Project on Concrete Mix Design for various grades of Concrete
AIM:
To Calculate the concrete mix design for M35 grade concrete with fly ash & M50 grade concrete without fly ash.
INTRODUCTION:
Concrete mix design is the process of finding the right proportions of cement, sand, and aggregates for concrete to achieve target strength in structures.
So, the concrete mix design can be stated as Concrete Mix = Cement:Sand: Aggregates. The concrete mix design involves various steps, calculations, and laboratory testing to find the right mix proportions.
The design is done according to the requirements of concrete strength. The benefit of concrete mix design is that it provides the right proportions of materials, thus making the concrete construction economical in achieving the required strength of structural members. As the quantity of concrete required for large constructions is huge, the economy in the number of materials such as cement makes the project construction economical.
This project consists of two parts, the first part deals with the design of M35 grade concrete with fly ash and the second part deals with the design of M50 grade concrete without fly ash.
OBJECTIVE:
The objective of this project is to produce a mix design for M35 grade concrete containing fly ash and M50 grade concrete without fly ash. The mix will be prepared as per IS method. The concrete mix proportioning guidelines are taken from the code IS 10262:2009 & IS 456:2000
PART 1:
Mix design of M30 Grade concrete with fly ash designed as per IS 10262:2009 & IS 456:2000
1: Stipulations of concrete mix design
a) Grade designation : M35
b) Type of cement : OPC 43 Grade conforming IS 8112
c) Maximum nominal size of aggregate : 20mm
d) Minimum cement content : 320 kg/m^3 (IS 456:2000)
e) Maximum water-cement ratio : 0.45 (Table 5 of IS 456:2000)
f) Workability : 100 mm slump
g) Exposure condition : Severe (For Reinforced Concrete)
h) Method of concrete placing : Pumping
i) Degree of supervision : Good
j) Type of aggregate : Crushed Angular Aggregates
k) Maximum cement content : 450 kg/m^3
l) Chemical admixture type : Super Plasticizer
m) Type of Minereal admixture : Fly ash confirming to IS 3812(Part 1)
2. Test data for materials:
a) Cement used : OPC 43 grade confirming to IS 8112
b) Specific gravity of cement : 3.15
c) Mineral admixture : Fly ash confirming to IS 3812(Part 1)
d) Specific gravity of fly ash : 2.2
e) Chemical admixture type : Super Plasticizer confirming to IS 9103
f) specific garvity of:
Coarse aggregate : 2.74
Fine aggregate : 2.74
g) Water absorption:
Coarse aggregate : 0.5 %
Fine aggregate : 2.5 %
h) Free surface moisture:
Coarse aggregate : Nil
Fine aggregate : Nil
i) Sieve analysis:
1) Coarse aggregate : Conforming to all in aggregates of Table 2 of IS 383
2) Fine aggregate : Conforming 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 = characteristics compressive strength at 28 days, and
S = standard deviation.
From Table I of IS 10262:2009, Standard Deviation, S = 5 N/mm^2. Therefore, target strength = 35 + 1.65 x 5 = 43.25 N/mm^2.
4. Selection of w/c ratio
The maximum water-cement ratio to design M35 grade concrete is 0.45 (From Table 5 of IS 456-2000).
Based on experience, adopt w/c ratio is 0.44
0.44 < 0.45 Hence ok.
Water-cement Ratio = 0.44
5. Selection of water content
From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 liters (for 25 to 50 mm 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 20% and above
Based on trials water content reduction of 25% has been achieved with a plasticizer.
Hence the arrived water content = 197*0.75 = 148 litre
6. Calculation of Cement Content and Fly ash
w/c Ratio = 0.44
Cement Content = 148/0.44 = 336 kg/m^3
From Table 5 of IS 456, Minimum cement content for ‘severe’ exposure conditions = 320kg/m^3
336 kg/m^3 > 320 kg/m^3, hence ok.
Now, to proportion a 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 increase in cementitious material can be warranted. An increase in cementitious material content and its percentage may be based on experience and trial (This example is with an increase of 10% cementitious material content)
Cementitious material content = 336 x 1.10 = 370 kg/m^3
Water content = 148 kg/m^3
So water-cement ratio = 148/370 = 0.4
Fly ash at 30% total cementitious material content = 370 x 30% = 111 kg/m^3
Cement (OPC) = 370-111= 259 kg/m^3
Saving of cement while using fly ash = 336-259= 77 kg/m^3 and
Fly ash being utilized = 111 kg/m^3
7. Proportion of volume of coarse aggregate and fine aggregate:
From Table 3 of (IS 10262:2009) Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I) for water-cement ratio = 0.6.
In the present case, the water-cement ratio is 0.44.
Therefore, the 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 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).
Therefore, corrected of the volume of coarse aggregate for the water-cement ratio of 0.44 = 0.632
(NOTE – In case the coarse aggregate is not angular, then also the volume of coarse aggregate may be required to be increased suitably based on experience.)
For pumpable concrete, these values should be reduced up to 10%.
Therefore, volume of coarse aggregate =0.632 x 0.9 =0.568.
Volume of fine aggregate content = 1 – 0.568= 0.431.
