Project on Concrete Mix Design for various grades of Concrete
Aim:
- To prepare the concrete mix design for M35 grade concrete with fly ash and M50 grade concrete without fly ash.
Introduction:
The mix design for concrete is calculated to proportioning the concrete ingredients to provide required strength and durability. Indian standard code books such as (IS 10262-2019, IS 456-2000, IS 10262-2009) are refered for guidelines.
Step by step procedure :The concrete mix design for M35 grade concrete with flyash:
- Stipulations:
Grade of concrete = M35
Type of cement = OPC 43 grade confirming to IS 8112
Type of admixture is Fly ash
Maximum nominal size of aggregate is 20mm
Minimum cement content 320kg/m^3
Maximum water cement ratio 0.45
Workability = 100mm
Exposure condition is extreme
Degree of supervision is good
Type of aggregate is crushed angular aggregate
Method of placing concrete is pumping
Maximum cement content 450kg/m^3
- Test data for materials:
Specific gravity of cement is 3.25
Specific gravity of flyash is 2.2
Chemical admixture is superplasticizer
Specofic gravity of coarse aggregate 2.74
Specific gravity of fine aggregate 2.74
Water absorption of coarse aggregate 0.5%
Water obsorption of fine aggregate 1.0%
- Target mean strength:
ft= fck +1.65 * S
(fck = 35, standard deviation value for M35 is 5 as per IS 10262-2009 table 1)
ft=35+1.65*5
Target mean strength =43.25N/mm^2
- Selection of water cement ratio:
As per IS 456-2000 from table 5
For extreme condition is 0.4
- Selection of water content:
As per table 2 IS 10262-2009 water content for 20mm coarse aggregate 186kg for 25 and 50mm slump range
So our slump range is 100mm for every increase in slump 25mm, 3% of water content is added.
So 6% of 186kg or litre water content is added to 186kg or litre.
Estimated water content for 100mm slump =186+6/100*186 = 197.16 litre
Water content reduction of 20% is achieved with superplastisizers
Hence arrived water content = 197.16*0.8=157.6 litre
- Calculation of cement content and flyash:
Water cement ratio =0.4
Cement content =157.6/0.4=394kg/m^3
As per IS 456-2000 the minimum cement for extreme exposure condition is 360kg/m^3.
We got 394kg/m^3 which is greater than 360kg/m^3.
Hence ok.
To proportion the mix containing fly ash the following steps are suggested.
- The percentage of fly ash needs to be decided based on the project requirement and quality of materials.
- In some cases increase the cementitious material can be warned. An increase in cementitious material content and its percentage is based on experience and trails.
In this increase of 10%, cementitious material content is considered.
Cementitious material content =394*1.10=433.4 kg/m^3
Water content=157.6 litre
Water cement ratio = 158/433=0.36
Flyash 30% of total cementitious material content =433*0.3=129.9=130kg/m^3
Cement = 433-130=303kg/m^3
Flyash =130kg/m^3
- Proportion of the volume of coarse aggregate and fine agregate content:
From table 5 of IS 10262-2019, the volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (Zone 2) for water a cement ratio of 0.5 =0.62. For reduction of 0.05 value of w/c ratio it incearses the volume of coarse aggregate is 0.01. So for w/c ratio of 0.4, the volume of coarse aggregate is increased by 0.02.
Then the corrected proportion of the volume of coarse aggregate for the water cement ratio of 0.4=0.64.
For pumpable concrete, these values should be reduced by 10 percent. Therefore, volume of coarse aggregate=0.64*0.90=0.576.
Volume of fine aggregate content=1-0.576=0.424.
