Project on Concrete Mix Design for various grades of Concrete

Aim:- To determine the workability of the fresh concrete by using IS 456:2000 and IS 10262:2019

Introduction

The process of selecting suitable ingredients for producing concrete of required strength, durability and workability as economical as possible is known as concrete mix design

There are 3 types of concrete mixes are there

1. Nominal mix
2. Standard mix
3. Design mix

Now a days we are using a Nominal mix for small projects and Design mix for large projects which require high strength and durability (as per design)

The materials which required to do the concrete mix are cement, fine aggregate, coarse aggregate and water

These materials should be tested before the concrete mix

Advantages of mix design

• Design mix is more scientific than nominal mix
• The cost can be reduced by using locally available materials which satisfy the standard condition and it can be used to concrete mix design
• It gives a high strength and it's based on the trial and error method
• As the water-cement ratio decreases the strength of the concrete increases

Procedure for concrete mix design

Given data

• Grade of concrete
• maximum size of aggregate
• Minimum cement content
• Maximum water-cement ratio
• Workability in terms of slump
• Exposure condition
• Maximum temperature at pouring point
• Early age strength (if required)
• Grading zone of fine aggregate
• Type of aggregate
• Maximum cement content
• Admixture used
• Specific gravity of all materials used
• Moisture content(free)

1. Target mean strength

f'ck= fck+1.65*S

f'ck = target average compressive strength at 28 days

fck = characteristic compressive strength at 28days

S = Standard deviation (from table 2 of IS 10262:2019)

2.Selection of water-cement ratio

From table 5 of IS 456:2000 the value can be taken based on the exposure condition

3.Selection of water-content

From table 4 of IS 10262:2019 maximum water content for 20mm aggregate = 186lit (for 25-50mm slump range)

(For additional slump 3% may be added for every 25mm slump)

4. Selection of cement-content

This value is taken from w/c ratio

Minimum cement content is taken from table 5 of IS 456:2000

5. Volume of coarse aggregate and fine aggregate can be determined from table 5 of IS 10262:2019 (selecting depending upon fine aggregate zone)

6. The mix calculation per unit volume of concrete shall be as follows

• Volume of concrete = 1m^3

• Volume of cement = (Mass of cement /Specific gravity of cement) * (1/1000)

• Volume of water = (Mass of water/Specific gravity of water) * (1/1000)

• Volume of chemical admixture = (Mass of chemical admixture /Specific gravity of chemical admixture) * (1/1000)

Mass of chemical admixture = 2% of cementitious material

• Volume of chemical admixture = (Mass of chemical admixture /Specific gravity of chemical admixture) * (1/1000)

• Volume of aggregate (fine aggregate and coarse aggregate ) = (a-(b+c+d))

• Mass of coarse aggregate = e*volume of coarse aggregate * specific gravity of coarse aggregate * 1000

• Mass of fine aggregate = e*volume of fine aggregate * specific gravity of fine aggregate * 1000

7. Mix proportion for trial mix

• Cement =Kg/m^3
• Water = Kg/m^3
• Fine aggregate = Kg/m^3
• Coarse aggregate = Kg/m^3
• Chemical admixture = Kg/m^3
• Water-cement ratio =

8. Trial mix ratio = cement : fine aggregate : coarse aggregate

Concrete mix design for M-35 grade with fly ash

Aim:- To determine the workability of the fresh concrete by using IS 456:2000 and IS 10262:2019 for concrete mix design for M-35 grade with fly ash

Introduction

The process of selecting suitable ingredients for producing concrete of required strength, durability and workability as economical as possible is known as concrete mix design

Code books used are - IS456:2000 and IS 10262:2019

Step 1 :-Stipulation for proportion

Here all the values, types of ingredients, conditions and methods are assumption except grade of designation because the values are not mentioned in questions

