Challenge

Project on Concrete Mix Design for various grades of Concrete

VVaibhav Patil17 Mar 2022

Project 1st- Calculate Mix Design for M35 grade concrete with fly ash & M50 grade concrete without fly ash

Part 1 - M35 with fly ash

Aim of project: to calculate the mix design for M35 concrete with fly ash for achieving full strength with economical within 28 days of curing.

Introduction: We use fly ash for designing mix proportion of M35 grade concrete with all proper manner according to all IS codes i.e. IS 456:2000, IS 10262:2009, IS 8112, IS 9103, IS 383 & IS 3812 part 1

Procedure in detail

1) Stipulations For Proportioning

Grade designation : M35
Type of cement : OPC 43 Grade conforming IS 8112
Maximum nominal size of aggregate : 20mm
Minimum cement content : 320 kg/m3 (IS 456:2000)
Maximum water-cement ratio : 0.45 (Table 5 of IS 456:2000)
Workability : 100 slump
Exposure condition : sever (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

2) Test Data For Materials

Cement used : OPC 43 Grade conforming IS 8112
Specific gravity of cement : 3.15
Chemical admixture : Super Plasticizer conforming to IS 9103
Specific gravity of

Coarse aggregate : 2.74
Fine aggregate : 2.74
chemical admixture: 2.2

e. Water absorption:

Coarse aggregate : 0.5 %
Fine aggregate : 1 %

f) Free (surface) moisture:

Coarse aggregate : Nil
Fine aggregate : Nil

g) Sieve analysis:

Coarse aggregate: Conforming to all in aggregates of Table 2 of IS 383
Fine aggregate : Conforming to Grading Zone I of Table 4 of

3) TARGET STRENGTH FOR MIX PROPORTIONING

f’ck = fck + 1.65 s
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. Therefore, target strength = 35 + 1.65 x 5 = 43.25 N/mm2.

4) selection of water cement ratio

From table 5, IS456:2000 for sever explosure max. water cement ratio is = 0.45 based on experience, adopted water cement ratio is 0.40

Therefore 0.40 < 0.45, hence ok

5) selection of water content

Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 litre (for 25 to 50 mm slump range) Estimated water content for 100 mm slump = 186+ (6/186) = 197 litre.

[As superplasticiser is used, the water content can be reduced up to 20% and above best on trail water content reduction of 29% is achieved with plasticiser]

Hence the arrived water content = 197*0.71= 140 liter

6) calculate cement content

Water cement ratio is= 0.4

Cement content (Cement + Fly Ash Content) = 140/0.4 = 350kg/m^3

From table 5, IS 456 minimum cement content for sever exposure condition= 320kg/m^3 and it is 350kg/M^3 > 320kg/m^3

Now, to proportion mix containing fly ash following steps are suggested

a) the % of fly ash needs to be decided on the basis of the project requuirement and quality of material

b) in some cases increase in cementious material can be warrented. Increase in cementious material cement and its percentage maybe based on experience and trial (this example is with increase with 10 % cementious material concrete)

cementious material content = 350 x 1.10 = 385 kg/m^3

water content = 140 kg/m^3

so water cement ratio = 140/385 = 0.364

fly ash @ 30% total cementious material content = 385 x 30% = 115 kg/m^3

cement (OPC) = 385 - 115 = 270 kg/m^3

saving of cement while using fly ash = 350 - 270 = 80 kg/m^3

fly ash being utilized = 115 kg/m^3

7) proportion of volume of coarse aggregate and fine aggregate

table-3, IS 10262:2009, volume of course aggregate corresponding to 20mm size aggregate and Fine aggregate (zone1) for water cement ratio=0.6 in the present case water cement ratioi =0.40

therfore, the volume of coarse aggregate need to be increased to decrease the Fine aggregate content

As the water-cement ratio is lower by 0.10. 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 0.40 = 0.62

NOTE – In case the coarse aggregate is not angular one, then also volume of coarse aggregate may be required to be increased suitably based on experience.

For pumpable concrete these values should be reduced up to 10%.

Therefore, volume of coarse aggregate =0.62 x 0.9 =0.56. &

Volume of fine aggregate content = 1 – 0.56= 0.44.

8) Mix calculation:

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]x1/1000

= 270/3.15 x 1/1000= 0.086m^3

c) volume of fly ash = [mass of fly ash/specific gravity of fly ash]x1/1000

= 115/2.2 x 1/1000= 0.052m^3

d) volume of water = [mass of water/ specific gravity of of water] x 1/1000

= 140/1 x 1/1000= 0.140m^3

e) volume of chemical admixtures= [mass of admixture/specific gravity of admixture] x 1/1000

= 7.6/1.145 x 1/1000= 0.006m^3

f) volume of aggregate = ( a- (b+c+d+e)

= (1-(0.086+0.052+0.140+0.006))= 0.716m^3

g) mass of coarse aggregate = e x volume of coarse aggregate x specific gravity of coarse aggregate x 1000

= 0.716x 0.56 x 2.74 x 1000 = 1098 kg/m^3

h) mass of fine aggregate= e x volume of fine aggregate x specific gravity of fine aggregate x 1000

= 0.716 x 0.44 x 2.74 x 1000 = 863 kg/m^3

Result :-

grade of concrete = M35 (by using fly ash)

cement = 270kg/m^3

Fly ash = 115 kg/m^3

water = 140kg/m^3

fine aggreagte = 863 kg/m^3

coarse aggreagte = 1098kg/m^3

chemical admixture = 7.6 kg/m^3

w/c ratio = 0.364

Trial mix ratio = 1:2.24:2.85

10) The slump shall he measured and the water content and dosage of admixture shall be adjusted for achieving the required slump based on trial , if required. The mix proportions shall he reworked for the actual water content and checked for durability requirements.

11) Two more trials having variation of ± 10 percent of water-cement ratio in A-10 shall be carried out and a graph between three water-cement ratios and their corresponding strengths shall he plotted to work out the mix proportions for the given target strength for field trials. However, durability requirement shall be met.

Part 2 - M50 without fly ash

Aim of project: to calculate the mix design for M50 concrete without fly ash for achieving full strength with economical within 28 days of curing.

Introduction: Without using fly ash for designing mix proportion of M50 grade concrete with all proper manner according to all IS codes i.e. IS 456:2000, IS 10262:2009, IS 8112 & IS 9103, IS 383