Project on Concrete Mix Design for various grades of Concrete

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

Aim:

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

Introduction:

Concrete mix design is the method of finding the precise proportion of cement, sand and aggrgates in concrete to achieve the target strength in structures, therefore concrete mix can be stated as concrete mix as cement:sand:aggragates. the design is done according to the requirement of concrete strength. so, we can achieve the desirable properties of concrete either it is in fresh state or in hardened state. the fresh concrete properties like workability, setting time and hardened concrete properties like durability, compressive strength etc., are attained surely by this method. use of additives like admixtures, retarders etc,. other than basic ingredients are used to improve the proprties of mix. this project consists of two parts, the first part deals with the design of M35 grade design mix with flyash and the second part deals with M50 grade concrete mix without fly ash.

Objective:

The objective of this project is to produce mix design for M35 grade concrete containing fly ash and M50 grade concrete. the mix will be prepared as per IS method: concrete mix proportioning from IS10262:2009 and recommended guidelines from IS10262:1982.

This covers the mix design calculation of M35 Grade Concrete with Ground Granulated Blast Furnace Slag (GGBS) admixture and Poly Carboxylite type super plasticiser as per Indian Standard Codebook IS10262(2009) – Guidelines for Concrete Mix Proportioning.

Mix Design calculation procedure is the same when either GGBS or Fly ash are used, the only change will be the specific gravity of the admixture. The specific gravity of fly ash ranges from 2.1 to 3 whereas specific gravity of GGBS is 2.85. Superplasticizers are required for all high strength concrete to get good workability and good strength in concrete.

Volume calculations:

• a) volume of concrete
• b) volume of cement = ( mass of cement/ specific gravity of cement)* 1/1000
• c) volume of water = ( mass of water / specific gravity of water)* 1/1000
• d) volume of admixture = ( mass of admixture / specific gravity of admixture)* 1/1000
• e) vol. of fine and coarse aggregate = (a-(b+c+d))
• f) mass of coarse aggregate = e * vol. of CA * specific gravity of CA
• g) mass of fine aggregate = e * vol. of FA * specific gravity of FA

1. STIPULATIONS FOR PROPORTIONING OF M35 GRADE CONCRETE

This section deals with conditions and requirements of the concrete to be made.

A	Grade Designation	M35
B	Type of Cement	OPC 53
C	Type of Admixture	Fly ash
D	Maximum Nominal Size of Aggregate	20mm
E	Minimum Cement Content	340kg	Table 5-IS456
F	Maximum Cement Content	450kg	As per code
G	Partial replacement of cement by Fly ash	30%	as per requirement
H	Maximum W/C ratio	0.45	Table 5-IS456
I	Workability	100mm
J	Chemical Admixture	PCS Type

1. TEST DATA FOR MATERIALS

Materials should be tested in the laboratory as per tests given in the codebook and their properties should be found. Values of the material properties will be used in the design process and to check the quality of the material with the help of codebook standards. Standard values are taken here for calculation purpose.

A	Cement Used	OPC 53	Confirming to IS8112
B	Specific Gravity of Cement	3.15	Test – IS: 2720
C	Mineral Admixture	Fly ash	Confirming to IS12089
D	Specific Gravity of Fly ash	2.90
E	Chemical Admixture	@0.6%	IS9103
F	Specific Gravity of		Test – IS 2386
	Coarse Aggregate	2.74
	Fine Aggregate	2.74
	Admixture PCE based	1.12
G	Water Absorption		Test – IS 2386
	Coarse aggregate	0.5 %
	Fine aggregate	1 %
H	Sieve Analysis		Test – IS 2386
	Coarse aggregate		Confirming to Table 2-IS383
	Fine aggregate	Zone II	Confirming to Table 4-IS383

III. TARGET STRENGTH FOR MIX PROPORTIONS OF M35 GRADE CONCRETE

Strength of the concrete may deviate slightly depends on the quality of the material, method of mixing and construction practices. Hence target strength (F_ck) should be higher than the required strength of the concrete (f_ck). Value of standard deviation(s) for different grade of concrete is given in Table 1 of IS456.

Fck	= fck+1.65s	“S” from Table1-IS10262
Fck	= 35+1.65×5
Fck	= 43.25 N/mm2

1. SELECTION OF WATER-CEMENT RATIO

The maximum water-cement ratio for different grade of concrete is given in Table 5-IS456. You can reduce the water-cement ratio based on your requirements. Water-cement ratio directly affects the strength of the concrete.

