Project on Concrete Mix Design for various grades of Concrete

Aim and Introduction :

• Here the main aim of the project is to determine the mix design calculation of M35 concrete grade by using IS CODE - 456 , 10262 and for test - 2720.
• This mix design calculation procedure is the same when either GGBS or Fly ash is 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 the specific gravity of GGBS is 2.85.
• Superplasticizers are required for all high strength concrete to get good workability and good strength in concrete.

Objective:

• The objective of this project is to produce a 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 guidelines from IS 10262:2009 and recommented guide lines from IS 10262:1982.

Equations used :

1)Target mean strength

f’ck =fck + 1.65s

Where

• f’ck = target average compressive strength at 28 days
• fck = characteristics compressive strength at 28 days, and
• s = standard deviation

2)Cement content

• Cement content = water content / water-cement ratio

3) Volume Calculations

• (a) Volume of concrete
• (b) Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x 1/1000
• (c) Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000
• (d)Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000
• (e) Volume of all in aggregate =[a-(b+c+d)]
• (f) Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000
• (g) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000

Concrete Mix Design for M35 grade concrete with fly ash:

Proportioning of M35 grade :

1	Grade Designation	M35
2	Type of Cement	OPC 53
3	Type of Admixture	Fly ash
4	Maximum Nominal Size of Aggregate	20mm
5	Minimum Cement Content	340kg	Table 5-IS456
6	Maximum Cement Content	450kg	As per code
7	Partial replacement of cement by Fly ash	30%	as per requirement
8	Maximum W/C ratio	0.45	Table 5-IS456
9	Workability	100mm
10	Chemical admixtures	PCS type

• Materials should be tested in the laboratory as per tests given in the codebook and their properties should be found.
• The 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 purposes.

1	Cement Used	OPC 53	Confirming to IS8112
2	Specific Gravity of Cement	3.15	Test – IS: 2720
3	Mineral Admixture	Fly ash	Confirming to IS12089
4	Specific Gravity of Fly ash	2.90
5	Chemical Admixture	@0.6%	IS9103
6	Specific Gravity of		Test – IS 2386
	Coarse Aggregate	2.74
	Fine Aggregate	2.74
	Admixture PCE based	1.12
7	Water Absorption		Test – IS 2386
	Coarse aggregate	0.5 %
	Fine aggregate	1 %
8	Sieve Analysis		Test – IS 2386
	Coarse aggregate		Confirming to Table 2-IS383
	Fine aggregate	Zone II	Confirming to Table 4-IS383

• The 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).
• 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-IS10262
Fck	= 35+1.65×5
Fck	= 43.25 N/mm2

• The maximum water-cement ratio for different grades of concrete is given in Table 5-IS456.
• You can reduce the water-cement ratio based on your requirements.
• The 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

• Maximum water content from the table 186lt
• 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 so 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.
• The 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

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

Coarse and Fine aggregates:

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

Mix design calculation:

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
7	Coarse Aggregate (C.A)	= F * C.A ratio * S.G * 1000
		= 0.71*0.63 *2.74 *1000
		= 1225.6 kg
8	Fine Aggregate (F.A)	= F * F.A ratio * S.G * 1000
		= 0.71*0.37*2.74 *1000
		=719.8 kg

Results of mix design :

S.No.	MATERIALS	QUANTITY
1	Cement	275 kg
2	Fly ash	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

Part 2- Concrete Mix Design for M50 grade concrete:

Proportioning of M35 grade :

1	Grade Designation	M50
2	Type of Cement	OPC 53
3	Maximum Nominal Size of Aggregate	20mm
4	Minimum Cement Content	340kg	Table 5-IS456
5	Maximum Cement Content	450kg	As per code
6	Maximum W/C ratio	0.45	Table 5-IS456
7	Workability	100mm
8	Chemical admixtures	Super platizers

• Materials should be tested in the laboratory as per tests given in the codebook and their properties should be found.
• The 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 purposes.

1	Cement Used	OPC 53	Confirming to IS8112
2	Specific Gravity of Cement	3.15	Test – IS: 2720
3	Chemical Admixture	@0.6%	IS9103
4	Specific Gravity of		Test – IS 2386
	Coarse Aggregate	2.74
	Fine Aggregate	2.64
	Admixture PCE based	1.12
5	Water Absorption		Test – IS 2386
	Coarse aggregate	0.5 %
	Fine aggregate	1 %
6	Sieve Analysis		Test – IS 2386
	Coarse aggregate		Confirming to Table 2-IS383
	Fine aggregate	Zone II	Confirming to Table 4-IS383

• The 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).
• 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-IS10262
Fck	= 50+1.65×5
Fck	= 58.25 N/mm2

• The maximum water-cement ratio for different grades of concrete is given in Table 5-IS456.
• You can reduce the water-cement ratio based on your requirements.
• The 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

• Maximum water content from the table 186lt
• 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 so 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.
• The 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 *0.8
	=158
Adopted Water Content	=158 L

Cement content :

Adopted Water Cement Ratio	=0.45
Total Cementitious requirement	= Water Content / WaterCement ratio
	=158/0.45
	=351.44 kg

Coarse and Fine aggregates:

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

Mix design calculation:

1	Volume of Concrete	= 1 cu.m
2	Total Volume of Cement	= Cement/(S.G*1000)
		= 351.44/(3.15*1000)
		= 0.1128 cu.m
3	Volume of Water	=Water /(S.G*1000)
		= 158/(1*1000)
		= 0.158 cu.m
4	Volume of Superplasticizers	= Superplasticizers /(S.G*1000)
		= 2.35/(1.12*1000)
		= 0.002 cu.m
5	Total Aggregates requirement	= 1 – (2+3+4)
		=1 -(0.1128+0.160+0.002)
		=0.72 cu.m
7	Coarse Aggregate (C.A)	= F * C.A ratio * S.G * 1000
		= 0.72*0.63 *2.74 *1000
		= 1242.8 kg
8	Fine Aggregate (F.A)	= F * F.A ratio * S.G * 1000
		= 0.72*0.37*2.74 *1000
		=729.8 kg

Results of mix design :

S.No.	MATERIALS	QUANTITY
1	Cement	351 kg
2	Fine Aggregate	730 kg
3	Coarse Aggregate (20mm)	1243 kg
4	WATER	158 L
5	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 :F.A: C.A: Water = 1:2.28:3.12:0.5

APPENDIX

1) PHYSICAL CHARACTERSTICS OF DIFFERENT TYPES OF OPC CEMENT

2) Table – 5 Minimum Cement Content, Maximum Water-Cement Ratio and Minimum Grade of Concrete for Different Exposures with Normal Weight Aggregate of 20 mm Nominal Maximum Size IS: 456-2000

3) Table 2 of IS 383: Grade size distribution for different nominal sizes of coarse aggregate

4) Table 4 of IS 383: Grading of fine aggregate

5) Table I of IS 10262:2009: Assumed standard deviations

6) Table 2 of IS 10262:2009: maximum water content for 20 mm aggregate