# 20 Things a Civil Engineer Should Know

## Basic things or knowledge a civil engineer should know.

M5 = 1:4:8

M10= 1:3:6

M15= 1:2:4

M20= 1:1.5:3

M25= 1:1:2

### CLEAR COVER TO MAIN REINFORCEMENT:

1.FOOTINGS : 50 mm

2.RAFT FOUNDATION.TOP : 50 mm

3.RAFT FOUNDATION.BOTTOM/SIDES : 75 mm

4.STRAP BEAM : 50 mm

6.COLUMN : 40 mm

7.SHEAR WALL : 25 mm

8.BEAMS : 25 mm

9.SLABS : 15 mm

10.FLAT SLAB : 20 mm

11.STAIRCASE : 15 mm

12.RET. WALL : 20/ 25 mm on earth

13.WATER RETAINING STRUCTURES : 20/30 mm

### WEIGHT OF ROD PER METER LENGTH:

DIA WEIGHT PER METER

6mm = 0.222Kg

8mm = 0.395 Kg

10mm = 0.616 Kg

12mm = 0.888 Kg

16mm = 1.578 Kg

20mm = 2.466 Kg

25mm = 3.853 Kg

32mm = 6.313 Kg

40mm = 9.865 Kg

1bag cement-50kg

1feet-0.3048m

1m-3.28ft

1sq.m-10.76sq.f ¬t

1cu.m-35.28cu.f ¬t

1acre-43560sq.f ¬t

1cent-435.6sq.f ¬t

1hectare-2.47ac ¬re

1acre-100cent-4 ¬046.724sq.m

1ground-2400sq. ¬ft

1unit-100cu.ft- ¬2.83cu.m 1square-100sq.f ¬t

1 M LENGTH STEEL ROD I ITS VOLUME

V=(Pi/4)*Dia x DiaX L=(3.14/4)x D x D X 1 (for

1m length) Density of Steel=7850 kg/ cub meter

Weight = Volume x Density=(3.14/4)x D x D X

1×7850 (if D is in mm ) So = ((3.14/4)x D x D X

1×7850)/(1000×1000) = Dodd/162.27

### DESIGN MIX:

M10 ( 1 : 3.92 : 5.62)

Cement : 210 Kg/ M 3

20 mm Jelly : 708 Kg/ M 3

12.5 mm Jelly : 472 Kg/ M 3

River sand : 823 Kg/ M 3

Total water : 185 Kg/ M 3

Fresh concrete density: 2398 Kg/M 3

M20 ( 1 : 2.48 : 3.55)

Cement : 320 Kg/ M 3

20 mm Jelly : 683 Kg/ M 3

12.5 mm Jelly : 455 Kg/ M 3

River sand : 794 Kg/ M 3

Total water : 176 Kg/ M 3

Fresh concrete density: 2430 Kg/ M 3

M25 ( 1 : 2.28 : 3.27)

Cement : 340 Kg/ M 3

20 mm Jelly : 667 Kg/ M 3

12.5 mm Jelly : 445 Kg/ M 3

River sand : 775 Kg/ M 3

Total water : 185 Kg/ M 3

Fresh concrete density: 2414 Kg/ M 3

Note: sand 775 + 2% moisture, Water185 -20.5 =

164 Liters,

M30 ( 1 : 2 : 2.87)

Cement : 380 Kg/ M 3

20 mm Jelly : 654 Kg/ M 3

12.5 mm Jelly : 436 Kg/ M 3

River sand : 760 Kg/ M 3

Total water : 187 Kg/ M 3

Fresh concrete density: 2420 Kg/ M 3

Note: Sand = 760 Kg with 2% moisture

(170.80+15.20)

M35 ( 1 : 1.79 : 2.57)

Cement : 410 Kg/ M 3

20 mm Jelly : 632 Kg/ M 3

12.5 mm Jelly : 421 Kg/ M 3

River sand : 735 Kg/ M 3

Total water : 200 Kg/ M 3

Fresh concrete density: 2400 Kg/ M 3

Note: sand = 735 + 2%, Water = 200- 14.7 =

185.30,

M40 ( 1 : 1.67 : 2.39)

Cement : 430 Kg/ M 3

20 mm Jelly : 618 Kg/ M 3

12.5 mm Jelly : 412 Kg/ M 3

River sand : 718 Kg/ M 3

Water Cement ratio : 0.43

Note: Sand = 718 + Bulk age 1%

M45 ( 1 : 1.58 : 2.26)