Maximum W/C ratio	=0.45	Table 5-IS456
Adopted W/C ratio	=0.45

1. SELECTION OF WATER CONTENT

Maximum Water Content

=186 L

Table 2-IS1026

Above water-content is for 25 to 50mm slump but the slump we require is 100mm. hence we need to increase the water content to get the required slump for good workability. Clause 4.2 of IS1026 suggests an increase of 3% of water content from its original value for every increase of 25mm. Here we have a 50mm increase in the water content hence we have to increase the water content by 6 %.

Water-content for 100mm Slump	=186+(0.06*186)
	=197.16 L

Since superplasticizers are used water content can be reduced to get good strength of concrete. Percentage of reduction of water depends on the type of superplasticizers used in the concrete.

Percentage of Reduction in water content	=20%
Water content requirement after SP	=198 – (0.20*198)
	=157.73
Adopted Water Content	=160 L

1. CALCULATION OF CEMENT AND FLY ASH CONTENT

Adopted Water Cement Ratio	=0.45
Total Cementitious (Cement +Fly ash) requirement	= Water Content / WaterCement ratio
	=160/0.45
	=355.55 kg

Since Fly ash is used the amount of Cementitious content (Cement+Fly ash) shall be increased to get good workability and strength. the percentage of increase depending on experience and research. Here we increased the cementitious content by 1.1 %.

Final Cementitious Content (Cement+Fly ash)	= 356*1.1
	=391.6 kg
Minimum Cement Content required for ‘severe’ exposure	=340kg	Table 5-IS456
Adopted Cementious content	=391.6 kg	> 340kg

Fly ash content requirement	= 391.6 * 0.30	30% replacement
	= 117.48 ~ 118 kg
Cement Content requirement	=Cementious content – Fly ash
	=391.6-117.48
	= 274.12

Calculation of Super Plasticiers @ 0.6 percent to the mass of cementitious content = = 391.6*(0.6/100) = 2.35 kg

VII COARSE AND FINE AGGREGATE

Coarse Aggregate ratio	= 0.62	Table3-IS10262 (For W/C =0.5)
Coarse Aggregate ratio for 0.45 w/c ratio	= 0.63	(adding 0.01 for every decrease .05 and vice versa)
Final Fine Aggregate ratio	= 0.37	(1-0.63) = 0.37

VIII MIX CALCULATIONS OF M35 GRADE CONCRETE

A	Volume of Concrete	= 1 cu.m
B	Total Volume of Cement	= Cement/(S.G*1000)
		= 275/(3.15*1000)
		= 0.087 cu.m
C	Total Volume of Fly ash	= Flyash/(S.G*1000)
		= 118/(2.5*1000)
		= 0.041 cu.m
D	Volume of Water	=Water /(S.G*1000)
		= 160/(1*1000)
		= 0.160 cu.m
E	Volume of Superplasticizers	= Superplasticizers /(S.G*1000)
		= 2.35/(1.12*1000)
		= 0.002 cu.m
F	Total Aggregates requirement	= A – (B+C+D+E)
		=1 -(0.087 +0.041+0.160+0.002)
		=0.71 cu.m
G	Coarse Aggregate (C.A)	= F * C.A ratio * S.G * 1000
		= 0.71*0.63 *2.74 *1000
		= 1225.6 kg
I	Fine Aggregate (F.A)	= F * F.A ratio * S.G * 1000
		= 0.71*0.37*2.74 *1000
		=719.8 kg

Cement Flyash Sand Aggregate Water and Superplasticizer needed for M35 grade concrete

S.No.	MATERIALS	QUANTITY
1	Cement	275 kg
2	Flyash	118 kg
3	Fine Aggregate	720 kg
4	Coarse Aggregate (20mm)	1226 kg
5	WATER	160 L
6	PCE based SuperPlasticizer	2 L

To find the design mix ratio divide the calculated value of all materials by the weight of cement. Therefore Mix Ratio of M35 Grade concrete by weight is Cement : Flyash: F.A : C.A : Water = 1:0.4:2.6:4.46:0.58

This trail mix ratio should match the workability, durability and minimum concrete strength of M35 grade of concrete.

