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

1. STIPULATIONS FOR PROPORTIONING OF M35 GRADE CONCRETE

This section has Specifications of the materials 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-IS 456
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-IS 456
I	Workability	100mm
J	Chemical Admixture	PCS Type

1. TEST DATA FOR MATERIALS

Various laboratory tests on materials are required to use in this action. Standard values are assumed below.

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		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-IS 383
	Fine aggregate	Zone II	Confirming to Table 4-IS 383

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

1. SELECTION OF WATER-CEMENT RATIO

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-IS 456
Adopted W/C ratio	=0.45

1. SELECTION OF WATER CONTENT

Maximum Water Content

=186 L

Table 2-IS 1026

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 IS 1026 suggests to increases 3% of water-content to get an extra 25mm slump. Hence we 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 we are using superplasticizers water-content can be reduced inorder 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

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 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-IS 456
Adopted Cementitious content	=391.6 kg	> 340kg

Fly ash content requirement	= 391.6 * 0.30	30% replacement
	= 117.48 ~ 118 kg
Cement Content requirement	=Cementitious 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-IS 10262 (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)
		= 0.087m3
C	Total Volume of Fly ash	= Flyash/(S.G*1000)
		= 118/(2.5*1000)
		= 0.041m3
D	Volume of Water	=Water /(S.G*1000)
		= 160/(1*1000)
		= 0.160m3
E	Volume of Superplasticizers	= Superplasticizers /(S.G*1000)
		= 2.35/(1.12*1000)
		= 0.002m3
F	Total Aggregates requirement	= A – (B+C+D+E)
		=1 -(0.087 +0.041+0.160+0.002)
		=0.71m3
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.

STIPULATIONS FOR PROPORTIONING OF M50 GRADE CONCRETE

Stipulations for proportioning
Type of Concrete	RCC
Grade Designation	M50
Shape of Particle	Angular
Slump	50 mm
Water- Cement Ratio	0.45
Exposure Condition	Severe
Concrete Placement	Pump
Degree of Supervision	Good

The different experimental data required for the desired mix are shown in the table below:

Sieve analysis
Fine Aggregate	Zone 1
Coarse Aggregate	20 mm

Chemical Admixture
Volume ( By mass of cement)	2%
Water Content Reduction	Zero

Test data for materials
Standard Deviation	5 MPa
Specific Gravity of Fine Aggregate	2.74
Specific Gravity of Coarse Aggregate	2.74
Specific Gravity of Cement	3.15
Specific Gravity of Admixture	1.145
Water absorption of Fine Aggregate	1.0 %
Water absorption of Coarse Aggregate	0.5%
Free Surface Moisture of Fine Aggregate	Zero
Free Surface Moisture of Coarse Aggregate	Zero

Step by step detailed procedure for concrete mix design of M50 grade as per IS – 10262:2009 and IS- 456:2000

Step 1: Calculate the target mean compressive strength at 28 days

Target mean compressive strength	Characteristic strength + 1.65 X Standard Deviation
Target mean compressive strength	50 + 1.65 X 5 = 58.25 N/mm2

Where sufficient test results for a particular grade of concrete are not available, the value of standard deviation could be taken from Table 1 of IS-10262.

Step 2: Selection of maximum water/cement ratio

The maximum water-cement ratio should be selected as per Table 5 of IS – 456: 2000.

Maximum water-cement ratio	0.45
​ Adopted water-cement ratio	0.45

Step 3: Estimation of entrapped air

For the maximum size of aggregate used the air content is estimated.

Step 4: Selection of water content and fine to total aggregate ratio

The selection of water content is based on Table 2 of IS 10262:2009.

Maximum water content for 20 mm aggregate and a slump value of 25 to 50 mm = 186.00 L.

Estimated water content

186 litres

Step 5: Calculation of Cement content

The cement content per unit volume of concrete is computed from Table 5 of IS 456:2000:

Minimum cement content for severe exposure condition	320 kg/m3
cement content	186/0.45 = 413.33 kg/m3

Step 6: Calculation of aggregate content

Volume of coarse aggregate per unit volume of total aggregate for corresponding to 20 mm maximum size and zone 1 of fine aggregate = 0.60 – Table 3 of IS 10262:2009.

Correction:

Based on water cement ratio	0.01
Based on placement	10.00

Hence Volume:

Coarse aggregate	0.55
Fine aggregate	0.45

V = [W+()+()⋅()]×()]

Ca =

Mass of Coarse aggregate	1027.08 kg/m3
Mass of Fine aggregate	843.74 kg/m3​

Step 7: Computation of actual quantities required for a concrete mix – Trial mix

Water Correction

Extra quantity of water to be added

Coarse aggregate	5.14 kg
Fine aggregate	8.44 kg

Mix Design
Cement	413 kg/m3
Water	200 kg/m3
Fine Aggregate	835 kg/m3
Coarse Aggregate	1022 kg/m3

Cement : Coarse Aggregate : Fine Aggregate = 1 : 2.35 : 2.86