Project on Concrete Mix Design for various grades of Concrete

ANSWER 1:

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
F	Maximum Cement Content	450kg
G	Partial replacement of cement by Fly ash	30%
H	Maximum W/C ratio	0.45
I	Workability	100mm
J	Chemical Admixture	PCS Type

A	Cement Used	OPC 53
B	Specific Gravity of Cement	3.15
C	Mineral Admixture	Fly ash
D	Specific Gravity of Fly ash	2.90
E	Chemical Admixture	@0.6%
F	Specific Gravity of
	Coarse Aggregate	2.74
	Fine Aggregate	2.74
	Admixture PCE based	1.12
G	Water Absorption
	Coarse aggregate	0.5 %
	Fine aggregate	1 %

1. TARGET STRENGTH FOR MIX PROPORTIONS OF M35 GRADE CONCRETE

Fck	= fck+1.65s
Fck	= 35+1.65×5
Fck	= 43.25 N/mm2

1. SELECTION OF WATER-CEMENT RATIO

Maximum W/C ratio	=0.45
Adopted W/C ratio	=0.45

1. SELECTION OF WATER CONTENT

Maximum Water Content

=186 L

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
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	(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

ANSWER 2:

Stipulations for Concrete Mix Design

Grade designation : M 50

Type of cement : OPC 53 grade confirming to IS 8112

Maximum nominal size of aggregate : 20 mm

Minimum cement content : 320 kg/m³

Maximum water-cement ratio : 0.45

Workability : 100 mm (slump)

Exposure condition : severe (for reinforced concrete)

Method of concrete placing : Pumping

Degree of supervision : Good

Type of aggregate : Crushed angular aggregate

Maximum cement content : 450 kg/m³

Chemical admixture type : Super Plasticizer

Test Data for Materials

The following data are collected by performing standard tests in a laboratory.

Specific gravity of cement : 3.15

Specific gravity of coarse aggregate : 2.74

Specific gravity of fine aggregate : 2.74

:

: 2.56

Procedure for Concrete Mix Design of M 50 Concrete

1. Target Strength for Mix Proportioning

f_target = f_ck + 1.65 x s

f_target denotes the Target Average Compressive Strength at 28 days,

f_ck denotes the Characteristic Compressive Strength at 28 days,

‘s’ stands for Standard Deviation

According to the table 1 of IS: 10262-2009 ,

standard deviation, s = 5.0 N/mm²

Therefore, target strength = 50 + 1.65 x 5.0 = 58.25 N/mm²

2. Selection of Water/Cement Ratio

From Table 5 of IS 456 : 2000,

Maximum water-cement ratio = 0.45

3. Selection of Water Content

From Table 2 of IS 456, maximum water content =186 litres (for 25 to 50 mm slump range) for 20 mm aggregate.

Estimated water content for 100 mm slump =186+(6/100) x 186 =197 litres.

(Note: If Super plasticizer is used, the water content can be reduced up to 20% and above.)

Based on trials with Super plasticizer water content reduction of 29% has been achieved, Hence the arrived water content = 197 – [197 x (29/100)] = 140 litres.

4. Calculation of Cement Content

Water-cement ratio = 0.40

Based on previous experience

Cement content = 140/0.4 = 350 kg/m³

From Table 5 of IS 456, minimum cement content for ‘severe exposure’ condition = 320 kg/m³

350 kg/m³ > 320 kg/m³, hence, O.K.

5. Proportion of Volume of Coarse Aggregate and Fine Aggregate Content

From Table 3 of IS 10262. volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I) for a water-cement ratio of 0.60

In the present case the water cement ratio =0.40.

In the present case, the water-cement ratio is 0.40. Therefore. the volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.10. 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 the water-cement ratio).

Therefore. the corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.4- = 0.62.

For pumpable concrete, these values should be reduced by 10 percent.

Therefore, volume of coarse aggregate = 0.62 x 0.9 = 0.56.

Volume of fine aggregate content =1 – 0.56= 0.44

6. Mix Calculations
7. a) Volume of concrete = 1m³
8. b) Volume of cement = (Mass of Cement/ Its Specific Gravity ) X (1/1000)

= (350/3.15) X (1/1000)

= 0.111 m³

1. c) Volume of Water = (Mass of water/specific gravity of water) X (1/1000)

= (140/1) X (1/1000)

= 0.140 m³

1. d) Volume of Superplasticizer = (Mass of Superplasticizer / Specific gravity of admixture) X (1/1000)

= (7.6/1.145) X (1/1000)

= 0.006 m³

1. e) Volume of all aggregate = (a – (b + c + d))

= 1 – (0.111 + 0.140+0.006)

= 0.743 m³

1. e) Mass of coarse aggregate = Volume of All Aggregate 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

1. f) Mass of fine aggregate = Volume of all aggregate X volume of fine aggregate X Specific gravity of fine aggregate X 1000

= 0.743 x 0.44 x 2.74 x 1000

= 896 kg/m3

7. Concrete Mix Proportions

Cement = 350 kg/m³

Water = 140 kg/m³

Super plasticizer = 7 kg/m³

Fine aggregates = 896 kg/m³

Coarse aggregate = 1140 kg/m³

W/c = 0.40

TRIAL MIX RATIO : 1: 2.56: 3.26