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Project on Concrete Mix Design for various grades of Concrete

MMuthukumaran Venkatesan26 Aug 2022
DESIGN

1. Calculate the Concrete Mix Design for M35 grade concrete with fly ash :

Introduction:

Concrete is a cpmposite building material made by mixing cement, fine aggregate, coarse aggregate and water is definite proportion.

Concretre mix design:

Concrete mix design is a systematic process of choosing relative proportion of various ingredients from available material that gives desired workability. It is also a step by step procedure in determining water cemet ratio, water content estimation of course and fine aggregate content done in a laboratry with material to be used. The concrete mix design is a process of selecting suitable ingredient for producing concrete of required strength, durability and workability as economical as possible.

Aim:

The aim of this project is to provide the step and procedure in cslculating the desgin mix of M35 concrete with fly ash.

Test Procedures:

  1. Grade Designation - M35.
  2. Type of cement - OPC 43 Grade.
  3. TYpe of mineral admixture - Fly ash.
  4. Maximun norminnal size of aggregate - 20mm.
  5. Minimum cement content and maximum W/C ratio to be adopted - severe.
  6. Workability - 120mm(slump).
  7. Method of concrete placing - Pumping.
  8. Degree of supervision - Good.
  9. Type of aggregate - Crushed angular aggregate.
  10. Maximum cement content (OPC Content) - As per IS 456:2000
  11. Chemical admixture type - Super plasticizer - Normal.

Test data for material:

  1. Cement used - OPC 43 Grade.
  2. Specific Gravity of cemant - 3.15.
  3. FLy ash - Confirmed to IS 3812.
  4. Specific gravity of fly ash - 2.2
  5. Chemical Admixture - Super plasticizer.
  6. Specific Gravity of coarse aggregate - 2.74
  7. Specific Gravity of Fine aggreagate - 2.65
  8. Water absorption of Coarse and fine aggregate - Nil
  9. Seive analysis of coarse aggregate - Conforming to grade table 7 of IS 383
  10. Seive analysis of fine aggreagte - Conforming to grading zone II of table 9 of IS 383

STEP I: Target Strength for mix proportion:

f'ck=fck+1.65S

fck=35.

S=5 ( from IS 10262:2019 table 1)

f'ck = 35 + 1.65(5) = 43.25 N/mm^2.

STEP II: Selection of Water Cement Ratio:

METHOD 1:

Using IS 10262:2019 Fig 1 Compressive strength of concrete is 43.25N/mm^2. So curve number 2 is selected. from that we can assume that the water cement rartio is 0.4

METHOD 2:

Using IS 456:2000 Table 5 with severe wether condition the water cement ratio is takes as 0.45

from these method the least amount is taken as water cemnt ratio so 0.40 is taken as W/C ratio.

STEP III: Selection of Water Content:

From IS 10262:2019 Table 4 Water content for 20mm aggregate 186kg for slump value 25-50. For increase of 25mm slump value 3% of kg should be increased.

We have slump vale of 120mm, so we have to add 8.4% 0.085* 186 = 15.62

186 + 15.62 = 201.62 we can take as 202kg/m^3

Due to adding superplasticizer water content is reduced to 23%

100% - 23% = 77%

Hence 202 * 0.77 = 155.54 we can take as 156.kg/m^3.

STEP IV: Calculating Cement Content:

Cement content = Wayer content / Water-Cemenat ratio. = 156/0.40 = 390kg/m^3.

From IS 456:2000 Table 5 minimum cement content for M35 is 320 kg/m^3 we have got 390kg/m^3, hence it is correct

To proportion a mix cintaining fly ash thw following steps are suggested.

  • Decided the percentage fly ash to be used based on project required and quanlity of fly ash.
  • In certain situation, increase in cementitious materials content may be warranted . the decision on increase in cementitious materials content and its percentage may be based on experience and trials

[NOTE: This illustration example is with increase of 10% cementitious materials content.]

cementitious material contenet = 390*1.10 = 429kg/m^3

water content = 156kg/m^3

Water-cementitious ratio = 156/429 = 0.36.

Fly ash @30% of cementitious = 429 * 30/100 = 128.7 let us take as 129 kg/m^3

Cement OPC = 429 - 129 = 300kg/m^3.

As per IS 456:2000 minimum ement content should be 320kg/m^3

so we are reducing fly ash content to 25% and make a trail.

Fly ash @25% of cementitious = 429 * 25/100= 107.25 let ua assume as 107.

cement OPC = 429 - 107 = 322kg/m^3

As per IS456:2000 the minimum cement content is 320kg/m^3, we got 322 kg/m^3 hence it is large we can proceed.