1. Grade designation = M-35
2. Type of cement = OPC 43 grade confirming IS 8112
3. Maximum nominal size of aggregate = 20mm
4. Minimum cement content = 320 Kg/m^3 (From table 5 of IS 456:2000 - Exposure condition)
5. Maximum water-cement ratio = 0.45 (From table 5 of IS 456:2000 - Exposure condition)
6. Workability = 100mm (Slump value for pumpable concrete)
7. Exposure condition = Severe (for reinforced concrete)
8. Method of concrete placing = Pumping
9. Degree of supervision = Good
10. Type of aggregate = Crushed angular aggregate
11. Maximum cement content = 450 Kg/m^3
12. Chemical admixture type = Super Plasticizer

Step 2:- Test data for materials

1. Cement used = OPC 43 grade confirming to IS8112
2. Specific gravity of cement = 3.15
3. Specific gravity of fly ash = 2.2
4. Chemical admixture = Super plasticizer confirming to IS 9103
5. Specific gravity of coarse and fine aggregate = 2.74
6. Water absorption for coarse aggregate = 0.5%, for fine aggregate = 1.0%
7. Free surface moisture for coarse and fine aggregate = Nil
8. Sieve analysis for coarse aggregate confirming to table 2 of IS 383 and for fine aggregate confirming to grading zone 1 of table 4 of IS 383

Step 3:- Target strength mix

f'ck= fck+1.65*S

f'ck = target average compressive strength at 28 days

fck = characteristic compressive strength at 28days

S = Standard deviation

From table 2 of IS 10262:2019 standard deviation S = 5 N/mm^2

f'ck = 35+1.65*5

f'ck = 43.25 N/mm^2

Target mean strength = 43.25 N/mm^2

Step 4:- Selection of water-cement ratio

From table 5 of IS 456:2000 for severe exposure maximum water-cement ratio = 0.45

By using a fig 1 of IS 10262:2019 w/c ratio = 0.38

0.38<0.45 ( take lesser value)

Water-cement ratio = 0.38

Hence ok

Step 5:- Selection of water content

From table 4 of IS 10262:2019 maximum water content for 20mm aggregate = 186lit (for 25-50mm slump range)

Estimate water content for 100 mm slump = 186 + 6/100 * 186

= 197.16 = 198 lit

As a super plasticizer is used the water content can be reduced up to 30%

Based on trial water content reduction of 27% is achieved with plasticizer

Hence arrived content = 198*0.73 = 144.54 = 145 lit

Step 6:- Calculation of cement content

Water-cement ratio = 0.38

Cement content = 145/0.38 = 382= 382 Kg/m^3

From table 5 of IS 456:2000 minimum cement content for severe exposure condition = 320 Kg/m^3

382 Kg/m^3 > 320 Kg/m^3 Hence ok

Take a higher value 382 Kg/m^3

Now to proportion a mix containing fly ash the following steps are suggested

• The percentage of the fly ash needed to be decided based on project requirement and quality of materials
• In some cases increases in cementitious materials can be warranted. Increase in cementitious material content and its percentage may be based on experience and trial

Increase 10% of cementitious material content

Cementitious material content = 382*1.10 = 420 Kg/m^3

Water content = 145 Kg/m^3

so water-cement ratio = 145/420 = 0.345

Fly ash @ 30% total cementitious material = 420*(30/100) = 126 Kg/m^3

Cement (OPC) = 420-126 = 294 Kg/m^3

Saving cement by using fly ash = 382-294 = 88 Kg/m^3

Fly ash being utilized = 126 Kg/m^3

Step 7:- Proportion of volume of coarse aggregate and fine aggregate content

From table 5 of IS 10262:2019 volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone1) for water-cement ratio of 0.5 = 0.6

In the present case the water-cement ratio is 0.38

The water-cement ratio is reduced to 0.12 therefore the volume of the coarse aggregate needs to be increased to decrease the fine aggregate content

As water-cement ratio is lower by 0.12 the proportion of coarse aggregate is increased by 0.024

Therefore correct volume of coarse aggregate for w/c ratio of 0.29= 0.6+0.024 = 0.624

For pumpable concrete these values are reduced by 10%

therefore volume of coarse aggregate = 0.624*0.9 = 0.56

Volume of fine aggregate = 1-0.56 = 0.44

Step 8:-Mix calculation

The mix calculation per unit volume of concrete shall be as follows

a) Volume of concrete = 1m^3

b) Volume of cement = (Mass of cement /Specific gravity of cement) * (1/1000)

