Project on Concrete Mix Design for various grades of Concrete
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 selecting suitable ingredients of concrete and determining their relative proportions of concrete to achieve strength and durability as economical as possible. It involves various steps, calculations and laboratory testing to find right mix proportions. This process is usually adopted for structures which requires higher grade of concrete such as M25 and above . Concrete mix = Cement : Sand : Coarse aggregates by adding additives can improve properties of the mix. There are some guide lines to be followed while using the mix design,IS method: concrete mix proportioning guidelines(Bureau of Indian Standards -IS 10262-2009) and recommended guidelines for concrete mix design IS 10262-1982.In this project ,first calculating mix design for M35 grade concrete with fly ash and then calculating the mix design for M50 grade concrete without fly ash
EQUATIONS USED
TARGET MEAN STENGTH OF MIX PROPORTIONING
f'ck=fck+1.65S
f'ck=target average compressive strength at 28days
fck=characterastic compressive strength at 28days
S = standard deviation
MIX CALCULATION
- a.volume of concrete= 1metercube
- b.volume of cement = [mass of cement/ specific gravity of cement]*1/1000
- c.volume of water = [mass of water/ specific gravity of water]*1/1000
- d.volume of chemical admixture =[mass of chemical admixture/ specific gravity of chemical admixture]*1/1000
- e. volume of aggreagte( fine and coarse aggregate) =[a-(b+c+d)]
- f.mass of coarse aggregate = e* volume of coarse aggregate*specific gravity of coarse aggregate*1000
- g. mass of fine aggregate = e* volume of fine aggregate*specific gravity of fine aggregate*1000
PROCEDURE
1.To calculate the concrete mix design for M35 grade concrete with fly ash
STEP1
Stipulations for proportioning
- Grade designation : M35
- Type of cement: OPC 43 grade conforming 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/m3( Table 5 of IS 456 -2000- Exposure condition)
- Maximum w/c 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 placing:pumbing
- Degree of supervision: good
- Type of aggregate:crushed angular aggregate
- Maximum cement content:450 kg/m3
- Chemical admixture type: superplasticizer
STEP2
Test data for materials
- Cement used:OPC 43 grade confirming to IS 8112
- Specific gravity of cement:3.15
- Fly ash:confirming to IS 3812(part1)
- Specific gravity of fly ash:2.2
- chemical admixture: superplasticizer confirming to IS 9103
- specific gravity of coarse aggregate:2.74
- specific gravity of fine aggregate:2.74
- water absorption coarse aggregate:0.5%
- water absorption fine aggregate:1%
- free surface moisture coarse aggregate:nil
- free surface moisture fine aggregate:nil
- sieve analysis of coarse aggregate: confirming to table 2 of IS 383
- sieve analysis of fine aggregate:confirming to grading zone 1 of table 4 of IS 383
STEP3
TARGET STENGTH OF MIX PROPORTIONING
f'ck=fck+1.65S
f'ck=target average compressive strength at 28days
fck=characterastic compressive strength at 28days
S = standard deviation
Standard deviation of M35 =5N/mm2 (from table 1 , IS 10262:2009)
f'ck =fck+1.65*S
f'ck=35+1.65*5
f'ck =43.25N/mm2
Target mean strength =43.25N/mm2
STEP4
SELECTION OF WATER -CEMENT RATIO
The maximum w/c ratio to design M35 grade concrete can be found in table 5 IS 456:2000 for severe exposure
maximum w/c ratio =o.45
From the gragh between compressive strength and w/c ratio, using 28day compressive strength of concrete = target mean strength=43.25 N/mm2 , from gragh we will get w/c ratio as 0.35
from graph we will get w/c ratio as 0.35
from the above two values we will take w/c ratio as 0.35
W/C ratio=0.35
STEP5
SELECTION OF WATER CONTENT
- Selection of water content from table 2of 10262:2009
- The maximum water content for 25mm to 50mm slump =186Kg=186litre
- For additional slump 3% may be added for every 25mm slump
- Table 2 maximum water content per cubic meter of concrete for nominal maximum size of aggregate(clauses 4.2, A-5 and B-5)
|
NOMINAL MAXIMUM SIZE OF AGGREGATE (mm) |
MAXIMUM WATER CONTENT(Kg) |
|
10 |
208 |
|
20 |
186 |
|
40 |
165 |
- Estimated water content for 100mm slump =186+(6/100)*186=197litre
- As superplasticizer is used the water content can be reduced upto 30%
- Based on trials water content reduction of 29% is achieved with plasticizer
- Hence achieved water content = 197*0.71=140litre
STEP6
CALCULATION OF CEMENT CONTENT
w=140Kg
w/c ratio =0.35
Cementitious material ( cement+fly ash) content= 140/0.35
