Project on Concrete Mix Design for various grades of Concrete
PROBLEM 1:
AIM:
To calculate the concrete mix design for M35 grade concrete with flyash.
INTRODUCTION:
Concrete mix design is the calculation to achieve the correct mix proportion of the ingredients of the concrete i.e., cement, fine aggregate, coarse aggregate, admixtures, etc., Each ingredient has specific properties and quality. All ingredients are tested for its properties and it should be considered for mix design. A good concrete mix design ensures a safe and durable structure. M35 grade comes under nominal mix design.
CODES USED:
- IS 456 : 2000 - Plain and Reinforced Concrete - Code of Practice
- IS 10262 : 2019 - Concrete Mix Proportioning - Guidelines
- IS 8112 - Specification for 43 grade Ordinary Portland Cement
- IS 3812 (Part I) - Specification for Pulverized fuel ash
- IS 383 : 2016 - Specification for Coarse and Fine Aggregate for Concrete
ASSUMED DATA:
Type of cement : OPC 43 grade conforming to IS 8112
Type of Mineral Admixture : Flyash conforming to IS 3812 (Part I)
Type of chemical admixture : Superplasticizer
Minimum cement content : 340 kg/m^3
Maximum nominal size of aggregate : 20 mm
Workabiltiy : 75 mm
Exposure condition : Severe (for RCC)
Method of concrete : Pumpable concrete
Type of aggregate : Crushed angular aggregate
Sieve Analysis for Coarse aggregate conforming to Table 2 of IS 383
Sieve Analysis for Fine aggregate conforming to Zone II of Table 4 of IS 383
TEST DATA:
Specific gravity of cement = 3.15
Specific gravity of flyash = 2.2
Specific gravity of chemical admixture = 1.145
Specific gravity of coarse aggregate = 2.74
Specific gravity of fine aggregate = 2.74
Water absorption for coarse aggregate = 0.5%
Water absorption for fine aggregate = 1.0%
Free surface moisture for CA & FA = NIL
PROCEDURE:
1) Target mean strength , ft = fck+1.65*S = 35 + 1.65*5
= 43.25 N/mm^2
2) From Table 5 of IS 456 : 2000 w/c ratio is 0.45 and from the graph of IS 10262 : 2019 w/c ratio is 0.38
Hence, the lowest value is taken. w/c ratio = 0.38
3) For slump value 75 mm and for 20 mm aggregate as per Table 4 of IS 10262 : 2019
Water content = 186 + (186*(3/100)) = 191.58 litre
As superplasticizer is used water content can be reduced upto 30%
Hence, Water content = 191.58*0.7 = 134 litre
4) Cement content = W/(w/c) = 134/0.38 = 352 kg which is more than 340 kg ( min. cement content from Table 5 fo IS 456 : 2000)
Increase in 10% cementitious material can be done.
Cementitious material content = 352*1.1 = 387 kg
Water content = 134 litre
New w/c ratio = 134/387 = 0.34
Fly ash @ 30% cementitious material = 387*0.3 = 116 kg
Cement content = 387-116 = 271 kg
Cement saved = 352-271 = 81 kg
5) As per Table 5 of IS 10262 : 2019 Volume of CA per unit Volume of total aggregate for Zone II for w/c ratio 0.5 = 0.62
Here, w/c ratio = 0.34
For 0.10 decrease in w/c ratio Volume of CA is increased by 0.02.
Volume of CA = 0.652 and for pumpable concrete this value is reduced by 10%
Hence, Volume of CA = 0.652 * 0.9 = 0.59
Volume of FA = 1 - 0.59 = 0.41
6) a) Volume of Concrete = 1 m^3
b) Volume of cement = `(Massof Cement)/(Sp.gr.of cement)xx1/1000`
= (271/3.15)*(1/1000)
= 0.086 m^3
c) Volume of flyash = `(Mass of flyash)/(Sp.gr.of flyash)xx1/1000`
= (116/2.2)*(1/1000)
= 0.052 m^3
d) Volume of water = `(Mass of Water)/(Sp.gr.of Water)xx1/1000`
= (134/1)*(1/1000)
= 0.134 m^3
Mass of chemical admixture is 2% of the cementitious material = 387*0.02 = 7.74 kg
e) Volume of Chemical Admixture = `(Mass of Chemical Admixture)/(Sp.gr.of Chemical Admixture)xx1/1000`
= (7.74/1.145)*(1/1000)
= 0.007 m^3
f) Volume of total aggregate = `a-(b+c+d+e)`
= 1 - (0.086+0.052+0.134+0.007)
= 0.721 m^3
g) Mass of Coarse Aggregate = `fxxVolume of CAxxSp.gr.of CAxx1000`
= 0.721*0.59*2.74*1000
= 1165.57 kg/m^3
h) Mass of Fine Aggregate = `fxxVolume of FAxxSp.gr.of FAxx1000`
= 0.721*0.41*2.74*1000
= 810 kg/m^3
7) Mix Proportions
Cement = 271 kg/m^3
Flyash = 116 kg/m^3
Water = 134 kg/m^3
Fine Aggregate = 810 kg/m^3
Coarse Aggregate = 1165 kg/m^3
Chemical Admixture = 7.74 kg/m^3
W/C ratio = 0.34
RESULT:
Hence from the above mix proportions, the mix design ratio is arrived as,
Mix Ratio is 1 : 2.98 : 4.3
which means for 1 unit of cement, 2.98 units of fine aggregate and 4.3 units of coarse aggregate are added for concrete mix during batching.
