Project on Concrete Mix Design for various grades of Concrete

AIM: To calculate the Concrete Mix Design for M35 grade concrete with fly ash and M50 grade concrete without fly ash.

Introduction: Concrete mix design is the method of finding the precise proportion of cement,sand and aggregates for concrete to achieve the target strength in structures.The design is done according to the requirements of concrete strength. So, we can achieve the desirable properties of concrete either it is in fresh stage or in hardened state. This project consists of two parts dealing with design of M35 grade concrete with fly ash and M50 grade concrete without using fly ash as a content.

Objective: The objective of this project is to produce a mix design foR M35 grade concrete containing fly ash and M50 grade concrete without fly ash. This design mix will be prepared with reference from IS 10262:2009 and recommended guidelines from IS 10262:1982.

PROCEDURE:

• STIPULATION FOR PROPORTIONING OF M35 GRADE CONCRETE

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 -IS 456
F	Maximum Cement Content	450 kg	As per code
G	Partial replacement of cement by Fly ash	30%	as per requirement
H	Maximum w/c ratio	0.45	Table 5- IS 456
I	Workability	100mm
J	Chemical Admixture	PCS Type

TEST DATA FOR MATERIALS

A	Cement Used	OPC 53	Confirming to IS 8112
B	Specific Gravity of Cement	3.15	Test - IS 2720
C	Mineral Admixture	Fly ash	Confirming to Is 12089
D	Specific Gravity of Fly ash	2.90
E	Chemical Admixture	@0.6%	IS 9103
F	Specific Gravity of Coarse Aggregate Fine Aggregate Admixture PCE based	2.74 2.74 1.12	Test - IS 2386
G	Water Absorption Coarse Aggregate Fine Aggregate	0.5% 1%	Test - IS 2386
H	Sieve Analysis Coarse Aggregate Fine Aggregate	Zone II	Confirming to Table 4 - IS 383

• TARGET STRENGTH FOR MIX PROPORTIONS OF M35 GRADE CONCRETE

From Table 1 - IS 10262

Target Strength (Fck) = Required Strength of the Concret(fck) + 1.65s

= 35 + 1.65 X 5 = 43.25 N/mm^2

• SELECTION OF WATER- CEMENT RATIO

Maximum w/c ratio = 0.45 from Table 5 - IS 456

Adopted W/C ratio = 0.40

• SELECTION OF WATER CONTENT

Maximum water content = 186 L from Table 2 - IS 1026

Above water content is from 25 to 50 mm slump, but we need 100mm slump for concrete as per specification.So, we need to increase the water- content to get th required slump. Clause 4.2 of IS 1026 suggest that to increase 3% of water content to get an extra 25 mm slump. Hence,we need to increase water content by 6% to get an additional 50 mm slump fo our concrete.

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

Since we are using superplasticizers water-content can be reduced inorder to get strength in concrete

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

• CALCUATION OF CEMENT AND FLY ASH CONTENT

Adopted w/c ratio = 0.40

Total Cmentitious (cement + fly ash) requirement = water content / (water cement ratio)

= 160 / 0.40 = 400 Kg

Since Fly ash is used the amount of cementitious content shall be increased to get good workability. 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) = 400*1.10 = 440 kg

Minimum cement content required for severe exposure = 340 kg from Table 5-IS 456

Adopted Cementitious content = 440 kg > 340 kg

Fly ash content requirement = 440*0.30 = 132 kg

Cement Content Requirement = Cementitious content - Fly ash = 440 - 132 = 308 kg

Calculation of Super [email protected] percent to the mass of cementtitious content = 440*(0.6/100)

= 2.64 kg

• COARSE AND FINE AGGREGATE

Coarse Aggregate ratio	= 0.62	Table 3 - IS 10262 ( FOR W/C =0.5)
Coarse aggregate ratio for 0.40 w/c ratio	= 0.64	(adding 0.01 for every decrease .05 and vice versa)
Final Fine Aggregate ratio	= 0.36	( 1-0.64) = 0.36

• MIX CALCULATIONS OF M35 GRADE CONCRETE

A	Volume of Concrete	=1cu.m
B	Total Volume of Cement	= Cement/ (sp.gravity*1000) = 308 / (3.15*1000) = 0.0978 cu.m
C	Total Volume of Fly Ash	= Fly ash / ( S.G*1000) = 132 / (2.5*1000) = 0.0529 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) = 2.64 / (1.12*1000) = 0.0023 cu.m
F	Total Aggregates requirement	= A - (B+C+D+E) = 1- (0.0978+0.05290+.160+.0023) = 0.69 cu.m
G	Coarse Aggregate (C.A)	= F*C.A ratio*S.G*1000 = 0.69*0.64*2.74*1000 = 1209.984 kg
H	Fine Aggregate ( F.A)	= F*F.A ratio*S.G*1000 = 0.69*0.36*2.74*1000 = 680.616 kg

