Project on Concrete Mix Design for various grades of Concrete
Project: Project on concrete mix design for M35 grade of concrete with fly ash and M50 grade of concrete without fly ash
Aim: To calculate the concrete mix design for M35 grade of concrete with fly ash and M50 grade of concrete without fly ash.
Introduction: Concrete mix design is the method of finding the precise proportion of cement, sand and aggregate for concrete to achive the target strength in structures, i.e. cement: sand: aggregates. this project consist of two parts, the first part deal with the design of M35 grade of concrete with fly ash and second part is the design of M50 grade of concrete without fly ash.
Objective: The objective is to produce a mix design for M35 grade concrete containing fly ash and M50 grade of concrete without fly ash. The mix is prepared as per IS method: concrete mix proportioning guidelines from IS 10262:2009 and recommended guidelines from IS10262:1982.
Equations used:
1) Target mean strength:
f'ck = fck + 1.65 S
where
- f'ck = target average compressive strength at 28 days
- fck = cherecterstics compressive strength at 28 days, and
- S = Standard deviation
2) Cement Content:
Cement content = water content / water cement ratio
3) Volume calculations:
- Volume of cement= (mass of cement / specific gravity of cement) x 1/1000
- Volume of water= (mass of water / specific gravity of water) x 1/1000
- Volume of chemical admixture = (Mass of admixture / specific gravity of admixture) x 1/1000
- Volume of all in aggregate = [a-(b+c+d)]
- mass of coarse aggregate = e x volume of coarse aggregate x specific gravity of fine aggregate x 1000
- mass of fine aggregate = e x volume of fine aggregate x specific gravity of fine aggregate x 1000
Part 1 : To calculate the concrete mix design for M35 grade of concrete with fly ash.
Step 1 : stipulation for concrete design mix
Grade designation : M35
Type of cement : OPC 43 grade confirming to IS 8112
Type of mineral admixture : Fly ash confirming to IS 3812 (part-1)
Maximum nominal size of aggregate : 20 mm
Minimum cement content : 320 kg per m3 (Table-5 of IS 456:2000- Exposure condition)
Maximum water cemnt ratio : 0.45 (table 5 of IS 456:2000 exposure condition)
Workability : 100 mm ( slump value for pumpable concrete)
Exposure condition : Severe
Method of cocrete placing : pumping
Degree of supervision : Good
Type of aggregate : Crushed angular aggregate
Maximum cement content : 450 kg/m3
Chemical admixture type : superplasticizer
Step-2 Test data for materials
Specific gravity of cement : 3.15
Specific gravity of fly ash : 2.2
Specific gravity of coarse aggregate : 2.74
Specific gravity of fine aggregate : 2.74
water absorbtion of coarse aggregate : 0.5%
water absorbtion of fine aggregate : 1%
Free surface moisture of coarse aggregate : nil
Free surface moisture of fine aggregate : nil
Sieve analysis of coarse aggregate : Confirming to table 2 of IS 383
Sieve analysis of fine aggregate : Confirming to grading zone II of table 4 of IS 383
Step-3 Target strength for mix proportioning
f'ck=fck+1.65S
= 35+1.65*5
= 43.25 N/mm2
where
- f'ck= Target average compressive strength at 28 days
- fck= cherecterstics compressive strength at 28 days, and
- S= standard deviation
from table I of IS 10262:2009 standard deviation S = 5 N/mm2
Target mean strength = 43.25 N/mm2
Step-4 Selection of water-cement ratio
The maximum water cement ratio to design M50 grade concrete can be found from table-5 of IS 456-2000.
max. water-cement ratio = 0.45
Based on experience adopted water cement ratio is 0.44
0.44<0.45, hence ok
adopted water-cement ratio = 0.44
Step-5 Selection of water content
From table 2 of IS 10262:2009, max. 186 litre
Clause 4.2 suggests incressing of 3% of water content for every extra 25 mm slump from 50 mm slump. so a 6% is to be added to it.
186 + 186 * (6/100) = 197 litre.
(note: If superplasticizer is used, the water content can be reduced up to 20% and above.)
