Project on Concrete Mix Design for various grades of Concrete
AIM: To calculate the concrete mix design for m35 grade concrete with fly ash and m50 grade concrete without flyash.
INTRODUCTION: Concrete mix design is the method of finding accurate proportion of cemnet,sand,and aggregates for concrete to achieve target strength in structures. so concrete mix design can be stated as concrete mix in terms of cement,sand,aggregates.This project comsists of two parts 1st deals with m35 grade cement with flyash and 2nd deals with m50 grade concrete without flyash.
At first we do design mix for M35 Grade with flyash:
STEP 1: stipulations for concrete design mix
Grade designation: M35
Type of cemnet: OPC 43 GRADE confirming to IS 8112
Type of minieral admixture: Fly ash confirming to IS 3812(Part1)
max nominal size of aggregate : 20mm
min cement content : 320kg/m3 ( table 5 IS 456:2000 -Exposure condition
max w/c ratio : 0.45 (table 5 of IS 456:2000)
Wokability: 100mm( slump value for pumpable concrete)
Exposure condition: severe (For Reincforced concrete)
Method of concrete : pumping
Degree of supervision: Good
Type of aggrehgate : Crushed angular aggregates
Max cement content : 450kg/m3
Chemical admixture type : Superplasticizer
Step 2: TEST DATA FOR MATERIALS
Cement used : OPC 43
Specific gravity of cement : 3.15
Fly ash confirming to IS 3812 part 1
Specific gravity of fly ash : 2.2
Chemical admixture: Siper 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%
Free surface moisture of coarse aggregate : Nil
Sieve analysis of coarse aggregate - Conforming to Table 2 of IS 383
Sieve analysis of 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
= 35 + 1.65 x 5 = 43.25 N/mm², s=std deviation=5N/mm2 From table IS 10262:2009
Step 4 : Selcection of water cement ratio
Max water cement ratio = 0.45 for M50
Based on experince adopt water cement ratio as 0.44 < 0.45, so OK
Step 5 : SELECTION OF WATER CONTENT
is 186 litre.
Clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm slump.so a 6% is to be addeed.
so 186+(6/100)*186=197 litre.
since superplastizer is used 20% reduction can be made so 0.8*197=158 litre.
reduction of 20% has been achieved ,hence the arrived water content
water required is 158 litres
Step 6: calculation of cement and fly ash required
Adopted w/c ratio= 0.44
Total cementitous ( cement + fly ash) requirement=158/0.44=359 kg/m3.
To attain good workability an extra 10% is increased
so final cementitious content =359*1.10=395kg
From table 5 of is 456,minimum cement content for severe exposure conditions =320kg
395kg>320kg 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 = 395x0.3 = 118.5kg/m³
cement required = 395-118 =277kg/m³
Cement quantity saved due to fly ash addition = 350-277=73kg/m³
cemntitious material ,cement and fly ash required is 395kg/m³,277 kg/m³ and 118 kg/m³ and new water-cement ratio is 0.4 respectively.
Step 7: voloume of coarse aggregate and fine aggregate content
from table 3 of (IS 10262:2009) voloume of ca to 20 mm size and fa for water-cement ratio of 0.5 is 0.62
so corrected propotion of voloume of ca for water-cement ratio of 0.44= 0.632
For pumpable concrete these values should be reduced up to 10%.therefore vol of ca =0.632*0.9=0.568
vol of fa =1-0.568=0.431.
Step 8: Mix calculations
a) vol of concrete = 1m³
b) vol of cement =[mass of cement ]/[specific gravity of cemnet ]*1/1000= [277/3.15]x(1/1000)=0.087m³
c) vol of fly ash=[mass of fly ash ]/[specific gravity of flyash]*1/1000= [118/2.2]x(1/1000)=0.053
d) vol of water=[mass of water ]/[specific gravity of water ]*1/1000 =[158/1)x(1/1000)=0.158m³
e) vol of chemical admixture=[mass of CA ]/[specific gravity of CA ]*1/1000= [7.6/1.145]X[1/1000]=0.006m³
f) vol of all aggregates=[a-(b+c+d+e)]= [1-(0.087+0.053+0.158+0.006)]=0.696m³
g) Mass of CA= fxvol of CA X SG of FA X 1000=0.696X0.568X2.74X1000=1077Kg/m³
h) Mass of FA =f x vol of FA x SG of FA x 1000= 0.693x0.431x2.74x1000=822 kg/m³
Step 9: Mix propotions
cement - 277kg/m³
fly ash - 118kg/m³
water - 158 kg/m³
Fine aggregate - 822 kg/m³
Coarse aggregate 20mm - 1077 kg/m³
Chemical admixture - 7.18 kg/m³
W/C ratio [lowest w/c ratio is selected) = 0.4
Mix propotion by weight = 1:2.08:2.72
step 10:
slump shall be measured,water content and dosage of admixture shall be adjusted for achievng required slump on trail.
step 11:
Two more trails having variation of 10% of water - cement ratio shall be carried out and a graph between three water - cemnt ratio shall be plotted to work out mix propotions for given target for field trails.
