M35 Grade Concrete Mix Design with Fly Ash – IS10262

M35 Grade Concrete Mix Design with Fly Ash – IS10262

This article covers the mix design calculation of M35 Grade Concrete with Ground Granulated Blast Furnace Slag (GGBS) admixture and Poly Carboxylite type superplasticizer as per Indian Standard Codebook IS10262(2009) – Guidelines for Concrete Mix Proportioning.

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.

I. STIPULATIONS FOR PROPORTIONING OF M35 GRADE CONCRETE

This section deals with the conditions and requirements of the concrete to be made.

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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 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.

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 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

IV. 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-IS456
Adopted W/C ratio	=0.45

V. SELECTION OF WATER CONTENT

Maximum Water Content

=186 L

Table 2-IS1026

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 hence 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

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 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

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 and Superplasticizer 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

Er.SP.ASWINPALANIAPPAN., M.E.,(Strut/.,)

Structural Engineer

Madras Terrace Architectural Works

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