Project on Concrete Mix Design for various grades of Concrete

AIM:

I am performing this project to find a design mix for M35 grade concrete with fly ash and M50 grade concrete without fly ash.

INTRODUCTION:

Concrete is one of the most widely used and versatile building materials. It comprises different ingredients that have various functions, concrete as a building material is made from cement, aggregate that is rock and sand, admixtures (optional) and water in definite proportion. The properties of concrete mainly depend on the mixing of these ingredients, concrete act as a binder material that binds the materials together and cement in combination with aggregate acts as a strong building material all these ingredients help in modifying the properties of the fresh as well as harden concrete. In short, these materials are like members of the family and they perform their role in such a manner that they contribute to the overall sucess of the concrete as a whole family.

MATERIALS:

1. Cement
2. Fine aggregate
3. Coarse aggregate
4. Water
5. Admixtures (Superplasticizers)
6. Fly ash.            

DATA PROVIDED FOR M35 GRADE CONCRETE:

1. Grade of concrete = M35
2. Type of cement = 43
3. Maximum nominal size of aggregate = 20 mm
4. Minimum cement content = 320 `frac{kg}{m^3}`
5. Maximum water-cement ratio = 0.45
6. Workability = True slump at 100 mm
7. Environmental exposure = Severe
8. Method of concrete placing = Pumping
9. Degree of supervision = Good 
10. Type of aggregate = Crush angular
11. Maximum cement content = 450 `frac{kg}{m^3}`
12. Chemical admixtures = Superplasticizers, fly ash
13. Specific gravity of cement = 3.15
14. Specific gravity of fly ash = 2.2
15. Specific gravity of coarse aggregate = 2.74
16. Specific gravity of fine aggregate = 2.74
17. Sieve analysis of fine aggregate = Zone 1 (table-4, IS 383)
18. Sieve analysis of coarse aggregate = Table-2, IS 383.                    

PROCEDURE FOR M35 DESIGN MIX WITH THE USE OF FLY ASH:

1) The first step in our design mix is to find the target mean strength as target mean strength acts as a benchmark to our design mix. The target mean strength of concrete mix is using the following formula from IS 10262-2009,

f'ck = fck + 1.65`times`S

Where, f'ck = Characteristics compressive strength of concrete at 28 days, S= Standard deviation (values from table-1)

Step 1: Target mean strength:

From IS 10262-2009, Table-1

f'ck = fck + 1.65`times`S

f'ck = 35 + 1.65`times`5

f'ck = 43.25 `frac{N}{mm^2}`.

2) Based on reinforced concrete or plain cement concrete select the water-cement ratio for the given Exposure condition

Step 2: Find the water-cement ratio based on Environment exposure:

As per IS 456-2000, Table-5

w/c ratio = 0.45, Based on experience take 0.4

Minimum cement content = 320 `frac{kg}{m^2}`.

3) Selection of water content is taken from table-2, IS 10262-2009. The maximum water content for 25 mm to 50 mm slump values is given, for additional slump 3% may be added for every 25 mm slump. Also, make sure that the aggregate is dry.

Step 3: Selection of water content from Table-2, IS 10262-2009

Water content is 186

True slump at 100 mm 

= 186 + 186`times`0.06

=197 lit

Use of superplasticizers reduces water content by 30%

After observation = 29%

= 197`times`0.71

= 140 lit.

4) Next is a selection of cement content. We can take it from the water-cement ratio, minimum cement content can be taken from Table-5, IS 456-2000

Step 4: Selection of cement content:

Cement content of the concrete mix = `frac{W}{w/c}`

=1400.4

=350 kg

350>320 ... So ok

Now total cementitious materials (cement + fly ash) = 350

There is an increase of 10% of cementitious materials due to the addition of fly ash = 350`times`1.1

=385 `frac{kg}{m^3}`

Water content = 140 `frac{kg}{m^3}`

So, water-cement ratio = `frac{140}{385}`

=0.364

Fly ash at 30% cementitious materials

Fly ash = 385`times`0.3

= 115 `frac{kg}{m^3}`

Cement = 385-115

= 270 `frac{kg}{m^3}`

Cement saved = 80 `frac{kg}{m^3}`.