= (294/3.15)*(1/1000) = 0.093m^3

c) Volume of fly ash = (Mass of fly ash /Specific gravity of fly ash) * (1/1000)

= (126/2.2)*(1/1000) = 0.057m^3

d) Volume of water = (Mass of water/Specific gravity of water) * (1/1000)

= (145/1)*(1/1000) = 0.145 m^3

e) Volume of chemical admixture = (Mass of chemical admixture /Specific gravity of chemical admixture) * (1/1000)

Mass of chemical admixture = 2% of cementitious material

= (420*2/100) = 8.4

Volume of chemical admixture = (Mass of chemical admixture /Specific gravity of chemical admixture) * (1/1000)

= (8.4/1.145)*(1/1000) = 0.007m^3

f) Volume of aggregate (fine aggregate and coarse aggregate ) = (a-(b+c+d+e))

= (1-(0.093+0.057+0.145+0.007)

= 0.698 m^3

g) Mass of coarse aggregate = f*volume of coarse aggregate * specific gravity of coarse aggregate * 1000

= 0.698*0.56*2.74*1000 = 1071Kg/m^3

h) Mass of fine aggregate = f*volume of fine aggregate * specific gravity of fine aggregate * 1000

= 0.698*0.44*2.74*1000 = 842Kg/m^3

Step 9:- Mix proportion for trial mix

• Cement =294 Kg/m^3
• Fly ash = 126 Kg/m^3
• Water = 145 Kg/m^3
• Fine aggregate = 842 Kg/m^3
• Coarse aggregate = 1071 Kg/m^3
• Chemical admixture = 8.4 Kg/m^3
• Water-cement ratio = 0.345

Trial mix ratio = 1:2:2.55

Result

• The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving required slump on trial. The mix proportion shall be worked for the actual water content and checked for durability required.
• Two or more trials having variation of 10% of water-cement ratio is carried out by using a graph from fig 1 of IS 10262:2019 and corresponding corresponding strength shall be plotted to workout the mix proportion for given target strength for field trials.

Concrete mix design for M-50 grade without fly ash

Aim:- To determine the workability of the fresh concrete by using IS 456:2000 and IS 10262:2019 for concrete mix design for M-50 grade without fly ash

Introduction

The process of selecting suitable ingredients for producing concrete of required strength, durability and workability as economical as possible is known as concrete mix design

Code books used are - IS456:2000 and IS 10262:2019

Step 1 :-Stipulation for proportion

Here all the values, types of ingredients, conditions and methods are assumption except grade of designation because the values are not mentioned in questions

1. Grade designation = M-50
2. Type of cement = OPC 43 grade confirming IS 8112
3. Maximum nominal size of aggregate = 20mm
4. Minimum cement content = 320 Kg/m^3 (From table 5 of IS 456:2000 - Exposure condition)
5. Maximum water-cement ratio = 0.45 (From table 5 of IS 456:2000 - Exposure condition)
6. Workability = 100mm (Slump value for pumpable concrete)
7. Exposure condition = Severe (for reinforced concrete)
8. Method of concrete placing = Pumping
9. Degree of supervision = Good
10. Type of aggregate = Crushed angular aggregate
11. Maximum cement content = 450 Kg/m^3
12. Chemical admixture type = Super Plasticizer

Step 2:- Test data for materials

1. Cement used = OPC 43 grade confirming to IS8112
2. Specific gravity of cement = 3.15
3. Chemical admixture = Super plasticizer confirming to IS 9103
4. Specific gravity of coarse and fine aggregate = 2.74
5. Water absorption for coarse aggregate = 0.5%, for fine aggregate = 1.0%
6. Free surface moisture for coarse and fine aggregate = Nil
7. Sieve analysis for coarse aggregate confirming to table 2 of IS 383 and for fine aggregate confirming to grading zone 1 of table 4 of IS 383

