Project on Concrete Mix Design for various grades of Concrete

Aim-

1. Calculation of the mix design concrete i.e., M35 grade of concrete with fly ash, which gives the minimum compressive strength 35N/mm² after 28days at a certain curing period.
2. Calculation of the mix design concrete i.e., M50 grade of concrete without fly ash, which gives the minimum compressive strength 50N/mm² after 28days at a certain curing period.

Introduction-

Concrete is a versatile material which is widely used in construction of structures, the basic material are cement aggregate and water, proper batching of these ingredients produces a good quality of concrete. Design concrete gives desire strength of the structure. Design concrete is a scientific calculation which design by the structural engineer and the mix proportion are determine by the concrete producer. Different grade of design mix concrete like M30, M35, M40, M50.

Procedure-

The design of concrete follow different codes to make a proper grade of concrete. Materials are tested by the following codes.

Calculation of Concrete Mix for M35 With Fly Ash

1. Stipulations for Proportioning-

1. Grade of Concrete: M35
2. Type of cement: OPC 43 grade confirming to IS 8112
3. Type of mineral: Fly Ash confirming to IS 3812
4. Maximum nominal size of aggregate: 20 mm
5. Minimum cement content: 340 kg/m3(from table 5 of IS 456:2000 based on exposure condition)
6. Maximum water-cement ratio: 0.45 (from table 5 of IS 456:2000 based on exposure condition)
7. Workability: 100mm (slump for pumping)
8. Exposure condition: Very Severe (for reinforced concrete)
9. Method of concrete placing: Pumping
10. Degree of supervision: Good
11. Type of aggregate: Crushed angular aggregate
12. Maximum Cement Content: 450 kg/m3
13. Chemical Admixture Type: Super Plasticizer

1. Test Data for Material-

1. Cement used: OPC 43 grade confirming to IS 8112
2. Specific Gravity of cement: 3.15
3. Fly Ash: confirming to IS 3812
4. Specific Gravity of Fly ash: 2.2
5. Chemical admixture: superplasticizer confirming to IS 9103
6. Specific Gravity of superplasticizer: 1.145
7. Specific Gravity of fine aggregate: 2.74
8. Specific Gravity of coarse aggregate: 2.74
9. Water absorption for Coarse aggregate: 0.5%
10. Water absorption for Fine aggregate: 1.0%
11. Moisture content: Free
12. Sieve analysis for coarse aggregate: confirming to Table 2 of IS 383
13. Sieve analysis for fine aggregate: confirming to grading zone 1 of Table 4 of IS 383

1. Calculate Target Mean Strength-

F’ck= fck+1.65S

F’ck=35+1.65*5

F’ck=43.25N/mm²

where,

F’ck= target average compressive strength

fck= characteristics compressive strength

S= Standard deviation 5N/mm² (taken from table 1 of IS 10262:2009)

Table 1 of IS 10262:2009
Grade	Standard deviation (S)
M10	3.5N/mm³
M15	3.5N/mm³
M20	4N/mm³
M25	4N/mm³
M30	5N/mm³
M35	5N/mm³
M40	5N/mm³
M45	5N/mm³
M50	5N/mm³

1. Selection of Water-Cement Ratio-

Water cement ratio taken from table 5 of IS 456:2000 for very severe condition=0.45,

W/C=0.45

Exposure	Plain cement concrete			Reinforce cement concrete
	max. cement content	water cement ratio	grade of concrete	max. cement content	water cement ratio	grade of concrete
mild	220kg/m³	0.6	-	300kg/m³	0.55	M20
moderate	240kg/m³	0.6	M15	300kg/m³	0.5	M25
severe	250kg/m³	0.5	M20	320kg/m³	0.45	M30
Very severe	260kg/m³	0.45	M20	340kg/m³	0.45	M35
extreme	280kg/m³	0.4	M25	360kg/m³	0.4	M40

1. Selection of Water Content-

Maximum water content for 20mm aggregate=186litres for slump range 25mm-50mm (table 2 of IS 10262:2009)

For 100mm slump so we increase water 6% i.e., 186+(0.06*186) =197litres.

