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

PROPORTIONING OF M35 GRADE OF CONCRETE

Grade Designation M35

Type of Cement Opc53

Type of Admixture Fly ash

Maximum Nominal Size 20mm

Minimum Cement Content 340kg

Maximum Cement Content 450kg

Partial replacement
of cement by Fly ash 30%

Maximum W/C ratio 0.45

Workability 100mm

Chemical Admixture Pcs type

II. TEST DATA FOR MATERIALS

a) Cement used Opc53

b) Specific gravity of cement 3.15

c) Chemical admixture Fly ash

d) Specific gravity of fly ash 2.2

1) Coarse aggregate 2.74

2) Fine aggregate 2.74

e) Water absorption:

1) Coarse aggregate 0.5%

2) Fine aggregate 1%

III. TARGET STRENGTH FOR MIX PROPORTIONS OF M35 GRADE CONCRETE

• The strength of the concrete may deviate based on the quality of the material, method of mixing and construction practices.
• Hence target strength (Fck) should be higher than the required strength of the concrete (fck).
• The value of standard deviation(s) for different grades of concrete is given in Table 1 of IS456.

Fck	= fck+1.65s	“S” from Table1-IS 10262
Fck	= 35+1.65×5
Fck	= 43.25 N/mm2

IV. SELECTION OF WATER-CEMENT RATIO

• The maximum water-cement ratio for different grades of concrete is given in Table IS 456.
• The Water-cement ratio directly affects the strength of the concrete.

Maximum W/C ratio	=0.45	Table 5 – IS 456
Adopted W/C ratio	=0.45

V. SELECTION OF WATER CONTENT

Maximum Water Content

=186 L

Table 2 - IS1026

Above water-content is for 25 to 50mm slump, but we need 100mm slump for our concert as per specification.

So, we need to increase the water-content to get the required slump.

Clause 4.2 of IS1026 suggests to increases 3% of water-content to get an extra 25mm slump.

Hence, to increase water content by 6% to get an additional 50mm slump for our concrete.

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

Since, using superplasticizers water-content can be reduced in order to get strength in concrete.

The amount of water-content to be reduced depends on the type of superplasticizer.

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

VI. CALCULATION OF CEMENT AND FLY ASH CONTENT

Adopted Water Cement Ratio	=0.45
Total Cementitious (Cement +Fly ash) requirement	= Water Content / Water Cement 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 cementitious content to be increased depends on the experience and research. Here we have increased the cementitious content by 10%.

Final Cementitious Content (Cement + Fly ash)	= 356*1.10
	=391.6 kg
Minimum Cement Content required for ‘severe’ exposure	=340kg	Table 5-IS456
Adopted Cementous content	=391.6 kg	> 340kg

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

Calculation of Super Plasticizers @ 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
Coarse Aggregate ratio for 0.45 w/c ratio	= 0.63
Final Fine Aggregate ratio	= 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	= Fly ash/ (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

IX. Cement Fly ash Sand Aggregate Water and Superplasticizer needed for M35 grade concrete

Cement – 275 kg

Fly ash - 118 kg

Fine aggregate – 720 kg

Coarse aggregate – 1226 kg

Water – 160 liters

PCE based superplasticizer – 2L

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: Fly ash: F.A: C.A: Water = 1:2.6:4.46

Part 2 : Mix proportion for M50 grade concrete without Fly ash

I. PROPORTIONING OF M50 GRADE OF CONCRETE

Grade Designation M50

Type of Cement Opc53

Maximum Nominal Size 20mm

Minimum Cement Content 320kg

Maximum Cement Content 450kg

Maximum W/C ratio 0.45

Workability 100mm slump value

Chemical Admixture Super plasticizer

II. TEST DATA FOR MATERIALS

a) Cement used Opc53

b) Specific gravity of cement 3.15

c) Chemical admixture Super plasticizer

d) Specific gravity of

1) Coarse aggregate 2.74

2) Fine aggregate 2.64

e) Water absorption:

1) Coarse aggregate 0.5%

2) Fine aggregate 1%

III. TARGET STRENGTH FOR MIX PROPORTIONS OF M35 GRADE CONCRETE

• The strength of the concrete may deviate based on the quality of the material, method of mixing and construction practices.
• Hence target strength (Fck) should be higher than the required strength of the concrete (fck).
• The value of standard deviation(s) for different grades of concrete is given in Table 1 of IS456.

Fck	= fck+1.65s	“S” from Table1-IS 10262
Fck	= 50+1.65×5
Fck	= 58.25 N/mm2

IV. SELECTION OF WATER-CEMENT RATIO

• The maximum water-cement ratio for different grades of concrete is given in Table IS 456.
• The Water-cement ratio directly affects the strength of the concrete.

Maximum W/C ratio	=0.45	Table 5 – IS 456
Adopted W/C ratio	=0.44

V. SELECTION OF WATER CONTENT

Maximum Water Content

=186 L

Table 2 - IS1026

Above water-content is for 25 to 50mm slump, but we need 100mm slump for our concert as per specification.

So, we need to increase the water-content to get the required slump.

Clause 4.2 of IS1026 suggests to increases 3% of water-content to get an extra 25mm slump.

Hence, to increase water content by 6% to get an additional 50mm slump for our concrete.

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

Since, using superplasticizers water-content can be reduced in order to get strength in concrete.

The amount of water-content to be reduced depends on the type of superplasticizer.

Percentage of Reduction in water content	=20%
Water content requirement after SP	=198 – (0.20*198)
	=157.73
Adopted Water Content	=158 L

VI. CALCULATION OF CEMENT

Adopted Water Cement Ratio	=0.44
Total Cementitious (Cement +Fly ash) requirement	= Water Content / Water Cement ratio
	=158/0.44
	=359 kg

VII COARSE AND FINE AGGREGATE

Coarse Aggregate ratio	= 0.62
Coarse Aggregate ratio for 0.45 w/c ratio	= 0.63
Final Fine Aggregate ratio	= 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)
		= 359/ (3.15*1000)
		= 0.114 cu.m
C	Volume of Water	=Water / (S.G*1000)
		= 158/ (1*1000)
		= 0.158 cu.m
D	Volume of Chemical admixture	= Chemical admixtures / (S.G*1000)
		= 7.6/ (1.145*1/1000)
		= 0.006 cu.m
E	Total Aggregates requirement	= A – (B+C+D+E)
		=1 -(0.114 +0.158+0.006)
		=0.722 cu.m
F	Coarse Aggregate (C.A)	= F * C.A ratio * S.G * 1000
		= 0.72*0.568 *2.74 *1000
		= 1123.6 kg
G	Fine Aggregate (F.A)	= F * F.A ratio * S.G * 1000
		= 0.72*0.431*2.74 *1000
		=821.8 kg

IX. Mix proportions for Cement, Sand, Aggregate, Water needed for M50 grade concrete

Cement – 359 kg

Fine aggregate – 821 kg

Coarse aggregate – 1123 kg

Water – 158 liters

Chemical admixture – 7.18 Kg/m3

To find the design mix ratio divide the calculated value of all materials by the weight of cement. Therefore, Mix Ratio of M50 Grade concrete by weight is,

Mix proportion by weight 1:2.28: 3.12

RESULTS:

Mix proportion by weight M35 grade of concrete with fly ash is 1:2.6:4.46

Mix proportion by weight M50 grade of concrete without fly ash is 1:2.28: 3.12