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 method of finding the precise proportion of cement, sand and aggregates for concrete to achieve the target strength in structures, therefore concrete design can be stated as concrete mix in terms of cement: sand: aggregates.the design is done according to requirements of concrete strength. The concrete properties like workability, setting time, compressive strength, durability are attained by this method. The mix is prepared as per IS method proportioning guidelines from IS 10262:2009 and recommended guidelines from IS 10262:1982.
PART 1: To calculate concrete mix design for M35 grade concrete with fly ash
STEP 1- Stipulations for concrete mix design
Grade designation - M35 grade
Type of cement - OPC 43grade confirming to IS 8112
Type of mineral admixture - fly ash confirming to IS 3812
Maximum nominal size of aggregate - 20mm
Minimum cement content - 320 kg/m3(from table 5 of IS 456:2000- Exposure condition)
Maximum cement content - 450kg/m3
Degree of supervision - Good
Maximum water-cement ratio - 0.45 (from table 5 of IS 456:2000-Exposure condition)
Workability - 50-75mm slupm value for pumpable concrete
Exposer condition - severe ( for reinforced concrete)
Type of aggregate - Crushed angular aggregate
Admixture type - super plasticizer
Method of concrete placing - pumping
STEP 2 - Test data for materials
Specific gravity of cement - 3.15
Specific gravity of Fly ash - 2.2
Specific gravity of fine aggregate - 2.75
Specific gravity of coarse aggregate - 2.75
Water absorption of fine aggregate - 1.0%
Water absorption of Coarse aggragte - 0.5%
Free surface moisture - 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 proportion
f'ck = fck + 1.65S
Where,
f'ck = target Average compressive strength at 28days
fck = charecteristic compressive strength at 28days
S = Standard deviation (From Table I of IS 10262:2009, Standard Deviation is 5 N/mm2)
f'ck = 35 + 1.65 x 5 = 43.25 N/mm2
STEP 4 - Selection of water ccement ratio
from table 5 IS 456:2000 for severe exposure maximum water-cement ratio=0.45
STEP 5 - Selection of water content
From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate is 186 litre for 25-50mm slump value
Estimated water content for 75mm slump= 186+0.03*186=191.58 litres.
Based on trials with super plasticizer water content reduction of 20% has been achieved, hence the arrived water content =191*0.8= 153L
STEP 6- Calculation of cement content and Fly ash
Water-cement ratio = 0.45
Cement content = 153/0.45= 340.58kg/m3
From Table 5 of IS 456, Minimum cement content for Severe exposure condition is 320kg/m3.
It is 340.58kg/m3 grater than 320kg/m3 hence OK.
The cementitious content has to be increased 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%
Cementitious material content = 340.58*1.10= 375kg/m3
New water-cement ratio = 153/375= 0.4
Fly ash content is taken as 30% of the total cementitious content = 375*0.3=112.5kg/m3
Cement required = 375-112.5= 262.5kg/m3
Quantity of cement saved by additon of Fly ash= 350-262= 88kg/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 = 0.62
The corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.45= 0.63
For pumpable concrete, these values should be reduced by 10%.
