Project on Concrete Mix Design for various grades of Concrete

1. Aim:-Concrete mix design for M35 grade of concrete with fly ash

• Introduction:-
• For grades above M20 design mix is adopted
• Mix design is the most rational and intelluctual approach for selection of different materials with their proportions in suitable amount
• Design mix is more scientific than nominal mix
• It is used for extensive and important construction projects
• There are some guidlines for making a concrete mix design are:-
• IS method:Concrete mix proportioning guidelines(Bureau of indian standards -IS 10262-2019) and recommened guidelines for concrete mix design-IS 10262-2009
• BS method(British standard -BS EN 206-1 and its complimentary standars BS 8500 part1 and part2)
• ACI method (American standard -ACI 211, 211-91 reapproved 2002
• We are going to design according to IS 10262-2019

A-1 STIPULATIONS FOR PROPORTIONING

a) Grade designation : M35
b) Type of cement : OPC 43 grade conforming to IS 269
c) Type of mineral admixture : Fly ash conforming to IS 3812 (Part1)
d) Maximum nominal size of aggregate : 20 mm
e) Minimum cement content and maximum
water-cement ratio to be adopted : Severe(for reinforced concrete)
and/or
Exposure conditions as per Table 3 and Table 5 of IS 456
f) Workability : 100 mm (slump)
g) Method of concrete placing : Pumping
h) Degree of supervision : Good
j) Type of aggregate : Crushed angular aggregate
k) Maximum cement content (OPC content) : As per IS 456
m) Chemical admixture type : Superplasticizer- normal

A-2 TEST DATA FOR MATERIALS

a) Cement used : OPC 43 grade conforming to IS 269
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 (at SSD condition) : 2.74
2) Fine aggregate (at SSD condition) : 2.65
3) Chemical admixture : 1.145
g) Water absorption
1) Coarse aggregate : 0.5 percent
2) Fine aggregate : 1.0 percent
3) Free surface moisture:nil for both coarse and fine aggregate

A-3 Target strength of mix proportioning

• Fmean=Fck+1.65s
• Fmean=target average compressive strength based on 28 days
• Fck=characterstic compressive strength based on 28 days
• s=standard deviation
• From table 2,standard deviation =5n/mm2
• Fmean=fck+1.65s
• Fmean=35+1.65*5=43.25N/mm2

A-4 Approximate air content

• From Table 3, the approximate amount of entrapped
  air to be expected in normal (non-air-entrained)
  concrete is 1.0 percent for 20 mm nominal maximum
  size of aggregate.

A-5 Selection of water/cement ratio

• From Fig. 1, the free water-cement ratio required for
  the target strength of 43.25 N/mm2 is 0.37 for OPC 43
  grade curve. This is lower than the maximum value of
  0.45 prescribed for ‘severe’ exposure for reinforced
  concrete as per Table 5 of IS 456.
  0.37 < 0.45, hence Ok.

A-6 Selection of water content

• From Table 4, water content = 186 kg (for 50 mm
  slump) for 20 mm aggregate.
  Estimated water content for 100 mm slump (increasing
  at the rate of 3 percent for every 25 mm slump)
  
• 186+(6/100)*186=197.16 kg
• As super plasticizer is used, the water content may be
  reduced.
  Based on trial data, the water content reduction of
  23 percent is considered while using superplasticizer
  at the rate 1.0 percent by weight of cement.
  Hence the arrived water content=197.16*0.77=152kg

A-7 Calculation of cement content

• Water-cement ratio = 0.37
  Cement content = 152/0.37
  = 411kg/m3
  
  There is increase of 10% cementious content
  Cementitious material content
  
  
• Cementious material content=411*1.1=452kg/m3
• Water content=152kg/m3
• so,w/c ratio=152/452=0.336
• Fly ash @30%total cementious material content=452*0.30=136 kg/m3
• Cement=452-136=316kg/m3
• Fly ash being utilized=136kg/m3

A-8 Proportion of volume of coarse aggregate and fine aggregate

• from Table 5, volume of coarse aggregate corresponding
  to 20 mm size aggregate and fine aggregate (Zone II)
  for water-cement ratio of 0.50 = 0.62.
  In the present case water-cementitious ratio is 0.336.
  Therefore, volume of coarse aggregate is required to
  be increased to decrease the fine aggregate content. As
  the water-cement ratio is lower by 0.164, the proportion
  of volume of coarse aggregate is increased by 0.0328
  (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-cementitious
  ratio of 0.389 = 0.62 + 0.0328= 0.6528
• For pumpable concrete these values may be reduced by 10%
• Therefore volume of coarse aggregates=0.6528*0.9=0.587 say 0.59m3
• Volume of fine cement=1-0.59=0.41m3

A-9 Mix calculations

• Totalvolume=1m3
• Volume of entrapped air in wet concrete=0.01m3
• volume of cement=(Mass of cement/specific gravity of cement)*1/1000=(316/3.15)*1/1000=0.1m3
• Volume of fly ash=(mass of fly ash/specific gravity of fly ash)*1/1000=(136/2.2)*1/1000=0.061m3
• Volume of water=(152/1)*1/1000=0.152
• Volume of chemical admixture=(4.74/1.145)*1/1000=0.004m3
• Volume of all in aggregate=(1-0.01)-(0.1+0.061+0.152+0.004)=0.673m3
• Mass of coarse aggregate=volume of aggregate*volume of coarse aggregate*sg of coarse aggregate*1000=0.673*0.59*2.65*1000=1052.21kg/m3
• Mass of fine aggregate=0.673*0.41*2.65*1000=731.214kg/m3