PROBLEM 2:
AIM:
To calculate the concrete mix design for M50 grade concrete without flyash.
INTRODUCTION:
Concrete mix design is the calculation to achieve the correct mix proportion of the ingredients of the concrete i.e., cement, fine aggregate, coarse aggregate, admixtures, etc., Each ingredient has specific properties and quality. All ingredients are tested for its properties and it should be considered for mix design. A good concrete mix design ensures a safe and durable structure. M50 grade comes under high strength mix design. These mix designs are carried out by engineers and it cannot be applied for another project. Each project needs a separate mix design calculation which depends upon the requirement of strength, type and method of concreting, quality of ingredients used, etc.,
CODES USED:
- IS 456 : 2000 - Plain and Reinforced Concrete - Code of Practice
- IS 10262 : 2019 - Concrete Mix Proportioning - Guidelines
- IS 8112 - Specification for 43 grade Ordinary Portland Cement
- IS 3812 (Part I) - Specification for Pulverized fuel ash
- IS 383 : 2016 - Specification for Coarse and Fine Aggregate for Concrete
ASSUMED DATA:
Type of cement : OPC 43 grade conforming to IS 8112
Type of chemical admixture : Superplasticizer
Minimum cement content : 360 kg/m^3
Maximum nominal size of aggregate : 20 mm
Workabiltiy : 100 mm
Exposure condition : Extreme (for RCC)
Method of concrete : Pumpable concrete
Type of aggregate : Crushed angular aggregate
Sieve Analysis for Coarse aggregate conforming to Table 2 of IS 383
Sieve Analysis for Fine aggregate conforming to Zone II of Table 4 of IS 383
TEST DATA:
Specific gravity of cement = 3.15
Specific gravity of flyash = 2.2
Specific gravity of chemical admixture = 1.145
Specific gravity of coarse aggregate = 2.74
Specific gravity of fine aggregate = 2.74
Water absorption for coarse aggregate = 0.5%
Water absorption for fine aggregate = 1.0%
Free surface moisture for CA & FA = NIL
PROCEDURE:
1) Target mean strength , ft = fck+1.65*S = 50 + 1.65*5
= 58.25 N/mm^2
2) From Table 5 of IS 456 : 2000 w/c ratio is 0.40 and from the graph of IS 10262 : 2019 w/c ratio is 0.28
Hence, the lowest value is taken. w/c ratio = 0.28
3) For slump value 100 mm and for 20 mm aggregate as per Table 4 of IS 10262 : 2019
Water content = 186 + (186*(6/100)) = 197.16 litre
As superplasticizer is used water content can be reduced upto 30%
Hence, Water content = 197.16*0.7 = 138 litre
4) Cement content = W/(w/c) = 138/0.28 = 493 kg which is more than 360 kg ( min. cement content from Table 5 fo IS 456 : 2000)
5) As per Table 5 of IS 10262 : 2019 Volume of CA per unit Volume of total aggregate for Zone II for w/c ratio 0.5 = 0.62
Here, w/c ratio = 0.28
For 0.10 decrease in w/c ratio Volume of CA is increased by 0.02.
Volume of CA = 0.664 and for pumpable concrete this value is reduced by 10%
Hence, Volume of CA = 0.664 * 0.9 = 0.60
Volume of FA = 1 - 0.60 = 0.40
6) a) Volume of Concrete = 1 m^3
b) Volume of cement = `(Massof Cement)/(Sp.gr.of cement)xx1/1000`
= `493/3.15xx1/1000`
= 0.156 m^3
c) Volume of water = `(Mass of Water)/(Sp.gr.of Water)xx1/1000`
= `138/1xx1/1000`
= 0.138 m^3
Mass of chemical admixture is 2% of the cementitious material = 493*0.02 = 9.86 kg
d) Volume of Chemical Admixture = `(Mass of Chemical Admixture)/(Sp.gr.of Chemical Admixture)xx1/1000`
= `9.86/1.145xx1/1000`
= 0.008 m^3
e) Volume of total aggregate = `a-(b+c+d)`
= 1 - (0.156+0.138+0.008)
= 0.698 m^3
f) Mass of Coarse Aggregate = `exxVolume of CAxxSp.gr.of CAxx1000`
= `0.698xx0.60xx2.74xx1000`
= 1147.50 kg/m^3
g) Mass of Fine Aggregate = `exxVolume of FAxxSp.gr.of FAxx1000`
= `0.698xx0.40xx2.74xx1000`
= 765 kg/m^3
7) Mix Proportions
Cement = 493 kg/m^3
Water = 138 kg/m^3
Fine Aggregate = 765 kg/m^3
Coarse Aggregate = 1147.50 kg/m^3
Chemical Admixture = 9.86 kg/m^3
W/C ratio = 0.28
RESULT:
Hence from the above mix proportions, the mix design ratio is arrived as,
Mix Ratio is 1 : 1.55 : 2.33
which means for 1 unit of cement, 1.55 units of fine aggregate and 2.33 units of coarse aggregate are added for concrete mix during batching.