Project on Concrete Mix Design for various grades of Concrete

Q1 M35 Grade of Concrete with fly ash

• 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-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

• 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 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

• 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-IS10262
Fck	= 35+1.65×5
Fck	= 43.25 N/mm2

• 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

• SELECTION OF WATER CONTENT

Maximum Water Content

=186 L

Table 2-IS1026

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 IS1026 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 in order 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

• CALCULATION OF CEMENT AND FLY ASH CONTENT

Adopted Water Cement Ratio	=0.45
Total Cementitious (Cement +Fly ash) requirement	= Water Content / Water Cement 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-IS456
Adopted Cementous content	=391.6 kg	> 340kg
Fly ash content requirement	= 391.6 * 0.30	30% replacement
	= 117.48 ~ 118 kg
Cement Content requirement	=Cementous content – Fly ash
	=391.6-117.48
	= 274.12

Calculation of Super Plasticizers @ 0.6 percent to the mass of cementitious content = =391.6*(0.6/100) = 2.35 kg

• 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

• 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	= Fly ash/(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 Fly ash Sand Aggregate Water and Superplasticizer needed for M35 grade concrete

Sr. 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: Fly ash: F.A: C.A: Water = 1:0.4:2.6:4.46:0.58

Q2 M50 Grade of Concrete without fly ash

1. Given Data

Grade of Concrete = M-50
Type of cement are used = O.P.C-43 grade
Brand of cement = Local Brand
Admixture = Poly Carboxylate based admixture
Fine Aggregate = Zone-II graded sand

2. Gravity
   Cement = 3.16
   Fine Aggregate = 2.62
   Coarse Aggregate (20mm) = 2.64
   Coarse Aggregate (10mm) = 2.65

Minimum Cement content in concrete mix =400 kg / m3
Maximum water cement ratio to be used in concrete mix = 0.45

3. Mix Calculation
   
4. Assume water cement ratio to be used in ths particular mix design = 0.35
5. Approximate water content for 20 mm max. Size of aggregate in concrete mix is = 180 kg /m3.
   1. As plasticizer type of admixture was used in this experiment so, reduction of water content may be assumed by 20%.
   2. Now after reduction net water content = 180 X 0.8 = 144 kg /m3

Water cement ratio in proposed concrete mix design = 0.35
Water content to be used per cum of concrete = 144 kg

• Cement content used in concrete mix = 144/0.35 = 411.4 kg / m3
• Say cement content in concrete mix = 412 kg / m3 (As per consideration Minimum cement content 400 kg / m3)
  Hence it is O.K.

• Calculation for quantity of C.A. & F.A.:
  • Volume of concrete taken in mix design = 1 m3
    Volume of cement for mix design = 412 / (3.16 X 1000) = 0.1308 m3
    Volume of water in mix design = 144 / (1 X 1000) = 0.1440 m3
    Volume of Admixture in mix design= 4.995 / (1.145 X 1000) = 0.0043 m3
    Total weight of other materials except coarse aggregate in concrete mix design = 0.1308 + 0.1440 +0.0043 = 0.2791 m3
  • Volume of coarse and fine aggregate = 1 – 0.2791 = 0.7209 m3
    Volume of F.A. In concrete mix design = 0.7209 X 0.33 = 0.2379 m3 (Assuming that 33% by volume of total aggregate)
  • Volume of C.A. In concrete mix design = 0.7209 – 0.2379 = 0.4830 m3
  • Therefore, weight of F.A. In concrete mix design= 0.2379 X 2.62 X 1000 = 623.298 kg/ m3
  • Now weight of F.A. In mix design of concrete = 621 kg/ m3
  • Therefore, weight of C.A. in concrete mix design= 0.4830 X 2.655 X 1000 = 1282.365 kg/ m3
  • Say weight of C.A. = 1284 kg/ m3
  • Considering the ratio of coarse aggregate i.e., 20 mm: 10 mm = 0.55:0.45
    20 mm size aggregate quantity= 706 kg.
    10 mm size aggregate quantity = 578 kg.
  • The cohesiveness and workability of concrete has been maintained by proper concrete test process.
  • Hence Mix details of M 50 grade of concrete per m3 basis volume of total mix quantity
    Increasing cement, water, admixture content by 2.5% by various trial and error process,

Total Quantity of Material in M50 Grade of Concrete

Cement quantity= 412 X 1.025 = 422 kg
Water quantity= 144 X 1.025 = 147.65 kg
Fine aggregate quantity= 621 kg
Coarse aggregate 20 mm total quantity= 706 kg.
Coarse aggregate 10 mm quantity= 578 kg.
Admixture quantity by weight = 1.2 % by weight of cement = 5.064 kg.

Water: cement: F.A.: C.A. = 0.35: 1: 1.473: 3.044