Based on trials with super plasticizer water content reduction of 20% = 197 - 197*20%
= 197 - 39.4
= 157.6 or 158 litre.
water required = 158 litre
Step-6 Calculation of cement and fly ash required
Adopted w/c ratio = 0.44
Total cementitious (cement + fly ash requirement) water content/ water cemnt ratio = 158/0.44 = 359 kg/m3
The cementitious content has to be incressed in order to attain good workability and strength. the increment required is determined on the basis of experience and research. here we are increasing cementitious content by 10%.
final cementitious content = 359 * 1.10 = 395 kg
From table 5 of IS 456, minimum cement content for "severe exposure" conditions = 320 kg
395 kg/m3 > 320 kg/m3 hence ok.
Cementitious material content = 395
New water cement ratio = 158/395 = 0.4
Fly ash content is taken as 30% of the total cemntitious content : 395 * 0.3 = 118.5 kg/m3
cement required = 395 - 118 = 277 kg/m3
cement quantity saved due to fly ash addition = 350 - 277 = 73 kg/m3
Cementitious material, cement and fly ash required is 395 kg/m3 , 277 kg/m3 and 118 kg/m3 and the new water cement ratio is 0.4 respectively.
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) for water- cement ratio of 0.50 is : 0.62
In the present case water cement ratio is 0.44. therefore, volume of coarse aggregate is required to increased to decrease the fine aggregate content. as the water cemnt ratio is lower by 0.06. the proportion of volume of coarse aggregate is incressed 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
For pumpable concrete these value 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
Volume of fine aggregate and coarse aggregate is 0.431 and 0.568
Step-8 Mix calculations
For mix calculations as per unit volume of concrete shall be as follows:
a) Volume of concrete : 1m3
b) Volume of cement = (mass of cement/specific gravity of cement) x (1/1000)
= (277/3.15) x (1/1000)
= 0.087 m3
c) Volume of fly ash = (mass of fly ash/specific gravity of fly ash) x (1/1000)
= (118/2.2) x (1/1000)
= 0.053
d) Volume of water = (mass of water/sp. gravity of water) x (1/1000)
= (158/1)x (1/1000)
= 0.158 m3
e) volume of chemical admixture = (mass of admixture/ sp. gravity of admixture) x (1/1000)
= (7.6/1.145) x (1/1000)
= 0.006
f) volume of all in aggregate = [a-(b+c+d+e)]
= [ 1-(0.087+0.053+0.158+0.006)]
= 0.696 m3
g) Mass of coarse aggregate = f x volume of coarse aggregate x specific gravity of coarse aggregate x 1000
= 0.696 x 0.568 x 2.74 x 1000
= 1077 kg/m3
h) mass of fine aggregate = f x volume of fine aggregate x specific gravity of fine aggregate x 1000
= 0.696 x 0.431 x 2.74 x 1000
= 822 kg/m3
Step-9 Mix proportions
Cement : 277 kg/m3
Fly ash : 118 kg/m3
Water : 158 lt/m3
Fine aggregate : 822 kg/m3
Coarse aggregate : 1077 kg/m3
chemical admixture : 7.18 kg/m3
Water cement ratio (lowest w/c ratio is selected) : 0.4
Mix proportion by weight : 1:2.08:2.72
Step-10 The slump shall be measured, the water content and dosage of admixture shall be adjusted for achiving the required slump for trial. the mix proportion shall be reworked for the actual water content and checked for durability requirements.
Step-11 Two more trials having veriation of 10% of water-cement ratio shall be carried out and the graph between three water cement ratios and corresponding strengths shall be ploted to work out the mix proportions for the given target for field trials.
