Challenge

Project on Concrete Mix Design for various grades of Concrete

AAnaz Mn12 Dec 2022

DESIGN

Calculate the Concrete Mix Design for M35 grade concrete with fly ash & M50 grade concrete without Fly ash

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AIM:

To calculate the Concrete Mix Design for M35 grade concrete with fly ash and M50 grade concrete without fly ash

INTRODUCTION:

Concrete mix design is a systematic process of choosing economical relative proportions of various ingredients from available material that gives the concrete of the desired workability. The process of selecting suitable ingredients for producing concrete of required strength durability and workability as economically as possible is known as concrete Mix design.
The project is consisting of two parts, the first part depicts the design of M35-grade cement with fly ash and the second part is about the design of M50-grade concrete without fly ash

OBJECTIVES:

To achieve the desired workability in the plastic stage, To achieve the desired minimum strength in the hardened stage, to achieve the desired durability in the specified environmental condition, and to produce concrete as economically as possible.

CODES FOR CONCRETE MIX DESIGN:

IS 10262: 2009
IS 456: 2000
IS 8112
IS 9103
IS 3812 (part 1)

PART A: Mix design for M35 grade concrete with fly ash

STEP 1:-

STIPULATION FOR CONCRETE MIX DESIGN:

Grade designation	M35
Type of cement	OPC 43 grade confirming to IS 8112
Type of mineral admixture	Fly ash (confirming to IS 3812 Part 1)
Maximum nominal size of aggregate	20mm
Minimum cement content	320kg/m3 (Table 5 of IS 456-2000 Exposure condition)
Maximum water-cement ratio	0.45 (Table 5 of IS 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	450kg/m3
Chemical admixture type	Superplasticizer

STEP 2:-

TEST DATA FOR MATERIALS:

Cement used	OPC 43 grade confirming to IS 8112
The specific gravity of cement	3.15
Flash	Confirming to IS 3812(Part 1)
The specific gravity of fly ash	2.2
Chemical admixture	Superplasticizers confirming to IS 9103
The specific gravity of coarse aggregate	2.74
The 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
Free surface moisture of fine aggregate	Nil
Sieve analysis of coarse aggregate	Confirming table 2 of IS 383
Sieve analysis fine aggregate	Confirming to Grading zone I of table 4 of IS 383

STEP 3:-

TARGET STRENGTH OF MIX PROPORTIONING:

Target mean Strength f'ck = fck + 1.65*s

= 35+(1.65x5)

= 43.25 N/mm2

Were;

fck-Characteristics Compressive strength = 35N/mm2
f'ck-Target Average Compressive Strength at 28 days
S- Standard Deviation
From table-1 of IS-10262:2009, Standard Deviation S= 5N/mm2

STEP 4:-

SELECTION OF WATER-CEMENT RATIO;

The maximum water-cement ratio for severe exposure is 0.45 (From table 5 of IS456:2000)
From figure 1 of the IS10262:2019.
The graph shows the water-cement ratio as 0.40

0.40 < 0.45, hence OK.

STEP 5:-

SELECTION OF WATER CONTENT:

From table 2 of IS 10262-2009, the maximum water content for 20mm aggregates is 186 liters (for 25 to 50mm slump range).
Estimated water content for 100mm slump =186+(6/100 x 186)

=197 liters

As superplasticizers are used, the water content can be reduced to 30%.
Based on trials water content reduction of 29% is achieved with plasticizers.
Hence arrived water content= 197-(197x0.29)

= 140 liters.

STEP 6:-

CALCULATION OF CEMENT AND FLY ASH:

Adopted water-cement ratio= of 0.4
Total cementitious material required(cement+flyash) = water content/ water-cement ratio

=140/0.4

= 350 kg/m3

From table 5 of IS456:2000 minimum cement content for severe exposure condition= 320kg/m3

350kg/m3 > 320kg/m3,

Hence okay.

Now to proportion, a mix containing fly ash the following steps are suggested
The percentage of fly ash needs to be decided based on project requirements and the quality of materials
In some case increase in cementitious material can be warranted. An increase in cementitious material content and its percentage may be based on experience and trial. Here we are increasing cementitious content by 10%.
Then cementitious material content= 350 x 1.1

= 385kg/m3

water content=140kg/m3
so, water-cement ratio= 140/385

= 0.36

Fly ash content is taken as 30% of the total cementitious material= 385x (30/100)

=115.5 kg/m3

Cement required (OPC) = 385-115.5

= 269.5 kg/m3

Saving of cement while using fly ash= 350 -269.5

= 80.5 kg/m3

Fly ash begin utilized =115.5 kg/m3
CEMENTITIOUS MATERIAL, CEMENT, AND FLYASH REQUIRED IS 385kg/m3, 269.5 kg/m3, and 115.5 kg/m3 and the revised water-cement ratio is 0.36 respectively.

