Project on Concrete Mix Design for various grades of Concrete

AIM : To find the mix proportion of M35 grade Concrete with Fly ash and M50 grade Concrete without Fly ash using Mix Design.

Introduction to Mix Design:

Concrete mix design is the process of finding right proportions of cement, sand and aggregates for concrete to achieve decided target strength in structures. This process is usually adopted for structures which requires higher grades of concrete such as M25 and above and used in large construction projects where quantity of concrete consumption is huge. Concrete mix design provides the right proportions of materials, thus making the concrete construction economical in achieving required strength of structural members.

Properties of Mix Design of concrete :-

• These mixes are designed by Structural Engineer and the mix proportions are determined by the Concrete Producer.
• The design mix approach results in the production of concrete with appropriate properties most economically.
• In design mix concrete, proportion of the concrete ingredients are properly determined with the relative ratio to achieve the concrete of desire strength.
• Design Mix is more scientific method and is widely used for more extensive and important concrete work.
• Mix design is based on actual available material to be used in construction works. Locally available material can satisfy the criteria and can be used for making Mix design concrete, so that the cost can be reduced for importing material from outside.
• Quantity of ingredient used are rational and it's neither overused nor underused.
• It is based on laboratory trail/error experiment method and it gives assurance of strength.

• There are some guidelines available for making a Design mix concrete such as :-

1. IS Method : Concrete mix proportioning guidelines (Bureau of Indian Standards - IS 10262-2009) and Recommended Guidelines for Concrete Mix Design - IS 10262-1982.
2. BS Method : British Standards - BS EN 206-1 and its Complementary standards BS 8500 part 1 & 2.
3. ACI Method : American Standard - ACI 211, 211-91, Reapproved - 2002.

Mix Design for M35 Grade Concrete with Fly Ash

Aim : To find the mix proportion of M35 grade Concrete with Fly ash

Procedure :

Step 1 : STIPULATIONS FOR PROPORTIONING :

1. Grade designation : M35
2. Type of cement : OPC 43 Grade conforming IS 8122
3. Type of mineral admixture : Fly ash conforming to IS 3812 (Part 1)
4. Maximum nominal size of aggregate : 20mm
5. Minimum cement content : 320 kg/`m^3` (From Table 5 of IS 456:2000 - Exposure condition)
6. Maximum water-cement ratio : 0.45 (From Table 5 of IS 456:2000 - Exposure condition)
7. Workability : 100 mm slump (Slump value for pumpable Concrete)
8. Exposure condition : Severe (For Reinforced Concrete)
9. Method of concrete placing : Pumping
10. Degree of supervision : Good
11. Type of aggregate : Crushed Angular Aggregates
12. Maximum cement content : 450 kg/`m^3`
13. Chemical admixture type : Superplasticizer

Step 2 : TEST DATA FOR MATERIALS :

a. Cement used : OPC 43 Grade conforming IS 8112

b. Specific gravity of cement : 3.15

c. Fly ash : Conforming to IS 3812 (Part 1)

d. Specific gravity of Fly ash : 2.2

e. Chemical admixture : Superplasticizer conforming to IS 9103

f. Specific gravity of :-

1. Coarse aggregate 20mm : 2.74
2. Fine aggregate : 2.74

g. Water absorption :-

1. Coarse aggregate : 0.5 %
2. Fine aggregate : 1.0 %

h. Free surface moisture:

1. Coarse aggregate : Nil
2. Fine aggregate : Nil

e. Sieve analysis:

1. Coarse aggregate : Conforming to Table 2 of IS 383
2. Fine aggregate : Conforming to Grading Zone I of Table 4 of IS 383

Step 3 : TARGET STRENGTH FOR MIX PROPORTIONING :

• f’ck = fck + 1.65*S

where,

• f’ck = target average compressive strength at 28 days,
• fck = characteristics compressive strength at 28 days, and
• S = standard deviation.

here, fck = 35 N/`mm^2`

From Table 8 of IS 10262:2009, Standard Deviation, S = 5 N/`mm^2`.

Therefore, target strength = 35 + 1.65 x 5 = 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 is 0.45
• Based on experience, adopted water-cement ratio is 0.4
• 0.4 < 0.45, Hence OK.

Step 5 : SELECTION OF WATER CONTENT :

• From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 litre (for 25 to 50 mm slump range)
• For additional slump, 3% of water content is added for every 25mm slump value
• Therefore, Estimated water content for 100 mm slump = 186 + (6/100)*186

= 197 litre.

• As Super plasticizer is used, the water content can be reduced upto 20% and above.

• Based on trials with Superplasticizer, water content reduction of 25% has been achieved,

Hence, the arrived water content = 197-[197 x (25/100)] = 148 litre.

Step 6 : CALCULATION OF CEMENT AND FLY ASH CONTENT :

• Water-Cement Ratio = 0.4
• Cementitious Material(Cement + Fly ash) Content = 148/0.4 = 370 kg/`m^3`

• From Table 5 of IS 456 : 2000, minimum cement content for ‘Severe’ exposure conditions 320kg/`m^3`

Thus, 370 kg/`m^3` > 320 kg/`m^3`, Hence OK.