Due to addition of admixture, decrease water 20%. The actual water to be used =197-(197*0.2) =158litres

W=158 litres

Table 2 of IS 10262:2009
Sl. No.	Nominal maximum size of aggregate	Maximum water content
1	10mm	208kg
2	20mm	186kg
3	40mm	165kg

1. Calculation of Cement and Fly Ash content=

Water-cement ratio(W/C) =0.45

158/0.45=350Kg/m³

From Table 5 of IS 456, the minimum cement content for Very Severe exposure condition is 340kg/m³

350Kg/m³> 340Kg/m³, hence ok

Now, to proportion a mix containing fly ash the following steps are suggested:

1. Decide the percentage fly ash to be used based on project requirement and quality of materials
2. In certain situations, increase in cementitious material content may be warranted, the decision on increase in cementitious material content and its percentage may be based on experience and trial, we increase of 10 percent cementitious material content.

Cementitious material content= 350+(0.1*350) = 385 kg/m³

Water Content= 158kg/m³

So, water-cement ratio=158/385=0.410

Fly ash at 30% of total cementitious material content= 385 x 30% =115 kg/m³

Cement (OPC) = 385 - 115 =270 kg/m³

Saving of cement while using fly ash = 350 - 270 = 80 kg/m³, and

Fly ash being utilized = 115 kg/m³

1. The Proportion of the Volume of Coarse Aggregate and Fine Aggregate Content=

From Table 3 of IS 10262:2009, the Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I) for a water-cement ratio of 0.50 = 0.60

We have actual water content is 0.41, Its less by (0.5-0.41) = 0.09

As the water-ratio is reduced, it is desirable to increase the coarse aggregate proportion to reduce the fine aggregate content. The coarse aggregate is increased at rate of 0.01 for every decrease in water ratio of 0.05, in this situation water ratio decrease so we increase the coarse aggregate by 0.018 i.e., 0.60+0.018=0.618, concrete done by pumping so we decrease 10% coarse aggregate due to angular aggregate. 0.618- (0.618 *0.1) =0.556 this is coarse aggregate. Hence the fine aggregate=1-0.556=0.444

Table 3 of IS 10262:2009
Sl. No.	Nominal maximum size of aggregate	Volume of Coarse Aggregate per Unit Volume of Total Aggregate for Different Zones of Fine Aggregate
		zone 4	zone 3	zone 2	zone1
1	10mm	0.5	0.48	0.46	0.44
2	20mm	0.66	0.64	0.62	0.6
3	40mm	0.75	0.73	0.71	0.69

1. Mix Calculations-

1. Volume of concrete = 1m³
2. Volume of cement = (Mass of cement/specific gravity of Cement) X (1/1000)

= (270/3.15) X (1/1000)

= 0.086 m³

1. Volume of fly ash = (Mass of fly ash /specific gravity of fly ash) X (1/1000)

= (115/2.2) X (1/1000)

=0.052 m³

1. Volume of water = (Mass of water/specific gravity of water) X (1/1000)

= (158/1) X (1/1000)

= 0.158 m³

1. Volume of admixture = (Mass of admixture / Specific gravity of admixture) X (1/1000)

= (7/1.145) X (1/1000)

= 0.006 m³

(Mass of plasticizer=2% of cementitious material i.e.,350*0.02=7kg)

1. Volume of all aggregate = (a – (b + c + d+ e))

= 1 – (0.086 + 0.052 + 0.158 + 0.006)

= 0.698 m³

1. Mass of coarse aggregate = Volume of all Aggregate X Volume of Coarse Aggregate X Specific Gravity of Coarse Aggregate X 1000