PART 2: To calcualate concrete mix design for M50 grade concrete without fly ash:
Step 1 : stipulations for concrete design mix
grade designation : M50
Type of cemnt : opc 53 grade confirming to IS BIS 12269 - 1987
Max nominal size of agg : 20mm
Min cemnet content: 320kg/m³
Max water - cemnet ratio: 0.45
Workabilty: 100mm( slump value for pumpable concrete)
Exposure condition : severe
Method of concrete : pumping
degree of supervision: good
type of agg : crushed angular aggregates
max cement content : 45 kg/m³
chemical admxture: 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 fine aggragate:1.0%
free surface moisture of coasre aggregate :nil
sieve analysis coarse aggregate: conforming to table 2 of is 383
sieve analysis : conforming to grading zone ii of table 4 of is 383
step 3: Target strength for mix proportioning :
f'ck=fck+1.65s
50+1.65x5= 58.25n/mm²
Target mean strength =58.25n/mm²
Step 4: selection of water-cement ratio
max water-cement ratio to design M50 grade concrete can be found from table 5 of is 456-2000 max severe exposure =0.45
adopt w/c ratio 0.44
0.44<0.45, hence ok
adopted w/c ratio= 0.44
step 5: selection of water content:
from table 2 of is 10262:2009, max water content 186 litre (for 25 to 50 mm slump for 20mm aggregate
clause 4.2 suggests incrasing of 3% of wtaer content for every extra 25mm slump.so a 6% is to be added to it.
186+(6/100)*186=197 litre
estimated water content for 100 mm slump
based on trails with supoer plastizers wtaer content reduction of 20% has been achieved,hence the arrived water content is 197x0.8=158litre.
water required 158 litres
step 6: calc of cement required
Adopt w/c ratio= 0.44
cement content =158/0.44=359kg/m³
From table 5 of is 456,minimum cement content for severe exposure condtions=320kg/m³
359kg/m³
cement reqired is 359 kg/m³
step 7: voloume of coarse aggregate and fine aggregate content
from table 3 of ( is 10262:2009) voloume of coarse aggregate corresponding to 20 mm size and fine aggregate (zone ii) for water-cement ratio 0.50 is 0.62
therefore corrected proportion of voloume of coarse aggregate for the water-cement ratio of 0.44 =0.632
for pumpable concrete these values should be reduced up to 10%=0.632x0.9=0.568
voloume of fine aggregate content=1-0.576=0.431
voloume of fine aggregate=1-0.576=0.431
vol of fine aggregate and coarse aggregate is 0.431 and 0.568 respectively
step 8: mix calcualtions
The mix calculations per unit vol of concrete shall be as follows:
a) vol of concrete :1m³
b)vol of cemnent= [mass of cement ]/[specific gravity of cement]x1/1000: (359/3.15)x(1/1000)=0.114m³
c) vol of water =[mass of water ]/[specific gravity of water]x1/1000: (158/1)x(1/1000)=0.158m³
d)vol of CA =[mass of CA ]/[specific gravity of CA]x1/1000: (7.6/1.145)X(1/1000)=0.006m³
e)vol of all in aggregate =[a-(b+c+d) =[1-(0.114+0.158+0.006)=0.722m³
f) mass of CA = e x vol of CA X SG of FA X1000=0.722X0.568X2.74X1000=1123KG/M³
g) mass of fine aggreagate = e xvol of fine aggregate x sg of fine aggregate x1000= 0.722x0.431x2.64x1000=821kg/m³
step 9: MIX PROPOTIONS
Cement: 359kg/m³
water : 158kg/m³
fine aggregate =821 kg/m³
coarse aggregate 20mm :1123kg/m³
chemical admxture= 7.18kg/m³
water-cement ratio =0.44
mix propotion by weight : 1:2.28:3.12
step 10
slump shall be measured,water content and dosage of admixture shall be adjusted for achievng required slump on trail.
step 11
Two more trails having variation of 10% of water - cement ratio shall be carried out and a graph between three water - cemnt ratio shall be plotted to work out mix propotions for given target for field trails.
RESULTS :
Mix propotion by weight of M35 Grade of concrete with fly ash is 1:2.08:2.72 and its water cemnt ratio was found to be 0.4.
mix propotion by weight of m50 grade of concrete without fly ash is 1:2.28:3.12 and its water-cemnt ratio was found to be 0.44.