Project on Concrete Mix Design for various grades of Concrete

Answers

A) M35 grade concrete

Aim

To Calculate the Concrete Mix Design for M35 grade concrete with fly ash

Introduction

• The calculated mix proportions shall be checked by means of trial batches.Workability of the Mix shall be measured.
  The mix shall be carefully observed for freedom from segregation and bleeding and its finishing properties.
  If the measured workability of Mix is different from the stipulated value, the water and or admixture content shall be adjusted suitably.

Procedure

Design mix Propotion

1. • Grade designation M 35
   • Type of cement OPC 43 grade conforming to IS 8112 Fly ash conforming to IS 3812 (Part 1)
   • Type of mineral admixture Fly ash conforming to IS 3812 (Part 1)
   • Maximum nominal size of aggregate 20 mm
   • Minimum cement content 320 kg/m³
   • Maximum water-cement ratio 0.45
   • Workability 100 mm (slump)
   • Exposure condition Severe (for reinforced concrete)
   • Method of concrete placing Pumping
   • Degree of supervision Good
   • Type of aggregate Crushed angular aggregate
   • Maximum cement (OPC) content 450 kg/m³
   • Chemical admixture type Superplasticizer

Test data for materials

1. Cement used OPC 43 grade conforming to IS 8112
2. Specific gravity of cement 3.15
3. fly ashConforming to IS 3812 (Part I)
4. Specific gravity of fly ash 2.2
5. Chemical admixture Superplasticizer conforming to IS 9103
6. Specific gravity of:
• Coarse aggregate 2.74
• Fine aggregate 2.74
7. Water absorption:
• Coarse aggregate 0.5 percent
• Fine aggregate 1.0 percent
8. Free (surface) moisture:
• Coarse aggregate Nil
• Fine aggregate Nil
9. Sieve analysis:
• Coarse aggregate Conforming to grading Zone I of Table 4 of IS 383
• Fine aggregate Conforming to grading Zone I of Table 4 of IS 383

Target mean strength

F’ck=Fck+1.65S

From Table 2, standard deviation, S = 5 N/mm²

F’ck = target average compressive strength at 28 days,

Fck= characteristic compressive strength at 28 days,

S= standard deviation

Mean strength=35+1.65(5)

Target mean strength =43.25N/MM²

Approximate air content

From Table 3, (non-air-entrained) concrete is 1.0 percent for 20 mm nominal maximum size of aggregate.

Selection of water-cement ratio

This is lower than the maximum value of 0.45 prescribed for ‘severe’ exposure for reinforced concrete as per Table 5 of IS 456.

0.40< 0.45, hence O.K.

Selection of water content

From Table 2 of IS 10262:2009, water content = 186 kg (for 50 mm slump) for 20 mm aggregate.

Estimated water content for 100 mm slump

=186+(6/100)*186=197Lit

we are using the super platicizer,we have the reduse of 29% of water

=197*0.71=140Lit

Calculation of cement content

Cement content (cement + flyash) =140/0.4

=350Kg/m³

water cement Ratio= 0.4

From Table 5 of IS 456, minimum cement content for ‘severe’ exposure condition = 320 kg/m³

350 kg/m³> 320 kg/m³ ,hence ok

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

• Decide the percentage fly ash to be used based on project requirement and quality of materials.
• In certain situations increase in cernentitious material content may be warranted, The decision on increase
  in cementitious material content and its percentage may be based on experience and trial.

Cementitious material content 350 x 1.10 = 385 Kg/m³

Water Content 140 Kg/m³

Water cement ratio 140/385 =0.36

Fly ash @ 30% of total cementitious material content 385*30%= 115Kg/m³

Cementl content (OPC) 385-115=270Kg/m³

therefore the cement content saved was 350-270=80Kg/m³

Proportion of volume of coarse aggregate and fine aggregate content

• From Table 3. volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I)
  for water-cement ratio of 0.50 =0.60.
• In the present case water-cement ratio is 0.40. Therefore. volume of coarse aggregate is requ ired (0 be increased
  to decrease the line aggregate content.
• As the water-cement ratio is lower hy 0.10. the proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio) ,

Therefore. corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.40 = 0.62

For pumpable concrete these values should be reduced by 10 percent.

Therefore. volume of coarse aggregate =0.62 x 0.9 =0.56.
Volume of fine aggregate content = I - 0.56 = 0.44.

MIX

A)Total volume = 1 m³

B)Volume of cement=

(MASS OF CEMENT/SPECIFIC GRIVITY OF CEMENT)*(1/1000)=(270/3.15)*(1/1000)=0.086m³

C)Volume of fly ash=

(MASS OF FLY ASH/SPECIFIC GRIVITY OF FLY ASH)*(1/1000)=(115/2.2)*(1/1000)=0.052m³

D)volume of water

(MASS OF WATER/SPECIFIC GRIVITY OF WATER)*(1/1000)=(140/1)*(1/1000)=0.140m³

E)Volume of chemical admixture (superplasticizer) (@ 1.0 percent by mass of cementitious material

(MASS OF CHEMICAL ADMIXTURE/SPECIFIC GRIVITY OF CEMENT)*(1/1000)=(7.6/1.145)*(1/1000)=0.006m³

F) Volume of all in aggregate = (a-(b+c+d+e))

