Project on Concrete Mix Design for various grades of Concrete
1.Calculate the Concrete Mix Design for M35 Grade Concrete with Fly Ash & M50 Grade Concrete Without Fly Ash?
Ans: To Calculate the concrete mix design for M35 Grade concrete with Fly ash
Step 1
Grade designation : M35
Type of Cement : OPC M43 Grade conforming to IS 8112
Type of mineral admixture : Fly ash conforming to IS 3812 (Part 1)
Maximum nominal size of aggregate : 20MM
Minimum cement content : 320 kg/ m^3 (Table 5 IS 456:2000 Exposure condition)
Maximum water – cement : 0.45 (Table 5 of IS 456:2000 Exposure condition)
Workability : 100MM (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 aggregates
Maximum cement content : 450kg/m^3
Chemical admixture type : Super plasticizer
Step 2
Test Data for materials
Cement used : OPC 43 Grade conforming IS 8112
Specific gravity cement : 3.15
Fly ash : Conforming to IS 3812 (part 1)
Specific gravity to Fly ash : 2.1
Chemical admixture : Super plasticizer conforming to IS 9103
Specific gravity of coarse aggregate : 2.74
Specific gravity of fine aggregate : 2.74
Water absorption of coarse aggregate : 1.0%
Free surface moisture of coarse aggregate : Nil
Free surface moisture of fine aggregate : Nil
Sieve analysis : Coarse aggregate conforming to table 2 of IS 383
Sieve analysis : Fine aggregate to grading Zone 1 of table of IS 383
Step 3
Target strength for mix proportioning
f’ck = fck + 1.65 X S
f’ck = Target compressive strength of 28 days
f’ck = Characteristics compressive strength at 28 days
S = Standard deviation
From table 1 of IS 10262: 2009 standard deviations S = 5N/MM^2
= 35 +1.65 X 5
= 43.25 N/MM^2
Step 4
Selection of water – cement ratio
The maximum water cement ratio to design
M50 Grade concrete can maximum Water cement ratio be found
From Table 5 of IS = 0.45 456: 2000 for sever exposure
Based on Experience adopted water cement ratio is 0.40
0.40 < 0.45 Hence ok
Step 5
Selection of water content
From Table 2 of IS 10262: 2000 maximum
186 litres (For 25 to 50mm slump range)
Estimated water content for 100mm slump = 186 + 6/100 X 186
= 197 litres
As super-Plastizer is used the water content can be reduced up to 20% and above
Based on trails water content reduction of 29% is achieved with plasticizer
Hence the arrived water content = 197 X 0.71
= 140 litres
Step 6
Calculation of cement content
Water cement ratio = 0.40
Cementitious material (cement + Fly ash) content = 140/ 0.4
=350 kg/m^3
From table 5 IS 456: 2000 minimum cement content for sever condition = 320kg/m^3
350kg/m^3 > 320kg/m^3 Hence ok
Now to Proportion a mix containing fly ash the following steps suggested
- The percentage of fly ash needs to be decided based on project requirement quality of materials
- In some cases, increase in cementitious materials can be warranted increase in cementitious materials
Content and its percentage may be based on experienced and trials
(This example is with increase of 10% cementitious materials content)
Cementitious material content = 350 X 1.10 = 385kg/m^3
Water content = 140 kg/m^3
So, water – cement ration = 140 / 385 = 0.364
Fly ash @ 30% total cementitious material = 385 X 30% = 115kg/M^3
Cement (OPC) = 385 – 115 = 270kg/m^3
Saving of cement while using fly ash = 350 – 270 = 80kg/m^3
Fly ash being utilized = 115kg/m^34
Step 7
Proportion of volume of coarse aggregate and fine aggregate content
From Table 3 of IS 10262: 2009 volume of coarse aggregate corresponding to 20mm size aggregate
and fine aggregate (Zone – 1) for water cement ratio 0.5 = 0.
