Project on Concrete Mix Design for various grades of Concrete
AIM: To calculate the concrete mix design for M35 grade concrete with fly ash & M50 grade concrete without fly ash.
INTRODUCTION: concrete mix design is the method of finding the precise proportion of cement,sand and aggregate for concrete to achieve the target strength in structurs,therefor concrete mix design can be stated as concrete mix in terms of cement:sand:aggregates. the design is done according to the requirements of concrete strength. so, we can achieve the desirableproperties of concete either it is in fresh stage or in hardened stage. the fresh concee propertie like workabiity, setting time and hardened concrete properties lie compressive strength, durability etc. are attend suerly by this method. use of additives like admixtures, retardersetc. other than basic ingrediants are used to improve the properties of mix. this project consist of two parts, the first part deals with the design of M35 grade cement with fly ash as a part of it and second part is the design of M50 grade concrete without fly ash.
OBJECTIVE: the objective of this project is to produce a mix design for M35 grade concrete containing fly ash and M50 grade concrete. the mix will be prepared as per IS METHOD: concrete mix proportioning guidelines from IS 10262:2009 and recommented guidelines from IS 10262:1982.
EQUATIONS USED:
1) Target means strength
f'ck=fck + 1.65s , (1) f'ck= target average compressive strength at 28 days, (2) fck = charecteristics compressive strength at 28 days,and (3) 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 aggregates = e x
volume of coarse aggregate x specific gravity of fine aggregate x 1000, (g) mass of fine aggregate = e x volume of fine aggregates x specific gravity of fine aggregate x 1000.
PART 1: To calculate the concrete mix design for M35 grade concrete with fly ash:
M35 grade concrete with fly ash
STEP 1: Stipulations for concrete design mix
Grade designation M35
Type of cement opc 43 grade confirming to lS 8112
type of mineral admixture fly ash confirming to lS 3812 (part 1)
maximum nominal size of aggregate 20mm
minimum cement content 320kg/m^3 (table 5 of lS 456:2000-exposure condition)
maximum water-cement ratio 0.45 (table 5 of lS 456:2000 exposure condition)
workability 100mm (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/m^3
chemical admixture type super cast sizer
STEP 2: Test data for material
Cement used opc 43 grade conforming lS 8112
specific gravity of cement 3.15
fly ash confirming to lS 3812 (part 1)
specific gravity of fly ash 2.2
chemical admxture super plasticizer conforming to lS 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
sieve analysis:coarse aggregate conforming to table 2 of lS 383
sieve analysis:fine aggregate conforming to grading zone ll of table 4 of lS 383
STEP 3: Target strength for mix proportioning
f'ck = fck +1.65s
(a) f'ck = target average compressive strength at 28 days
(b) fck = charecteristics compressive strength at 28 days, and 35 + 1.65 x 5 = 43.25 N/mm^2
(c) s = standard deviation from table l of lS 10262:2009 ,standard deviation, s= 5 N/mm^2
Target means strength= 43.25 N/mm^2
Step 4: selection of water - cement ratio
the maximum water-cement ratio to design M50 grade concrete can be found from table 5 of lS 456-2000. maximum W/C ratio = 0.45
based on experience adopted water cement ratio is .44
0.44<0.45, hence ok.
Adopted W/C ratio = 0.44
Step 5: selection of water content
from table 2 of lS 10262:2009, maximum 186 litre (for 25 to 5 mm water content for 20 slump range) mm aggregate
clause 4.2 suggests increasing of 3% of water content for every extra 25 mm slump from 50 mm slump. so a 6% is to be added to it 186 + (6/100)*186=197 litre
estimated water content for 100 mm slump (note if super plasticizer is use, the water content can be reduced up to 20% and above)
based on trials wirh super plasticizer water content reduction of 20% has been achieved, hence the arrived water content 197*0.8 = 158 litre
water required 158 litre.
Step 6: calculations of cement and fly ash required
adopted W/C ratio 0.44
total cementitious (cement + fly ash)requirement = 158/0.44=359 kg/m^3
water cement / water cement ratio
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 lS 456, minimum cement content for 'severe' exposure conditions 320kg
395 kg/ m^3>320 kg/m^3, 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/m^3
cement required 395-118=277 kg/m^3
cement quantity saved due to fly ash addition 350-277=73 kg/m^3
Cementitious material,cement and fly ash required is 395 kg/m^3, 277 kg/m^3 and 118 kg/m^3 and the new water - cement ratio is 0.4 respectively
Step 7: Volume of coarse aggregate and fine aggregate content
from table 3 of (lS10262:2009) volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (zone ll) for water-cement ratio of 0.50 is 0.62
in the present case water-cment 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) 0.632
for pumpable concrete these value should be reduced up to 10%. therefore, volume of coarse aggregate 0.632x0.9=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 m^3
b) volume of cement = [Mass of cement] / [Specific gravity of cement]x 1/1000 (277/3.15) x (1/1000)=0.087 m^3
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) = 0.158m^3
e) volume of chemical admixture=[Mass of admixture] / [Specific gravity of admixture]x1/1000 (7.6/1.145)x (1/1000)=0.006 m^3
f) volume of all in aggregate = [a-(b+c+d+e)] [1-(0.087+0.053+0.158+0.006)]= 0.696m^3
g) Mass of coarse aggregate=f x volume of coarse aggregate x specific gravity of fine aggregate x 1000 0.696 x 0.568 x 2.74 x 1000= 1077 kg/m^3
h) Mass of fine aggregate =f x volume of fine aggregate x Specific gravity of fine aggregate x1000 0.696 x 0.431 x 2.74 x 1000= 822 kg/m^3
Step 9: Mix proportions
cement 277 kg/m^3
fly ash 118 kg/m^3
water 158 l/m^3
fine aggregate 822 kg/m^3
coarse aggregate 20mm 1077 kg/m^3
chemical admixture 7.18 kg/m^3
water - cement ratio (lowest W/C ratio is selected) o.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 the graph between three water-cement ratio and corresponding strengths shall be plotted to work out the mix proportion for the given target for field trials.