Part-2 To calculate the concrete mix design for M50 grade concrete without fly ash:
Step-1 Stipulations for concrete design mix
Grade designation : M50
Type of cement : OPC 53 grade confirming to IS BIS 12269-1987
Maximum nominal size of aggregate : 20 mm
Minimum cement content : 320 kg/m3 (Table-5 of IS 456:2000- Explosure condition)
Maximum water - cement ratio : 0.45 (Table 5 of IS 456:2000 Exposure condition)
Workability : 100 mm (Slump value for pumpable concrete)
Exposure condition : Severe (For reinforced concrete )
Method of concrete placing : pumping
Degree of supervision : Good
Type of aggregate : Crushed angular aggregate
Maximum cement content : 450 kg/m3
Chemical admixture type : super plasticizer
Step-2 Test data for materials
Cement used : OPC 53 grade confirming IS 12269-1987
specific gravity of cement : 3.15
Chemical admixture : Super plasticizer confirming to IS 9103
Specific gravity of coarse aggregate : 2.74
Specific gravity of fine aggregate : 2.64
Water absorbtion for coarse aggregate : 0.5%
Water absorbtion for fine aggregate : 1.0%
Free surface moisture of coarse aggregate : nil
Free surface moisture of coarse aggregate : nil
Sieve analysis of coarse aggregate : confirming to table 2 of IS 383
Sieve analysis of fine aggregate : Confirming to grading zone II of table 4 of IS 383
Step-3 Target strength of mix proportioning
f'ck = fck + 1.65 S
= 50+ 1.65 * 5
= 58.25 N/mm2
where f'ck = Target average compressive strength at 28 days
fck = cherecterstics compressive strength at 28 days
S = Standard deviation = 5 N/mm2
Target mean strength = 58.25 N/mm2
Step-4 Selection of water cemnt ratio
The max. water-cement ratio to design M50 grade concrete can be found from table 5 of IS 456-2000 for severe exposure.
max. water-cement ratio = 0.45
Based on experience adobted water cement ratio is 0.44
0.44<0.45, hence ok
adopted w/c ratio = 0.44
Step-5 selection of water content
From table 2 of IS 10262:2009, max. water content for 50 mm aggregate = 186 lit. ( for 25 to 50 mm slump range)
Clause 4.2 suggests incressing of 3% of water content for every extra 25 mm slump from 50 mm slump. so a 6% is to be added to it.
= 186 + 186*(6/100)
= 197 lit.
Estimated water content for 100 mm slump (Note: if super plasticizer is used, the water content can be reduced up to 20% and above).
Based on trial with super plasticizer water content reduction of 20% has been achived, hence arrived water content = 197 x 0.8
= 158 lit.
Water required 158 litre.
Step-6 Calculations of cement required
Adopted water-cement ratio : 0.44
Cement content : 158/0.44 = 359 kg/m3
From table 5 of IS 456, minimum cement content for 'severe' exposure conditions : 320 kg/m3
359 kg/m3 > 320 kg/m3 hence ok.
Cement required is 359 kg/m3
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) for water-cement ratio of 0.50 is = 0.62
In the present case water-cement ratio is 0.44. therefore, volume of coarse aggregate is required to be incressed to decrease the fine aggregate content. as the water-cement ratio is lowered by 0.06.
the proportion of volume of coarse aggregate is increased by 0.02.
therefore corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.44 : 0.632
for pumpable concrete these value should be reduced up to 10%. therefore, volume of coarse aggregate
= 0.632 x 0.9 = 0.568
Volume of fine aggregate content : 1- 0.576 = 0.431
Volume of fine aggregate and coarse aggregate is 0.431 and 0.568 respectively.
Step-8 Mix calculations
The mix calculations per unit volume of concrete shall be as follows:
a) Volume of concrete : 1m3
b) Volume of cement = (mass of cement/sp. gravity of cement) x (1/1000)
= (395/3.15) x (1/1000)
= 0.114 m3
c) Volume of water = (mass of water/sp. gravity of water x (1/1000)
= (158/1) x (1/1000)
= 0.158 m3
d) Volume of chemical admixturesn = (mass of admixture/sp. 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 m3
f) Mass of coarse aggregate = e x volume of coarse aggregate x sp. gravity of coarse aggregate x 1000
= 0.722 x 0.568 x 2.74 x 1000
= 1123 kg/m3
g) Mass of fine aggregate = e x vol. of fine aggregate x sp. gravity of fine aggregate x 1000
= 0.722 x 0.431 x 2.64 x 1000
= 821 kg/m3
Step-9 Mix propotions
Cement : 359 kg/m3
water : 158 lit/m3
fine aggregate : 821 kg/m3
coarse aggregate : 1123 kg/m3
chemical admixture : 7.18 kg/m3
Water-Cement ratio : 0.44
Mix proportion by weight : 1:2.28:3.12
Step-10 The slump shall be measured, the water cement and dosage of admixture shall adjusted for achiving the required slump on trial. the mix proportion shall be reworked for the actual water content and checked for durability requirements.
Step-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 protect 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.
Mix proportion by weight of M50 grade of concrete without fly ash is 1:2.28:3.12 and its water cemnt ratio was found to be 0.44.