Project on Concrete Mix Design for various grades of Concrete

Ans:-Calculation of concrete mix design for m35 grade concrete with fly ash :-

Aim :- Here the aim is to calculate the conrete mix design for M35 grade of concrete with fly ash.

Introduction :-As we know that , concrete mix design is a process of selecting suitable ingredients for producing concrete of required strength, durability and workability as economically as possible and is termed as concrete mix design. The compressive strength of concrete depends upon the quality and quantity of cement, water and aggregates and also on mixing, batching, placing, compacting and curing.

The objective is to achieve predetermined minimum strength and durability in most economical manner.

Procedure :-The procedure involves the following steps :-

Step 1 :- stipulations for proportioning :-

a. Grade designation :- M35

b. Type of cement :- OPC grade conforming to IS 8112

c. Type of mineral admixture :- Fly ash conforming to IS 3812(part1)

d. Maximum nominal size of aggregate :- 20 mm

e. Minimum cement content :- 320kg/m3 (from table 5 of IS 456:2000 , Exposure condition)

f. Maximum water cement ratio :- 0.45 ( from table 5 of IS 456:2000 , Exposure condtion )

g. Workability :- 100mm ( slump value for pumpable concrete )

h. Exposure condition :- severe ( for reinforced concrete )

i. Method of concrete placing :- pumping

j. Degree of supervision :- Good

k. Type of aggregate :- crushed angular aggregate

l. Maximum cement content :- 450kg/m3

m. Chemical admixture type :- Superplasticizer

Step 2 :- test data for materials

a. Cement used :- OPC 43 grade conforming to Is 8112

b. Specific gravity of cement :- 3.15

c.Fly ash :- conforming to IS 3812 (part1)

d. Specific gravity of fly ash :- 2.2

e. Chemical admixture :- superplasticizer conforming to IS 9103

f. Specific gravity of coarse aggregate :- 2.74

g. Specific gravity of fine aggregate :- 2.74

h. Water absorption of coarse aggregate :- 0.5%

i. Water absorption of fine aggregate :- 1.0%

j. Free surface moisture of coarse aggregate :- Nil

k. Free surface moisture of fine aggregate :- Nil

l. Sieve analysis of coarse and fine aggregate :-

For coarse aggregate :-

IS sieve sizes( mm)	Analysis of C.A.fraction		% of diff.fractions			Remarks
	(1)	(2)	(1) {60%}	(2) {40%}	Combined (100%)
20	100	100	60	40	100	Conforming to table 2 of IS 383
10	0	71.20	0	28.5	28.5
4.75		9.40		3.7	3.7
2.36		0

For fine aggregate conforming to grading zone 1 of table 4 of IS 383

Step 3 :- calculation of target strength for mix proportioning :-

F'ck = Fck + 1.65S

where,

Fck is the compressive strength of concrete

S is the standard deviation that is assumed from Table 8 of IS- 10262

So,

F'ck = 35 + 1.65 x 5

F'ck = 43.25 N/mm2

Step 4. Selection of water cement ratio :-

from table 5 of IS 456:2000 for severe exposure, the maximum water cement ratio is 0.45

So based on experience we will adopt a water cement ratio of 0.40.

that is w/c ratio = 0.40

Step 5. Selection of water content :-

From table 2 of IS 10262:2009 , maximum water content for 20mm aggregate is186l (for 25mm to 50mm slump)

	S.no	Nominal maximum size of aggregate (mm)	Max.Water content (kg)
	1.	10	208
	2.	20	186
	3.	40	165

Estimated water content for 100 mm slump :- 186 + 6/100 x 186

i.e = 197L

We are using superplasticizers therefore the water content is reduced by 30%.

So based on trial water content reduction of 29% is achieved with plasticizers.

Therefore,

Water content = 197 x 0.7L

Water content = 140L

Step 6. Calculation of cement content :-

cementitious material ( cement + fly ash ) = 140/0.4

Therefore = 350kg/m3

From table 5 of IS 456 , min. Cement content for severe exposure condition is 320 kg/m3

350kg/m3 > 320 kg/m3

Hence ok.