5) Volume of coarse aggregate and fine aggregate are taken from Table-3, IS 10262-2009

Step 5: Volume of aggregate (CA and FA):

Table-3 of IS 10262-2009

FA = Zone 1; 0.6

Value of w/c = 0.4

So increase in volume of coarse aggregate and decrease in volume of water content. As the water-cement ratio is decreased by 0.10 so increase by 0.02

Water-cement ratio of coarse aggregate = 0.4 = 0.62

[ For pumpable concrete value decreases by 10% ]

Volume of CA = 0.62`times`0.9

=0.56

Volume of FA = 1-0.56

=0.44

6) Perform mix calculations for all the materials.

Step 6: Mix calculation:

a) Volume of concrete = 1 `m^3`

b) The volume of cement = `frac{ mass of cement }{ specific gravity of cement} times frac{1}{1000}`

= `frac{270}{3.15} times frac{1}{1000}`

= 0.0086 `m^3`

c) The volume of fly ash = `frac{mass of fly ash}{specific gravity of fly ash} times frac{1}{1000}`

= `frac{115}{2.2} times frac{1}{1000}`

= 0.052 `m^3`

d) The volume of water = `frac{mass of water}{specific gravity of water} times frac{1}{1000}`

= `frac{140}{1} times frac{1}{1000}`

= 0.140

e) The volume of chemical admixture = `frac{mass of admixture}{specific gravity of admixture} times frac{1}{1000}`

= `frac{7.6}{1.145} times frac{1}{1000}`

= 0.006 `m^3`

f) Volume of aggregate (FA and CA)

= [a-(b+c+d+e)]

= (1-(0.086+0.052+0.140+0.006)]

=0.716 `m^3`

g) Mass of CA

=0.716`times`0.56`times`2.74`times`1000

= 1098 kg

h) Mass of FA

= 0.716`times`0.44`times`2.74`times`1000

= 863 kg

7) State all the mix proportions we got after calculating mix calculations of material.

Step 7: 

Cement = 270 `frac{kg}{m^3}`

Fly ash = 115 `frac{kg}{m^3}`

Water = 140 `frac{kg}{m^3}`

FA = 863 kg

CA = 1098 kg

Chemical admixtures = 7 `frac{kg}{m^3}`

Water-cement ratio = 0.36

Trail mix ratio = 1:2.24:2.85

[Using this mix ratio perform an experiments to find if the concrete meets the target mean strength, if yes go ahead with this design mix, if no alter few values and calculator new design mix till the target mean strength is reached.]

DATA PROVIDED FOR M50 GRADE CONCRETE:

1. Grade of concrete = M50
2. Type of cement = 43
3. Maximum nominal size of aggregate = 20 mm
4. Minimum cement content = 320 `frac{kg}{m^3}`
5. Maximum water-cement ratio = 0.45
6. Workability = True slump at 100 mm 
7. Environmental exposure = Severe
8. Method of concrete placing = Pumping
9. Degree of supervision = Good
10. Type of aggregate = Crush angular
11. Maximum cement content = 450 `frac{kg}{m^3}`
12. Chemical admixtures = Superplasticizers
13. Specific gravity of cement = 3.15
14. Specific gravity of coarse aggregate = 2.74
15. Specific gravity of fine aggregate = 2.74
16. Sieve analysis of fine aggregate = Zone 1 (Table 4, IS 383)
17. Sieve analysis of coarse aggregate = Table-2, IS 383.

PROCEDURE FOR M50 DESIGN MIX WITHOUT FLY ASH:

1) The first step in our design mix is to find the target mean strength as target mean strength acts as a benchmark to our design mix. The target mean strength of concrete mix is using the following formula from IS 10262-2009,

f'ck = fck + 1.65`times`S

Where, fck = Chracteristic compressive strength of concrete at 28 days, S = Standard deviation (values from table 1)

Step 1: Target mean strength:

From IS 10262-2009, Table 1

f'ck = fck + 1.65`times`S

f'ck = 50 + 1.65`times`5

f'ck = 58.25 `frac{N}{mm^2}` 

2) Based on reinforced concrete or plain cement concrete select the water-cement ratio for the given exposure condition.