• RESULT
  

S.No.	MATERIALS	QUANTITY
1	Cement	308 kg
2	Flyash	132 kg
3	Fine Aggregate	681 kg
4	Coarse Aggregate (20 mm)	1210 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 : C.A : F.A : Water = 1: 0.43 : 3.93 : 2.21 : 0.52

• PRECAUTION

1. This trial mix ratio should match the workability, durability, minimum strength of M35 Grade cocnrete
2. If it does not satisfy the above criteria two or more trials for increase accuracy by 10% should be done

AIM : Mix design of M50 grade concrete

STIPULATION FOR CONCRETE MIX DESIGN :

• Grade designation : M50
• Type of Cement : OPC 53 Grade confirming to IS 8112
• Maximum nominal size of aggregate : 20 mm
• Minimum cement content : 360 kg/m^3
• Maximum water-cement ratio : 0.35
• Workability : 50-75 mm (slump)
• Exposure condition : Extreme (for reinforced concrete)
• Method of concrete placing : Pumping
• Degree of supervision : Good
• Type of Aggregate : Crushed angular aggregate
• Maximum cement content : 450 kg/m^3
• Chemical admixture type : Superplasticizer

TEST DATA FOR MATERIALS :

The following data are collected by performing standard test in a laboratory:

• Specific gravity of cement : 3.12
• Specific gravity of Coarse aggregate : 2.74
• Specific gravity of Fine aggregate : 2.56

PROCEDURE FOR CONCRETE MIX DESIGN OF M50 CONCRETE :

• Target strength for Mix Proportioning :

Target compressive strength at 28 days = Characteristic compressive strength at 28 days + 1.65*s

where, s =standard deviation

According to the Table 1 of IS:10262 -2009, s = 5.0 N/mm^2

Therefore, target strength = 50 + 1.65*5 = 58.25 N/mm^2

• SELECTION OF WATER -CEMENT RATIO :

From Table 5 of IS 456 :2000, Maximum water-cement ratio = 0.35

Hence, adopted water -cement ratio = 0.34

• SELECTION OF WATER CONTENT :

From Table 2 of IS 456 :2000 , maximum water content = 186 litres (for 25 -50 mm slump range) for 20mm aggregate.

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

(Note : If superplasticizer is used, the water content can be reduced upto 20% and above)

Based on trials with superplasticizer water content reduction of 27% has been achieved.Hence, the arrived water content = 197 - {197*(27/100)} = 143 litres

• CALCULATION OF CEMENT CONTENT :

Water- cement ratio = 0.34

Cement content = 143 / 0.34 = 420.58 kg/m^3

From Table 5 of IS456:2000, minimum cement content for 'Extreme exposure' condition = 360 kg/m^3 Here, 421 kg/m^3 > 360kg/m^3, hence O.K.

• 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 II) for a water-cement ratio of 0.50 = 0.62

In the present case, the water-cement ratio is 0.35. Therefore, the volume of coarse aggregate is required to be increased to decrease the fine agregate content. Therefore, the corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.34 = 0.65

For pumpable concrete, these values should be decreased by 10%.

Therefore,volume of coarse aggregate = 0.65 x 0.9 = 0.585

Volume of fine aggregate = 1- 0.585 = 0.415

• MIX CALCULATIONS:

1. Volume of Concrete = 1 m^3
2. Volume of Cement = Mass of cement / (sp.gr*1000) = 421 / (3.12*1000) = 0.131 m^3
3. Volume of Water = Mass of water / (sp.gr*1000) = 143/(1*1000) = 0.143 m^3
4. Volume Superplasticizer = 8.2 / (1.145*1000) = 0.007 m^3
5. Volume of all aggregate = {a-(b+c+d)} = 1-(0.13+0.143+0.007) = 0.719m^3
6. Mass of coarse aggregate = Volume of coarse aggregate x Volume of Coarse aggregate x Specific gr. of concreete x 1000 = 0.719 x 0.585 x 2.74 x 1000 = 1152.48 kg
7. Mass of fine aggregate = Volume of all aggregate x Volume of fine aggregate x Sp.gr of fine aggregate x 1000 = 0.719 x 0.415 x 2.56 x 1000 = 763.86 kg

• CONCRETE MIX PROPORTIONS:

S.No.	MATERIALS	QUANTITY
1.	Cement	410 kg
2.	Water	143 kg
3.	Superplasticizer	7 kg
4.	Fine Aggergate	764 kg
5.	Coarse Aggregate	1153 kg

Mix ratio of M50 Grade concrete mix proportion by weight is Cement : C.A : F.A : Water = 1:2.81:1.86: 0.35

• PRECAUTION

1. This trial mix ratio should match the workability, durability, minimum strength of M35 Grade cocnrete
2. If it does not satisfy the above criteria two or more trials for increase accuracy by 10% should be done