1) What is M20 grade of concrete?
Ans:
2) What is workability of concrete?
Ans:
Workability mean’s: the easy of placing and compaction of concrete.
3) What is Bleeding in concrete?
Ans:
In bleeding, water comes out to the surface of the concrete, due to maximum
compaction or vibration.
4) What is the Unit Weight of concrete?
Ans:
The unit weight of concrete
depends on the
type of aggregates and amount of voids.
As per IS 456-2000, Unit weight of P.C.C is
24KN/m3 (2400 Kg/Cum) and R.C.C is 25KN/m3 (2500 Kg/Cum).
5) What
are the types of a slump?
Ans: Type of Slump:
1.
True Slump: The concrete mass after the test
when slumps evenly all around without disintegration is called the true
slump
2.
Shear Slump: When one-half of the concrete mass
slides down the other are called the shear slump. This type of slump
is obtained in a lean concrete mix.
3.
Collapse Slump: when the sample is collapsed
due to adding excessive water, it is known as collapse slump.
4.
Zero Slump: For very stiff or dry mixes it does not show any changes of the slump after
removing the slump cone.
6) What
is the initial and final setting time of ideal cement
mix?
Ans: Initial setting time for ideal cement mix is around 30 minutes for almost all kind of cements. For masonry cement it can be 90 minutes. Final setting time of ideal cement mix should be 10 hours at max. For masonry cement it shouldn't exceed 24 hours.
7) What
is the difference between OPC and PPC?
Ans:
OPC (Ordinary Portland Cement)
|
PPC (Portland Pozzolana Cement)
|
PPC is variation of OPC i.e. when Pozzolana
materials namely fly ash, volcanic ash, are added to OPC in ratio of 15% to
35% by weight.
|
PPC is variation of OPC i.e. when Pozzolana
materials namely fly ash, volcanic ash, are added to OPC in ratio of 15% to
35% by weight.
|
OPC is Available in 3-grades namely 33,43,53.
|
Whereas PPC available in only one grade which matches strength of Grade 33
of OPC after curing
|
OPC is costlier compare to other cement.
|
PPC is Cheaper than OPC since it includes
natural and industrial wastes.
|
8) Which cement is used in heavy structures OPC or PPC and why?
Ans:
I) Heat of Hydration is fast and it gains
95% early strength in curing of 7 days
2) It have good durability but it got its strength at max at a point of time.
3) OPC is always good for construction of bridges, flyovers.
4) Here heat of hydration is slow and it gains 75% of strength in curing of 7 days.
5) Durability of PPC is more it become stronger as it becomes older.
6) It is Highly resistant to sulphate attacks hence its prime use is in construction of dams, foundations, buildings near sea shore. reservoirs, marine construction.
2) It have good durability but it got its strength at max at a point of time.
3) OPC is always good for construction of bridges, flyovers.
4) Here heat of hydration is slow and it gains 75% of strength in curing of 7 days.
5) Durability of PPC is more it become stronger as it becomes older.
6) It is Highly resistant to sulphate attacks hence its prime use is in construction of dams, foundations, buildings near sea shore. reservoirs, marine construction.
9) What is Height
of drop of concrete?
Ans: Concrete should be poured from a height of 0.9m to 1.5m. To prevent the
making of voids inside the Concrete casting.
10) What
is the Unit weight of cement mortar?
Ans: Cement mortar - 2000 kg/ m.
11) What is the curing time in days for different
type of cement?
Ans:
Super Sulphate cement =7 days
Ordinary Portland cement 10 days
Cement having admixture = 14 days.
Ordinary Portland cement 10 days
Cement having admixture = 14 days.
12) How much Volume of cement Bag (50 Kg)?
Ans:
0.0347M3 or 1.23 CFT.
13) What is
mix ratio of different grades of concrete?
Ans: M5 = 1:5:10
M7.5 = 1:4:8
M10 = 1:3:6
M15 = 1:2:4
M20 = 1:1.5:3
M25 = 1:1:2
M30 = 1:1:1.
14) From where we obtained Standard sand in India?
Ans: Ennore
=Madras (Chennai) (T.N) used for testing.
15) Write Test and their purposes?
Ans:
Test
|
Purpose
|
Slump
test
|
Workability
of concrete
|
Rebound
hammer test
|
Strength
of concrete at site
|
Vicat
apparatus test
|
Initial
and final setting time of cement
|
LE-
Charelier –apparatus test
|
Soundness
of cement
|
Casagrande
apparatus test
|
Liquid
limit of soil
|
16) What are the values of Slump for different types of
construction?
Ans:
Value
in (mm)
|
Workability
|
Type
of construction
|
0-25
mm
|
Very
low workability
|
Road
making, where power operating machine are used for vibration &
compaction.
|
25-50
mm
|
Low
workability
|
Less
reinforced sections, Pavements, Slabs, Beams, Strap footing.
|
50-100
mm
|
Medium
workability
|
Heavy
reinforced structures Columns, Rafts, Beams, Slabs, Walls.
|
100-175
mm
|
High
workability
|
In-situ
piling & very heavy reinforced structures like Dams etc.
|
17) How
many days we can used cement from the date of manufacturing?
Or
What is the Expiry date of cement?
Ans: 3 months.
18)
What is the function of sand in mortar?
Ans:
Provide core strength, i.e. compressive and tensile strength & Increase density.