=400kg/m3
from table 5 of IS 456 minimum cement content for severe exposure condition =320kg/m3
400kg/m3>320kg/m3 Hence ok
Increase in cementitious material content and its percentage may be based on experience and trial inorder to attain strength and durability.Here we are increasing cementitious property by 10%
Cementitious material content =400*1.10=440kg/m3
from table 5 of IS 456 minimum cement content for severe exposure condition =320kg/m3
440kg/m3>320kg/m3 Hence ok
So, new water cement ratio=140/440=0.32
Fly ash content is 30% of total cementitious material content
440*.3=132kg/m3
Cement (OPC)=440-132=308kg/m3
Cement quantity saved while using fly ash=400-308=92kg/m3
Cementitious material, cement and fly ash required is 440kg/m3,308 kg/m3and132kg/m3
New water-cement ratio=0.32
STEP7
PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE
1.From table 3 of IS 10262:2009 volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate
(Zone 1) for w/c ratio=0.60
2.in the present case w/c ratio is 0.35
therefore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content
3.as the w/c ratio is lower by 0.10 , the proportion of volume of coarse aggregate is increased by 0.02 ( at the rate of+/-0.01 for every +/-0.05 change in w/c ratio)
therefore corrected volume of coarse aggregate for w/c ratio of 0.35=0.63
(Note: if coarse aggregate is not of granular type, then also the volume of coarse aggregate may be required to be increased suitably based on experience)
4.for pumpable concrete these values are reduced by 10%
volume of coarse aggregate = 0.63*0.9=0.567
volume of fine aggregate = 1-0.567=0.433
STEP8
MIX CALCULATIONS
Mix calculation for unit volume of concrete
a.volume of concrete= 1m3
b.volume of cement = [mass of cement/ specific gravity of cement]*1/1000
=(308/3.15)*(1/1000)
=0.097m3
c.volume of fly ash=(132/2.2)*(1/1000)
=0.06m3
d.volume of water = [mass of water/ specific gravity of water]*1/1000
=(140/1)*(1/1000)
=o.140m3
e.volume of chemical admixture =[mass of chemical admixture/ specific gravity of chemical admixture]*1/1000
=(7.6/1.145)*(1/1000)
=0.006m3
f.volume of aggreagte( fine and coarse aggregate) =[a-(b+c+d+e)]
=[1-(0.097+0.06+0.140+0.006)]
=0.697m3
g.mass of coarse aggregate = e* volume of coarse aggregate*specific gravity of coarse aggregate*1000
=0.697*0.567*2.74*1000
=1082kg/m3
h.mass of fine aggregate = e* volume of fine aggregate*specific gravity of fine aggregate*1000
=0.697*0.433*2.74*1000
=826kg/m3
STEP9
MIX PRPORTION FOR TRIAL NUMBER 1
Cement=308kg/m3
fly ash=132kg/m3
water=140kg/m3
coarse aggregate=1082kg/m3
fine aggregate=826kg/m3
chemical admixture =7kg/m3
w/c ratio=0.32
trial mix ratio=1:2.68:3.51
STEP10
The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving the required slump on trail.The mix proportion shall be reworked for the actual water content and checked for durability requirement
STEP11
Two or more trials having variations of 10% of w/c ratio in clause 10 shall be carried out and a graph beween 3 w/c ratos and corresponding strength shall be plotted to workout the mix proportions for the given target strength for field trials howerever the durability shall be met
2.To Calculate the Concrete Mix Design for M50 grade concrete without Fly ash
STEP1
Stipulation for proportioning
- Grade designation : M50
- Type of cement: OPC 53 grade confirming to IS 12269
- Maximum nominal size of aggregate :20 mm
- Minimum cement content: 320 kg/m3( Table 5 of IS 456 -2000- Exposure condition)
- Maximum w/c 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 placing:pumbing
- Degree of supervision: good
- Type of aggregate:crushed angular aggregate
- Maximum cement content:450 kg/m3
- Chemical admixture type: superplasticizer
STEP2
Test data for materials
- Cement used:OPC 53 grade confirming to IS 12269
- Specific gravity of cement:3.15
- chemical admixture: superplasticizer confirming to IS 9103
- specific gravity of coarse aggregate:2.74
- specific gravity of fine aggregate:2.74
- water absorption coarse aggregate:0.5%
- water absorption fine aggregate:1%
- free surface moisture coarse aggregate:nil
- free surface moisture fine aggregate:nil
- sieve analysis of coarse aggregate: confirming to table 2 of IS 383
- sieve analysis of fine aggregate:confirming to grading zone 1 of table 4 of IS 383
STEP3
TARGET STENGTH OF MIX PROPORTIONING
f'ck=fck+1.65S
f'ck=target average compressive strength at 28days
fck=characterastic compressive strength at 28days
S = standard deviation
