Construction Technology_Concrete Mix Design_Project 1

Concrete mix design for M35 grade concrete with flyash:

Aim: Concrete mix design for M35 grade concrete with fly ash.

Procedure:

Requirements for proportioning:

• Grade designation = M35
• Type of cement = OPC 43 grade confirming to IS 8112
• Type of mineral admixture = Fly ash conforming to IS 3812(part-1)
• Maximum nominal size of aggregate = 20mm
• Minimum cement content = 300 kg/`m^3` (From table 5 of IS 456:2000-Exposure condition)
• Maximum water-cement ratio= 0.50 (From table 5 of IS 456:2000-Exposure condition)
• Slump value = 70mm
• Exposure condition = Moderate (for reinforced concrete)
• Method of concrete placing = pumping
• Degree of supervision = Good
• Type of aggregate = Crushed angular aggregate
• Chemical admixture = Super plasticizer.

Test data for materials:

• Cement used = OPC 43 grade conforming to IS 8112
• Specific gravity of cement = 3.15
• Fly ash = Conforming to IS 3812(part-1)
• Specific gravity of fly ash = 2.2
• Chemical admixture = Superplasticizer conforming to IS 9103
• Specific gravity of coarse aggregate and fine aggregate = 2.74
• Water absorption of coarse aggregate = 0.5%
• Water absorption of fine aggregate = 1.0%
• Free surface moisture of coarse and fine aggregate is Nil.

Target mean strength of concrete:

• Target mean strength of concrete,f'ck = fck+1.65S
• where, fck=characteristics compressive strength at 28 days.
• S= standard deviation(IS 10262-2009,table-1)
• Given concrete grade is M35
• Compressive strength after 28 days is 30N/`mm^2`.
• Standard deviation is 5 N/ `mm^2`.(As per IS 10262-2009, table-1)

• Now fck= fck+1.65S = 35+(1.65X5) = 43.25 N/`mm^2`.

Selection of water cement ratio:

• From the table-5 of IS 456: 2000 for moderate exposure, maximum water cement ratio = 0.50
• Based on experience, adopt the water cement ratio as 0.45.

• Hence, the W/C ratio = 0.45.
• Then 0.45<0.50.

Water content:

• As per IS 10262-2009 (table-2) the maximum nominal size of aggregate is 20 mm.
• So, the standard slump value is between 25mm to 50mm.
• The water content for the 20 mm maximum size of aggregate is 186 litres
• The estimated water content for 70mm slump = 186+`3/100X180`= 192 litres

• Then the superplastisizer is used, the water content is reduced by 30%. Based on the trials & errors, we assume 29% reduction using plastisizer.
• Hence the water content = 191 X `71/100` = 136 litres.

Calculation of cement content:

1. W/C ratio = 0.45.
2. Water content = 136 litres
3. Cement = `136/0.45` = 303 kg/`m^3`.

From table-5 of IS 456-2000, the minimum cement content for moderate exposure condition is 300 kg/`m^3`.

Hence, 303 kg/`m^3`> 300 kg/`m^3`.

Now the percentage of fly ash needs to be decided based on project requirements and quality of materials.In some cases increase in cementitious material can be warranted. The cementitious material content is increased by 10%.

• Cementitious material content = 303 x 1.10 = 334 kg/`m^3`.
• Water content = 136 kg/`m^3`.
• water cement ratio = 136/334 = 0.40
• Fly ash @ 30% total cementitious material content = 334 x 30% = 101 kg/`m^3`.
• Cement(OPC) = 334-101 = 233 kg/`m^3`.
• Saving of cement while using fly ash = 303-233 = 70kg/`m^3`.
• Fly ash being utilized = 101 kg/`m^3`.

Proportion of volume coarse aggregate and fine aggregate content:

• From table-3 of IS 10262-2009, volume of coarse aggregate corresponding to 20mm size and the fine aggregate(Zone-1) for water cement ratio = 0.6.

