Project on Concrete Mix Design for various grades of Concrete

 1)Target mean strength

f’ck =fck + 1.65s

Where

• f’ck = target average compressive strength at 28 days

• fck = characteristics compressive strength at 28 days, and

• s = standard deviation

2)Cement content

Cement content = water content / water-cement ratio

3) Volume Calculations

• (a) Volume of concrete

• (b) Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x 1/1000

• (c) Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000

• (d)Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000

• (e) Volume of all in aggregate =[a-(b+c+d)]

• (f) Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000

• (g) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000

• M35 grade concrete with Fly ash
  STEP 1: STIPULATION FOR CONCRETE DESIGN MIX
  Grade designation	M35
  Type of cement	OPC 43 Grade confirming to IS 8112
  Type of mineral admixture	Fly ash confirming to IS 3812 (Part 1)
  Maximum nominal size of aggregate	20 mm
  Minimum cement content	320 kg/m3 (Table 5 of  IS 456:2000- Exposure condition)
  Maximum water-cement ratio	0.45 (Table 5 of IS 456:2000 Exposure   condition)
  Workability	100 mm (slump value for pumpable concrete)
  Exposure condition	Severe (For Reinforced Concrete)
  Method of concrete placing	Pumping
  Degree of supervision	Good
  Type of aggregate	Crushed Angular Aggregates
  Maximum cement content	450 kg/m3
  Chemical admixture type	Super Plasticizer
  STEP 2: TEST DATA FOR MATERIALS
  Cement used	OPC 43 Grade conforming IS 8112
  Specific gravity of cement	3.15
  Fly ash	confirming to IS 3812 (Part 1)
  Specific gravity of fly ash	2.2
  Chemical admixture	Super Plasticizer conforming to IS 9103
  Specific gravity of coarse aggregate	2.74
  Specific gravity of fine aggregate	2.74
  Water absorption of coarse aggregate	0.5%
  Water absorption of fine aggregate	1.0%
  Free surface moisture of Coarse aggregate	Nil
  Free surface moisture of  Coarse aggregate	Nil
  Sieve analysis: Coarse aggregate	Conforming to Table 2 of IS 383
  Sieve analysis: Fine aggregate	Conforming to Grading Zone II of Table 4 of IS 383
  STEP 3: TARGET STRENGTH FOR MIX PROPORTIONING
  f’ck =fck + 1.65s Where f’ck = target average compressive strength at 28 days fck = characteristics compressive strength at 28 days, and s = standard deviation From Table I of IS 10262:2009, Standard Deviation, s = 5 N/mm2.	35 + 1.65 x 5 = 43.25 N/mm2
  Target mean strength = 43.25 N/mm2
  STEP 4: SELECTION OF WATER-CEMENT RATIO
  The maximum water-cement ratio to design M50 grade concrete can be found from Table 5 of IS 456-2000.	Maximum W/C ratio =0.45
  Based on experience adopted water cement ratio is .44 0.44<0>
  Adopted W/C ratio=0.44
  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)
  Clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm slump. So a 6% is to be added to it Estimated water content for 100 mm slump	186+ (6/100)*186 = 197 litre.
  (Note: If Super plasticizer is used, the water content can be reduced up to 20% and above.) Based on trials with Super plasticizer water content reduction of 20% has been achieved, Hence the arrived water content	197*0.8 = 158 litre
  Water required 158 litres
  EP 6: CALCULATION OF CEMENT AND FLY ASH REQUIRED
  Adopted w/c Ratio	0.44
  Total cementitious (Cement + fly ash)requirement = Water content/ Water Cement ratio	158/0.44 = 359 kg/m3
  The cementitious content has to be increased in order to attain good workability and strength. The increment required is determined on the basis of experience and research. Here we are increasing cementitious content by 10%
  Final cementitious content	359 X 1.10 = 395 kg
  From Table 5 of IS 456, Minimum cement content for ‘Severe’ exposure conditions	320 kg
  395 kg/m3 > 320 kg/m3 hence ok.
  Cementitious material content	395
  New water cement ratio	158/395 =0.4
  Fly ash content is taken as 30% of the total cementitious content	395 X .3 = 118.5 kg/m3
  Cement required	395 – 118 = 277 kg/m3
  Cement quantity saved due to fly ash addition	350-277 = 73 kg/m3
  Cementitious material, cement  and fly ash required is 395 kg/m3 , 277 kg/m3and 118 kg/m3 and the new water-cement ratio is 0.4 respectively
  STEP 7: 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 II) for water-cement ratio of 0.50 is	0.62.
  In the present case water-cement ratio is 0.44. Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.06. 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 0.44	0.632
  For pumpable concrete these values should be reduced up to 10%. Therefore, volume of coarse aggregate	0.632 x 0.9 =0.568.
  Volume of fine aggregate content	1 – 0.568 =0.431
  Volume of fine aggregate and coarse aggregate is  0.431 and .568
  STEP 8: MIX CALCULATIONS
  The mix calculations as per unit volume of concrete shall be as follows:
  a) Volume of concrete	1 m3
  b) Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x 1/1000	(277/3.15) X (1/1000) =0.087m3
  c) Volume of fly ash = [Mass of  fly ash] / [Specific Gravity of fly ash] x 1/1000	(118/2.2) X (1/1000) =0.053
  d) Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000	(158/1) X (1/1000) = 0.158m3
  e) Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000	(7.6/1.145) X (1/1000) =0.006 m3
  f) Volume of all in aggregate =  [a-(b+c+d+e)]	[1-(0.087+0.053+0.158+0.006)] = 0.696m3
  g) Mass of coarse aggregate= f x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000	0.696x 0.568 x 2.74 x 1000 = 1077 kg/m3
  h) Mass of fine aggregate= f x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000	0.696x 0.431x 2.74 x 1000 = 822 kg/m3
  STEP 9: MIX PROPORTIONS
  Cement	277 kg/m3
  Fly ash	118 kg/m3
  Water	158 l/m3
  Fine aggregate	822 kg/m3
  Coarse aggregate 20mm	1077 kg/m3
  Chemical admixture	7.18 kg/m3
  Water-cement ratio (lowest W/C ratio is selected)	0.4
  Mix Proportion By weight	1:2.08:2.72
  STEP 10: The slump shall be measured, the water content and dosage of admixture shall be adjusted for achieving the required slump on trial. The mix proportion shall be reworked for the actual water content and checked for durability requirements
  STEP 11: Two more trials having variation of 10% of water-cement ratio shall be carried out and a graph between three water- cement ratios and corresponding strengths shall be plotted to work out the mix proportions for the given target for field trials.