STEP V: Volume of coarse and fine aggregare:

  1. From IS 10262:2019 table 5 Volume of coarse aggregate corresponding to 20mm size aggreate nad fine aggregate Zone II for water cement ratio of 0.50 = 0.62.
  2. In the present case water ratio is 0.36. therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate conntent. As the water cement ratio is lowe by 0.14, the proporting of volume of coarse aggregate is imcreased by 0.0346(At the ratio of + or - 0.01for every + or - 0.05 change in water cement ratio). therefore corrected proportion of volume of coarse aggregate for the water cementitous ratio 0.36 = 0.62 +0.0346 = 0.654.

For pumpable concrete these values may be reduced by upto 10% (From 5.52 in IS 10262:2019)

Therefore 10% reduction is considered.

the volume of coarse aggregate = 0.654* 0.9 = 0.59m^3

Volumae of fine aggregate = 1 - 0.59 = 0.41m^3

STEP VI: Mix Calculation:

Volume of concrete = 1m^3
Volume of cemnt = mass of cement/specific gravity of cement * 1/1000 = 320/3.15 * 1/1000 = 0.102m^3
Volume of fly ash = mass of flyash/specific gravity of flyash * 1/1000 = 107/2.2 * 1/1000 = 0.049m^3
Volume of water = mass of water/specific gravity of water * 1/1000 = 156/1 * 1/1000 = 0.156m^3
Volume of chemical admixture superplastizicer @ 1% of mass of cementitious material = mass of chemical admixture/specific gravity of chemical; admixture * 1/1000 = 4.29/1.145 * 1/1000 = 0.004m^3
Volume of coarse and fine aggregate = a-(b+c+d+e) = 1 - (0.102+0.049+0.156+0.004) = 0.689m^3.
Mass of coarse aggregate = f* (volume of coarse aggregate*specific gravity of coarse aggregate)* 1000 = 0.689*0.59*2.74*1000 = 1114kg/m^3
Mass of fine aggregate = f*(volume of fine aggregate*specific gravity of fine aggregate)* 1000 = 0.689*0.41*2.65*1000 = 749kg/m^3

STEP VII Mix proportion for trial:

Cement - 320kg/m^3
Flyash - 107kg/m^3
Water - 156kg/m^3
Fine aggregate - 749kg/m^3
Coarse aggregate - 1114kg/m^3
Chemical admixture - 4.29kg/m^3
Free water cementitious material ratio - 0.36

Conculusion:

The MIX DESIGN we got is 1:2.34:3.48

2. Calculate the Concrete Mix Design for M50 :

Introduction:

Concrete is a cpmposite building material made by mixing cement, fine aggregate, coarse aggregate and water is definite proportion.

Concretre mix design:

Concrete mix design is a systematic process of choosing relative proportion of various ingredients from available material that gives desired workability. It is also a step by step procedure in determining water cemet ratio, water content estimation of course and fine aggregate content done in a laboratry with material to be used. The concrete mix design is a process of selecting suitable ingredient for producing concrete of required strength, durability and workability as economical as possible.

Aim:

The aim of this project is to provide the step and procedure in cslculating the desgin mix of M50 concrete.

Test Procedures:

  1. Grade Designation - M35.
  2. Type of cement - OPC 43 Grade.
  3. Maximun norminnal size of aggregate - 20mm.
  4. Minimum cement content and maximum W/C ratio to be adopted - severe.
  5. Workability - 75mm(slump).
  6. Method of concrete placing - chute ( No Pumpable)
  7. Degree of supervision - Good.
  8. Type of aggregate - Crushed angular aggregate.
  9. Maximum cement content (OPC Content) - 450 kg/m^3
  10. Chemical admixture type - Super plasticizer - Normal.

Test data for material:

  1. Cement used - OPC 43 Grade.
  2. Specific Gravity of cemant - 2.88.
  3. Chemical Admixture - Super plasticizer.
  4. Specific Gravity of coarse aggregate [at saturated surface dry (SSSD) condition] - 2.74
  5. Specific Gravity of Fine aggreagate[at saturated surface dry (SSSD) condition] - 2.65
  6. Specific Gravity of Chemical admixture - 1.145
  7. Water absorption of Coarse aggregate - 0.5
  8. Water absroption of fine aggregate - 1.0
  9. Seive analysis of coarse aggregate - Conforming to grade table 7 of IS 383
  10. Seive analysis of fine aggreagte - Conforming to grading zone II of table 9 of IS 383

STEP I: Target Strength for mix proportion:

f'ck = fck + 1.65S

fck=50.

S=5 ( from IS 10262:2019 table 1)

f'ck = 50 + 1.65(5) = 58.25 N/mm^2.