For mix containing fly ash the following steps are taken :-

1. The percentage of fly ash needs to be decided based on project requirement and quality of material.

2. In some cases increase in cement based materials can be warranted. Increase in cement content and its percent may be based on experience and trial. This example is with increase of 10% cementitious material content.

a. Cementitious material content = 350 x 1.10 = 385kg/m3

b.Water content = 140kg/m3

c. Water cement ratio = 140/385 = 0.364

d. Fly ash @ 30% total cementitious content = 385 x 30% = 115kg/m3

e.Cement (OPC) = 385 - 115 = 270kg/m3

f. Saving of cement by using fly ash = 385 - 270 = 80kg/m3

g. Fly ash utilised = 115kg/m3

Step 7. Proportion of volume of coarse aggregate and fine aggregate :-

From table 3 of IS 10262 : 2009 ,

S.no	Nominal Max.Size of Aggregate(mm)	volume of coarse aggregate per unit volume of total aggregate for different zones of fine aggregate Zone 4 Zone 3 Zone 2 Zone 1
1.	10	0.50 0.48 0.46 0.44
2.	20	0.66 0.64 0.62 0.60
3.	40	0.75 0.73 0.71 0.69

volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate of zone 1 for water cement ratio of 0.5 = 0.6

In present case , cement ratio is 0.40

Therefore volume of coarse aggregate needs to be increased to decrease the fine aggregate.

As 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 w/c ratio)

Therefore corrected volume of coarse aggregate for water cement ratio of 0.40 is 0.62

So,

For pumpable concrete values are reduced by 10%

Volume of coarse aggregate = 0.62 x 0.7 = 0.56

Volume of fine aggregate = 1- 0.56 = 0.44

Step 8. Mix calculations :-

a. Volume of concrete = 1m3

b. Volume of cement = mass of cement/ Specific gravity of cement x 1/1000

= 270/3.15 x 1/1000

= 0.086

c. Volume of fly ash :- 115/2.2 x 1/1000

= 0.052 m3

d. Volume of water = 140/1 x 1/1000

= 0.140 m3

e. Volume of chemical admixture = 7.6/1.145 x 1/1000

= 0.006 m3

f. Volume of aggregate ie. Fine aggregate and coarse aggregate

= { a - ( b + c + d + e ) }

= { 1 - ( 0.086 + 0.052 + 0.140 + 0.006 ) }

= 0.716 m3

g. Mass of course aggregate = 0.716 x 0.56 x 2.74 x 1000

= 1098kg/m3

h. Mass of fine aggregate = 0.716 x 0.44 x 2.74 x 1000

= 863 kg/m3

Step 9.Mix proportions for trial number 1 :-

1. Cement = 270kg/m3

2. Fly ash = 115kg/m3

3. Water = 140kg/m3

4. Fine aggregate = 863 kg/m3

5. Coarse aggregate = 1098 kg/m3

6. Chemical admixture = 7 kg/m3

7.W/C ratio = 0.364

Trial mix ratio :- 1 : 2.24 : 2.85

Step 10. The slump shall be measured and the water content and dosage of admixture Shalby adjusted for receiving the required slump on trial. The mix proportion shall be reworked for the actual water content and checked for the durability requirement.

Step 11. two more mixed trials having variation of 10% of water cement ratio in clause 10 shall be carried out and a graph between the 3 water cement ratio and corresponding strengths shall be plotted to work out the mix proportions for the given target strength for field trials.

Result :- Therefore the trial mix ratio for the concrete mix proportioning of m35 grade of concrete is 1 : 2.24 : 2.85

Ans. Calculation of concrete mix designing for m50 grade of concrete without fly ash :-

Aim :- here the aim is to calculate the concrete mix design for m50 grade of concrete without the use of fly ash.

Introduction :-

Concrete mix design is a process of selecting suitable ingredients for producing concrete of required strength, durability and workability as economically as possible and is termed as concrete mix design. The compressive strength of concrete depends upon the quality and quantity of cement, water and aggregates and also on mixing, batching, placing, compacting and curing.

The objective is to achieve predetermined minimum strength and durability in most economical manner.

Procedure :-

Its procedure involve the following steps :-

Step 1. Concrete mix proportioning

1. Grade designation - M50

2. Type of cement - OPC 43 grade conforming to IS 8112

3. Maximum nominal size of aggregate - 20mm

4. Minimum cement content - 320 kg/m3 ( table 5 IS 456:2000 - exposure condition)

5. Maximum water cement ratio - 0.45

6.Workability - 100mm (slump value for pumpable concrete)

7.Exposure condition - severe (reinforced concrete)

8.Method of concrete placing - Pumping

9.Degree of Supervision - Good

10.Type of agg. - Crushed angular agg.

11.Max. cement content - 450 kg/m3

12.Chemical admixture - Suoerplasticizers

Step 2. Test data for materials :-

1. Cement used is ordinary Portland cement of grade 43 and it grades conforming to IS 8112

2. Specific gravity of cement is 3.5

3. Chemical admixture used is superplasticizer conforming to IS 9103

4. Specific gravity of coarse aggregate is 2.74 and fine aggregate is also 2.74

5. The water absorption for coarse aggregate is 0.5 % and fine aggregate is 1.0 %

6. The free surface moisture for Court agreed and fine aggregate is Nil

7.Sieve analysis

For C.A.