PART 2: 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 lS BlS 12269 - 1987
maximum nominal size of aggregate 20mm
minimum cement content 320 kg/m^3 (table 5 of lS 456:2000- exposure condition)
maximum water-cement ratio 0.45 (table 5 of lS 456:2000 exposure condition)
workability 100mm (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 aggregate
maximum cement content 450 kg/m^3
chemical admixture type super plasticizer
Stp 2: Test data for materials
opc 53 grade conforming lS 12269-11987
specific gravity of cement 3.15
chemical admixture super plasticizer conforming to lS 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 lS 383
seive analysis: fine aggregate conforming to grading zone ll of table 4 of lS 383
Step 3: Target strength for mix proportioning
f'ck = fck + 1.65s
(a) f'ck = target average compressive strength at 28 days
(b) fck = characteristics compressive strength at 28 days 50+1.65 x 5=58.25 N/mm^2
(c) s = standard deviation
from table l of lS 10262:2009,standard deviation, s=5 N/mm^2
Target mean strength = 58.25N/mm^2
Step 4: selection of water cement ratio
the maximum water- cement ratio to design M50 grade concrete can be found from table 5 of lS 456-2000 for severe exposure.
based on experience adopted water cement ratio is .44 , 0.44 < 0.45, hence ok.
Adopted W/C ratio = 0.44
Step 5: selection of water content
from table 2 of lS 10262:2009, maximm water content for 20mm aggregate 186 litre (for 25 to 50 mm slump range)
clause 4.2 suggests increasing 3% of water content for every extra 25 mm slump from 50mm slump. so a 6% is to be added to it 186 + (6/100)*186 = 197 litre
eatimated water content for 100 mm slump (NOTE:- if super plasticizer is used, the water content can be reduced upto 20% and above).
based on trials with super plasticizer water content reduction of 20% has been achieved hence the arrived water content
water required 158 litre
Step 6: calculation of cement required
adopted w/c ratio 0.44
cement content 158/0.44=359 kg/m^3
from table 5 of lS 456, minimum cement content for 'severe' exposure conditions 320 kg/m^3
359 kg/m^3 > 320 kg/m^3, hence ok
cement required is 359 kg/m^3
Step 7: volume of coarse aggregate and fine aggregate content
from table 3 of (lS 10262:2009) volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone ll) 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 compable concrete these values should be reduced upto 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 calculation per unit volume of concrete shall be as follows:
a) volume of concrete 1m^3
b) volume of cement = [Mass of cement] / [specific gravity of cement] x 1/1000 (359/3.15)x(1/1000) = 0.114m^3
c) volume of water = [Mass of water] / [specific gravity of water] x 1/1000 (158/1)x(1/1000) = 0.158m^3
d) volume of chemical admixture = [Mass of admixture] / [specific gravity of admixture] x 1/1000 (7.6/1.145)x(1/1000) = 0.006m^3
e) volume of all in aggregate = [a-(b+c+d)] [1-(0.114+0.158+0.006 = 0.722m^3]
f) mass of coarse aggregate = e x volume of coarse aggregate x specific gravity of fine aggregate x 1000 0.722x0.568x2.74x1000 = 1123 kg/m^3
g) mass of fine aggregate = e x volume of fine aggregate x specific gravity of fine aggregate x 1000 0.722x0.431x2.64x1000 = 821 kg/m^3
Step 9: mix proportions
cement 359 kg/m^3
water 158 l/m ^3
fine aggregate 821 kg/m^3
coarse aggregate 20 mm 1123 kg/m^3
chemical admixture 7.18 kg/m^3
water-cement ratio 0.44
mix proportion by weight 1:2.28:3.12
Step 10: the slump shall be measured,the watr 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.
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 proportion for the given target for field trials.
Results:
mix proportion by weight of M35 grade of concete with fly ash is 1:2.08:2.72 and its water-cement ratio was found to be 0.4.
mix proportion by weight of M50 grade of concrete without fly ash as is 1:2.28:3.12 and its water-cement ratio was found to be 0.44.