Project on Concrete Mix Design for various grades of Concrete
AIM: Mix proportioning for a concrete of M35 grade using fly ash by using IS 10262: 2009 code
Introduction: Mix design is defined as the process of selecting suitable concrete ingredients and finding their proportions and producing certain minimum strength of concrete and durability as economically as possible. The first object is to achieve stipulated minimum concrete strength and durability. The second is to make concrete in most economical manner.
Cost wise concrete mainly depends on material and labour cost. Labour cost, by ways of formwork, batching, mixing, transporting and curing is almost same for good and bad concrete. Therefore, attention is mainly taken on cost materials, since cost of cement is many times more than cost of all other ingredients, attention is taken to use less cement as possible consistent with strength and durability.
Stipulations for proportioning:
a) Grade designation : M35
b) Type of cement : OPC 43 grade conforming to Is 8112
c) Type of mineral admixture: Fly ash conforming to IS 3812 (Part 1)
d) Maximum nominal size of aggregate : 20mm
e) Minimum cement content : 320 kg/m3
f) Maximum water-cement ratio : 0.45
g) Workability : 100mm (slump)
h) Exposure condition : Severe (for reinforced concrete)
i) Method of concrete placing : Pumping
j) Degree of supervision : Good
k) Type of aggregate : Crushed angular aggregate
l) Maximum (OPC) cement content: 450 kg/m3
m) Chemical admixture type : Superplasticizer
Test data for materials:
a) Cement used : OPC 43 grade
b) Specific gravity of cement : 3.15
c) Specific gravity of flyash : 2.2
d) Chemical admixture : Superplasticizer conforming to IS 9103
e) Specific gravity of :
1. Coarse aggregate: 2.74
2. Fine aggregate: 2.74
f) Water absorption :
1. Coarse aggregate: 0.5%
2. Fine aggregate: 1%
g) Free surface moisture:
1. Coarse aggregate: Nil
2. Fine aggregate: Nil
h) Sieve analysis:
1. Coarse aggregate: Conforming to table 2 of IS 383
2. Fine aggregate: Conforming to grading Zone 1 of table 4 of IS 383
1. Target mean strength (f'ck):
f'ck = fck + 1.65 X s
f'ck = Target average compressive strength at 28 days
fck = Characteristics compressive strength at 28 days
s = Standard deviation
Standard deviation is taken from table 1 as per IS 10262: 2009 (or) from table 8 as per IS 456: 2000
For M35 grade as per IS 10262: 2009, table1 S= 5 N/mm2
f'ck = 35 + 1.65 x 5 = 43.25 N/mm2
2. Selection of W/C ratio:
As per table 5 of IS 456: 2000, Max free W/C ratio according to environmental exposure conditions
For Severe exposure environmental conditions, maximum w/c ratio is 0.45 taken.
3. Selection of Water content:
From table 2 of IS 10262, maximum water content for 20mm nominal size of aggregate
The values are given for 25 to 50mm slump
for every increase of 25mm slump, 3% water content is increased
For 20mm nominal size, water content is 186 litre
For 100mm slump, estimated water content = 186 + 186 x 0.06 = 197 litre
If superplasticizer is used, water content is reduced upto 30% and if plasticizer is used, it is reduced upto 10%
so, water content is reduced by 29% based on trails
197 x 0.71= 140 litres
4. Calculation of Cement and Fly ash:
w/c = 0.45
Cementitious material + Fly ash content = (water content) / 0.45
= 140/0.45 = 311.11 kg/m3 < 320kg/m3
IS 456 table 5 , permits minimum cement content for severe exposure condition is = 320 kg/m3
So take, Cement + Fly ash = 320kg/m3
Since flyash is not as active as cement, the cementitious material content is increased by some percentage based on experience, In this 10% increase is considered
Cementitious material content = 320 x 1.1 = 352 kg/m3
Water content= 140 kg/m3
so, w/c ratio= 140/352 = 0.397 = 0.4(say)
Let us take fly ash content, 30% of total cementitious material content = 352 x 0.3= 105.6 kg/m3 = say 105 kg/m3
Fly ash content = 105 kg/m3
Cement content = 352-105= 247 kg/m3
5. Proportion of volume of coarse and fine aggregate content:
From table 3 of IS 10262, Volume of coarse aggregate for 20mm nominal size and fine aggregate on zone 1 for w/c ratio 0.5 is equal to 0.6
For every increase of w/c ratio by 0.05, volume of coarse aggregate is decreased by 1% and for every 0.05 decrease in w/c ratio, volume of coarse aggregate is increased by 1%
In this problem, w/c = 0.45
It is decreased by 0.05, so volume of coarse aggregate is increased by 1%