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

a) The percentage fly ash needs to be decided based on project requirement and quality of materials.

b) In certain situations, increase in cernentitious material content may be warranted. Increase in cementitious material content and its percentage may be based on experience and trial (This example is with increase of 10% cementitious material content.)

Cementitious material content	= 370 * 1.10 = 407 kg/`m^3`
Water Content	= 148 kg/`m^3`
So, water-cement ratio	= 148/407 = 0.363
Fly ash @ 30% of total cementitious material content	= 407 * (30/100) = 122 kg/`m^3`
Cement (OPC)	= 407 - 122 = 285 kg/`m^3`
Saving of cement while using fly ash	= 370 - 285 = 85 kg/`m^3`, and
Fly ash being utilized	= 122 kg/`m^3`

Step 7 : PROPORTIO0N OF 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 I) for water-cement ratio (0.5) = 0.6

• In the present case, water-cement ratio is 0.4. Therefore, volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
• As the water-cement ratio is lower by 0.1, the proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every `pm` 0.05 change in water-cement ratio).

Therefore, corrected volume of coarse aggregate for the water-cement ratio of 0.4 = 0.62

Now, For Pumpable Concrete, these values should be reduced by upto 10%.

• Therefore, volume of coarse aggregate = 0.62 - [(10/100) * 0.62] = 0.56
• Volume of fine aggregate content = (1 – 0.56) = 0.44

Step 8 : MIX CALCULATIONS :

The mix calculations per unit volume of concrete shall be as follows:

a) Volume of concrete = 1 `m^3`

b) Volume of cement = (Mass of cement) / {(Specific Gravity of Cement) * 1000}
= 285/{3.15 * 1000}
= 0.09 `m^3`

c) Volume of Fly ash = (Mass of Fly ash) / {(Specific Gravity of Fly ash) * 1000}

= 122/{2.2 * 1000}

= 0.055`m^3`

d) Volume of water = (Mass of water) / {(Specific Gravity of water) * 1000}
= 148/{1 * 1000}
= 0.148 `m^3`

e) Volume of chemical admixture = (Mass of admixture) / {(Specific Gravity of admixture) * 1000}

(@ 2.0% by mass of cementitious material) = 7.4/{1.145 * 1000}

= 0.006 `m^3`

f) Volume of all in aggregate = [a-(b+c+d+e)]
= [1-(0.09+0.055+0.148+0.006)]
= 0.701 `m^3`

g) Mass of coarse aggregate = f * Volume of Coarse Aggregate * Specific Gravity of Coarse Aggregate * 1000
= 0.701 * 0.56 * 2.74 * 1000
= 1076 kg/`m^3`

h) Mass of fine aggregate = f * Volume of Fine Aggregate * Specific Gravity of Fine Aggregate * 1000
= 0.701 * 0.44 * 2.74 * 1000
= 845 kg/`m^3`

Step 9 : MIX PROPORTIONS :

Cement	= 285 kg/`m^3`
Fly ash	= 122 kg/`m^3`
Water	= 148 litre / kg/`m^3`
Fine Aggregate	= 845 kg/`m^3`
Coarse Aggregate	= 1076 kg/`m^3`
Chemical Admixture	= 7.4 kg/`m^3`
Water-Cement Ratio	= 0.4
MIX RATIO	= 1 : 2.07 : 2.64

Step 10 : The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving
the required slump based on trial. The mix proportions shall he reworked for the actual water content and checked for durability requirements.

Step 11 : Two more trials having variation of 10% of water-cement ratio in Clause X shall be carried out and a
graph between three water-cement ratios and their corresponding strengths shall be plotted to work out the mix
proportions for the given target strength for field trials. However, durability requirement shall be met.

RESULT : The mix proportion of concrete ingredients for grade M35 concrete with Fly ash used as some part of cementetious material along with cement is 1 : 2.07 : 2.64

• The result says, for 1 bag of cementitious material (cement + fly ash), 2.07 bags of sand and 2.64 bags of course aggregate is required.
• For each 1 bag of Cementitious material, 30% of Cement is replaced by Fly ash.
• For example, 50kg of cementitious bag should contain 35 Kg of Cement and 15 Kg of Fly ash.
• And for 50 kg of cementitious material, 103.5 Kg of sand and 132 Kg of course aggregates are required.

Mix Design for M50 Grade Concrete

Aim : To find the mix proportion of M50 grade Concrete without Fly ash

Procedure :

Step 1 : STIPULATIONS FOR PROPORTIONING :

1. Grade designation : M50
2. Type of cement : OPC 43 Grade conforming IS 8122
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 : 100 mm slump (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 Aggregates
11. Maximum cement content : 450 kg/`m^3`
12. Chemical admixture type : Superplasticizer