A-10 Mix proportions for trial

• Cement=316m3
• fly assh=136m3
• Water=152kgm3
• Fine aggregate=731.21kg/m3
• Coarse aggregate=1052.21m3
• Chemical admixture=4.74m3
• Free w/c ratio=0.336m3
• Trial mix ratio=1:2.31:3.32

2. Aim: Concrete mix design for M50 grade concrete without fly ash

Introduction:

• For grades above M20 design mix is adopted
• Mix design is the most rational and intelluctual approach for selection of different materials with their proportions in suitable amount
• Design mix is more scientific than nominal mix
• It is used for extensive and important construction projects
• There are some guidlines for making a concrete mix design are:-
• IS method:Concrete mix proportioning guidelines(Bureau of indian standards -IS 10262-2019) and recommened guidelines for concrete mix design-IS 10262-2009
• BS method(British standard -BS EN 206-1 and its complimentary standars BS 8500 part1 and part2)
• ACI method (American standard -ACI 211, 211-91 reapproved 2002
• We are going to design according to IS 10262-2019

• A-1 STIPULATIONS FOR PROPORTIONING
  
  a) Grade designation : M50
  b) Type of cement : OPC 43 grade conforming to IS 269
  c) Maximum nominal size of aggregate : 20 mm
  d) Minimum cement content and maximum
  water-cement ratio to be adopted : Severe(for reinforced concrete)
  and/or
  Exposure conditions as per Table 3 and Table 5 of IS 456
  f) Workability : 150-175 mm (slump)
  g) Method of concrete placing : Pumping
  h) Degree of supervision : Good
  j) Type of aggregate : Crushed angular aggregate
  k) Maximum cement content (OPC content) : As per IS 456
  m) Chemical admixture type : Superplasticizer- normal

  
  A-2 TEST DATA FOR MATERIALS

  
  a) Cement used : OPC 43 grade conforming to IS 269
  b) Specific gravity of cement : 3.15
  c) Chemical admixture : Superplasticizer conforming to IS 9103
  d) Specific gravity of
  1) Coarse aggregate : 2.74
  2) Fine aggregate : 2.65
  3) Chemical admixture : 1.145
  g) Water absorption
  1) Coarse aggregate(SSD condition) : 0.5 percent
  2) Fine aggregate (SSD condition): 1.0 percent
  3) Free surface moisture:nil for both coarse and fine aggregate

  A-3 Target strength of mix proportioning

  • Fmean=Fck+1.65s
  • Fmean=target average compressive strength based on 28 days
  • Fck=characterstic compressive strength based on 28 days
  • s=standard deviation
  • From table 2,standard deviation =5n/mm2
  • Fmean=fck+1.65s
  • Fmean=50+1.65*5=58.25N/mm2

  A-4 Approximate air content

  • From Table 3, the approximate amount of entrapped
    air to be expected in normal (non-air-entrained)
    concrete is 1.0 percent for 20 mm nominal maximum
    size of aggregate.

  A-5 Selection of water/cement ratio

  • From table -5 of IS 456 maximum free water content ratio is 0.45 for severe exposure conditions
  • This is irrespective of grade of concrete
  • We may adopt a lower value based on experience
  • Let us adopt 0.42

  A-6 Selection of water content

  • From Table 4, water content = 186 kg (for 50 mm
    slump) for 20 mm aggregate.
    Estimated water content for 150-175 mm slump (increasing
    at the rate of 3 percent for every 25 mm slump)
    
  • 186+(15/100)*186=214kg
  • As super plasticizer is used, the water content may be
    reduced.
    Based on trial data, the water content reduction of
    23 percent is considered while using superplasticizer
    at the rate 1.0 percent by weight of cement.
    Hence the arrived water content=214*0.77=165kg

  A-7 Calculation of cement content

  • Water-cement ratio = 0.42
    Cement content = 165/0.42
    = 393kg/m3
    
    
  • Water content=165kg/m3
  • so,w/c ratio=165/393=0.42
    

• A-8 Proportion of volume of coarse aggregate and fine aggregate

  • from Table 5, volume of coarse aggregate corresponding
    to 20 mm size aggregate and fine aggregate (Zone II)
    for water-cement ratio of 0.50 = 0.62.
    In the present case water-cementitious ratio is 0.42.
    Therefore, volume of coarse aggregate is required to
    be increased to decrease the fine aggregate content. As
    the water-cement ratio is lower by 0.08, the proportion
    of volume of coarse aggregate is increased by 0.016
    (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-cementitious
    ratio of 0.389 = 0.62 + 0.016= 0.636
  • For pumpable concrete these values may be reduced by 10%
  • Therefore volume of coarse aggregates=0.636*0.9=0.572 say 0.58m3
  • Volume of fine cement=1-0.58=0.42m3

  A-9 Mix calculations

  • Totalvolume=1m3
  • Volume of entrapped air in wet concrete=0.01m3
  • volume of cement=(Mass of cement/specific gravity of cement)*1/1000=(393/3.15)*1/1000=0.124m3
  • Volume of water=(165/1)*1/1000=0.165
  • Volume of chemical admixture=(4.74/1.145)*1/1000=0.004m3
  • Volume of all in aggregate=(1-0.01)-(0.124+0.165+0.004)=0.697m3
  • Mass of coarse aggregate=volume of aggregate*volume of coarse aggregate*sg of coarse aggregate*1000=0.697*0.58*2.65*1000=1071.28kg/m3
  • Mass of fine aggregate=0.697*0.42*2.65*1000=775.761kg/m3

  A-10 Mix proportions for trial

  • Cement=393m3
  • Water=165kgm3
  • Fine aggregate=775.76kg/m3
  • Coarse aggregate=1071.28m3
  • Free w/c ratio=0.42m3
  • Trial mix ratio=1:1.97:2.725