corrected volume of coarse aggregate = 0.6+0.01= 0.61
For pumpable concrete volume of coarse aggregate is reduced by 10%
Volume of coarse aggregate = 0.61 x 0.9 = 0.55
Volume of fine aggregate = 1-0.55 =0.45
6. MIX Calculations:
The mix calculations per unit volume of concrete
a) Volume of concrete = 1m3
b) Volume of cement = (Mass of cement/ Specific gravity of cement) X (1/1000) = 247/(3.15*1000) = 0.0784m3
c) Volume of fly ash = ( Mass of fly ash/ Specific gravity of fly ash ) X (1/1000) = 105/(2.2*1000) = 0.048m3
d) Volume of water = ( Mass of water/ Specific gravity of water ) X (1/1000) = 140/(1*1000) = 0.140m3
e) Volume of chemical admixture (superplasticizer) @ 2% by mass of cementitious material content
= ( Mass of admixture/ Specific gravity of admixture) X (1/1000)
Mass of admixture = 0.02*352 = 7.04 kg/m3
Volume of admixture = 7.04/( 1.145*1000)= 0.006m3
f) Volume of aggregates = [a - (b+c+d+e)] = 1-(0.0784+0.048+0.14+0.006) = 0.7276m3
g) Mass of coarse aggregate = f x Volume of coarse aggregate x Specific gravity of coarse aggregate x 1000
=0.7276 x 0.55 x 2.74 x 1000 = 1096.5kg
h) Mass of fine aggregate = f x Volume of fine aggregate x Specific gravity of fine aggregate x 1000
=0.7276 x 0.45 x 2.74 x 1000 = 897kg
7. Mix proprtions for Trial number 1:
Cement = 247 kg/m3
Fly ash = 105 kg/m3
Water = 140 kg/m3
Fine aggregate = 897kg
Coarse aggregate = 1096.5 kg
Chemical admixture = 7 kg/m3
W/c ratio = 0.4
8. The slump can be measured and the amount of admixture and water shall be adjusted for achieving the required slump based on trail. If required, the mix proportions shall be reworked for actual water content and durability requirements are checked.
9. Two more trials having variation of around 10% of w/c ratio is carried out and graph is plotted between three w/c ratios and corresponding strengths to workout the mix proportions for the given target strength for field trials, and durability requirements are reached.
AIM: Mix proportioning for a concrete of M50 grade without fly ash by using IS 10262: 2009 code
Introduction: Mix design is defined as the process of selecting suitable concrete ingredients and finding their proportions and producing certain minimum strength of concrete and durability as economically as possible. The first object is to achieve stipulated minimum concrete strength and durability. The second is to make concrete in most economical manner.
Cost wise concrete mainly depends on material and labour cost. Labour cost, by ways of formwork, batching, mixing, transporting and curing is almost same for good and bad concrete. Therefore, attention is mainly taken on cost materials, since cost of cement is many times more than cost of all other ingredients, attention is taken to use less cement as possible consistent with strength and durability.
Stipulations for proportioning:
a) Grade designation : M50
b) Type of cement : OPC 43 grade conforming to Is 8112
c) Maximum nominal size of aggregate : 20mm
d) Minimum cement content : 320 kg/m3
e) Maximum water-cement ratio : 0.45
f) Workability : 125mm (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 aggregate
k) Maximum (OPC) cement content: 450 kg/m3
l) Chemical admixture type : Superplasticizer
Test data for materials:
a) Cement used : OPC 43 grade
b) Specific gravity of cement : 3.15
c) Chemical admixture : Superplasticizer conforming to IS 9103
d) Specific gravity of :
1. Coarse aggregate: 2.74
2. Fine aggregate: 2.74
e) Water absorption :
1. Coarse aggregate: 0.5%
2. Fine aggregate: 1%
f) Free surface moisture:
1. Coarse aggregate: Nil
2. Fine aggregate: Nil
g) Sieve analysis:
1. Coarse aggregate: Conforming to table 2 of IS 383
2. Fine aggregate: Conforming to grading Zone 1 of table 4 of IS 383
1. Target mean strength (f'ck):
f'ck = fck + 1.65 X s
f'ck = Target average compressive strength at 28 days
fck = Characteristics compressive strength at 28 days
s = Standard deviation
Standard deviation is taken from table 1 as per IS 10262: 2009 (or) from table 8 as per IS 456: 2000
For M50 grade as per IS 10262: 2009, table1 S= 5 N/mm2
f'ck = 50 + 1.65 x 5 = 58.25 N/mm2
2. Selection of W/C ratio:
As per table 5 of IS 456: 2000, Maximum free W/C ratio according to environmental exposure conditions
For Severe exposure environmental conditions, maximum w/c ratio is 0.45 taken.
