3
Step :9
Mix proportion
Cement = 350 kg/m^3
Water = 140 kg/m^3
Fine aggregate= 863 kg/m^3
Coarse aggregate = 1173 kg/m^3
Chemical admixture = 7 kg/m^3
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 field trials.However, durability shall be met.
Result : The mix design for M 35 grade of concrete without fly ash is 1 : 2.46 : 3.35