Project on Concrete Mix Design for various grades of Concrete
MIX DESIGN PROJECT 1
AIM:
To calculate the mix design for M35 concrete with flyash.
ASSUMPTIONS:
Grade of concrete – M35
Type of cement – OPC
Type of admixtures – Flyash
Maximum nominal size of aggregate – 20mm
Specific gravity of cement = 3.15
Minimum cement content =320 kg/m3(table 5 of IS456-2000/ exposure condition)
Maximum water cement ratio = 0.45 (table 5 of IS456-2000/ exposure condition)
Workability = 100mm ( slump value for pumpable concrete)
Exposure condition = severe (for reinforced concrete)
Method of placing concrete – pumping
Degree of supervision = good
Type of aggregate = crushed angular aggregate
Maximum cement content= 450kg/m3
Chemical admixture type = super plasticizer
Water absorption of coarse aggregate = 0.5%
Water absorption of fine aggregate = 1.0%
Specific gravity of coarse aggregate = 2.74
Specific gravity of fine aggregate = 2.74
STEP 1: CALCULATION OF TARGET MEAN STRENGTH
Target mean strength f’ck=fck+1.65s
Where f’ck = target mean strength
fck = characteristic compressive strength
s = standard deviation
from table 1 IS 10262 : 2009
s = 5 N/mm2
f’ck = 35 +(1.65X5)
= 43.25 N/mm2
Step 2: SELECTION OF WATER CEMENT RATIO
Given
M35
Assume,
Exposure condition = Extreme (for reinforced concrete)
From table 5 IS456:2000
HENCE
Extreme w/c ratio = 0.4
M35 w/c ratio = 0.45
lower water cement ratio= better workability
0.40<0.45
Therefore water cement ration is taken as 0.40
Minimum cement content = 360 kg/m3
STEP 3: SELECTION OF WATER CONTENT
Assume
Nominal size of aggregate = 20mm
Table 2- IS10262: 2009
Minimum water content = 186 lit
Slump range from 25 to 50mm
As superplasticizers (20% reduced)= 186X80/100 =148.8
Water content = 149 lit
STEP 4: CALCULATION OF CEMENTITIOUS CONTENT (CEMENT + FLYASH)
Water cement ratio =w/c= 0.40
Water content = W= 149kg
Cementitious content = c= 149/0.40=372.5=370 kg/m3
Minimum cement content = 360 kg/m3
360<370 kg/m3
Increased by 10%
370X0.10 + 370= 407kg/m3
W=149kg
Water cement ratio = 149/407 =0.366
Flyash at 30% total cementitious material content= 407X30/100
= 122kg/m3
Cement (ordinary Portland cement )= 407-122= 285kg/m3
Saving of cement while using fly ash = 370-285 = 85kg/m3
Fly ash = 122kg/m3
STEP 5: VOLUMEOF COARSE AGGREGATES AND FINE AGGREGATES
Fine aggregates are sieved according to zone 1 of table 2 IS 383
Coarse aggregate are sieved according to table 2 IS 383
According ,
Table 3 IS10262:2009
Nominal size of aggregate = 20mm
Fine aggregate (zone 1)
Therefore,
Volume of coarse aggregate = 0.60
Water cement ratio = 0.4
So, volume of coarse aggregate = 0.62
Volume of fine aggregate= 1-0.62=0.38
STEP 6: MIX CALCULATIONS
- Volume of concrete =1m3
- Volume of cement=(285/3.15)x1/1000 = 0.090m3
- Volume of flyash =(122/2.2)x1/1000=0.55m3
- Volume of water=(149/1)x1/1000= 0.149m3
- Volume of admixtures=(7.6/1.145)x1/1000=0.006m3
- Volume coarse aggregate and fine aggregate= a-(b+c+d+e)=1-(0.090+0.055+0.149+0.006) =0.7m3
- Mass of coarse aggregate=0.7x0.62x2.74x1000=1189.16kg/m3
- Mass of fine aggregate= 0.7x0.38x2.74x1000=728 kg/m3
RESULTS :
Cement = 285kg/m3
Flyash = 122kg/m3
Water = 149kg
Coarse aggregate = 1189kg/m3
Fine aggregate =728kg/m3
Chemical admixture = 7.6 kg/m3
Water cement ratio = 0.366
Trial mix ratio= 285:728:1189 = 1:2.55:4.17
The above trial mix should match the required workability, durability, minimum strength of M35 grade concrete.
If the requirement is satisfied then two or more trials are done for 10% increase.