Cement : 450 Kg/ M 3

20 mm Jelly : 626 Kg/ M 3

12.5 mm Jelly : 417 Kg/ M 3

River sand : 727 Kg/ M 3 + Bulk age 1%

Water Cement ratio : 0.43

M50 ( 1 : 1.44 : 2.23)

Cement : 450 Kg/ M 3

20 mm Jelly : 590 Kg/ M 3

12.5 mm Jelly : 483 Kg/ M 3

River sand : 689 Kg/ M 3 + Bulk age 12%

Water Cement ratio : 0.36 (188 Kg)

Micro silica : 30 Kg

Super flow 6.7% of cement

1 cubic meter contains 500 bricks

The Standard size of the 1st class brick is 190mm

x 90mm x

90mm and motor joint should be 10mm thick

So brick with motor=200 x 100 x 100.

Volume of 1st class brick = 0.19 x 0.09 X 0.09 =

0.001539

cu.m

Volume of 1st class brick with motor =0.2 x 0.1 x

0.1=0.002

cu.m

No. on bricks per 1cu.m= 1/volume of1st class

brick with

motor

=1/0.002

= 500 no’s of bricks

#### STANDARD CONVERSION FACTORS

INCH = 25.4 MILLIMETRE

FOOT = 0.3048 METRE

YARD = 0.9144 METRE

MILE = 1.6093 KILOMETER

ACRE = 0.4047 HECTARE

POUND = 0.4536 KILOGRAM

DEGREE FARENHEIT X 5/9 – 32 = DEGREE

CELSIUS

MILLIMETRE= 0.0394 INCH

METRE = 3.2808FOOT

METRE = 1.0936YARD

A rope having length 100cm.You can form any

shape using this rope (Example: Triangle,

Rectangle, etc.,). Which shape will covers

maximum area

1 Newton = o.101971 kg

1 mm2 = 0.01 cm2

1 cm2 = 100 mm2

1 mm2 = 20 N

100 mm2 = 2000N

1 cm2 = 2000N

2000 N = 203.942 kg

So 20 N/ mm2 = 203.942 kg / cm2

RATIO IS 1:1.5:3

then volume is 1+1.5+3=5.5

Some Civil Engineering Field Questions Answers

What is the FM(Fineness Modulus)?

Answer: FM( Fineness Modulus is an empirical figure obtained by summing up the cumulative percentage of materials retained on each of the sieve excluding 0.075 mm sieve and dividing the sum by 100.

• What is the FM value for Sand and Stone?

Answer: For sand the FM value varies from 2.5-4.0 and for stone FM value varies between 6.5 8.0.

• What is LAA?

Answer: LAA means Los Angeles Abrasion Test which represents the strength of stone to withstand with the abrasion that occurs during the life cycle of the stone.

If the W/C cement ration is less what will be the strength of concrete?

Answer: If W/C ratio decreases concrete strength will rise up.

• What is Compaction?

Answer: Compaction is a process by which the volume of the soil decreases by using any mechanical devices and by pulling out the available air in the soil.

• What is Consolidation?

Consolidation is a natural process by which the soil volume reduces and it becomes in compacted form by pulling out the water and decreasing the pore spaces between the particles

Say name of the compaction test methods?

Answer : 1. Standard Proctor Test 2. Modified Proctor Test

• How can you measure workability of the concrete on field?

Answer: Workability can be measured by slump test.

• What is the normal slump value for concrete?

Answer: Normally slump vale varies between 50 mm-100 mm for normal concrete.

• What is the dimensions of Slump Mold?

Answer: Height=12 inch, Top width=4 inch and bottom width= 8 inch

What are the types of slump?

Answer: Slump in concrete are of three types:

True slump

Shear slump

Collapse slump

• What is Dewatering?

Answer: Dewatering means removing the water from any specified construction place so that the construction work can run smoothly.

• What is Hydration?

Answer: Hydration is the reaction between cement and water.

• What test is done to measure the required compaction on field?

Answer: Compaction test by sand cone replacement method.

• Why do we use steel in concrete? why not other metals?

We use steel in concrete as the co-efficient of thermal expansion of concrete and steel is almost same and steel has very good strength to withstand with the tensile loads.

• How do designers design the compressed member when there is no use of steel?

Answer: Then it was designed to produce very small to no tensile stress in the section so that the section will be very large.

• What is Geo-textile?

Answer: Geo-textile is a permeable synthetic fabric that is produced from polyester, ploy ethylene to separate the soil or to filter the materials, or to protect the banks from being eroded.

• What types of soil is sand?