Therefore, Volume of fine aggregate and coarse aggregate is 0.43 and 0.57
8. Mix Calculations
The mix calculations 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] x 1000}
= 259/{3.15 x 1000}
= 0.082 m^3
c) Volume of fly ash = Mass of fly ash/{[Specific Gravity of fly ash] x 1000}
= 111/{2.2 x 1000}
= 0.05 m^3
d) Volume of water = Mass of water/ {[Specific Gravity of water] x 1000}
= 148/{1 x 1000}
= 0.148 m^3
e) Volume of chemical admixture = Mass of chemical admixture/ {[Specific Gravity of water] x 1000}
=7.6/1.145 x 1/1000
=0.006 m^3
f) Volume of all in aggregate = [a-(b+c+d+e)]
= [1-(0.082+0.05+0.148+0.006)]
= 0.714 m^3
g) Mass of coarse aggregate = e x Volume of Coarse Aggregate x Specific Gravity of coarse Aggregate x 1000
= 0.714x 0.57 x 2.74 x 1000
= 1115 kg/m^3
h) Mass of fine aggregate = e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000
= 0.743x 0.43 x 2.74 x 1000
= 875 kg/m3
9. Mix Proportions
Cement = 259 kg/m^3
Fly ash = 111 kg/m^3
Water = 148 kg/m^3
Fine aggregate = 875 kg/m^3
Coarse aggregate = 1115 kg/m^3
Chemical admixture = 7 kg/m3^3
Water-cement ratio = 0.40
Trial Mix Ratio = 1:3.37:4.3
PART 2:
Mix design of M50 Grade concrete designed as per IS 10262:2009 & IS 456:2000
1: Stipulations of concrete mix design
a) Grade designation :M50
b) Type of cement : OPC 43 Grade conforming IS 8112
c) Maximum nominal size of aggregate : 20mm
d) Minimum cement content : 320 kg/m^3 (IS 456:2000)
e) Maximum water-cement ratio : 0.45 (Table 5 of IS 456:2000)
f) Workability : 100 mm slump
g) Exposure condition : Severe (For Reinforced Concrete)
h) Method of concrete placing : Pumping
i) Degree of supervision : Good
j) Type of aggregate : Crushed Angular Aggregates
k) Maximum cement content : 450 kg/m^3
l) Chemical admixture type : Super Plasticizer
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 type : Super Plasticizer confirming to IS 9103
d) specific garvity of:
Coarse aggregate : 2.74
Fine aggregate : 2.74
e) Water absorption:
Coarse aggregate : 0.5 %
Fine aggregate : 2.5 %
f) Free surface moisture:
Coarse aggregate : Nil
Fine aggregate : Nil
g) Sieve analysis:
1) Coarse aggregate : Conforming to all in aggregates of Table 2 of IS 383
2) Fine aggregate : Conforming 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 = characteristics compressive strength at 28 days, and
S = standard deviation.
From Table I of IS 10262:2009, Standard Deviation, S = 5 N/mm^2. Therefore, target strength = 50 + 1.65 x 5 = 58.25 N/mm^2.
4. Selection of w/c ratio:
Adopted maximum water-cement ratio = 0.45 From Table 5 of IS 456-2000 for severe exposure.
Based on experience, adopt w/c ratio is 0.44
0.44 < 0.45 Hence ok.
5. Selection of water content:
From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 litre (for 25 to 50 mm slump range)
Estimated water content for 100 mm slump = 186+ (6/186) = 197 litre.
As Super plasticizer is used, the water content can be reduced upto 20% and above
Based on trials water content reduction of 20% has been achieved with plasticizer.
Hence the arrived water content = 197*0.8 = 158 litre
6. Calculation of Cement Content:
w/c Ratio = 0.44
Cement Content = 158/0.44 = 359 kg/m^3
From Table 5 of IS 456, Minimum cement content for ‘severe’ exposure conditions = 320kg/m^3
350 kg/m^3 > 320 kg/m^3, hence ok.
7. Proportion of volume of coarse aggregate and fine aggregate:
From Table 3 of (IS 10262:2009) Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I) for water-cement ratio = 0.6.
In the present case, the water-cement ratio is 0.44.
Therefore, the 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 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).
Therefore, corrected the volume of coarse aggregate for the water-cement ratio of 0.44 = 0.632
(NOTE – In case the coarse aggregate is not angular, then also the volume of coarse aggregate may be required to be increased suitably based on experience.)
For pumpable concrete, these values should be reduced up to 10%.
Therefore, volume of coarse aggregate =0.632 x 0.9 =0.568.
Volume of fine aggregate content = 1 – 0.568= 0.43.
The volume of fine and coarse aggregate is 0.43 and 0.57.
8. Mix Calculations:
The mix calculations 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] x 1000}
= 359/{3.15 x 1000}
= 0.114 m^3
c) Volume of water = Mass of water/ {[Specific Gravity of water] x 1000}
= 158/{1 x 1000}
= 0.158 m^3
d) Volume of chemical admixture = Mass of chemical admixture/ {[Specific Gravity of water] x 1000}
=7.6/1.145 x 1/1000
=0.006 m^3
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 = e x Volume of Coarse Aggregate x Specific Gravity of coarse Aggregate x 1000
= 0.722x 0.57 x 2.74 x 1000
= 1128 kg/m^3
g) Mass of fine aggregate = e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000
= 0.722x 0.43x 2.74 x 1000
= 820 kg/m3
9. Mix Proportions:
Cement = 359 kg/m^3
Water = 158 kg/m^3
Fine aggregate = 820 kg/m^3
Coarse aggregate = 1128 kg/m^3
Chemical admixture = 7 kg/m3^3
Water-cement ratio = 0.44
Trial Mix Ratio = 1:2.28:3.14
10: The slump shall be measured and 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 duravility requirements.
11. Two more trials having variation of 10% of water-cement ratio in Clause X shall be carried out and the graph between three water-cement ratios and corresponding strength shall be plotted to work out the mix proportions for the given target strength for field trials. However, durability shall be met.
RESULT:
Mix Proportion of M35 grade concrete with fly ash is 1:3.37:4.3 and the water-cement ratio is 0.4
Mix Proportion of M50 grade concrete without fly ash is 1:2.28:3.14 and the water-cement ratio is 0.44