STEP 7:-

VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:

From table-3 of IS-10262:2009, the volume of coarse aggregate corresponds to 20mm size aggregate and fine aggregate (Zone-1) for water cement ratio. = 0.6
in the Present case, the water-cement ratio is 0.4
Therefore, the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
As the water-cement ratio is lowered by 0.1, the proportion of the volume of coarse aggregate is increased by 0.02 (at the rate of +/-0.01 for every +/- 0.05 change in water-cement ratio)
Hence the Corrected value of Coarse aggregate for water -cement ratio = 0.64

(If Coarse aggregate is not angular type, then also the volume of coarse aggregate may be required to be increased suitably, based on experience)

For pumpable concrete, these are reduced by 10%
The volume of coarse aggregate = 0.64 x 0.9

=0.576

Volume of fine aggregate = 1 - 0.576

= 0.424

THE VOLUME OF COARSE AND FINE AGGREGATES ARE 0.567& 0.424 RESPECTIVELY

STEP 8:-

MIX CALCULATIONS:

The mix calculations as per unit volume of concrete

a) volume of concrete=1m3
b) volume of cement= (mass of cement/specific gravity of cement) x (1/1000)

= (269.5/3.15) x (1/1000)

=0.0855 m3

c) volume of fly ash= (mass of fly ash/specific gravity of fly ash) x (1/1000)

= (115.5/2.2) x (1/1000)

=0.0525 m3

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

= (140/1) x (1/1000)

=0.140 m3

e) volume of chemical admixture= (mass of chemical admixture/specific gravity of admixture) x (1/1000)

= (7.9/1.145) x (1/1000)

= 0.0068 m3

f) volume of aggregates (FA & CA) = a-(b+c+d+e)

=1 - (0.0855+0.0525+0.140+0.0068)

=0.715 m3

g) mass of coarse aggregate= f x volume of coarse aggregates x specific gravity of coarse aggregate x1000

=0.715 x0.576 x2.74 x1000

=1128 kg/m3

h) mass of fine aggregate= f x volume of fine aggregates specific gravity of fine aggregate x1000

=0.715 x0.424 x2.74 x1000

=830.6 kg/m3

STEP 9:-

MIX PROPORTIONS:

Mass of

Cement =265.5 kg/m3
Flyash =115.5 kg/m3
Water = 140k g/m3
Fine aggregate = 830.6 kg/m3
Coarse aggregate = 1128kg/m3
Chemical admixture =7.9kg/m3
Water-cement ratio = 0.4

CEMENT	FA	CA	WATER
265.5	830.6	1128	140
1	3.12	4.24	0.4

MIX PROPORTION RATIO = 1 : 3.12 : 4.24

STEP 10:

The slump can be measured, and the water content and dosage of admixture shall be adjusted for achieving the required slump on trial.
The mix proportion shall be reworked for actual water content and checked for the durability requirement

STEP 11:

Two more trials with variations of 10% of the water-cement ratio shall be carried out.
A graph between three water-cement ratios and corresponding strengths shall be plotted to work out the mix proportions for the given target for field trials.

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PART B: Mix design for M50 grade concrete without fly ash

STEP 1:-

Stipulations for Concrete mix design:

Grade designation	M50
Type of cement	OPC 53 grade confirming to IS 8112
Maximum nominal size of aggregate	20mm
Minimum cement content	320kg/m3( Table 5 of IS 456-2000 Exposure condition)
Maximum water-cement ratio	0.45( Table 5 of IS 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	450kg/m3
Chemical admixture type	Superplasticizer

STEP 2:-

Test data for materials:

Cement used	OPC 53 grade confirming to IS 8112
The specific gravity of cement	3.15
Chemical admixture	Superplasticizers confirming to IS 9103
The specific gravity of coarse aggregate	2.74
The 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
Free surface moisture of fine aggregate	Nil
Sieve analysis of coarse aggregate	Confirming table 2 of IS 383
Sieve analysis fine aggregate	Confirming to Grading zone I of table 4 of IS 383

STEP 3:-

TARGET STRENGTH OF MIX PROPORTIONING:

Target mean Strength f'ck = fck + 1.65xs

= 50+(1.65x5)

= 58.25 N/mm2

Were;

fck-Characteristics Compressive strength = 50N/mm2
f'ck-Target Average Compressive Strength at 28 days
S- Standard Deviation
From table-1 of IS-10262:2009, Standard Deviation S= 5N/mm2