= 0.698 x 0.556 x 2.74 x 1000

= 1063.36 kg/m³

1. Mass of fine aggregate = Volume of all Aggregate X Volume of Fine Aggregate X Specific Gravity of Fine Aggregate X 1000

= 0.698 x 0.444 x 2.74 x 1000

= 849.16 kg/m³

1. Concrete mix proportion-

Cement = 270 kg/m³

Fly Ash= 115kg/m³

Water = 158 kg/m³

Super plasticizer = 7 kg/m³

Fine aggregates = 849.16 kg/m³

Coarse aggregate = 1063.36 kg/m³

W/C= 0.41

1. The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving the required slump based on trial, if required. The mix proportions shall be reworked for the actual water content and checked for durability requirements.
2. Two more trials having variation of ±10percent of water-cement ratio in (10) shall be carried out and a graph between three water-cement ratios and their corresponding strengths shall be plotted to work out the mix proportions for the given target strength for field trials. However, durability requirement shall be met.

Result- Trial mix ratio=1:2.21:2.76

Calculation of Concrete Mix for M50 Without Fly Ash

1. Stipulations for Proportioning-

1. Grade of Concrete: M50
2. Type of cement: OPC 53 grade confirming to IS 8112
3. Maximum nominal size of aggregate: 20 mm
4. Minimum cement content: 360 kg/m3(from table 5 of IS 456:2000 based on exposure condition)
5. Maximum water-cement ratio: 0.45 (from table 5 of IS 456:2000 based on exposure condition)
6. Workability: 125mm (slump for pumping)
7. Exposure condition: Extreme (for reinforced concrete)
8. Method of concrete placing: Pumping
9. Degree of supervision: Good
10. Type of aggregate: Crushed angular aggregate
11. Maximum Cement Content: 450 kg/m3
12. Chemical Admixture Type: Super Plasticizer

1. Test Data for Materials-

1. Cement used: OPC 53 grade confirming to IS 8112
2. Specific Gravity of cement: 3.15
3. Chemical admixture: superplasticizer confirming to IS 9103
4. Specific Gravity of superplasticizer: 1.145
5. Specific Gravity of fine aggregate: 2.74
6. Specific Gravity of coarse aggregate: 2.74
7. Water absorption for Coarse aggregate: 0.5%
8. Water absorption for Fine aggregate: 1.0%
9. Moisture content: Free
10. Sieve analysis for coarse aggregate: confirming to Table 2 of IS 383
11. Sieve analysis for fine aggregate: confirming to grading zone 1 of Table 4 of IS 383

1. Calculate Target Mean Strength-

F’ck= fck+1.65S

F’ck=50+1.65*5

F’ck=58.25N/mm²

where,

F’ck= target average compressive strength

fck= characteristics compressive strength

S= Standard deviation 5N/mm² (taken from table 1 of IS 10262:2009)

Table 1 of IS 10262:2009
Grade	Standard deviation (S)
M10	3.5N/mm³
M15	3.5N/mm³
M20	4N/mm³
M25	4N/mm³
M30	5N/mm³
M35	5N/mm³
M40	5N/mm³
M45	5N/mm³
M50	5N/mm³

1. Selection of Water-Cement Ratio-

Water cement ratio taken from table 5 of IS 456:2000 for extreme condition=0.4, based on experience adopted 0.35

W/C=0.35

Exposure	Plain cement concrete			Reinforce cement concrete
	max. cement content	water cement ratio	grade of concrete	max. cement content	water cement ratio	grade of concrete
mild	220kg/m³	0.6	-	300kg/m³	0.55	M20
moderate	240kg/m³	0.6	M15	300kg/m³	0.5	M25
severe	250kg/m³	0.5	M20	320kg/m³	0.45	M30
Very severe	260kg/m³	0.45	M20	340kg/m³	0.45	M35
extreme	280kg/m³	0.4	M25	360kg/m³	0.4	M40

1. Selection of Water Content-

Maximum water content for 20mm aggregate=186litres for slump range 25mm-50mm (table 2 of IS 10262:2009)

For 125mm slump so we increase water 9% i.e., 186+(0.09*186) =203litres.

