Project on Concrete Mix Design for various grades of Concrete
AIM:
Mix design for M35 grade concrete with fly ash.
PROCEDURE:
Step:1
Stipulations for proportioning
a. grade designation : m35
b. type of cement : OPC 43 grade conforming to IS 8112
c. type of mineral admixtures: fly ash confirming to IS3812
d. maximum nominal size of aggregate: 20mm
e. minimum cement content : 320Kg/m^3( table : 5 IS 456:2000 based on exposure condition)
f. maximum water cement ratio: 0.45(table : 5 IS 456-2000, based on exposure condition)
g. workability: 100mm slump value of pumpable concrete
h. exposure condition: severe( for reinforced concrete)
i. method of concrete placing : pumping
j. degree of supervisionn: good
k. type of aggregate: crushedangular aggregate
l. maximum cement content: 450Kg/m^3
m. chemical admixture type: superplaticizer
Step :2
Test data for materials
a. cement used : opc 43 grade
b. specific gravity of cement : 3.15
c. fly ash : conforming to IS 3812
d. specific gravity of fly ash : 2.2
e. chemical admixture : superplaticizer
f. specific gravity ofcourse aggregate : 2.74
specific gravity of fine aggregate : 2.74
g. water absorption:
course aggregate: 0.5%
fine aggregate: 1%
h. free surface moisture
course aggregate: nil
fine aggregate: nil
i. seive analysis
course aggregate: confirming to table 2 of IS 383
fine aggregate: conforming to gradinng zone 1 of table 4 IS 383
Step :3
To find target mean strength for mix proportiioning
target mean strength = f'ck= fck+1.65s
= 35+1.65*5
=43.25 N/mm^2
fck - comppressive strength of the concrete
s - standard deviation
Step :4
Selectiion of water-cement ratio
maximum w/c ratio=0.45( for severe condition, from table 5 of IS 456-2000)
on experience w/c ratio = 0.4
0.4<0.45, hence ok.
Step :5
calculation of water content
maximum water content for 20mm aggregate = 186 litres( table 2 of IS 1026:2009)
for 100 mm slump = 186+(6/100)*186
= 197 litres
superplaticizer is used, water content reduced upto 30%
based on trials water content reduction of 29% is achiived with plasticizer
hence arrived content = 197*0.71=140 litres
Step :6
Calculation of cement content
w/c ratio=0.4
cementanious marerial( cement+flyash)= 140/0.4
=350Kg/m^3
in table 5 of IS 456-2000, the cement content for swvere exposure = 320kg/m^3
350kg/m^3 > 320kg/m^3
hence ok.
to proportion the mic containing flyassh the folloeing steps are suggestedd;
a. the percentage of flysh need to bbe decided based on project requirment and quality of material.
b. in some cases increase in cementatius materrial can be warrned . increase in cementatious material content and its percentage may be based on exprience and trial
in this increase of 10% cementious material is considered
cementatious material content = 350*1.1=385kg/m^3
water content = 14kg/m^3
so, w/c ratio 140/385=0.364
flyash at 30% total cementatiouss material content= 35-30%=115kg/m^3
cement = 385-115=270kg/m^3
savinng of cement while using flyash = 350-270= 80kg/m^3
fly ash being utilized=115kg/m^3
Step :7
Proportion of volume of course aggregate and finne aggregate
from table 3 of IS 1026:2009, volume of course aggregate corresponfing to 20mm size aggregate and fine aggregate for water-cement ratio is 0.6
in present case the w/c ratio is 0.4
therefore the volume of course aggregate needs to be increased to decrease the finee aggregate
as the w/c ratio is lowered by0.1 the proportiion of volume of coursee aggregatee is increased by0.02
hence the corrected values ofcourse aggregate for the w/c ratio = 0.64
for pumpable concrete these are reduced by 10%
volume of course aggregate= 0.64*0.9=0.576
volume of fine aggregate= 1-0.576=0.424
Step :8
Mix calculations
mix calculation per unit volume of concrete:
a. volume of concrete = 1m^3
b. volume of cement = (mass of cement/specific gravity of cement)*1/1000
=(270/3.15)*1/1000=0.086m^3
c. voluume of flyash= (mass of fly ash/ specific gravity of fly ash)*1/1000
=(115/2.2)*1/1000=0.052m^3
d. volume of water= (mass of water / specific gravityof water )*1/1000
=(7.6/1.14)*1/1000=0.140m^3
e. volume of chemical admixture= ( mass of admixture / specific gravity of admixture)*1/1000
= (7.6/1.14)*1/1000=0.716m^3
f. volume of aggreegate( fine and course)= a-(b+c+d+e)
=1-(0.086+0.052+0.140+0.006)=0.716m^3
g. mass of coarsee aggregate=f*volume coarse aggregate*specific gravityof course aggregate*1000
=0.716*0.576*2.74*1000=1130kg/m^3
h. mass of fine aggregate= f*volume of fine aggregate* specific gravity of fine aggregate*1000
= 0.716*0.424*2.74*1000=831kg/m^3
Step :9
Mix proportion
cement=270kg/m^3
flt ash= 115kg/m^3
water=140kg/m^3
fine aggregate= 831kg/m^3
course aggregate=1130kg/m^3
chemical admixture=7kg/m^3
w/c ratio= 0.364
MIX RATIO 1:2.15:2.94
Step :10
the slump shall be measure and the water content and dosage of addmixturs shall be adjusted for aciving the required slump trial. the mix proportion shall be rewarded for the actual water content and checked for durability requirements
Step :11
two or more trials havinng variatioon of 10% of w/c ratio in clause 10 shell be carried out a graph between three w/c ratio and corresponding streength shall be plotted to work out the mix proportion for the given target strength for feild trials however durability shall be met.