• In the present case the water cement ratio is 0.45.
• Therefore the volume of coarse aggregate needs to be increased to decrese the fine aggregate content. As water content ratio is lower by 0.10, the proportion of volume of coarse aggregate is increased by 0.02.
• Therefore, corrected volume of aggregate for the water cement ratio of 0.45 = 0.62.
• For pumpable concrete these values are reduced by 10%.
• Therefore, volume of coarse aggregate = 0.62-10% = 0.52
• Volume of fine aggregate content =1-0.52 = 0.48.

Mix calculations:

The mix calculation per unit volume of concrete shall be as follows:

• Volume of concrete = 1 m^3
• Volume of cement = (Mass of cement/Specific gravity of cement)X(1/100)

= 233/3.15 X 1/1000

= 0.073 `m^3`.

• Volume if flyash = (Mass of flyash/specific gravity of fly ash)X(1/1000)

= 101/2.2 X 1/1000

=0.045 `m^3`.

• Volume of water = (Mass of water/ Specific gravity of water)X(1/1000)

= 136/1 X 1/1000

= 0.136 `m^3`.

• Volume of chemical admixture = (Mass of chemical admixture/specific gravity of admixture)X(1/1000)

= 7.6/1.145 X 1/1000

= 0.006 `m^3`.

• Volume of aggregate(CA & FA) = [a-(b+c+d+e)]

= [1-(0.073+0.045+0.136+0.006)]

= 0.74 `m^3`.

• Mass of coarse aggregate = f x volume of the coarse aggregate x specific gravity of coarse aggregate x 1000

= 0.74 x 0.52 x 2.74 x 1000

= 1054 kg/`m^3`.

• Mass of fine aggregate = f x volume of fine aggregate x specific gravity of fine aggregate x 1000

= 0.74 x 0.48 x 2.74 x 1000

= 973 kg/`m^3`.

Mix proportions:

Cement	= 233 kg/`m^3`
Fly ash	= 101 kg/`m^3`
Water	= 136 kg/`m^3`
Fine aggregate	= 973 kg/`m^3`
Coarse aggregate	= 1054 kg`m^3`
Chemical admixture	= 7 kg/`m^3`
Water cement ratio	= 0.40
Trial mix ratio	= 1:4.17:4.52

Result:

• The mix ratio of the M35 grade of concrete with flyash = 1:4.17:4.52

The slump shall be measured and the water content and dosage of admixtures shall be adjusted for achieving the required slump on trial. The mix proportion shall be rewoked for the actual water content for durability requirements.

Two more trials having variation of 10% of water cement ratio in clause X shall be carried out and graph between three water cement ratios and corresponding strengths shall be plotted to work out the mix proportions for the given target strength for field trials. However, durability shall be met.

Concrete mix design for M50 grade concrete without flyash:

Aim: Concrete mix design for M50 grade concrete with fly ash.

Procedure:

Requirements for proportioning:

• Grade designation = M50
• Type of cement = OPC 43 grade confirming to IS 8112
• Maximum nominal size of aggregate = 20mm
• Minimum cement content = 320 kg/`m^3` (From table 5 of IS 456:2000-Exposure condition)
• Maximum water-cement ratio= 0.45 (From table 5 of IS 456:2000-Exposure condition)
• Slump value = 100mm
• Exposure condition = severe (for reinforced concrete)
• Method of concrete placing = pumping
• Degree of supervision = Good
• Type of aggregate = Crushed angular aggregate
• Chemical admixture = Superplasticizer.

Test data for materials:

• Cement used = OPC 43 grade conforming to IS 8112
• Specific gravity of cement = 3.15
• Chemical admixture = Superplasticizer conforming to IS 9103
• Specific gravity of coarse aggregate and fine aggregate = 2.74
• Water absorption of coarse aggregate = 0.5%
• Water absorption of fine aggregate = 1.0%
• Free surface moisture of coarse and fine aggregate is Nil.

Target mean strength of concrete:

• Target mean strength of concrete,f'ck = fck+1.65S

where, fck=characteristics compressive strength at 28 days.