Step 2 : TEST DATA FOR MATERIALS :

a. Cement used : OPC 43 Grade conforming IS 8112

b. Specific gravity of cement : 3.15

c. Chemical admixture : Superplasticizer conforming to IS 9103

d. Specific gravity of :-

1. Coarse aggregate 20mm : 2.74
2. Fine aggregate : 2.74

e. Water absorption:-

1. Coarse aggregate : 0.5 %
2. Fine aggregate : 1.0 %

f. Free surface moisture:-

1. Coarse aggregate : Nil
2. Fine aggregate : Nil

g. Sieve analysis:-

1. Coarse aggregate : Conforming to all in aggregates of Table 2 of IS 383
2. Fine aggregate : Conforming to Grading Zone I of Table 4 of IS 383

Step 3 : TARGET STRENGTH FOR MIX PROPORTIONING :

• f’ck = fck + 1.65*S

where,

• f’ck = target average compressive strength at 28 days,
• fck = characteristics compressive strength at 28 days, and
• S = standard deviation.

here, fck = 50 N/`mm^2`

From Table 8 of IS 10262:2009, Standard Deviation, S = 5 N/`mm^2`.

Therefore, target strength = 50 + 1.65 x 5 = 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 is 0.45
• Based on experience, adopted water-cement ratio is 0.4
• 0.4 < 0.45, Hence OK.

Step 5 : SELECTION OF WATER CONTENT :

• From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 litre (for 25 to 50 mm slump range)
• For additional slump, 3% of water content is added for every 25mm slump value
• Estimated water content for 100 mm slump = 186 + (6/100)*186

= 197 litre

• As Super plasticizer is used, the water content can be reduced upto 20% and above.

• Based on trials with Superplasticizer, water content reduction of 29% has been achieved,

Hence, the arrived water content = 197-[197 x (29/100)] = 140 litre

Step 6 : CALCULATION OF CEMENT CONTENT :

• Water-Cement Ratio = 0.4
• Cement Content = 140/0.4 = 350 kg/`m^3`

• From Table 5 of IS 456 : 2000, minimum cement content for ‘Severe’ exposure conditions 320kg/`m^3`

Thus, 350 kg/`m^3` > 320 kg/`m^3`, Hence OK.

Step 7 : PROPORTIO0N OF 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 I) for water-cement ratio (0.5) = 0.6

• In the present case, water-cement ratio is 0.4. Therefore, volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
• As the water-cement ratio is lower by 0.1, the proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every `pm` 0.05 change in water-cement ratio).

Therefore, corrected volume of coarse aggregate for the water-cement ratio of 0.4 = 0.62

Now, For Pumpable Concrete, these values should be reduced by 10%.

• Therefore, volume of coarse aggregate = 0.62 x [(10/100) * 0.62] = 0.56
• Volume of fine aggregate content = (1 – 0.56) = 0.44

Step 8 : MIX CALCULATIONS :

The mix calculations per unit volume of concrete shall be as follows:

a) Volume of concrete = 1 `m^3`

b) Volume of cement = (Mass of cement) / {(Specific Gravity of Cement) * 1000}
= 350/{3.15 * 1000}
= 0.111`m^3`

c) Volume of water = (Mass of water) / {(Specific Gravity of water) * 1000}
= 140/{1 * 1000}
= 0.140 `m^3`

d) Volume of chemical admixture = (Mass of admixture) / {(Specific Gravity of admixture) * 1000}

(@ 2.0% by mass of cementitious material) = 7/{1.145 * 1000}

= 0.006 `m^3`

e) Volume of all in aggregate = [a-(b+c+d)]
= [1-(0.111 + 0.14 + 0.006)]
= 0.743 `m^3`

f) Mass of coarse aggregate = e * Volume of Coarse Aggregate * Specific Gravity of Coarse Aggregate * 1000
= 0.743 * 0.56 * 2.74 * 1000
= 1140 kg/`m^3`

g) Mass of fine aggregate = e * Volume of Fine Aggregate * Specific Gravity of Fine Aggregate * 1000
= 0.743 * 0.44 * 2.74 * 1000
= 896 kg/`m^3`

Step 9 : MIX PROPORTIONS :

Cement	= 350 kg/`m^3`
Water	= 140 litre / kg/`m^3`
Fine Aggregate	= 896 kg/`m^3`
Coarse Aggregate	= 1140 kg/`m^3`
Chemical Admixture	= 7 kg/`m^3`
Water-Cement Ratio	= 0.4
MIX RATIO	= 1 : 2.56 : 3.26

Step 10 : The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving
the required slump based on trial. The mix proportions shall he reworked for the actual water content and checked for durability requirements.

Step 11 : Two more trials having variation of 10% of water-cement ratio in Clause X shall be carried out and a
graph between three water-cement ratios and their corresponding strengths shall be plotted to work out the mix
proportions for the given target strength for field trials. However, durability requirement shall be met.

RESULT : The mix proportion of concrete ingredients for grade M35 concrete without Fly ash is 1 : 2.56 : 3.26

• The result says, for 1 bag of cement, 2.56 bags of sand and 3.26 bags of course aggregate is required.
• For example, for 50 Kg of Cement, 128 Kg of sand and 163 Kg of course aggregates are required.

Table used :-

1) Table 8 of IS 10262 : 2009 :-

2) Table 5 of IS 456 : 2000 :-

3) Table 2 of IS 10262 : 2009 :-

4) Table 3 of IS 10262 : 2009 :-