IS sieve size( mm)	analysis of	C.A.fraction	% of Diff	fractions		Remarks
	(1)	(2)	(1) (60%)	(2) (40%)	combined(100%)
20	100	100	60	40	100
10	0	71.20	0	28.5	28.5	Conforming to table 2 of IS 383
4.75		9.40		3.7	3.7
2.36		0

Fine aggregate is conforming to grading of zone 1 of table 4 of IS 383

Step 3. Target strength for mix proportioning :-

F'ck = Fck + 1.65 S (from table 1 of IS 10262 : 2009 , S= 5 N/mm2)

where,

Fck is the compressive strength of concrete

S is the standard deviation

So,

F'ck = 50 + 1.65 x 5

F'ck = 58.25 N/mm2

Step 4. Selection of water cement ratio :-

from table 5 of IS 456:2000 for severe condition ,

Maximum water cement ratio is 0.45

So the adopted water cement ratio is 0.40

Here 0.40 is smaller than 0.45 therefore it is OK to take 0.40 water cement ratio

Step 5. Selection of water content :-

From table 2 of IS 10262 : 2009 ,

S.no.	nominal maximum size of aggregate(mm)	maximum water content (kg)
1.	10	208
2.	20	186
3.	40	165

maximum water content for aggregate of 20 mm size is 186 litre for slump range of 25 to 50 mm.

Therefore the estimated water cement ratio for 100 mm slump is 186 + 6/100 x 186

So the calculated water cement ratio is 197 litre.

Here superplasticizers are used therefore the water content can be reduced upto 20% and above

Hence based on trial water content reduction of 29 % is achieved with plasticizers.

Therefore the water content will be 197 x 0.71 = 140 litre

Step 6. Calculation of cement content :-

W/c ratio is 0.4

Cement content = 140/0.4 = 350kg/ m3

From table 5 of IS 456 , minimum cement content for severe condition is 320 kg/m3

Therefore 350 is greater than 320 hence it is ok.

Step 7. Proportion of volume of coarse aggregate and fine aggregate content :-

From table 3 of IS code 10262:2009

S.no.		maximum nominal size of aggregate	volume of coarse aggregate per unit volume of total aggregate for different zones of fine aggregate Zone 4 Zone 3 Zone 2 Zone 1
1.		10	0.50 0.48 0.46 0.44
2.		20	0.66 0.64 0.62 0.60
3.		40	0.75 0.73 0.71 0.69

volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate of zone 1, for water cement ratio is 0.6

But here the water cement ratio is 0.4

Therefore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.

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 change +/- 0.05 change in w/ c ratio)

Therefore the volume of coarse aggregate for water cement ratio of 0.4 is 0.62

But for pumpable concrete this values are reduced by 10%

Therefore volume of coarse aggregate = 0.62 x 0.9 = 0.56

and volume of fine aggregate = 1.0.56 = 0.44

Step 8. Mix calculations :-

a. Volume of concrete - 1m3

b. Volume of cement = mass of cement/ specific gravity of cement x 1/1000

= 350/3.15 x 1/1000 = 0.111m3

c. Volume of water = 140/1 x 1/1000 = 0.140m3

d. Volume of chemical admixture = 7.6/1.145 x 1/1000 = 0.006 m3

e. Volume of aggregate = [a- (b+c+d)]

= [1- (0.111+ 0.140 + 0.006 ) ]

= 0.743 m3

f. Mass of course aggregate = e x volume of coarse aggregate x specific gravity of coarse aggregate x 1000

= 0.743 x 0.56 x 2.74 x 1000

= 1140 kg/m3

g. Mass of fine aggregate = e x volume of fine aggregate x specific gravity of fine aggregate x 1000

= 0.743 x 0.44 x 2.74 x 1000

= 896kg/m3

Step 9. Mix proportion for trial number 1.

Cement = 350kg/m3

Water = 140kg/m3

Fine aggregate = 896 kg/m3

Coarse aggregate = 1140 kg/m3

Chemical admixture = 7kg/m3

Water cement ratio =0.4

Trail mix ratio - 1 :2.56 : 3.26

Step 10. The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving the required slump on trial. The mix proportions shall be reworked for the actual water content and check for durability requirements

Step 11. 2 more trials having variation of 10% of water cement ratio shall be carried out and a graph between the three water cement ratios and corresponding strengths shall be plotted to work out the mix proportions for the given target strength for field trials

Result :-

As a result we get the calculated trial mix ratio as 1: 2.56 : 3.26