therefore volume of coarse aggregate = 0.63*0.9=0.567
Volume of fine aggregate content = 1-0.567= 0.433
STEP 8- Mix calculations
a) Volume of concrete =1m3
b) Volume of cement = (mass of cement/sp, gravity of cement)*(1/1000)= (262.5/3.15)*(1/1000)=0.083m3
Volume of Fly ash = 112.5/2.2*0.001=0.0051m3
c) Volume of water =( mass of water/sp, gravity of water)*(1/1000)=(153/1)*(1/1000)= 0.153m
d) Volume of super plasticizer= (mass of superplasicizer/sp,gravity of admixture)*(1/1000)
= (6.81/10145)*(1/1000)= 0.00594 m3
e) Volume of all aggregate = (a-(b+c+d))= 1-(0.112+0.083+0.153+0.00594)= 0.65 m3
f) Mass of coarse aggregate = volume of all aggregate*Volume of Coarse aggregate*specific gravity of CA*1000
= 0.65*0.567**2.74*1000 = 1010 Kg
g) Mass of Fine aggregate= volume of all aggregate*volume of fine aggregate*specific gravity of fine aggregate*1000
= 0.65*0.433*2.67*1000 = 746.26 kg
Step 9 - Concrete mix proportions
cement = 262.5 kg/m3
Fly ash = 112.5 kg/m3
water = 153 kg/m3
super plasticizer = 6.81 kg/m3
Fine aggregates = 746 kg/m3
Coarse aggregates = 1010 kg/m3
water-cement ratio = 0.40
RESULT: 1:2.18:3
PART 2 - The concret mix dessign for M50 grade concrete without Fly ash
STEP 1 - Stipulations
Grade designation - M35 grade
Type of cement - OPC 43grade confirming to IS 8112
Maximum nominal size of aggregate - 20mm
Minimum cement content - 320 kg/m3(from table 5 of IS 456:2000- Exposure condition)
Maximum cement content - 450kg/m3
Maximum water-cement ratio - 0.45 (from table 5 of IS 456:2000-Exposure condition)
Workability - 100mm slupm value for pumpable concrete
Exposer condition - severe ( for reinforced concrete)
Type of aggregate - Crushed angular aggregate
Admixture type - super plasticizer
Method of concrete placing - pumping
Degree of supervision - Good
Chemical admixture - superplasticizer
STEP 2 - Test data for materials
Specific gravity of cement - 3.15
Specific gravity of fine aggregate - 2.75
Specific gravity of coarse aggregate - 2.75
Water absorption of fine aggregate - 1.0%
Water absorption of Coarse aggragte - 0.5%
Free surface moisture - 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 proportion
f'ck = fck + 1.65S
Where,
f'ck = target Average compressive strength at 28days
fck = charecteristic compressive strength at 28days
S = Standard deviation (From Table I of IS 10262:2009, Standard Deviation is 5 N/mm2)
f'ck = 50+ 1.65 x 5 = 58.25 N/mm2
STEP 4 - Selection of water ccement ratio
from table 5 IS 456:2000 for severe exposure maximum water-cement ratio=0.45
Adopt 0.44 as water-cement ratio.
STEP 5 - Selection of water content
From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate is 186 litre for 25-50mm slump value
Estimated water content for 75mm slump= 186+0.06*186=197 litres.
Based on trials with super plasticizer water content reduction of 20% has been achieved, hence the arrived water content =197*0.8= 158L
STEP 6- Calculation of cement content
Water-cement ratio = 0.44
Cement content = 158/0.44= 359kg/m3
From Table 5 of IS 456, Minimum cement content for Severe exposure condition is 320kg/m3.
It is 359kg/m3 grater than 320kg/m3 hence OK.
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 = 0.62
The corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.45= 0.63
For pumpable concrete, these values should be reduced by 10%.
therefore volume of coarse aggregate = 0.63*0.9=0.568
Volume of fine aggregate content = 1-0.568= 0.431
STEP 8- Mix calculations
a) Volume of concrete =1m3
b) Volume of cement = (mass of cement/sp, gravity of cement)*(1/1000)= (359/3.15)*(1/1000)=0.114m3
c) Volume of water =( mass of water/sp, gravity of water)*(1/1000)=(158/1)*(1/1000)= 0.158m
d) Volume of super plasticizer= (mass of superplasicizer/sp,gravity of admixture)*(1/1000)
= (7.6/1.145)*(1/1000)= 0.006 m3
e) Volume of all aggregate = (a-(b+c+d))= 1-(0.114+0.153+0.006)= 0.722 m3
f) Mass of coarse aggregate = volume of all aggregate*Volume of Coarse aggregate*specific gravity of CA*1000
= 0.722*0.567*2.74*1000 = 1123 Kg/m3
g) Mass of Fine aggregate= volume of all aggregate*volume of fine aggregate*specific gravity of fine aggregate*1000
= 0.722*0.433*2.67*1000 = 821 kg/m3
Step 9 - Concrete mix proportions
cement = 359 kg/m3
water = 158 l/m3
super plasticizer = 7.18 kg/m3
Fine aggregates = 821 kg/m3
Coarse aggregates = 1123 kg/m3
RESULT: 1:2.28:3.12
RESULTS:
Mix Proportion 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 of M50 grade of concrete without fly ash is 1:2.28:3.12 and its water-cement ratio was found to be 0.44.