1.STIPULATIONS FOR PROPORTIONING
a) Grade designation : M35 RCC (Pile)
b) Type of cement :53 grade Ordinary Portland Cement conforming IS 12269
c) Maximum nominal size of coarse aggregate : 20 mm
d) Minimum amount of cement : 400 kg/m³ as IS 2911-Part 1/Sec 2 & IRC 78-2014.
e) Maximum water-cement ratio : 0.40 as per IRC 78 -2014 ,Cl 709.1.9
f) Workability : 150-200 mm slump as per IRC 78-2014 , Cl 709.1.9
g) Exposure condition : Moderate (For Reinforced Concrete)
h) Method of concrete placing : Trieme
j) Degree of supervision : Good
k) Type of aggregate : Crushed Angular Aggregates
l) Chemical admixture type : Super Plasticizer Normet
2.TEST DATA FOR MATERIALS
a) Cement used : Sagar 53 grade Ordinary Portland cement conforming IS 12269
b) Specific gravity of cement : 3.14
c) Chemical admixture : Super Plasticizer conforming to IS 9103
d) Specific gravity of
1) Coarse aggregate 20 mm : 2.799
2) Coarse aggregate 10 mm: 2.789
Combined Specific Gravity of aggregate ( 20 mm-45% & 10 mm 55% )=2.792
2) Fine aggregate : 2.517
e) Water absorption:
1) Coarse aggregate 20 mm : 0.41 %
2) Coarse aggregate 10 mm : 0.59
3) Fine aggregate : 1.87 %
f) Aggregate Impact Value : 20.52
g) Combined Flakiness & Elongation Index : 27.57 %
h) Sieve analysis:
1) Coarse aggregate: Conforming to all in aggregates of Table 2 of IS 383
2) Fine aggregate : Conforming to Grading Zone III of Table 4 of IS 383
3 TARGET STRENGTH FOR MIX PROPORTIONING
f’ck =fck + 1.65 s where
f’ck = average target compressive strength of concrete at 28 days,
fck = characteristics compressive strength of concrete at 28 days,
S = standard deviation.From table 1 of IS 456 & IS 10262 assumed Standard Deviation, s = 5 N/mm² ; therefore target strength of concrete = 35 + 1.65 x 5 = 43.25 N/mm². Can adopt this value while doing the concrete mix design those who are working other than highway project.
But as per MORT&H Table 1700.5 required target mean compressive strength = 35 + 12 = 47.00 N/mm² where 12 is the current margin. Adopt this value those who are working in highway project.
4 SELECTION OF WATER•CEMENT RATIO
Based on the trial , adopted water cement ration 0.40
From the Table 5 of IS 456 maximum Water Cement Ratio for moderate condition is 0.50
As per Section 709.1.9 of IRC 78, maximum water cement ratio is 0.40
so 0.40 is satisfying all codal provision whether it is IS 456 or MORT&H
0.40 < 0.50 = 0.40 hence ok.
5 SELECTION OF WATER CONTENT
From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 litre (for 25 to 50 mm slump range)
but for an increase by about 3 percent for every additional 25 mm slump so here estimated water content for 175 mm slump
= 186+(15/100) x 186
= 213.9 or 214 liter.
Based on trials with Super plasticizer water content reduction of 21.50% has been achieved.How it comes , see below calculation:
Water requirement , if we intended to keep cement 420 kg for & w/c ratio 0.40 for our concrete mix design calculated water will be 168.0 liter , so required reduction in water when using superplaticizer = 100 – (168/214 x 100) = 21.50 %.
Net required water = 214 – (214 x 21.50) % = 214 –46.1 = 167.99 liter say 168 liter.
Note :For 75 mm slump increase 3% , for 100 mm increase 6% , increase 9 % for 125 mm slump, increase 12 % for 150 mm slump & increase 15 % for 175 mm slump
6 CALCULATION OF CEMENT CONTENT
As discuss earlier adopted based on trial w/c Ratio = 0.40
Cement Content = 168.0/0.40 = 420 kg/m³
As per IS 2911-Part 1/Sec 2 minimum cement content for tremie concrete is 400 kg/m³.
(As per Section 709.1.9 of IRC 78 – 2014 minimum cement content 400 kg & maximum water cement ratio is 0.40 specified)
but we had taken 420 kg/m³ > 400 kg/m³ hence ok.
7 PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT
As per table number 3 of IS 10262:2009 volume of coarse aggregate for 20 mm nominal size aggregate and fine aggregate (Zone III) for having water-cement ratio of 0.50 =0.64 (a)
In the present case water-cement ratio is 0.40. Therefore. 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 volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio). As the water-cement ratio is lower by 0.10. The proportion of volume of coarse aggregate is increased by
= (0.10/0.05) = 2.0 times of 0.01 so 0.01 x 2.0= 0.020 (b)
= a+b = 0.64 + 0.020 =0.66
(at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio).
Therefore, corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.40 = 0.66
NOTE – In case the coarse aggregate is not angular one, then also volume of coarse
aggregate may be required to be increased suitably based on experience & Site conditions.
For pumpable concrete these values should be reduced up to 10%. Therefore, volume of coarse aggregate =0.66 x 0.9 =0.59.
Volume of fine aggregate content = 1 – 0.59 = 0.41.
8 MIX CALCULATIONS
The mix calculations per unit volume of concrete shall be as follows:
a) Volume of concrete = 1 m³
b) Volume of cement = [Mass of cement] / {[Specific Gravity of Cement] x 1000}
= 420/{3.15 x 1000} = 0.133 m³
c) Volume of water = [Mass of water] / {[Specific Gravity of water] x 1000}
= 168.0/{1 x 1000} = 0.168 m³
d) Base on trial we had kept admixture 1.0 percentage by weight of cement
Volume of admixture = [Mass of admixture ] / {[Specific Gravity of admixture ] x 1000}
= 4.2 /{1.090 x 1000}
= 0.0039 m³
e) Volume of all in aggregate = [a-(b+c+d)]
= [1-(0.133+0.168+0.0039)]
= 0.695 m³
f) Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of coarse Aggregate x 1000
= 0.695 x 0.59 x 2.792 x 1000
= 1144.86 kg/m³
g) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000
= 0.695 x 0.41 x 2.517 x 1000
= 724.22 kg/m³
9 MIX PROPORTIONS
Cement = 420 kg/m³
Water = 168.0 l/m³
Fine aggregate = 724.22 kg/m³
Coarse aggregate 20 mm = 1144.86 x 45 %= 515.19 kg/m³
Coarse aggregate 10 mm = 1144.86 x 55%= 629.67 kg/m³
Chemical admixture = 4.2 kg/m³
Water-cement ratio = 0.40
Calculation :
1. Aggregate 20 mm= 515.99/ (1+(0.41/100)} = 514.0 kg
2. Aggregate 10 mm = 629.67/ (1+(0.59/100)} = 725 kg
3. Sand = 724.44/ (1+(1.87/100)} = 626.0 kg
3. Water = 2460-420-711-514-626 = 189
NOTE
1.Do the trial in dry position as in practical in batching plant you can cot use aggregate in SSD condition.
2.Batch for trial is given in dry position.
3.Do the number of rials with variation of ± 10 percent of water-cement ratio & different cement content
4.Do the surface moisture correction whenever required.