In the present case the water cement ratio is 0.4
There fore the volume of coarse aggregate need to be increase to decrease the fine aggregate
content
As water cement ratio is lower by 0.10 the proportion of volume of coarse aggregate is increase by
0.02 (at the of -/+ 0.01 for every +- 0.5 change in water cement ratio)
Therefore, corrected proportion of volume of coarse aggregate for the water cement ratio of
0.40 = 0.62
(Note: If coarse aggregate is not of angular type also the volume of coarse aggregate may be
required to be increase suitably based on experience)
For pumpable concrete this value should be reduced by up to 10%
Therefore, Volume of coarse aggregate 0.62 X 0.9 = 0.558
Volume of fine aggregate 1-0.558 = 0.442
Volume of fine aggregate and coarse aggregate is 0.442 and 0.558 respectively
Step 8
Mix Calculation
The mix calculation per unit volume of concrete shall be as follows
- Volume of concrete = 1m^3
- Volume of cement = Mass of cement / Specific gravity of cement X 1/1000
= 270 / 3.15 X 1 / 1000
= 0.086m^3
- Volume of fly ash = Mass of fly ash / Specific gravity of fly ash X 1/1000
= 115 / 2.2 X 1 / 1000
= 0.052
- Volume of water = Mass of water / Specific gravity water X 1/1000
= 140/1 X1/1000
= 0.140m^3
- Volume of chemical admixture = Mass of admixture / Specific gravity admixture X 1/1000
= 7.6/1.145 X 1/1000
= 0.006m^3
Volume of aggregate (FA & CA) = [ a(b+c+d)]
= [ 1 (0.086+0.0.052+0.140+ 0.006]
= 0.716m^3
- g) Mass of coarse aggregate
= e X volume of coarse aggregate X specific gravity of coarse aggregate X 1000
= 0.716 X 0.558 X 2.74 X 1000
= 1095kg/m^3
- h) Mass of fine aggregate
= e X volume of fine aggregate X specific gravity of fine aggregate X 1000
= 0.716 X 0.442 X 2.74 X 1000
= 867kg/m^3
Step 9
Mix proportions for Trial number 1
Cement = 270kg/m^3
Fly ash = 115kg/m^3
Water = 140kg/m^3
Fine aggregate = 867kg/m^3
Coarse aggregate = 1095kg/m^3
Chemical admixture = 7kg/m^3
Water – cement ration = 0.364
Trial Mix ration = 1: 3.21: 4.05
Step 10
The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving required slump on trial. The mix proportion shall be reworked for the actual water content and checked for durability requirement
Step 11
Two more trial having variation if 10% water – cement ratio in clause X shall be carried out and a graph between three water – cement ratios and corresponding strength shall be plotted to work out the mix proportion for the given target strength for fields. However, durability shall be met.
2.To Calculate the concrete mix design for M50 Grade concrete without Fly ash?
Ans:
Step 1
Grade designation : M50
Type of Cement : OPC M53 Grade conforming to IS 8112
Maximum nominal size of aggregate : 20MM
Minimum cement content : 320 kg/ m^3 (Table 5 IS 456:2000 Exposure condition)
Maximum water – cement : 0.45 (Table 5 of IS 456:2000 Exposure condition)
Workability : 75MM (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 aggregates
Maximum cement content : 450kg/m^3
Chemical admixture type : Super plasticizer
Step 2
Test Data for materials
Cement used : OPC 53 Grade conforming IS 8112
Specific gravity cement : 3.15
Chemical admixture : Super plasticizer conforming to IS 9103
Specific gravity of coarse aggregate : 2.74
Specific gravity of fine aggregate : 2.74
Water absorption of coarse aggregate : 1.0%
Free surface moisture of coarse aggregate : Nil
Free surface moisture of fine aggregate : Nil
Sieve analysis : Coarse aggregate conforming to table 2 of IS 383
Sieve analysis : Fine aggregate to grading Zone 1 of table of IS 383
Step 3
Target strength for mix proportioning
f’ck = FCK + 1.65 X S
f’ck = Target compressive strength of 28 days
fck = Characteristics compressive strength at 28 days
S = Standard deviation
From table 1 of IS 10262: 2009 standard deviations S = 5N/MM^2
= 50+1.65 X 5
= 58.25 N/MM^2
Step 4
Selection of water – cement ratio.
