MIX DESIGN OF CONCRETE, GRADE M-25.

Name Of Work: Construction of Stadium with provision of concrete gallery, Roofing, Drain,

various rooms, sanitary and pipeline, flooring etc. at Railway Sports Complex at Kanchrapara.

Tender No:- 27 of 2011-12.

LOA No:- CAO/CON/WT/8760, Dtd.16.12.2011.

Concrete Mix- Design M-25

DESIGN PARAMETERS:

Grade Designation : M-25.

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

Maximum nominal size of aggregate : 20mm.

Minimum cement content : 385 Kg/cu.m.

Maximum water-cement ratio : 0.6

Workability : 75mm.

Exposure condition : Moderate.

Method of concrete placing : Manually.

Degree of supervision : Good.

Type of aggregate : Crushed angular aggtegate.

Maximum cement content : 450 kg/cu.m.

Test Data For Materials:

Cement Used : OPC-43 grade conforming IS 8112.

Specific gravity of cement : 3.15

Specific gravity of coarse aggregate : 2.89

Specific gravity of fine aggregate : 2.64

Water absorption:

Coarse aggregate : 0.5 percent.

Fine aggregate : 1.0 percent.

Free ( surface ) moisture:

Coarse aggregate : Nil.

Fine aggregate : Nil.

Page -2

Sieve analysis: Coarse aggregate

Sl.No.

IS Sieve Designation Passing % Limits Passing %

1. 40mm 100 1002. 20mm 97.6 95-1003. 4.75mm 32.5 30-504. 600microns 13.5 10-355. 150microns 0.8 0-6

Fine Aggregate: Conforming to grading Zone III of Table 4 of IS 383.

TARGET STRENGTH FOR MIX PROPORTIONING:

f’ck=fck + 1.65 s.

where

f’ck= target average compressive strength at 28 days,

fck= characteristic compressive strength at 28 days, and

s= standard deviation.

From Table 1 standard deviation, s= 4N/mm2.

Therefore, target strength= 25+1.65x4=31.6 N/mm2.

SELECTION OF WATER- CEMENT RATIO:

From Table 5 of IS 456, maximum water-cement ratio=0.42.

Based on experience, adopt water-cement ratio as 0.40.

0.40 < 0.42, hence (O.K.)

Volumetric adjustment of water content and sand percentage in different conditions as per table 44 of S.P.23

Change in condition Adjustment requiredWater content percentage Percentage sand in total

aggregate.For decreasing water cement ratio (0.6 to 0.42 ) that is 0.18

0 -3.6

For increasing compacting factor (0.8 to 0.85) that is 0.05

+1.5 0

For sand conforming to grading Zone III

0 -1.5

Total +1.5 -5.1

Therefore, Required sand content as Percentage of total aggregate by absolute

volume(35-5.1)=29.9%

Page-3

SELECTION OF WATER CONTENT:

Required water content = 186+1.5%=188.79kg/cu.m.

CALCULATION OF CEMENT CONTENT:

Water- cement ratio = 0.42

Cement- content = 188.79/0.42=449.50kg./cu.m. say, 450kg/cu.m.

From Table 5 of IS 456, minimum cement content for moderate exposure condition=320 kg/cu.m.

450kg/cu.m.> 320kg/cu.m, hence, O.K.

Determination of quantity fine and coarse aggregate:

From table 41, for specified maximum size of aggregate of 20mm, the amount of entrapped air in wet concrete is 2%.

FOR COARSE AGGREGATE:

V= [W+(C/Sc) + (Ca/Sca)/(1-P) ]x1/1000.

V= 1 cubic meter-2% of volume due to entrapped air in the concrete=0.98 cu.m.

W= 188.79kg. C= 450kg. Sc=3.15, P=29.9/100=0.299, Sca=2.89, Sfa=2.64.

Therefore, 980=[188.79+(450/3.15)+(Ca/2.89)/(1-0.299)]

Ca=1311.94kg/cu.m.

FOR FINE AGGREGATE:

V=[W+(C/Sc) + (fa/Sfa)/P]x1/1000

980=[188.79+(450/3.15)+(fa/2.64)/0.299]

fa=511.67kg./cu.m.

[ SUGGESTED MIX ( BY WEIGHT) FOR CONCRETE M-25 ]

Cement used

Mix Designation

Aggregate Max. size(mm)

Suggested Aggregate Mix Ratio.

Water Content(kg/cu.m)

Cement Content(kg/cu.m)

Water cement Ratio

Ordinary Portland 43grade cement

M-25 20 1:1.02:2.63 188.79 450 0.42

Designed Mix Proportion: 50kg.(one bag) ( For sample-I)

Cement= 50kg, Sand=51kg, 20mm=131.5KG. Water=22.0kg.

Page-4

Sample II

Cement used

Mix Designation

Aggregate Max. size(mm)

Suggested Aggregate Mix Ratio.

Water Content(kg/cu.m)

Cement Content(kg/cu.m)

Water cement Ratio

Ordinary Portland 43grade cement

M-25 20 1:1.09:2.85 188.79 460.46 0.41

Designed Mix Proportion: 50kg.(one bag) ( For sample-II)

Cement= 50kg, Sand=54.5kg, 20mm=142.5kg. Water=20.5kg.

Sample III

Cement used

Mix Designation

Aggregate Max. size(mm)

Suggested Aggregate Mix Ratio.

Water Content(kg/cu.m)

Cement Content(kg/cu.m)

Water cement Ratio

Ordinary Portland 43grade cement

M-25 20 1:1.22:3.10 188.79 425 0.44

Designed Mix Proportion: 50kg.(one bag) ( For sample-III)

Cement= 50kg, Sand=518.5kg, 20mm=155kg. Water=22.0kg.

THE END