If it does not satisfy the above criteria two or more trails for increase of 10% should be done

MIX DESIGN FOR M50 GRADE CONCRETE WITHOUT FLY ASH:

1. Stipulations for proportioning:

1. a) Grade designation : M50
2. b) Type of cement : OPC 53 Grade conforming to IS 8112
3. c) Max. nominal size of aggregate : 20mm
4. d) Min. cement content : 320kg/m^3 [From table IS 456 Exposure condition]
5. e) Max.cement content : 450kg/m^3 [As per code]
6. f) Max. water-cement ratio : 0.45 [From IS 456]
7. g) Exposure condition : Severe (For reinforced concrete)
8. i) Workability : 100mm
9. j) Chemical admixture : Super plasticizer
10. k) Method of concrete placing : Pumping
11. l) Degree of supervision : Good
12. m) Type of Aggregate : Crushed angular aggragate

Test data for materials:

1. a) Cement used : OPC 53 Grade conforming to IS1229-1989
2. b) Specific gravity of cement : 3.15
3. c) Chemical admixture : Super plasticizer conforming to IS1903
4. d) Specific gravity of CA : 2.74
5. e) Specific gravity of FA : 2.64
6. f) Water absorption of CA : 0.5%
7. g) Water absorption of FA : 1.0%
8. h) Free surface moisture of CA : Nil
9. i) Free surface moisture of FA : Nil
10. j) Sieve analysis: CA : Conforming to table 2 of IS383
11. k) Sieve analysis: FA : Conforming to grading zone II of table IS383

Target strength for mix proportioning:

f'ck=fck+1.65s

From table 1 of IS 10262:2009,

Standard deviation, s = 5 N/mm^2

f'ck = 50+1.65(5)

= 58.25 N/mm^2

4. Selection of water-cement ratio:

Maximum w/c ratio=0.45

It can be found from table 5 of IS456-2000 for severe exposure

Based on experience, adopted w/c ratio 0.44

0.44<0.45, hence ok

Adopted w/c ratio 0.44

5. Selection of water content:

From table 2 of IS 10262:2009 Max. water content for 20mm aggregate,

186litre (for 25 to 50mm slump range)

Increasing 3% of water content for every extra 25mm slump from 50mm slump so 6% is to added to it

186+(6/100)*186 = 197 litre

Estimated water content for 100mm slump,

if superplasticizer used 20% the water content is to be reduced up to and above

Based on trials with super plasticizer water content reduction of 20% has been achieved,

Hence the water content arrived

197*0.8 = 158lts

Water required = 158litres

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, Min. cement content for Severe exposure conditions,

320>359kg/m^3 Hence ok

Cement required 359kg/m^3

7. Volume of coarse and fine aggregate content:

From table 3 of IS 10262:2009 volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone II) for w/c ratio is 0.50 0.62

In the present case w/c ratio is 0.44. Therefore volume of coarse aggregate is to be increased to decreased on fine aggregate content. As the w/c ratio is lower by 0.06. The proportion of volume of coarse aggregate is increased by 0.02

Therefore corrected portion of volume of coarse aggregate for w/c ratio is 0.44 0.632

For pumpable concrete these values should be reduced upto 10%. Therefore volume of coarse aggregate

0.632x0.9 = 0.568

Volume of fine aggregate 1-0.576 = 0.431

Volume of fine aggregate and coarse aggregate is 0.431 and 0.568

8. Mix calculations:

1. a) Volume of concrete = 1m^3
2. b) Volume of cement = mass of cement/(S.G*1000)

= 359/(3.15*1000)

= 0. m^3

1. c) Volume of water = mass of water/(S.G*1000)

= 158/(1*1000)

= 0.158m^3

7. e) Volume of Chemical admixture = 7.6/(1.145*1000)

= 0.006m^3

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

= [1-(0.114+0.158+0.006)]

= 0.722m^3

1. g) Mass of coarse aggregate = e*vol. of C.A*S.G*1000

= 0.722*0.56*2.74*1000

= 1123kg

1. h) Mass of fine aggregate = 0.722*0.431*2.74*1000

= 821kg

9. Mix proportions for M50 grade concrete:

Cement = 359kg

Fine aggregate = 821kg

Coarse aggregate = 1123kg

Water =158l

W/c ratio = 0.44

Chemical admixture = 7.18

Mix Proportion by weight = 1:2.28:3.12

this trail mix ratio should match the workability, durability and minimum strength of design mix made for M50 grade concrete

If it does not satisfy the above criteria two or more trails for increase of 10% should be done