The maximum water cement ratio to design for M50 Grade concrete can maximum Water cement
ratio be found.
From Table 5 of IS = 0.45 456: 2000 for sever exposure
Based on Experience adopted water cement ratio is 0.40
0.40 < 0.45 Hence ok.
Step 5
Selection of water content
From Table 2 of IS 10262: 2000 maximum
186 liters (For 25 to 50mm slump range)
Estimated water content for 75mm slump = 186 + 3/100 X 186
= 192 liter
As superplastizer is used the water content can be reduced up to 20% and above
Based on trails water content reduction of 29% is achieved with plasticizer
Hence the arrived water content = 192 X 0.71
= 136 liter
Step 6
Calculation of cement content
Water cement ratio = 0.40
Cement content = 136/ 0.4
= 340kg/m^3
From the table 5 IS 456: 2000 minimum cement content for sever condition = 320kg/m^3
340kg/m^3 > 320kg/m^3 Hence ok
Step 7
Proportion of volume of coarse aggregate and fine aggregate content
From Table 3 of IS 10262: 2009 volume of coarse aggregate corresponding to 20mm 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 need to be increase to decrease the fine aggregate
content
As water cement ratio is lower by 0.10 the proportion of volume of coarse aggregate is increase by
0.02 (at the of -/+ 0.01 for every +- 0.5 change in water cement ratio
Therefore, corrected proportion of volume of coarse aggregate for the water cement ratio of
0.40 = 0.62
For pumpable concrete this value should be reduced by up to 10%
Therefore, Volume of coarse aggregate 0.62 X 0.9 = 0.558
Volume of fine aggregate 1-0.558 = 0.442
Volume of fine aggregate and coarse aggregate is 0.442 and 0.558 respectively
Step 8
Mix Calculation
The mix calculation per unit volume of concrete shall be as follows
- Volume of concrete = 1m^3
- Volume of cement = Mass of cement / Specific gravity of cement X 1/1000
= 340 / 3.15 X 1 / 1000
= 0.107m^3
- Volume of water = Mass of water / Specific gravity water X 1/1000
= 136/1 X1/1000
= 0.136m^3
- Volume of chemical admixture = Mass of admixture / Specific gravity admixture X 1/1000
= 7/1.145 X 1/1000
= 0.006m^3
Volume of aggregate (FA & CA) = [ a(b+c+d)]
= [ 1 (0.107+0.136+0.0060]
= 1.035m^3
Mass of coarse aggregate
= e X volume of course aggregate X specific gravity of coarse aggregate X 1000
= 1.035 X 0.558 X 2.74 X 1000
= 1582kg/m^3
Mass of fine aggregate
= e X volume of fine aggregate X specific gravity of fine aggregate X 1000
= 1.035 X 0.442 X 2.74 X 1000
= 1253kg/m^3
Step 9
Mix proportions for Trial number 1
Cement = 340kg/m^3
Water = 136kg/m^3
Fine aggregate = 1253kg/m^3
Coarse aggregate = 1582kg/m^3
Chemical admixture = 7kg/m^3
Water – cement ration = 0.4
Trial Mix ration = 1: 3.68: 4.65
Step 10
The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving required slump on trial. The mix proportion shall be reworked for the actual water content and checked for durability requirement
Step 11
Two more trial having variation if 10% water – cement ratio in clause X shall be carried out and a graph between three water – cement ratios and corresponding strength shall be plotted to work out the mix proportion for the given target strength for fields. However, durability shall be met