MIX DESIGN FOR M50 GRADE CONCRETE WITHOUT FLYASH
AIM:
To calculate the mix design for M50 concrete with0UT flyash.
ASSUMPTIONS:
Grade of concrete – M50
Type of cement – OPC53 grade confirming to BIS 12269-1987
Maximum nominal size of aggregate – 20mm
Specific gravity of cement = 3.15
Minimum cement content =320 kg/m3(table 5 of IS456-2000/ exposure condition)
Maximum water cement ratio = 0.45 (table 5 of IS456-2000/ exposure condition)
Workability = 100mm ( slump value for pumpable concrete)
Exposure condition = severe (for reinforced concrete)
Method of placing concrete – pumping
Degree of supervision = good
Type of aggregate = crushed angular aggregate
Maximum cement content= 450kg/m3
Chemical admixture type = super plasticizer
Water absorption of coarse aggregate = 0.5%
Water absorption of fine aggregate = 1.0%
Specific gravity of coarse aggregate = 2.74
Specific gravity of fine aggregate = 2.64
STEP 1: CALCULATION OF TARGET MEAN STRENGTH
Target mean strength f’ck=fck+1.65s
Where f’ck = target mean strength
fck = characteristic compressive strength
s = standard deviation
from table 1 IS 10262 : 2009
s = 5 N/mm2
f’ck = 50 +(1.65X5)
= 58.25 N/mm2
Step 2: SELECTION OF WATER CEMENT RATIO
Given
M50
Assume,
Exposure condition = severe exposure
From table 5 IS456:2000
HENCE
Severe exposure w/c ratio = 0.44
M50 w/c ratio = 0.45
lower water cement ratio= better workability
0.44<0.45
Therefore water cement ration is taken as 0.44
STEP 3: SELECTION OF WATER CONTENT
Assume
Nominal size of aggregate = 20mm
Table 2- IS10262: 2009
Minimum water content = 186 lit
Clause 4.2 suggests increasing of 3% of water content for every extra Slump range from 25 to 50mm. so a 6% is to be added to it =186+(6/100)x186 = 197 lit.
As superplasticizers (20% reduced)= 197X80/100 =158 lit
Water content = 158 lit
STEP 4: CALCULATION OF CEMENT
Water cement ratio =w/c= 0.44
Water content = W= 158kg
Cement content = c= 158/0.44=359 kg/m3
From table 5 of IS456, minimum cement content for severe exposure conditions=320kg/m3
359kg/m3> 320kg/m3
Hence ok
Cement content= 359kg/m3
STEP 4 : VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE
From table 3 of IS 10262:2009 volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone II) for 0.62 water -cement ratio of 0.50 is
Water-cement ratio obtained =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 the volume of coarse aggregate for the water-cement ratio 0.44 = 0.632
For pumpable concrete these values should be deduced up to 10% =0.632x 0.9=0.568
Volume of coarse aggregate =0.568
Volume of fine aggregate =1-0.568=0.432
STEP 5 MIX CALCULATIONS
The mix calculations per unit volume of concrete shall be as follows:
- Volume of concrete 1m3
- Volume of cement = (mass of cement)/(specific gravity of cement)x(1/1000)
=(359/3.15)x(1/1000)
=0.114m3
- Volume of water = (mass of water/specific gravity of water)x(1/1000)
=(158/1)x(1/1000)
=0.158m3
- Volume of chemical admixtures = (mass of admixtures/specific gravity of admixture)x(1/1000)
=(7.6/1.145)x (1/1000)
=0.006m3
- Volume of aggregate = a-(b+c+d)= 1-(0.114+0.158+0.006)
= 0.722m3
- Mass of coarse aggregate = e x volume of coarse aggregate specific gravity of fine aggregatex1000 = 0.722 x 0.568 x 2.74 x 1000 = 1123kg/m3
- Mass of fine aggregate = e x volume of fine aggregate x specific gravity x 1000
= 0.722 x 0.432 x 2.64 x 1000 = 821 kg/m3
STEP 6 MIX PROPORTIONS
Cement 359kg/m3
Water 158 lit
Fine aggregate 821 kg/m3
Coarse aggregate 1123kg/m3
Chemical admixture 7.18 kg/m3
Water – cement ratio 0.44
Mix proportion by weight 1 : 2.28 :3.12
The slump shall be measured and the water content and amount of admixtures are adjusted for achieving the required slump on trial. Two or more trials shall be carried out for actual water content so that the mix reaches the durability requirements.