Step 2: Find water-cement ratio based on Environment exposure:

As per IS 456-2000, Table-5:

w/c = 0.45, Based on experience take 0.4

Minimum cement content = 320 `frac{kg}{mm^2}`

3) Selection of water content is taken from table2, IS 10262:2009. The maximum water content for 25 mm to 50 mmm slum values is given, for additional slump, 3% may be added for every 25 mm slump. Also, make sure that the aggregate is dry.

Step 3: Selection of water content from Table-2, IS 10262:2009:

Water content is 186

True slump at 100 mm 

= 186 + 186`times`0.06

= 197 lit

Use of superplasticizers reduces water content by 30%

After observation = 29%

= 197`times`0.71

= 140 lit

4) Next is the selection of cement content. We can take it from the water-cement ratio, Minimum cement content can be taken from Table-5, IS 456:2000

C = `frac{W}{w/c}`

W = Water content 

w/c = water-cement ratio

Step 4: Selection of cement content:

Cement content of the concrete mix = `frac{W}{w/c}`

= 1400.4

= 350 kg

350>320 [minimum cement content] ... So ok.

5) Volume of coarse aggregate and fine aggregate are taken from Table-3 of IS 10262-2009.

Step 5: Volume of aggregate (CA and FA) Table-3 of IS 10262-2009

FA = Zone 1 ; 0.6

But value of w/c = 0.4

So increase in volume of coarse aggregate and decrease in volume of water content

As the water-cement ratio is decreased by 0.10 so increase by 0.02

Water-cement ratio of coarse aggregate = 0.4 = 0.62

[For pumpable concrete value decreased by 10%]

Volume of CA = 0.62`times`0.9

= 0.56

Volume of FA = 1-0.56

= 0.44.

6) Perform mix calculations for all the materials.

Step 6: Mix calculation

a) Volume of concrete = 1 `m^3`

b) The volume of cement = `frac{mass of cement} {Specific gravity of cement}``times``frac{1}{1000}` 

= `frac{350}{3.15}``times``frac{1}{1000}`

= 0.111 `m^3`

c) The volume of water = `frac{mass of water}{specific gravity of water}``times``frac{1}{1000}`

=`frac{140}{1} times frac{1}{1000}`

= 0.140 `m^3`

d) The volume of chemical admixture = `frac{mass of admixture}{specific gravity of admixture}timesfrac{1}{1000}`

= `frac{7.6}{1.145} times frac{1}{1000}`

= 0.006 `m^3`

e) Volume of aggregate (FA and CA)

= [a-(b+c+d)]

= [1-(0.111+0.140+0.006)]

= 0.743

f) Mass of CA 

= `0.743times0.56times2.74times1000`

= 1140 kg

g) Mass of FA 

=`0.743times0.44times2.74times1000`

= 896 kg.

7) State all the mix proportions we got after calculating mix calculations of material.

Step 7:

Cement = 350 kg

Water = 140 kg

FA = 896 kg

CA = 1140 kg

Chemical admixture = 7 kg

Water cement ratio = 0.4

Trail mix ratio = 1:2.56:3.26

[Using this mix ratio perform experiments to find the concrete meets the target mean strength, if yes go ahead with this design mix if no alter few values and calculator new design mix till the target mean strength is reached.]

RESULTS:

By performing this project we have gained the design mix for M35 concrete with fly ash and M50 concrete without fly ash.

(A) Trail mix ratio for M35 grade concrete with fly ash = 1:2.24:2.85 [We save 80 `frac{kg}{m^3}` of cement].

(B) Trail mix ratio for M50 grade concrete without fly ash = 1:2.56:3.26.

CONCLUSION:

I would like to conclude my project by stating that every design mix varies depending on the aggregates present, the state of aggregates and many other factors. Using this mix ratio perform experiments to find if the concrete meets the target mean strength, if yes go ahead with this design mix if no alter few values and calculator new design mix till the target mean strength is reached.

REFERENCES:

• IS 10262-2009, 2019
• IS 456-2000
• IS 383-1970, 2016
• SKILL-LYNC COURSE.