RESULT : the mix design for m35 grade of concrete with flyash is1:2.15:2.94
AIM:
Mix design for M50 grade concrete without flyash
Step 1: Stipulation for concrete design mix
grade designation : M50
type of cement : opc53
maximum nominal size of aggregate : 20mm
minimum cement content: 320kg/m^3( from table 5 of IS456-2000)
maximum water-cement ratio: 0.45(table 5 of IS456-2000)
workability : 100mm( slumpvalue for pumpable concrete)
exposure condition : severe
method of concrete placing : pumping
degree of supervision : good
type of aggregate : crushed angular aggregate
maximum cement content: 450kg/m^3
chemical admixture type: super plasticizers
STEP 2: Rest data for material
cement used : opc 53
specific gravity of cement : 3.15
chemical admixtures: super plasticizer conforminf to IS9103
speccific gravity of course aggregate: 2.74
specific gravity of fine aggregate: 2.64
water absorption of course aggregate:0.5%
water absorption of fine aggregate:1.0%
free surface moisture of course aggregate: nil
free surface moisture of fine aggregate: nil
sieve analysis :
course aggregate: table 2 of IS 383
fine aggregatee: table 4 of IS 383
STEP 3: Target strength for mix propostioning
f'ck=fck+1.65s
=50+(1.65*5)
=58.25n/mm^2
STEP 4: Selection of wateer cement ratio
the maximum w/c ratio to design M50 grade concrete can be found from table 5 of IS 456-2000 FOR EXPOSURE CONDITION
maximum w/c ratio = 0.45
based on experiene adopted water cement ratio is 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, maximum water conent for 20mm aggregate : 186 litre
suggest increase of 3% of water content for every extra 25mm slump from 50mm slump. so a 6% is to be added to it.
186+(6/100)*186=197 litre
estimated water content for 100mm slump
based on trials with superplasticizerwater content reduction of 20% has been achived
197*0.8=158 litre
Water required = 158litre
STEP 6: Calculation of cement required
adopted w/c ratio :0.44
cement content : 158/0.44=359kg/m^3
from table 5 of IS 456 minimum cement content for severe exposure : 320kg/m^3
STEP 7: Volume of course aggregate and fine aggregate
from table 3 of IS 10262:2009 volume of course aggregate corresponding to 20mm size aggregate and fine aggregate = 0.62
for water-cement ratio=0.50
corrected proportion of volume of course aggregate= 0.632
w/c ratio= 0.44
pumpable concrete these value should be reduced upto 10%
0.632*0.9=0.568
volume of fine aggregate content= 1-0.576=0.431
STEP 8: Mix calculations
the mix calculation per unit volume of concrete shell be follow.
a.volume of concrete=1m^3
b. volume of cement = 359/3.15*(1/1000)=0.114m^3
c. volume of water = (158/1)*(1/1000)=0.158m^3
d.volume of chemical adixture=(7.6/1.145)*(1/1000)=0.006m^3
e. volume of all in ggregate= 0.722m^3
f. mass of course aggregate= 1123kg/m^3
g. mass fine aggregate= 821kg/m^3
STEP 9: Mix proportions
cement= 359kg/m^3
water = 158i/m^3
fine aggregate= 821kg/m^3
course aggregate20mm = 1123kg/m^3
chemical admixture= 7.18kg/m^3
w/c ratio= 0.44
STEP 10:
the slump shell be measured the water content and dosage of admixture shell be adjusted for achieving the required slump on trial . the mix proportion shell be reworked for the actual water content and checked fo duraility requirment
STEP 11:
two more trials having variation of 10% of w/c ratio ratio shell be carried out and a graph between three water - cement ratio and corresponding strength shell be plotted to work out the mix proportion for the given target for field trials.
RESULT:
Mix proportion by weight of M50 grade of concree without flyash is 1:2.28:3.12 and its water cemen ratio was found to be 0.44