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 may be defined as the art of selecting suitable ingredients of concrete and determining their relative proportions with the object of producing concrete of certain minimum strength and durability as economically as possible.

The mix design calculation for M35 grade concrete with fly ash admixture and superplasticizer as per Indian standard codebook IS 10262 (2009)- Guidelines for concrete mix proportioning.

I. STIPULATIONS FOR PROPORTIONING OF M35 GRADE CONCRETE

This section contains specifications for the materials and requirements for the concrete to be manufactured. The specific gravity of Fly ash is 2.1 to 3, while the specific gravity of GGBS is 2.85. Use the appropriate specific gravity value based on the type of admixture used.

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-IS456
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-IS456
I	Workability	100mm
J	Chemical Admixture	PCS Type

II. TEST DATA FOR MATERIALS

Materials must be tested to find its below physicals and chemical properties. Standard values are considered below.

A	Cement Used	OPC 53	Confirming to IS8112
B	Specific Gravity of Cement	3.15	Test – IS: 2720
C	Mineral Admixture	Fly ash	Confirming to IS12089
D	Specific Gravity of Fly ash	2.90
E	Chemical Admixture	@0.6%	IS9103
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-IS383
	Fine aggregate	Zone II	Confirming to Table 4-IS383

III. TARGET STRENGTH FOR MIX PROPORTIONS OF M35 GRADE CONCRETE

The strength of concrete may vary depending on the quality of the material, the mixing method and the construction procedures. Therefore the target strength (Fck) must be greater than the required strength of the concrete (fck).

Table 1 of IS456 gives the standard deviation value (s) for different grade concretes.

Fck	= fck+1.65s	“S” from Table1-IS10262
Fck	= 35+1.65×5
Fck	= 43.25 N/mm2

IV. SELECTION OF WATER-CEMENT RATIO

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

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

V. SELECTION OF WATER CONTENT

Maximum Water Content

=186 L

Table 2-IS1026

The water content above is for a slump of 25 to 50 mm, but according to the specification our concrete requires a slump of 100 mm. Therefore, to get the desired slump, the water content must be increased. Clause 4.2 of IS1026 recommends increasing the water content by 3% to obtain an additional 25 mm slump. Therefore, to obtain a slump of 50 mm in addition to our concrete, the water content must be increased by 6%.

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

As we use super plasticizers we can reduce the water content to gain strength in the concrete. The amount of water-content to be reduced depends on the type of super plasticizer.

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 / WaterCement ratio
	=160/0.45
	=355.55 kg

Since flying ash is used, the amount of cementitious content (cement + fly ash) should be increased to get good performance and strength. The percentage of increasing cementitious content depends on 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 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	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

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 needed for M35 grade concrete

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

M50 grade concrete mix procedure-

Parameters for mix design M50

Grade Designation = M-50
Type of cement = O.P.C-43 grade
Fine Aggregate = Zone-II

Sp. Gravity
Cement = 3.15
Fine Aggregate = 2.61
Coarse Aggregate (20mm) = 2.65
Coarse Aggregate (10mm) = 2.66

Minimum Cement (As per code) =400 kg / m³
Maximum water cement ratio (As per code) = 0.45

Mix Calculation: –

1. Target Mean Strength = 50 + ( 5 X 1.65 ) = 58.25 Mpa

2. Selection of water cement ratio:-
Assume water-cement ratio = 0.35

3. Calculation of water: –
Approximate water content for 20mm max. Size of aggregate = 180 kg /m³ (As per Table No. 5 , IS : 10262 ).

Now water content = 180 X 0.8 = 144 kg /m³

5. Calculation for C.A. & F.A.-

Volume of concrete = 1 m³
Volume of cement = 412 / ( 3.15 X 1000 ) = 0.1308 m³
Volume of water = 144 / ( 1 X 1000 ) = 0.1440 m³
Total weight of other materials except coarse aggregate = 0.1308 + 0.1440 = 0.2748 m³

Volume of coarse and fine aggregate = 1 – 0.2748 = 0.7252 m³
Volume of F.A. = 0.7252 X 0.33 = 0.2394 m³ (Assuming 33% by volume of total aggregate )

Volume of C.A. = 0.7252 – 0.2394 = 0.4858 m³

Therefore weight of F.A. = 0.2394 X 2.61 X 1000 = 624.834 kg/ m³

Say weight of F.A. = 625 kg/ m³

Therefore weight of C.A. = 0.4858 X 2.655 X 1000 = 1289.799 kg/ m³

Say weight of C.A. = 1290 kg/ m³

Considering 20 mm: 10mm = 0.55: 0.45
20mm = 706 kg .
10mm = 578 kg .
Hence Mix details per m³

Cement = 412 X 1.025 = 422 kg
Water = 144 X 1.025 = 147.6 kg
Fine aggregate = 621 kg
Coarse aggregate 20 mm = 706 kg
Coarse aggregate 10 mm = 578 kg

Water: cement: F.A.: C.A. = 0.35: 1: 1.472: 3.043

• From both concrete mix designs, we got to know the all the concrete ingredients required to make concrete of required grade which gives desired properties as required in both plastic and hardened state of concrete.
• Concrete ingredients required for 1 cum of concrete and 1 bag (50 kgs) of cement are shown in the final quantities.