Project on Concrete Mix Design for various grades of Concrete

For M35 Mix Design With Fly Ash

Aim : Mix design for M 35 grade concrete with fly ash

Stipulations for Concrete Mix Design

a. Grade designation : M35

b. Type of cement : OPC 43 grade conforming to IS 8112

c. Type of mineral admixture: Fly ash confirming to IS 3812 ( Part 1)

d. Maximum nominal size of aggregates : 20mm

e. Minimum cement content : 320 kg/m^3 (Table :5 IS 456-2000,based on exposure condition)

f. Maximum water-cement ratio : 0.45 (Table :5 IS 456-2000,based on exposure condition)

g. Workability :100mm slump value of pumpable concrete

h. Exposure condition : Severe ( for reinforced concrete)

i. Method of concrete placing : Pumping

j. Degree of supervision : Good

k. Type of aggregate: Crushed angular aggregate

l. Maximum cement content : 450 kg/m3.

m. Chemical admixture type : Superplaticizer.

Test data for materials

a. Cement used : OPC 43 grade confirming to IS 8112

b. Specific gravity of cement : 3.15

c. Fly ash : Conforming to IS 3812 part 1

d. Specific gravity of flyash : 2.2

e. Chemical admixture : Superplaticizer conforming to IS 9103

f. Specific gravity of :

Coarse aggregate : 2.74

Fine aggregate : 2.74

g. Water absorption :

Coarse aggregate : 0.5%

Fine aggregate : 1%

h. Free surface moisture

Coarse aggregate : Nil

Fine aggregate : Nil

i. Seive analysis

Fine aggregate : Conforming to grading Zone 1 of table 4 IS 383.

To find target mean strength for mix proportioning

Target mean strength f'ck = fck +1.65s

= 35 +1.65x5 =43.25 N/mm2

fck- Characteristic compressive strength

s- Standard deviation

Selection of water-cement ratio

Maximum water-cement ratio =0.45 (for severe condition ,from table 5 of IS 456-2000)

On experience water-cement ratio =0.4

Calculation of water content

Maximum water content for 20mm aggregate =186 litres ( Table 2 of IS 1026:2009) for 25mm to 50mm slump range

For 100 mm slump = 186+(6/100)x186 =197 litres

As superplaticizer is used, the water content is reduced upto 30%

Based on trials water content reduction of 29% is achieved with plasticizer

Hence arrived water content = 197x0.71 = 140 litres

Calculation of cement content

Water - cement ratio = 0.4

Cementatious material ( Cement +flyash ) = 140/0.4 =350 kg

In table 5 of IS 456-2000, the cement content for severe exposure =320 kg

350 kg > 320kg

Hence OK.

To proportion the mix containing flyash the following steps are suggested :

a. The percentage of flyash need to be decided based on project requirement and qualityof materials.

b. In some cases increase in cementatious materials can be warrned . Increase in cementatious material content and its percentage may be based on experience and trial

In this increase of 10% cementatious material content is considered.

Cementatious material content = 350x1.1 = 385 Kg

Water content = 140Kkg

So, water- cement ratio = 140/385 = 0.364

Fly ash at 30% total cementatious material content = 35-30% = 115kg

Cement (OPC) =385-115 =270kg

Saving of cement while using flyash = 350-270= 80kg

Fly ash beign utilized = 115kg

Proportion of volume of coarse aggregate and fine aggregate content

From table 3 of IS 1026:2009 ,volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone 1 ) for water- cement ratio =0.6

In present case the water - cement ratio is 0.4

Therefore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content .

As the water- cement ratio is lowered by 0.1 ,the proportion of volume of coarse aggregate is increased by 0.02( at the rate of +/- 0.01 for every +/- 0.05 change in water- cement ratio)

Hence the corrected value ofcoarse aggregate for the water-cemnt ratio = 0.64

( If coarse aggregate is not of angular type, then also the volume of coarse aggregate may be required to be increased suitably ,based on experience)

For pumpable concrete, these are reduced by 10 %

Volume of coarse aggregate = 0.64x0.9 = 0.576

Volume of fine aggregate = 1-0.576 =0.424

Mix calculations

Mix calculation per unit volume of concrete:

a. Volume of concrete = 1 m3.

b. Volume of cement = (Mass of cement / Specific gravity of cement ) x1/1000

= (270/3.15 )x1/1000 =0.086 m3

c. Volume of flyash = (Mass of flyash / Specific gravity of flyash )x1/1000

= (115/2.2) x1/1000 = 0.052m3

d. Volume of water = ( Mass of water / Specific gravity of water)x1/1000

= (140/1)x1/1000 =0.140 m3

e. Volume of chemical admixture = ( Mass of admixture / specific gravity of admixture)x1/1000

=( 7.6/1.14)x1/1000 =0.006 m3

f. Volume of aggregate ( Fine and coarse) = a-(b+c+d+e)

= 1-(0.086+0.052+0.140+0.006) =0.716 m3

g. Mass of coarse aggregate = fx Volume of coarse aggregate x Specific gravity of coarse aggregate x1000