STEP II: Selection of Water Cement Ratio:

METHOD 1:

Using IS 10262:2019 Fig 1 Compressive strength of concrete is 58.25N/mm^2. So curve number 3 is selected. from that we can assume that the water cement rartio is 0.33

METHOD 2:

Using IS 456:2000 Table 5 with severe wether condition the water cement ratio is takes as 0.45

from these method the least amount is taken as water cemnt ratio so 0.33 is taken as W/C ratio.

STEP III: Selection of Water Content:

From IS 10262:2019 Table 4 Water content for 20mm aggregate 186kg for slump value 25-50. For increase of 25mm slump value 3% of kg should be increased.

We have slump vale of 75mm, so we have to add 3% 3/100 * 186 = 5.58

186 + 5.58 = 191.58 we can take as 192kg/m^3

Due to adding superplasticizer water content is reduced to 23%

100% - 23% = 77%

Hence 192 * 0.77 = 147.84 we can take as 148 kg/m^3.

STEP IV: Calculating Cement Content:

Cement content = Wayer content / Water-Cemenat ratio. = 149/0.33 = 448kg/m^3.

From GIven data data we have maximum cement contenet is 450 kg/m^3, we have 448lk/m^3, hence it is correct.

STEP V: Volume of coarse and fine aggregare:

  1. From IS 10262:2019 table 5 Volume of coarse aggregate corresponding to 20mm size aggreate nad fine aggregate Zone II for water cement ratio of 0.50 = 0.62.
  2. In the present case water ratio is 0.33. therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate conntent. As the water cement ratio is lowe by 0.17, the proporting of volume of coarse aggregate is imcreased by 0.034(At the ratio of + or - 0.01for every + or - 0.05 change in water cement ratio). therefore corrected proportion of volume of coarse aggregate for the water cementitous ratio 0.33 = 0.62 +0.034 = 0.654.
  3. Volume of fine aggregate 1 - 0.654 = 0.346.

STEP VI: Mix Calculation:

  1. Volume of concrete = 1m^3
  2. Volume of entraprd air content = 0.01m^3
  3. Volume of cemnt = mass of cement/specific gravity of cement * 1/1000 = 448/2.88 * 1/1000 = 0.169m^3
  4. Volume of water = mass of water/specific gravity of water * 1/1000 = 148/1 * 1/1000 = 0.148m^3
  5. Volume of chemical admixture superplastizicer @ 1% of mass of cementitious material = mass of chemical admixture/specific gravity of chemical; admixture * 1/1000 = 4.48/1.145 * 1/1000 = 0.004m^3
  6. Volume of coarse and fine aggregate = [(a-b) - (c+d+e)] = [ (1 - 0.01) - ( 0.169+0.148+0.004)] = 0.67m^3
  7. Mass of coarse aggregate = f* (volume of coarse aggregate*specific gravity of coarse aggregate)* 1000 = 0.67*0.654*2.74*1000 = 1147kg/m^3
  8. Mass of fine aggregate = f*(volume of fine aggregate*specific gravity of fine aggregate)* 1000 = 0.67*0.346*2.65*1000 = 614kg/m^3

STEP VII Mix proportion for trial:

Cement - 448kg/m^3
Water - 148kg/m^3
Fine aggregate - 614kg/m^3
Coarse aggregate - 1147kg/m^3
Chemical admixture - 4.48kg/m^3
Free water cementitious material ratio - 0.33

STEP VIII Adjustment of water in Coarse and Fine aggregate due to containment of moisture content:

  1. Fine aggregate (dry) = mass of fine aggregate in SSD condition / 1+ (water absorption/100) = 614 / 1+0.01 = 608kg
  2. Coarse aggregate (dry) = mass of coarse aggregatein SSD condition / 1+ (water absorption/100) = 1147 / 1 + 0.005 = 1141kg

The extra water to be added for absorption by Coarse and Fine aggregate

  • For Coarse aggregate = mass of coarse aggregate in SSD condition - mass of coarse aggregate in dry condition = 1141-1147 = 6kg
  • For Fine aggregate = mass of fine aggregate in SSD condition - mass of fine aggregate in dry condition = 608-614 = 6kg

The estimated requirement for added water, therefore it become = 148 + 6 + 6 = 160kg

Cement - 448kg/m^3
Water - 160kg/m^3
Fine aggregate - 608kg/m^3
Coarse aggregate - 1141kg/m^3
Chemical admixture - 4.48kg/m^3
Free water cementitious material ratio - 0.33

Conculusion:

The MIX DESIGN we got is 1:1.35:2.54

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