Interview Question's
What are the steps involved in the concreting
process, explain?
The major steps involved in the process of
concreting are as follows:
1. Batching: The process of measurement of the
different materials for the making of concrete is known as batching. batching
is usually done in two ways: volume batching and weight batching. In case of
volume batching the measurement is done in the form of volume whereas in the
case of weight batching it is done by the weight.
2. Mixing: In order to create good concrete, the
mixing of the materials should be first done in dry condition and after it wet
condition. The two general methods of mixing are: hand mixing and machine
mixing.
3. Transportation and placing of concrete: Once the
concrete mixture is created it must be transported to its final location. The
concrete is placed on form works and should always be dropped on its final
location as closely as possible.
4. Compaction of concrete: When concrete is placed
it can have air bubbles entrapped in it which can lead to the reduction of the
strength by 30%. In order to reduce the air bubbles the process of compaction
is performed. Compaction is generally performed in two ways: by hand or by the
use of vibrators.
Describe briefly the various methods of concrete
curing.
Curing is the process of maintaining the
moisture and temperature conditions for freshly deployed concrete. This is done
for small duration of time to allow the hardening of concrete. The methods that
are involved in saving the shrinkage of the concrete includes:
(a) Spraying of water: on walls, and columns can
be cured by sprinkling water.
(b) Wet covering of surface: can be cured by
using the surface with wet gunny bags or straw
(c) Ponding: the horizontal surfaces including
the slab and floors can be cured by stagnating the water.
(d) Steam curing: of pre-fabricated concrete
units steam can be cured by passing it over the units that are under closed
chambers. It allows faster curing process and results in faster recovery.
(e) Application of curing compounds: compounds
having calcium chloride can be applied on curing surface. This keeps the
surface wet for a very long time.
What do you understand by “preset” during the
installation process of bridge bearings?
During the installation of bridge bearings the
size of the upper plates is reduced to save the material costs. This process is
known as preset. Generally the upper bearing plate comprises of the following
components:
1. Length of bearing
2. 2 x irreversible movement.
3. 2 x reversible movement. The bearing
initially is placed right in the middle point of the upper bearing plate. No
directional effects of irreversible movement is considered. But since the
irreversible movement usually takes place in one direction only the displaced
direction is placed away from the midpoint. In such cases the length of the
upper plate is equal to the length of the length of the bearing + irreversible
movement + 2 x reversible movement.
Why are steel plates inserted inside bearings in
elastomeric bearings?
In order to make a elastomeric bearing act/
function as a soft spring it should be made to allow it to bulge laterally and
also the stiffness compression can be increased by simply increasing the
limiting amount of the lateral bulging. In many cases in order to increase the
compression stiffness of the bearing the usage of metal plates is made. Once
steel plates are included in the bearings the freedom of the bulge is
restricted dramatically, also the deflection of the bearing is reduced as
compared to a bearing without the presence of steel plates. The tensile
stresses of the bearings are induced into the steel plates. But the presence of
the metal plates does not affect the shear stiffness of the bearings.
What reinforcements are used in the process of
prestressing?
The major types of reinforcements used in
prestressing are:
Spalling Reinforcement: The spalling stresses leads to stress behind
the loaded area of the anchor blocks. This results in the breaking off of the
surface concrete. The most likely causes of such types of stresses are
Poisson`s effects strain interoperability or by the stress trajectory shapes.
Equilibrium reinforcements: This type of reinforcements are required where several anchorages exist where the prestressing loads are applied in a sequential manner.
Bursting
Reinforcements: These kinds of stresses
occur in cases where the stress trajectories are concave towards the line of
action of load. In order to reduce such stresses reinforcements in the form of
bursting is required.
What is the basic difference between QA and QC?
Quality Assurance is basically deals with defect
prevention and Quality control deals with defect identification.
No comments:
Post a Comment