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

= 0.716m³

G)Mass of coarse aggregate

f × Volume of coarse aggregate × Specific gravity of coarse aggregate × 1 000

= 0.716 × 0.56 × 2.75 × 1000

=1098Kg/m³

Mass of fine aggregate

= f × volume of fine aggregate × Specific gravity of fine aggregate × 1 000

= 0.716 × 0.44 × 2.75 × 1000

=863Kg/m³

Result

Cement 270Kg/m³

Flyash 115Kg/m³

Water 270Kg/m³

Coarse Aggregrate 1098Kg/m³

Fine aggregrate 863Kg/m³

Chemical Admixture 7Kg/m³

Water-cement ratio 0.364

trial mix 1:2.24:2.85

B) M50 grade concrete

Aim

To Calculate the Concrete Mix Design for M50 grade concrete without fly ash

Introduction

• The calculated mix proportions shall be checked by means of trial batches.Workability of the Mix shall be measured.
  The mix shall be carefully observed for freedom from segregation and bleeding and its finishing properties.
  If the measured workability of Mix is different from the stipulated value, the water and or admixture content shall be adjusted suitably.

Procedure

Design mix Propotion

1. • Grade designation M 50
   • Type of cement OPC 43 grade conforming to IS 8112
   • Maximum nominal size of aggregate 20 mm
   • Minimum cement content 320 kg/m³
   • Maximum water-cement ratio 0.45
   • Workability 100 mm (slump)
   • Exposure condition Severe (for reinforced concrete)
   • Method of concrete placing Pumping
   • Degree of supervision Good
   • Type of aggregate Crushed angular aggregate
   • Maximum cement (OPC) content 450 kg/m³
   • Chemical admixture type Superplasticizer

Test data for materials

1. Cement used OPC 43 grade conforming to IS 8112
2. Specific gravity of cement 3.15
3. Chemical admixture Superplasticizer conforming to IS 9103
4. Specific gravity of:
• Coarse aggregate 2.74
• Fine aggregate 2.74
5. Water absorption:
• Coarse aggregate 0.5 percent
• Fine aggregate 1.0 percent
6. Free (surface) moisture:
• Coarse aggregate Nil
• Fine aggregate Nil
7. Sieve analysis:
• Coarse aggregate Conforming to grading Zone I of Table 4 of IS 383
• Fine aggregate Conforming to grading Zone I of Table 4 of IS 383

Target mean strength

F’ck=Fck+1.65S

From Table 2, standard deviation, S = 5 N/mm²

F’ck = target average compressive strength at 28 days,

Fck= characteristic compressive strength at 28 days,

S= standard deviation

Mean strength=50+1.65(5)

Target mean streng th =58.25N/MM²

Selection of water-cement ratio

This is lower than the maximum value of 0.45 prescribed for ‘severe’ exposure for reinforced concrete as per Table 5 of IS 456.

0.40< 0.45, hence O.K.

Selection of water content

From Table 2 of IS 10262:2009, water content = 186 kg (for 50 mm slump) for 20 mm aggregate.

Estimated water content for 100 mm slump

=186+(6/100)*186=197Lit

we are using the super platicizer,we have the reduse of 29% of water

=197*0.71=140Lit

Calculation of cement content

Cement content =140/0.4

=350Kg/m³

water cement Ratio= 0.4

From Table 5 of IS 456, minimum cement content for ‘severe’ exposure condition = 320 kg/m³

350 kg/m³> 320 kg/m³ ,hence ok

Proportion of volume of coarse aggregate and fine aggregate content

• From Table 3. volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I)
  for water-cement ratio of 0.50 =0.60.
• In the present case water-cement ratio is 0.40. Therefore. volume of coarse aggregate is requ ired (0 be increased
  to decrease the line aggregate content.
• As the water-cement ratio is lower hy 0.10. the proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio) ,

Therefore. corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.40 = 0.62

For pumpable concrete these values should be reduced by 10 percent.

Therefore. volume of coarse aggregate =0.62 x 0.9 =0.56.
Volume of fine aggregate content = I - 0.56 = 0.44.

MIX

A)Total volume = 1 m³

B)Volume of cement=

(MASS OF CEMENT/SPECIFIC GRIVITY OF CEMENT)*(1/1000)=(350/3.15)*(1/1000)=0.111m³

C)volume of water

(MASS OF WATER/SPECIFIC GRIVITY OF WATER)*(1/1000)=(140/1)*(1/1000)=0.140m³

D)Volume of chemical admixture (superplasticizer) (@ 1.0 percent by mass of cementitious material

(MASS OF CHEMICAL ADMIXTURE/SPECIFIC GRIVITY OF CEMENT)*(1/1000)=(7/1.145)*(1/1000)=0.006m³

E) Volume of all in aggregate = (a-(b+c+d+e))

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

= 0.746m³

F)Mass of coarse aggregate

e× Volume of coarse aggregate × Specific gravity of coarse aggregate × 1 000

= 0.746 × 0.56 × 2.75 × 1000

=1140Kg/m³

Mass of fine aggregate

= e × volume of fine aggregate × Specific gravity of fine aggregate × 1 000

= 0.746 × 0.44 × 2.75 × 1000

=896Kg/m³

Result

Cement 350Kg/m³

Water 140Kg/m³

Coarse Aggregrate 1140Kg/m³

Fine aggregrate 896Kg/m³

Chemical Admixture 7Kg/m³

Water-cement ratio 0.40

trial mix 1:3.26:2.56