Project on Concrete Mix Design for various grades of Concrete

QUISTION NO : -

ANSWER :-

MIX DESIGN M35 GRADE CONCRETE WITH FLY ASH

STAPE 1 :-

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

TABLE 5 - minimum cement content , maximum water cement ratio and minimum grade of concrete for defferent exposures with normal weight aggregate of 20mm nominal maximum size

Sr no.	Exposure		plain concrete			reinforce concrete
		minimum cement content kg/m3	maximum free water cement ratio	minimum grade of concrete	minimum cement content kg/m3	maximum free water cement ratio	minimum grade of concrete
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)
a	mild	220	0.60	-	300	0.55	M20
b	moderate	240	0.60	M15	300	0.50	M25
c	severe	250	0.50	M20	320	0.45	M30
d	very severe	260	0.45	M20	340	0.45	M35
e	extreme	280	0.40	M25	360	0.40	M40

STAPE 2 :-

TEST DATA FOR MATERALS

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

TABLE 4 FINE AGGREGATE

IS SIEVE DESIGNATION		PERSENTAGE PASSING FOR
	GRADING ZOON 1	GRADING ZOON 2	GRADING ZOOM 3	GRADING ZOON 4
10mm	100	100	100	100
4.75mm	90 to 100	90 to 100	90 to 100	95 to 100
2.36mm	60 to 95	75 to 100	85 to 100	95 to 100
1.18mm	30 to 70	55 to 90	75 to 100	90 to 100
600 micron	15 to 34	35 to 59	60 to 79	80 to 100
300 micron	5 to 20	8 to 30	12 to 40	15 to 50
150 micron	0 to 10	0 to 10	0 to 10	0 to 15

STAPE -3

TARGET STRENGTH FOR MIX PROPOTIONS 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.

F'ck = fck+1.65s

F'ck =53+1.65*5

F'ck = 43.25 N/mm2

STAPE - 4

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

Adopted w/c ratio = 0.45

STAPE -5

SELECTION OF WATER CONTENT

Maximum water content = 186L

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 100mm Slump = 186+(0.06*186)

= 197.16L

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 conent = 20 percent

wayer content requirement after SP = 198 -(0.20*198)

=157.73

Adopted water content = 160L

STAPE - 6

CALCULATION OF CEMENT AND FLY ASH CONTENT

Adopted Water cement ratio = 0.45

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

= 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 =340 kg (table - 5 IS456 )

Adopted cementitious content = 391.6kg > 340 kg

Fly ash content requirement = 391.6 * 0.30 (30 percent replacment)

=117.48 aproximate 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

STAPE - 7

COARSE AND FINE AGGREGATE

coarse aggregate ratio = 0.62 (for w/c ratio = 0.5 )

coarse aggregate ratio for 0.45 w/c ratio = 0.63 (adding 0.01 for every decrease 0.05 and vice versa )

Final fine aggregate ratio = 0.37 (1-0.63 =0.37)

STAPE - 8

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	Flyash	118 kg
3	Fine Aggregate	720 kg
4	Coarse Aggregate (20mm)	1226 kg
5	WATER	160 L
6	PCE based SuperPlasticizer	2 L

MIX DESIGN M50 GRADE CONCRETE

The mix design M-50 grade (Using Admixture –Sikament) provided here is for reference purpose only. Actual site conditions vary and thus this should be adjusted as per the location and other factors.

Parameters for mix design M50

Grade Designation = M-50
Type of cement = O.P.C-43 grade
Admixture = Sika [Sikament 170 ( H ) ]
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 contract) =400 kg / m³
Maximum water cement ratio (As per contract) = 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 ). As plasticizer is proposed we can reduce water content by 20%.

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

^{4. Calculation of cement content:-
Water cement ratio = 0.35
Water content per cum of concrete = 144 kg
Cement content = 144/0.35 = 411.4 kg / m3
Say cement content = 412 kg / m3 (As per contract Minimum cement content 400 kg / m3 )
Hence O.K.}

5. Calculation for C.A. & F.A.: [ Formula’s can be seen in earlier posts]-

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
Volume of Admixture = 4.994 / (1.145 X 1000 ) = 0.0043 m³
Total weight of other materials except coarse aggregate = 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. = 0.7209 X 0.33 = 0.2379 m³ (Assuming 33% by volume of total aggregate )

Volume of C.A. = 0.7209 – 0.2379 = 0.4830 m³

Therefore weight of F.A. = 0.2379 X 2.61 X 1000 = 620.919 kg/ m³

Say weight of F.A. = 621 kg/ m³

Therefore weight of C.A. = 0.4830 X 2.655 X 1000 = 1282.365 kg/ m³

Say weight of C.A. = 1284 kg/ m³

Considering 20 mm: 10mm = 0.55: 0.45
20mm = 706 kg .
10mm = 578 kg .
Hence Mix details per m³
Increasing cement, water, admixture by 2.5% for this trial

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
Admixture = 1.2 % by weight of cement = 5.064 kg.

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

Observation: –
A. Mix was cohesive and homogeneous.
B. Slump = 120 mm
C. No. of cube casted = 9 Nos.
7 days average compressive strength = 52.07 MPa.
28 days average compressive strength = 62.52 MPa which is greater than 58.25MPa
Hence the mix accepted.