Standard deviation of M50 =5N/mm2 (from table 1 , IS 10262:2009)
f'ck =fck+1.65*S
f'ck=50+1.65*5
f'ck =58.25N/mm2
Target mean strength =58.25N/mm2
STEP4
SELECTION OF WATER -CEMENT RATIO
The maximum w/c ratio to design M30 grade concrete can be found in table 5 IS 456:2000 for severe exposure
maximum w/c ratio =o.45
From the gragh between compressive strength and w/c ratio, using 28day compressive strength of concrete = target mean strength=58.25 N/mm2 , from gragh we will get w/c ratio as 0.35
from graph we will get w/c ratio as 0.35
from the above two values we will take w/c ratio as 0.35
W/C ratio=0.35
STEP5
SELECTION OF WATER CONTENT
- Selection of water content from table 2of 10262:2009
- The maximum water content for 25mm to 50mm slump =186Kg=186litre
- For additional slump 3% may be added for every 25mm slump
- Table 2 maximum water content per cubic meter of concrete for nominal maximum size of aggregate(clauses 4.2, A-5 and B-5)
|
NOMINAL MAXIMUM SIZE OF AGGREGATE (mm) |
MAXIMUM WATER CONTENT(Kg) |
|
10 |
208 |
|
20 |
186 |
|
40 |
165 |
- Estimated water content for 100mm slump =186+(6/100)*186=197litre
- As superplasticizer is used the water content can be reduced upto 30%
- Based on trials water content reduction of 29% is achieved with plasticizer
- Hence achieved water content = 197*0.71=140litre
STEP6
CALCULATION OF CEMENT CONTENT
w=140Kg
w/c ratio =o.35
cement content (c)= 140/0.35
=400kg/m3
from table 5 of IS 456 minimum cement content for severe exposure condition =320kg/m3
400kg/m3>320kg/m3
hence ok
STEP7
PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE
1.From table 3 of IS 10262:2009 volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate
(Zone 1) for w/c ratio=0.60
2.in the present case w/c ratio is 0.35
therefore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content
3.as the w/c ratio is lower by 0.10 , the proportion of volume of coarse aggregate is increased by 0.02 ( at the rate of+/-0.01 for every +/-0.05 change in w/c ratio)
therefore corrected volume of coarse aggregate for w/c ratio of 0.35=0.63
(Note: if coarse aggregate is not of granular type, then also the volume of coarse aggregate may be required to be increased suitably based on experience)
4.for pumpable concrete these values are reduced by 10%
volume of coarse aggregate = 0.63*0.9=0.567
volume of fine aggregate = 1-0.567=0.433
STEP8
MIX CALCULATIONS
Mix calculation for unit volume of concrete
a.volume of concrete= 1m3
b.volume of cement = [mass of cement/ specific gravity of cement]*1/1000
=(400/3.15)*(1/1000)
=0.126m3
c.volume of water = [mass of water/ specific gravity of water]*1/1000
=(140/1)*(1/1000)
=o.140m3
d.volume of chemical admixture =[mass of chemical admixture/ specific gravity of chemical admixture]*1/1000
=(7.6/1.145)*(1/1000)
=0.006m3
f.volume of aggreagte( fine and coarse aggregate) =[a-(b+c+d)]
=[1-(0.126+0.140+0.006)]
=0.728m3
g.mass of coarse aggregate = e* volume of coarse aggregate*specific gravity of coarse aggregate*1000
=0.728*0.567*2.74*1000
=1131kg/m3
h.mass of fine aggregate = e* volume of fine aggregate*specific gravity of fine aggregate*1000
=0.728*0.433*2.74*1000
=864kg/m3
STEP9
MIX PRPORTION FOR TRIAL NUMBER 1
Cement=400kg/m3
water=140kg/m3
coarse aggregate=1131kg/m3
fine aggregate=864kg/m3
chemical admixture =7kg/m3
w/c ratio=0.35
trial mix ratio=1:2.16:2.82
STEP10
The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving the required slump on trail.The mix proportion shall be reworked for the actual water content and checked for durability requirement
STEP11
Two or more trials having variations of 10% of w/c ratio in clause 10 shall be carried out and a graph beween 3 w/c ratos and corresponding strength shall be plotted to workout the mix proportions for the given target strength for field trials howerever the durability shall be met
RESULT
Mix proportion for M35 grade concrete using fly ash
Cement=308kg/m3
fly ash=132kg/m3
water=140kg/m3
coarse aggregate=1082kg/m3
fine aggregate=826kg/m3
chemical admixture =7kg/m3
w/c ratio=0.32
trial mix ratio=1:2.68:3.51
Mix proportion for M50 grade concrete without using fly ash
Cement=400kg/m3
water=140kg/m3
coarse aggregate=1131kg/m3
fine aggregate=864kg/m3
chemical admixture =7kg/m3
w/c ratio=0.35
trial mix ratio=1:2.16:2.82
CONCLUSION
From this project we get to know that we can calculate mix proportions for different grades of concrete based on the material available , site conditions, test results etc.This is more scientific and economical method while comparing with others.