STEP 4:-

SELECTION OF WATER-CEMENT RATIO:

The maximum water-cement ratio for severe exposure is 0.45(From table 5 of IS456:2000)
From figure 1 of the IS10262:2019, Graph shows the water-cement ratio as 0.34

0.34<0.45

ADOPTED WATER-CEMENT RATIO=0.34

STEP 5:-

SELECTION OF WATER CONTENT:

From table 2 of IS 10262-2009, the maximum water content for 20mm aggregates is 186 liters (for 25 to 50mm slump range).
Estimated water content for 100mm slump=186+(6/100 x 186)

=197 liters

As superplasticizers are used, the water content can be reduced to 30%. Based on trials water content reduction of 29% is achieved with plasticizers
Hence arrived water content= 197-(197x0.29) = 140 liters.
WATER REQUIRED=140 LITRES

STEP 6:-

CALCULATION OF CEMENT:

Adopted water-cement ratio= of 0.34
Total cementitious material required(cement+flyash) = water content/ water-cement ratio

=140/0.34

= 412 kg/m3

From table 5 of IS456:2000 minimum cement content for severe exposure condition= 320kg/m3

412kg/m3>320kg/m3, hence okay.

CEMENT REQUIRED IS 412kg/m3

STEP 7:-

VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:

From table 3 of IS 10262:2009, the volume of coarse aggregate corresponds to 20mm size aggregate and fine aggregate for water cement ratio 0.5 is 0.60
In the present case, the water-cement ratio is 0.34. Therefore, the volume of coarse aggregate needs to be increased to decrease fine aggregate content
As the water-cement ratio is lowered by 0.1 the proportion of the 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 corrected volume of coarse aggregate for water cement ratio of 0.40 is 0.632.
NOTE- If the coarse aggregate is not of angular type, then also the volume of coarse aggregate may be required to increase based on experience.
For pumpable concrete, these values are reduced by 10%
Therefore, the volume of coarse aggregate= 0.632x0.9

=0.569

The volume of fine aggregates =1-0.569=0.431
THE VOLUME OF COARSE AND FINE AGGREGATES ARE 0.569& 0.431 RESPECTIVELY

STEP 8:-

MIX CALCULATIONS:

The mix calculations as per unit volume of concrete

a) volume of concrete=1m3
b) volume of cement= (mass of cement/specific gravity of cement) x (1/1000)

= (412/3.15) x (1/1000)

=0.131m3

c)volume of water = (mass of water/specific gravity of water) x (1/1000)

= (140/1) x (1/1000)

=0.140m3

d)volume of chemical admixture= (mass of chemical admixture/specific gravity of admixture) x (1/1000)

= (8.24/1.145) x (1/1000)

=0.007m3

e) volume of aggregates (Fine aggregates and Coarse aggregates) = a-(b+c+d)

=1-(0.131+0.140+0.007)

=0.722m3

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

=0.722x0.569x2.74x1000

=1126kg/m3

g) mass of fine aggregate= f x volume of fine aggregate x specific gravity of fine aggregate x 1000

=0.722x 0.431x2.74x1000

=853kg/m3

STEP 9:-

MIX PROPORTIONS:

Mass of

cement =412kg/m3
water = 140kg/m3
fine aggregate = 853kg/m3
coarse aggregate =1126kg/m3
chemical admixture =8.24kg/m3
water-cement ratio =0.34

CEMENT	FA	CA	WATER
412	853	1126	140
1	2.07	2.73	0.34

MIX PROPORTION BY WEIGHT 1:2.07:2.73

STEP 10:-

The slump can be measured, and the water content and dosage of admixture shall be adjusted for achieving the required slump on trial.
The mix proportion shall be reworked for actual water content and checked for the durability requirement

STEP 11:-

Two more trials with variations of 10% of the water-cement ratio shall be carried out.
A graph between three water-cement ratios and corresponding strengths shall be plotted to work out the mix proportions for the given target for field trials.

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RESULTS:-

PART -A: THE MIX RATIO FOR M30 GRADE CONCRETE WITH FLYASH IS = 1 : 3.12 : 4.24
PART -B: THE MIX RATIO FOR M50 GRADE CONCRETE WITHOUT FLYASH IS = 1 : 2.07 : 2.73

CONCLUSION:

Concrete mix design is the economical proportioning of concrete ingredients for better strength and durability based on the construction site.

APPENDIX:

Table 5 IS 456:2000, MINIMUM CEMENT CONTENT, MAXIMUM WATER-CEMENT RATIO, AND MINIMUM GRADE OF CONCRETE FOR DIFFERENT EXPOSURES WITH NORMAL WEIGHT AGGREGATE OF 20MM NOMINAL SIZE