= 0.716x0.576x2.74x1000 =1130kg

h. Mass of fine aggregate = fx Volume of fine aggregatex Specific gravity of fine aggreatex1000

= 0.716x0.424x2.74x1000= 831kg

Mix proportion

Cement = 270 kg

Fly ash = 115 kg

Water = 140kg

Fine aggregate = 831 kg

Coarse aggregate = 1130 kg

Chemical admixture = 7kg

Water- cement ratio = 0.364

Hence, Mix ratio 1: 2.15: 2.94

Remarks:

The slump shall be measured and the water content and dosage of admixyure shall be adjusted for achieving the required slump on trial . The mix proportion shall be reworked for the actual water content and checkedd for durability requirements.wo or more trials having variation of 10 % of water-cement ratio in above shall be carried out and a graph between three water -cement ratios and corresponding strengths shall be plotted to work out the mix proportions for the given target strength for feild trials .However durability shall be met.

Result : The mix design for M35 grade of concrete with flyash is 1: 2.15:2.94.

For M50 Mix Design

Aim : Mix design for M50 grade concrete

Stipulations for Concrete Mix Design

• Grade designation : M 50
• Type of cement : OPC 53 grade confirming to IS 8112
• Maximum nominal size of aggregate : 20 mm
• Minimum cement content : 360 kg/m³
• Maximum water-cement ratio : 0.35
• Workability : 50-75 mm (slump)
• Exposure condition : Extreme (for reinforced concrete)
• Method of concrete placing : Pumping
• Degree of supervision : Good
• Type of aggregate : Crushed angular aggregate
• Maximum cement content : 450 kg/m³
• Chemical admixture type : Super Plasticizer

Test Data for Materials

The following data are collected by performing standard tests in a laboratory.

Specific gravity of cement : 3.12

Specific gravity of Coarse Aggregate : 2.74

Specific gravity of Fine Aggregate : 2.56

Target Strength for Mix Proportioning

f_target = f_ck + 1.65 x s

f_target denotes the Target Average Compressive Strength at 28 days,

f_ck denotes the Characteristic Compressive Strength at 28 days,

‘s’ stands for Standard Deviation

According to the table 1 of IS-10262-2009,

Standard deviation, s = 5.0 N/mm²

Therefore, target strength = 50 + 1.65 x 5.0 = 58.25 N/mm²

Selection of Water/Cement Ratio:

Maximum water-cement ratio = 0.35 [From Table 5 of IS 456:2000 ]

Selection of Water Content

From Table 2 of IS 456:2000, maximum water content =186 litres (for 25 to 50 mm slump range) for 20 mm aggregate.

Estimated water content for 100 mm slump =186+(6/100) x 186 =197 litres.

(Note: If Super plasticizer is used, the water content can be reduced up to 20% and above.)

Based on trials with Super plasticizer water content reduction of 27% has been achieved,

Hence the arrived water content = 197 – [197 x (27/100)] = 143 litres.

Calculation of Cement Content

Water-cement ratio = 0.35

Cement content = 143/0.35 = 410 kg/m³

From Table 5 of IS 456:2000, minimum cement content for ‘Extreme exposure’ condition = 360 kg/m³

410 kg/m³ > 360 kg/m³, hence, O.K.

Proportion of Volume of Coarse Aggregate and Fine Aggregate Content

From Table 3 of IS 10262. 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.

In the present case, the water-cement ratio is 0.35. Therefore. the volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.10. the proportion of the volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in the water-cement ratio).

Therefore. the corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.35 = 0.65.

NOTE – In case the coarse aggregate is not angular one, then the volume of coarse aggregate may be increased by 10 percent based on experience.

For pumpable concrete, these values should be reduced by 10 percent.

Therefore, volume of coarse aggregate = 0.65 x 0.9 = 0.585.

Volume of fine aggregate content =1 – 0.585 =0.415

Mix Calculations

a) Volume of concrete = 1m³

b) Volume of cement = (Mass of Cement/ Its Specific Gravity ) X (1/1000)

= (410/3.12) X (1/1000)

= 0.131 m³

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

= (143/1) X (1/1000)

= 0.143 m³

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

= (8.2/1.145) X (1/1000)

= 0.007 m³

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

= 1 – (0.131 + 0.143+0.007)

= 0.719 m³

e) Mass of coarse aggregate = Volume of All Aggregate X Volume of Coarse Aggregate X Specific Gravity of Coarse Aggregate X 1000

= 0.719 x 0.585 x 2.74 x 1000

= 1152.48 kg

f) Mass of fine aggregate = Volume of all aggregate X volume of fine aggregate X Specific gravity of fine aggregate X 1000

= 0.719 x 0.415 x 2.56 x 1000

= 763.86 kg

Result :

Concrete Mix Proportions

• Cement = 410 kg/m³
• Water = 143 kg/m³
• Super plasticizer = 7 kg/m³
• Fine aggregates = 763.86 kg/m³
• Coarse aggregate = 1152.48 kg/m³
• W/c = 0.35