Step 3:- Target strength mix

f'ck= fck+1.65*S

f'ck = target average compressive strength at 28 days

fck = characteristic compressive strength at 28days

S = Standard deviation

From table 2 of IS 10262:2019 standard deviation S = 5 N/mm^2

f'ck = 50+1.65*5

f'ck = 58.25 N/mm^2

Target mean strength = 58.25 N/mm^2

Step 4:- Selection of water-cement ratio

From table 5 of IS 456:2000 for severe exposure maximum water-cement ratio = 0.45

By using a fig 1 of IS 10262:2019 w/c ratio = 0.29

0.29<0.45 ( take lesser value)

Water-cement ratio = 0.29

Hence ok

Step 5:- Selection of water content

From table 4 of IS 10262:2019 maximum water content for 20mm aggregate = 186lit (for 25-50mm slump range)

Estimate water content for 100 mm slump = 186 + 6/100 * 186

= 197.16 = 198 lit

As a super plasticizer is used the water content can be reduced up to 30%

Based on trial water content reduction of 27% is achieved with plasticizer

Hence arrived content = 198*0.73 = 144.54 = 145 lit

Step 6:- Calculation of cement content

Water-cement ratio = 0.29

Cement content = 145/0.29 = 500 = 500 Kg/m^3

From table 5 of IS 456:2000 minimum cement content for severe exposure condition = 320 Kg/m^3

500 Kg/m^3 > 320 Kg/m^3 Hence ok

Take a higher value 500 Kg/m^3

Step 7:- Proportion of volume of coarse aggregate and fine aggregate content

From table 5 of IS 10262:2019 volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone1) for water-cement ratio of 0.5 = 0.6

In the present case the water-cement ratio is 0.29

The water-cement ratio is reduced to 0.21 therefore the volume of the coarse aggregate needs to be increased to decrease the fine aggregate content

As water-cement ratio is lower by 0.21the proportion of coarse aggregate is increased by 0.042

Therefore correct volume of coarse aggregate for w/c ratio of 0.29= 0.6+0.042 = 0.642

For pumpable concrete these values are reduced by 10%

therefore volume of coarse aggregate = 0.642*0.9 = 0.58

Volume of fine aggregate = 1-0.58 = 0.42

Step 8:-Mix calculation

The mix calculation per unit volume of concrete shall be as follows

a) Volume of concrete = 1m^3

b) Volume of cement = (Mass of cement /Specific gravity of cement) * (1/1000)

= (500/3.15)*(1/1000) = 0.159 m^3

c) Volume of water = (Mass of water/Specific gravity of water) * (1/1000)

= (145/1)*(1/1000) = 0.145 m^3

d) Volume of chemical admixture = (Mass of chemical admixture /Specific gravity of chemical admixture) * (1/1000)

Mass of chemical admixture = 2% of cementitious material

= (500*2/100) = 10

Volume of chemical admixture = (Mass of chemical admixture /Specific gravity of chemical admixture) * (1/1000)

= (10/1.145)*(1/1000) = 0.009 m^3

e) Volume of aggregate (fine aggregate and coarse aggregate ) = (a-(b+c+d))

= (1-(0.159+0.145+0.009)

= 0.687 m^3

f) Mass of coarse aggregate = e*volume of coarse aggregate * specific gravity of coarse aggregate * 1000

= 0.687*0.58*2.74*1000 = 1092Kg/m^3

g) Mass of fine aggregate = e*volume of fine aggregate * specific gravity of fine aggregate * 1000

= 0.687*0.42*2.74*1000 = 791 Kg/m^3

Step 9:- Mix proportion for trial mix

• Cement =500 Kg/m^3
• Water = 145 Kg/m^3
• Fine aggregate = 791 Kg/m^3
• Coarse aggregate = 1092 Kg/m^3
• Chemical admixture = 10 Kg/m^3
• Water-cement ratio = 0.29

Trial mix ratio = 1:1.582:2.184

Result:-

• The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving required slump on trial. The mix proportion shall be worked for the actual water content and checked for durability required.
• Two or more trials having variation of 10% of water-cement ratio is carried out by using a graph from fig 1 of IS 10262:2019 and corresponding strength shall be plotted to workout the mix proportion for given target strength for field trials.