- Mix calculation:
a)Volume of concrete=1m^3
b)Volume of cement=(Mass of cement/sp. gravity of cement)*(1/1000)
=(303/3.25)*1/1000)
=0.093m^3
c)Volume of flyash=(Mass of flyash/sp. gravity of flyash)*(1/1000)
=(130/2.2)*(1/1000)
=0.059m^3
d)Volume of water=(Mass of water/sp. gravity of water)*(1/1000)
=(158/1)*(1/1000)
=0.158m^3
Volume of chemical admixture (superplastisizer) @2.0% by mass of cementitious material
=(Mass of superplastisizer/sp. gravity of superplastisizer)*(1/1000)
=(7.88/1.145)*1/1000)
=0.00688m^3
Volume of all aggregates =(a-(b+c+d+e))
=1-(0.093+0.059+0.158+0.00688))
=0.68 m^3
Mass of coarse aggregate =Volume of all aggregate*volume of CA*Sp. gravity CA*1000
=0.68*0.567*2.74*1000
=1073.2kg/m^3
Mass of fine aggrergate =Volume of all aggregate*volume of FA*Sp. gravity FA*1000
=0.68*0.424*2.74*1000
=790kg/m^3
- Mix proportions
Cement =303kg/m^3
Flyash =130kg/m^3
Water =158kg/m^3
Superplastisizer =7.88
Fine aggregate =790kg/m^3
Coarse aggregate =1073kg/m^3
Water cement ratio =0.4
- Result:
Mix proportion arrived 1:1.82:2.74
Step by step procedure for:-
The concrete mix design for M50 without flyash:
- Stipulation:
Grade of concrete M50
Type of cement is OPC 43 grade confirming to IS 8112
Maximum nominal size of aggregate 20mm
Minimum cement content is 320kg/m^3
Maximum water cement ratio is 0.45
Workability is 100mm slump
Exposure condition is extreme for reinforced concrete
Method of concrete placing: pumping
Degree of supervision is good
Type of aggregate is crushed angular aggregate
Maximum cement content 450kg/m^3
Chemical admixture type is super plasticizer
- Test data for materials:
Specific gravity of cement is 3.25
Chemical admixture is superplasticizer
Specofic gravity of coarse aggregate 2.74
Specific gravity of fine aggregate 2.74
Water absorption of coarse aggregate 0.5%
Water obsorption of fine aggregate 1.0%
- Target mean strength:
ft= fck +1.65 * S
(fck = 50, standard deviation value for M50 is 5 as per IS 10262-2009 table 1)
ft=50+1.65*5
Target mean strength =58.25N/mm^2
- Selection of water cement ratio:
As per IS 456-2000 from table 5
For extreme condition is 0.4
- Selection of water content:
As per table 2 IS 10262-2009 water content for 20mm coarse aggregate 186kg for 25 and 50mm slump range
So our slump range is 100mm for every increase in slump 25mm, 3% of water content is added.
So 6% of 186kg or litre water content is added to 186kg or litre.
Estimated water content for 100mm slump =186+6/100*186 = 197.16 litre
Water content reduction of 20% is achieved with superplastisizers
Hence arrived water content = 197.16*0.8=158 litre
- Calculation of cement content:
Water cement ratio =0.4
Cement content =157.6/0.4=394kg/m^3
As per IS 456-2000 the minimum cement for extrem e exposure condition is 360kg/m^3.
We got 394kg/m^3 which is greater than 360kg/m^3.
Hence ok.
- Proportion of the volume of coarse aggregate and fine agregate content:
From table 5 of IS 10262-2019, the volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (Zone 2) for water a cement ratio of 0.5 =0.62. For reduction of 0.05 value of w/c ratio it incearses the volume of coarse aggregate is 0.01. So for w/c ratio of 0.4, the volume of coarse aggregate is increased by 0.02.
Then the corrected proportion of the volume of coarse aggregate for the water cement ratio of 0.4=0.64.
For pumpable concrete, these values should be reduced by 10 percent of 100 percent.
Volume of coarse aggregate=0.64*0.90=0.576.
Volume of fine aggregate content=1-0.576=0.424.
- Mix calcution:
Volume of concrete=1 m^3
Volume of cement=(Mass of cement/sp. gravity of cement)*(1/1000)
=(394/3.25)*1/1000)
=0.121 m^3
Volume of water=(Mass of water/sp. gravity of water)*(1/1000)
=(158/1)*(1/1000)
=0.158 m^3
Volume of chemical admixture (superplastisizer) @1.5% by mass of cement material
=(Mass of superplastisizer/sp. gravity of superplastisizer)*(1/1000)
=(6/1.145)*1/1000)
=0.00524 m^3
Volume of all aggregates =(a-(b+c+d))
=1-(0.121+0.158+0.0052))
=0.7158 m^3
Mass of coarse aggregate =Volume of all aggregate*volume of CA*Sp. gravity CA*1000
=0.7158*0.576*2.74*1000
=1130 kg/m^3
Mass of fine aggrergate =Volume of all aggregate*volume of FA*Sp. gravity FA*1000
=0.7158*0.424*2.74*1000
=832 kg/m^3
- Mix proportions
Cement =394 kg/m^3
Water =158kg/m^3
Superplastisizer =6
Fine aggregate =832nkg/m^3
Coarse aggregate =1130 kg/m^3
Water cement ratio =0.4
- Result:
Mix proportion arrived 1:2.11:2.86