Due to addition of admixture, decrease water 29%. The actual water to be used =203-(203*0.29) =144litres

W=144 litres

Table 2 of IS 10262:2009
Sl. No.	Nominal maximum size of aggregate	Maximum water content
1	10mm	208kg
2	20mm	186kg
3	40mm	165kg

1. Calculation of Cement and Fly Ash content=

Water-cement ratio(W/C) =0.35

144/0.35=412Kg/m³

From Table 5 of IS 456, the minimum cement content for Extreme exposure condition is 360kg/m³

412Kg/m³> 360Kg/m³, hence ok

1. The Proportion of the Volume of Coarse Aggregate and Fine Aggregate Content=

From Table 3 of IS 10262:2009, the Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for a water-cement ratio of 0.50 = 0.62

We have actual water content is 0.35, Its less by (0.5-0.35) = 0.15

As the water-ratio is reduced, it is desirable to increase the coarse aggregate proportion to reduce the fine aggregate content. The coarse aggregate is increased at rate of 0.01 for every decrease in water ratio of 0.05, in this situation water ratio decrease so we increase the coarse aggregate by 0.03 i.e., 0.62+0.03=0.65, concrete done by pumping so we decrease 10% coarse aggregate due to angular aggregate. 0.65- (0.65 *0.1) =0.585 this is coarse aggregate. Hence the fine aggregate=1-0.556=0.415

Table 3 of IS 10262:2009
Sl. No.	Nominal maximum size of aggregate	Volume of Coarse Aggregate per Unit Volume of Total Aggregate for Different Zones of Fine Aggregate
		zone 4	zone 3	zone 2	zone1
1	10mm	0.5	0.48	0.46	0.44
2	20mm	0.66	0.64	0.62	0.6
3	40mm	0.75	0.73	0.71	0.69

1. Mix Calculations-

1. Volume of concrete = 1m³
2. Volume of cement = (Mass of cement/specific gravity of Cement) X (1/1000)

= (412/3.15) X (1/1000)

= 0.131 m³

1. Volume of water = (Mass of water/specific gravity of water) X (1/1000)

= (144/1) X (1/1000)

= 0.144 m³

1. Volume of admixture = (Mass of admixture / Specific gravity of admixture) X (1/1000)

= (8.24/1.145) X (1/1000)

= 0.007 m³

(Mass of plasticizer=2% of cementitious material i.e.,412*0.02=8.24kg)

1. Volume of all aggregate = (a – (b + c + d))

= 1 – (0.131 + 0.144 + 0.007)

= 0.718 m³

1. Mass of coarse aggregate = Volume of all Aggregate X Volume of Coarse Aggregate X Specific Gravity of Coarse Aggregate X 1000

= 0.718 x 0.585 x 2.74 x 1000

= 1150.88 kg/m³

1. Mass of fine aggregate = Volume of all Aggregate X Volume of Fine Aggregate X Specific Gravity of Fine Aggregate X 1000

= 0.718 x 0.415 x 2.74 x 1000

= 816.44 kg/m³

1. Concrete mix proportion-

Cement = 412 kg/m³

Water = 144 kg/m³

Super plasticizer = 8.24 kg/m³

Fine aggregates = 816.44 kg/m³

Coarse aggregate = 1150.88 kg/m³

W/C= 0.35

1. The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving the required slump based on trial, if required. The mix proportions shall be reworked for the actual water content and checked for durability requirements.
2. Two more trials having variation of ±10percent of water-cement ratio in (10) shall be carried out and a graph between three water-cement ratios and their corresponding strengths shall be plotted to work out the mix proportions for the given target strength for field trials. However, durability requirement shall be met.

Result- Trial mix ratio=1:2:2.8