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Various beams react differently to the load acted on them, let us go through following 2 beams
- Simply Supported beams & Continuous beams
For simply supported beams,
Compression acts on the top side whereas tension acts on the bottom side.
- Cantilever Beams
Cantilever beams react differently than continuous beams, In Cantilever beams, compression acts on the bottom side where as tension acts on the top side
The Properties Of Concrete In Plastic Stage are:
Plastic stage of concrete is that stage where concrete can be transported easily, moulded or poured into any place
- Good Workability:
Workability is the most important property of concrete. It may be defined as ‘ The ease with which the concrete can be mixed, transported, placed and compacted. ‘ A workable concrete mix doesn’t results in bleeding or segregation.
- Freedom from segregation :
- Freedom from bleeding :
A good concrete should be free from bleeding. The appearance of Water, along with some particles of cement and very fine sand on the surface of freshly placed concrete is known as bleeding.
- Prevention from harshness :
The concrete mix which doesn’t give smooth surface with a certain amount of trowelling is known as harsh mix.
USEFUL TIPS FOR CIVIL ENGINEERING INTERVIEW
GRADE OF CONCRETE:
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:
Footings : 50 mm
Raft Foundation Top : 50 mm
Raft Foundation Bottom : 75 mm
Raft Foundation Side : 75 mm
Beam : 25 mm
Strap Beam : 50 mm
Column :40 mm
Slab : 15 mm
flat Slab : 20 mm
Staircase : 15 mm
Retaining Wall : 20 – 25 mm
Water Retaining Structures : 2 0- 30 mm
Maximum water absorption by bricks – 15%
Compressive strength of bricks – 3.5 N/mm2
Density Of Bricks- 1600-1920 Kg/m3
Minimum thickness of slab – 125 mm
Dimension tolerance for cubes – +2
Maximum free fall of concrete – 1.50 m
Lapping should not be used for the bars having larger dia than 36 mm.
Binding wire required for steel reinforcement – 8 kg per MT
3 samples should be taken for every 100 m2 in core cutting test.
Maximum chair spacing – 1 m.
Minimum dia should be used in dowels rod – 12 mm.
Hook for strriups (one side) – 9D
No. of strriups = (clear span/spanning) + 1
Length of main steel in cantilever anchorage – 69D.
Minimum no. of bars in square column – 4
Minimum no. of bars in circular column – 6
Minimum dia of main bars and distributors in the slab – 8 mm.
Maximum dia of main bars and distributors in the slab – 1/8 of slab thickness.
All reinforcement should be free from mill scales, loose rust, and coats of paints , oil or any other substances.
Initial setting time should not be less than 30 minutes.
Final setting time should not be greater than 10 hours.
REQUIRED CURING DAYS:
Super sulfate cement – 7 days
Ordinary portland cement – 10 days
Cement with minerals and admixtures – 14 days.
SLUMP VALUE (IS456):
Lightly reinforced concrete : 25 – 75 mm.
Heavily reinforced concrete : 75 – 100 mm.
Trench fill : 100 – 150 mm ( for in-situ & tremie).
1 – 5 m3 : 1 No.
6 – 15 m3 : 2 No..
16 – 30 m3 :3 No.
31 -50 m3 : 4 No.
Above 50 m3 : 4 + 1 no. of addition for each 50 m3.
Lets calculate the rate analysis for 5 CuM Brickwork
Standard size of brick = 9 cm X 9 cm X 19 cm
Size of brick with cement mortar on both sides = 10 cm X 10 cm X 20 cm
No of Bricks in 5 CuM = 5 / ( 0.1 X 0.1 X 0.2 ) = 2500 Bricks
Mortar Required for 1 Cum = 5 – (2500 X 0.09 X 0.09 X 0.19) = 1.153 CuM
Mortar volume increases for frog filling, brick bonding & wastage by 15 %
So the volume of wet mortar becomes = 1.153 + (1.153 X .15 ) = 1.325
for Dry volume of mortar mixing we will have to consider 1/3 rd of more of wet volume
Therefore Volume = 1.325 + ( 1.325 / 3 ) = 1.766 CuM
Considering the mortar ratio as 1:4
Cement Quantity = ( 1 X 1.766 ) / ( 1+4 ) = 0.353 CuM
Cement Quantity in Bags of 50 Kg = 0.353 / 0.035 = 10.08 Bags
Sand Quantity in CuM = (4 X 1.766) / (1+4) = 1.41 CuM
There are 2 Types of cover provided to reinforcement in Civil Engineering
Clear Cover is the length between outer end of reinforcement to outer edge of concrete.
2. Nominal Cover
Nominal cover is the length from center of reinforcement to outer edge of concrete.
- Stress– Force applied on a body per Unit area is called as stress.It can be denoted by Stress= Force/Area.
- Strain– When a body is subjected to tensile force, the body undergoes change in length.
Change in length of the body to the original length is known as Strain.
Strain = Change in Length / Original Length
- Modulus of Elasticity / Young’s Modulus
Modulus of elasticity is the ratio of stress to the strain induced in a body
Young’s modulus is denoted by E
E= Stress / Strain
Below are the Reasons why steel is used in RCC structure not some other Metals, Non-metals or Alloys
- It is cheap and Easily available
- It possesses very high Tensile strength & elasticity
- It develops good bond with concrete
- Coefficient of expansion(12.6 X 10^-6) of steel is nearly equal to the same of concrete (14 X 10^-6) which means concrete and steel expand and shrink with almost same volume change when exposed to heat or cold.
Have you ever been asked for density of Cement, Sand, Aggregates & Water along with density of concrete in an job interview ?
If not you were lucky because here are the densities of all
Density of Concrete – 2400 Kg/m3
Density of Cement – 1440 kg/m3
Density of Water – 1000 Kg/m3
Density of Dry Sand – 1600 Kg/m3
Density of Wet Sand – 1850 Kg/m3
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Density of 20mm Aggregate – 1600 Kg/m3
Density of 10 mm Aggregate – 1700 Kg/m3
Density of Fly Ash – 750 Kg/m3
What is Workability ?
Workability of concrete is the ease with which it can be mixed, transported & placed in position in homogeneous state.
Workability of concrete can be found out by performing following tests
- Slump Test
- K-Slump Tester
- Compacting Factor Test
- Flow Test
- Kelly ball test
- Vee Bee Consistometer Test
Links will be provided soon for the above tests **Stay tuned ©Civilmafia.in