   

  PART 2:To Calculate the Concrete Mix Design for M50 grade concrete without fly ash:

   

  M50 grade concrete without Fly ash
  STEP 1: Stipulations for Concrete design mix
  Grade designation	M50
  Type of cement	OPC 53 Grade confirming to IS BIS 12269 - 1987
  Maximum nominal size of aggregate	20 mm
  Minimum cement content	320 kg/m3 (Table 5 of  IS 456:2000- Exposure condition)
  Maximum water-cement ratio	0.45 (Table 5 of IS 456:2000 Exposure   condition)
  Workability	100 mm (slump value for pumpable concrete)
  Exposure condition	Severe (For Reinforced Concrete)
  Method of concrete placing	Pumping
  Degree of supervision	Good
  Type of aggregate	Crushed Angular Aggregates
  Maximum cement content	450 kg/m3
  Chemical admixture type	Super Plasticizer
  STEP 2: TEST DATA FOR MATERIALS
  Cement used	OPC 53 Grade conforming IS 12269-1987
  Specific gravity of cement	3.15
  Chemical admixture	Super Plasticizer conforming to IS 9103
  Specific gravity of coarse aggregate	2.74
  Specific gravity of fine aggregate	2.64
  Water absorption of coarse aggregate	0.5%
  Water absorption of fine aggregate	1.0%
  Free surface moisture of Coarse aggregate	Nil
  Free surface moisture of  Coarse aggregate	Nil
  Sieve analysis: Coarse aggregate	Conforming to Table 2 of IS 383
  Sieve analysis: Fine aggregate	Conforming to Grading Zone II of Table 4 of IS 383
  STEP 3: TARGET STRENGTH FOR MIX PROPORTIONING
  f’ck =fck + 1.65s Where ·        f’ck = target average compressive strength at 28 days ·        fck = characteristics compressive strength at 28 days, and ·        s = standard deviation From Table I of IS 10262:2009, Standard Deviation, s = 5 N/mm2.	50 + 1.65 x 5 = 58.25 N/mm2
  Target mean strength = 58.25 N/mm2
  STEP 4: SELECTION OF WATER-CEMENT RATIO
  The maximum water-cement ratio to design M50 grade concrete can be found from Table 5 of IS 456-2000 for severe exposure.	Maximum W/C ratio =0.45
  Based on experience adopted water cement ratio is .44 0.44<0>
  Adopted W/C ratio=0.44
  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)
  Clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm slump. So a 6% is to be added to it Estimated water content for 100 mm slump	186+ (6/100)*186 = 197 litre.
  (Note: If Super plasticizer is used, the water content can be reduced up to 20% and above.) Based on trials with Super plasticizer water content reduction of 20% has been achieved, Hence the arrived water content	197 X 0.8 = 158 litre
  Water required 158 litres
  EP 6: CALCULATION OF CEMENT REQUIRED
  Adopted w/c Ratio	0.44
  Cement Content	158/0.44 = 359 kg/m3
  From Table 5 of IS 456, Minimum cement content for ‘Severe’ exposure conditions	320kg/m3
  359 kg/m3 > 320 kg/m3 hence ok.
  Cement required is  359 kg/m3
  STEP 7: 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 II) for water-cement ratio of 0.50 is	0.62.
  In the present case water-cement ratio is 0.44. Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.06. 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 0.44	0.632
  For pumpable concrete these values should be reduced up to 10%. Therefore, volume of coarse aggregate	0.632 x 0.9 =0.568.
  Volume of fine aggregate content	1 – 0.576 =0.431
  Volume of fine aggregate and coarse aggregate is 0.431 and .568 respectively
  STEP 8: MIX CALCULATIONS
  The mix calculations per unit volume of concrete shall be as follows:
  a) Volume of concrete	1 m3
  b) Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x 1/1000	(359/3.15) X (1/1000) =0.114m3
  c) Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000	(158/1) X (1/1000) = 0.158m3
  d) Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000	(7.6/1.145) X (1/1000) =0.006 m3
  e) Volume of all in aggregate =  [a-(b+c+d)]	[1-(0.114+0.158+0.006)] = 0.722m3
  f) Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000	0.722x 0.568 x 2.74 x 1000 = 1123 kg/m3
  g) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000	0.722x 0.431x 2.64 x 1000 = 821 kg/m3
  STEP 9: MIX PROPORTIONS
  Cement	359 kg/m3
  Water	158 l/m3
  Fine aggregate	821 kg/m3
  Coarse aggregate 20mm	1123 kg/m3
  Chemical admixture	7.18kg/m3
  Water-cement ratio	0.44
  Mix Proportion By weight	1:2.28:3.12