S= standard deviation(IS 10262-2009,table-1)

• Given concrete grade is M50
• Compressive strength after 28 days is 30N/`m^3`.
• Standard deviation is 5 N/`m^3`.(As per IS 10262-2009, table-1)

• Now fck= fck+1.65S = 50+(1.65X5) = 58.25 N/`mm^2`.

Selection of water cement ratio:

• From the table-5 of IS 456: 2000 for severe exposure, maximum water cement ratio = 0.45
• Based on experience, adopt the water cement ratio as 0.40.

• Hence, the W/C ratio = 0.40
• Then 0.40<0.45

Water content:

• As per IS 10262-2009 (table-2) the maximum nominal size of aggregate is 20 mm.
• So, the standard slump value is between 25mm to 50mm.
• The water content for the 20 mm maximum size of aggregate is 186 litres
• The estimated water content for 100mm slump = 186+`6/100X180`= 197 litres.

• Then the superplastisizer is used, the water content is reduced by 30%. Based on the trials & errors, we assume 29% reduction using plastisizer.
• Hence the water content = 197 X `71/100` = 139 litres.

Calculation of cement content:

• W/C ratio = 0.40
• Water content = 139 litres
• Cement = `139/0.40` = 347 kg/`m^3`.
• From table-5 of IS 456-2000, the minimum cement content for severe exposure condition is 320 kg/m^3.
• Hence, 347 kg/`m^3` > 320 kg/`m^3`.

Proportion of volume coarse aggregate and fine aggregate content:

• From table-3 of IS 10262-2009, volume of coarse aggregate corresponding to 20mm size and the fine aggregate(Zone-1) for water cement ratio = 0.6.

• In the present case the water cement ratio is 0.40.
• Therefore the volume of coarse aggregate needs to be increased to decrese the fine aggregate content. As water content ratio is lower by 0.10, the proportion of volume of coarse aggregate is increased by 0.02.
• Therefore, corrected volume of aggregate for the water cement ratio of 0.40 = 0.62.
• For pumpable concrete these values are reduced by 10%.
• Therefore, volume of coarse aggregate = 0.62-10% = 0.52
• Volume of fine aggregate content =1-0.52 = 0.48.

Mix calculations:

The mix calculation per unit volume of concrete shall be as follows:

• Volume of concrete = 1 m^3
• Volume of cement = (Mass of cement/Specific gravity of cement)X(1/100)

= 347/3.15 X 1/1000

= 0.110`m^3`.

• Volume of water = (Mass of water/ Specific gravity of water)X(1/1000)

= 139/1 X 1/1000

= 0.139 `m^3`.

• Volume of chemical admixture = (Mass of chemical admixture/specific gravity of admixture)X(1/1000)

= 7.6/1.145 X 1/1000

= 0.006 `m^3`.

• Volume of aggregate(CA & FA) = [a-(b+c+d)]

= [1-(0.110+0.139+0.006)]

= 0.745 `m^3`.

• Mass of coarse aggregate = f x volume of the coarse aggregate x specific gravity of coarse aggregate x 1000

= 0.745 x 0.52 x 2.74 x 1000

= 1065 kg/`m^3`

• Mass of fine aggregate = f x volume of fine aggregate x specific gravity of fine aggregate x 1000

= 0.745 x 0.48 x 2.74 x 1000

= 979 kg/`m^3`.

Mix proportions:

Cement	= 347 kg/`m^3`
Water	= 139 kg/`m^3`
Fine aggregate	= 979 kg/`m^3`
Coarse aggregate	= 1065 kg/`m^3`
Chemical admixture	= 7 kg/`m^3`
Water cement ratio	= 0.40
Trial mix ratio	= 1:2.82:3.06

Result:

• The mix ratio of the M50 grade of concrete without flyash = 1:2.82:3.06

The slump shall be measured and the water content and dosage of admixtures shall be adjusted for achieving the required slump on trial. The mix proportion shall be rewoked for the actual water content for durability requirements.Two more trials having variation of 10% of water cement ratio in clause X shall be carried out and graph between three water cement ratios and corresponding strengths shall be plotted to work out the mix proportions for the given target strength for field trials. However, durability shall be met.