Important Tips for civil Engineers Part ( 2 )
Thumb rule for Design Mix :
M 10 ( 1 : 3 : 5 )
Cement : 210 Kg/ M3
20 mm Jelly : 708 Kg/ M3
12.5 mm Jelly : 472 Kg/ M3
River sand : 823 Kg/ M3
Total water : 185 Kg/ M3
Fresh concrete density: 2398 Kg/M3
M 20 ( 1 : 2 : 3)
Cement : 320 Kg/ M3
20 mm Jelly : 683 Kg/ M3
12.5 mm Jelly : 455 Kg/ M3
River sand : 794 Kg/ M3
Total water : 176 Kg/ M3
Admixture : 0.7%
Fresh concrete density: 2430 Kg/ M3
M 25 ( 1 : 2 : 3)
Cement : 340 Kg/ M3
20 mm Jelly : 667 Kg/ M3
12.5 mm Jelly : 445 Kg/ M3
River sand : 775 Kg/ M3
Total water : 185 Kg/ M3
Admixture : 0.6%
Fresh concrete density: 2414 Kg/ M3
Note: sand 775 + 2% moisture, Water 185 -20.5 = 164 Liters,
Admixture = 0.5% is 100ml
M 30 ( 1 : 2 : 2.87)
Cement : 380 Kg/ M3
20 mm Jelly : 654 Kg/ M3
12.5 mm Jelly : 436 Kg/ M3
River sand : 760 Kg/ M3
Total water : 187 Kg/ M3
Admixture : 0.7%
Fresh concrete density: 2420 Kg/ M3
Note: Sand = 760 Kg with 2% moisture (170.80+15.20)
M 35 ( 1 : 1 : 2)
Cement : 410 Kg/ M3
20 mm Jelly : 632 Kg/ M3
12.5 mm Jelly : 421 Kg/ M3
River sand : 735 Kg/ M3
Total water : 200 Kg/ M3
Admixture : 0.7%
Fresh concrete density: 2400 Kg/ M3
Note: sand = 735 + 2%, Water = 200- 14.7 = 185.30,
Admixture = 0.7%
M 40 ( 1 : 1.6 : 2.3 )
Cement : 430 Kg/ M3
20 mm Jelly : 618 Kg/ M3
12.5 mm Jelly : 412 Kg/ M3
River sand : 718 Kg/ M3
Water Cement ratio : 0.43
Admixture : 0.7%
Note: Sand = 718 + Bulkage 1%
M 45 ( 1 : 1.5 : 2.2)
Cement : 450 Kg/ M3
20 mm Jelly : 626 Kg/ M3
12.5 mm Jelly : 417 Kg/ M3
River sand : 727 Kg/ M3+ Bulkage 1%
Water Cement ratio : 0.43
Admixture : 0.7%
M 50 ( 1 : 1.44 : 2.23)
Cement : 450 Kg/ M3
20 mm Jelly : 590 Kg/ M3
12.5 mm Jelly : 483 Kg/ M3
River sand : 689 Kg/ M3 + Bulkage 12%
Water Cement ratio : 0.36 (188 Kg)
Admixture : 1.20%3
Micro silica : 30 Kg
Super flow 6.7% of cement
Slump IS 456
Lightly reinforced 25 – 75 mm
Heavily reinforced 75 – 100 mm
Trench fill (insitu & Tremie) 100 – 150 mm
(For Termie vibrator not required)
TOLERANCE :–
Form work :- In C/S for columns & Beams deviation is = + 12 mm more (or) – 6 mm less in size
In footing plan = + 50 mm more (or) – 12 mm less size
In depth = + 0.05 D (specified thickness).
Reinforcement :- For effective depth D < 200 mm = + 10 mm
For effective depth D > 200 mm = + 15 mm
For Cover to reinforcement = + 10 mm
Maximum free fall of concrete = 1.50 m height.
TOLERANCE ON DIA IN LENGTH:-
0-25mm = + 0.5 %
25-35mm = + 0.6 %
35-50mm = + 0.8 %
TOLERANCE ON WEIGHT PER METRE:–
0-10mm = +7%
10-16mm = + 5%
16 and above = + 3%
TOLERANCE FOR CUTTING LENGTH :-
A) When the specified length is not given = + 75mm (or) – 25 mm
B) When the min. length is specified = + 50 mm (or) – 0 mm