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. 1. 2. 3. 4. 5.
IS Sieve Designation 40mm 20mm 4.75mm 600microns 150microns
Passing % 100 97.6 32.5 13.5 0.8
Limits Passing % 100 95-100 30-50 10-35 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. 2
From Table 1 standard deviation, s= 4N/mm . 2
Therefore, target strength= 25+1.65x4=31.6 N/mm .
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
For decreasing water cement ratio (0.6 to 0.42 ) that is 0.18 For increasing compacting factor (0.8 to 0.85) that is 0.05 For sand conforming to grading Zone III Total
Adjustment required Water content percentage 0
Percentage sand in total aggregate. -3.6
+1.5
0
0
-1.5
+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
Ordinary Portland 43grade cement
M-25
Aggregate Max. size(mm) 20
Suggested Aggregate Mix Ratio. 1:1.02:2.63
Water Content(kg/cu.m)
Cement Content(kg/cu.m)
188.79
450
Designed Mix Proportion: 50kg.(one bag) ( For sample-I)
Water cement Ratio 0.42
Cement= 50kg, Sand=51kg, 20mm=131.5KG. Water=22.0kg.
Page-4 Sample II Cement used
Mix Designation
Ordinary Portland 43grade cement
M-25
Aggregate Max. size(mm) 20
Suggested Aggregate Mix Ratio. 1:1.09:2.85
Water Content(kg/cu.m)
Cement Content(kg/cu.m)
188.79
460.46
Water cement Ratio 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
Ordinary Portland 43grade cement
M-25
Aggregate Max. size(mm) 20
Suggested Aggregate Mix Ratio. 1:1.22:3.10
Water Content(kg/cu.m)
Cement Content(kg/cu.m)
188.79
425
Designed Mix Proportion: 50kg.(one bag) ( For sample-III) Cement= 50kg, Sand=518.5kg, 20mm=155kg. Water=22.0kg.
THE END
Water cement Ratio 0.44