3. Selection of Water content:
From table 2 of IS 10262, maximum water content for 20mm nominal size of aggregate
The values are given for 25 to 50mm slump
for every increase of 25mm slump, 3% water content is increased
For 20mm nominal size, water content is 186 litre
For 125mm slump, estimated water content = 186 + 186 x 0.09 = 203 litre
If superplasticizer is used, water content is reduced upto 30% and if plasticizer is used, it is reduced upto 10%
so, water content is reduced by 25% based on trails
203 x 0.75= 152 litres
4. Calculation of Cement :
w/c = 0.45
Cementitious material = (water content) / 0.45
= 152/0.45 = 338 kg/m3 > 320 kg/m3
IS 456 table 5 , permits minimum cement content for severe exposure condition is = 320 kg/m3
Cement content = 338 kg/m3
5. Proportion of volume of coarse and fine aggregate content:
From table 3 of IS 10262, Volume of coarse aggregate for 20mm nominal size and fine aggregate on zone 1 for w/c ratio 0.5 is equal to 0.6
For every increase of w/c ratio by 0.05, volume of coarse aggregate is decreased by 1% and for every 0.05 decrease in w/c ratio, volume of coarse aggregate is increased by 1%
In this problem, w/c = 0.45
It is decreased by 0.05, so volume of coarse aggregate is increased by 1%
corrected volume of coarse aggregate = 0.6+0.01= 0.61
For pumpable concrete volume of coarse aggregate is reduced by 10%
Volume of coarse aggregate = 0.61 x 0.9 = 0.55
Volume of fine aggregate = 1-0.55 =0.45
6. MIX Calculations:
The mix calculations per unit volume of concrete
a) Volume of concrete = 1m3
b) Volume of cement = (Mass of cement/ Specific gravity of cement) X (1/1000) = 338/(3.15*1000) = 0.107 m3
c) Volume of water = ( Mass of water/ Specific gravity of water ) X (1/1000) = 152/(1*1000) = 0.152 m3
d) Volume of chemical admixture (superplasticizer) @ 2% by mass of cementitious material content
= ( Mass of admixture/ Specific gravity of admixture) X (1/1000)
Mass of admixture = 0.02*338 = 6.8 kg/m3
Volume of admixture = 6.8/( 1.145*1000)= 0.006m3
e) Volume of aggregates = [a - (b+c+d)] = 1-(0.107+0.152+0.006) = 0.735 m3
f) Mass of coarse aggregate = f x Volume of coarse aggregate x Specific gravity of coarse aggregate x 1000
=0.735 x 0.55 x 2.74 x 1000 = 1108 kg
g) Mass of fine aggregate = f x Volume of fine aggregate x Specific gravity of fine aggregate x 1000
=0.7276 x 0.45 x 2.74 x 1000 = 906 kg
7. Mix proprtions for Trial number 1:
Cement = 338 kg/m3
Water = 152 kg/m3
Fine aggregate = 906 kg
Coarse aggregate = 1108 kg
Chemical admixture = 6.8 kg/m3
W/c ratio = 0.45
8. The slump can be measured and the amount of admixture and water shall be adjusted for achieving the required slump based on trail. If required, the mix proportions shall be reworked for actual water content and durability requirements are checked.
9. Two more trials having variation of around 10% of w/c ratio is carried out and graph is plotted between three w/c ratios and corresponding strengths to workout the mix proportions for the given target strength for field trials, and durability requirements are reached.