Question { Mittal Steel, 131704 }

Grades of concrete

Answer

There are so many types of mixes design such as
M5,M10 Shall be used for PCC .but now a days M15 is
outdated for RCC construction,normally it can be used for
PCC work. As per latest INDIAN STANDARD CODES , the started
grade of concrete for RCC as M20.
For grade M20,M25 used for RCC structure.
After grade of M25 the mix design is prepared .depending
upon the type of structures higher grade of concrete is
used asM25,M30,M35,M40,M45,M50,M55,M60,M65,M70,M75,M80
etc.but in india the grade of concrete available upto M60
as per my knowledge, this is not perfect.

Question { Power Grid, 26365 }

what is mix design

Answer

The process of selecting suitable ingredients of concrete
and determining their relative amounts with the objective
of producing a concrete of the required, strength,
durability, and workability as economically as possible, is
termed the concrete mix design.
Requirements of concrete mix design

The requirements which form the basis of selection and
proportioning of mix ingredients are :

a ) The minimum compressive strength required from
structural consideration

b) The adequate workability necessary for full compaction
with the compacting equipment available.

c) Maximum water-cement ratio and/or maximum cement content
to give adequate durability for the particular site
conditions

d) Maximum cement content to avoid shrinkage cracking due
to temperature cycle in mass concrete.

Question { 72403 }

What is the difference between nominal mix and design mix?

Answer

Nominal mixes are those proportioned by the volume of the
main ingredients and usually written in order of the
ingredients thus Cement:Sand: Coarse aggregate (stone,
chippings). So a 1:3:6 is a nominal mix containing 1 volume
of cement, 3 volumes of sand and 6 volumes of coarse
aggregate.

Gauge boxes are generally used to batch the ingredients.
The problem with these types of mixes is that the quality
of the concrete is entirely dependant on the quality of the
materials. In other words, if you use the same gauge boxes
to weigh ingredients from different sources, you will most
likely have different concrete qualities.

Designed mixes on the other hand are specified as a grade
the producer of the concrete has to achieve usually in
terms of compressive strength but may include other
criteria (size of the stone, minimum amount of cement,
flexural strength, air content etc). So a grade 30 concrete
will be the same whether batched in Kansas City, Karachi,
Kingston-Upon-Hull or Kinshasa

Question { DLF, 32556 }

what does a civil engineer should know?

Answer

CIVIL ENGINEERING is one of the oldest and most extensive
branches of engineering. It focuses on aspects of public
works like transportation, water treatment, government
buildings, public facilities such as airports and train
stations, and other large scale projects which benefit the
public. A civil engineer must be able to design safe
structures which meet standard codes in the regions that
they are being built in. These structures must be designed
with maintenance, efficiency, and other economic concerns
in mind as well to ensure that they will endure through
years of use.

In terms of transportation, civil engineers build bridges,
tunnels, freeway interchanges, and other structures which
are designed to facilitate the smooth, even flow of traffic
while allowing for expansion and higher use rates. Water
treatment includes sewage plants, delivery systems for
fresh water, dams, and other facilities which handle both
fresh and waste water, while government buildings run the
gamut from police stations to city halls. A civil engineer
might also work on projects like a city power plant or a
major office building.

Pay for civil engineers tend to be reasonably high,
considering that these professionals are highly trained and
very skilled. Jobs in public service may not command as
much pay, but they may come with benefits and prominent
positions in the community, while private contractors can
woo civil engineers with very attractive benefits and
compensation packages. The position can also be dangerous,
depending on how much time a civil engineer spends in the
field, but it can also be very exciting, especially in
regions which are integrating cutting edge technology and
design techniques into their public works.

Question { Ramky, 17380 }

What is Bearing Capacity of Soil? How will you calculate
for a particular type of Soil?

Answer

Bearing capacity is the power of foundation soil to hold
the forces from the superstructure without undergoing shear
failure or excessive settlement. Foundation soil is that
portion of ground which is subjected to additional stresses
when foundation and superstructure are constructed on the
ground. The following are a few important terminologies
related to bearing capacity of soil.

Ultimate Bearing Capacity (qf) : It is the maximum pressure
that a foundation soil can withstand without undergoing
shear failure.

Net ultimate Bearing Capacity (qn) : It is the maximum
extra pressure (in addition to initial overburden pressure)
that a foundation soil can withstand without undergoing
shear failure.
qn = qf - qo
Here, qo represents the overburden pressure at foundation
level and is equal to үD for level ground without surcharge
where ү is the unit weight of soil and D is the depth to
foundation bottom from Ground Level.

Safe Bearing Capacity (qs) : It is the safe extra load the
foundation soil is subjected to in addition to initial
overburden pressure.

Here. F represents the factor of safety.

Allowable Bearing Pressure (qa) : It is the maximum
pressure the foundation soil is subjected to considering
both shear failure and settlement.

Question { 16905 }

what is specific gravity of soil?

Answer

Specific gravity is defined as the ratio of the unit weight
of soil solids to unit weight of water. The Specific
Gravity is needed for various calculations purposes in Soil
Mechanics, e.g. void ratio, density and unit weight.

For Sandy soil, i.e. soils mostly made of quartz, Specific
Gravity can be accurately estimated to be about 2.65,
whereas for silty and clayey soils, it may vary from 2.6 to
2.9.

Question { 38298 }

how many binding wire can be required for 1 metric tonne
steel?

Answer

commonly required the quantitity of binding wires are about
10 to 11 kgs is sufficient in common practice

Question { 8602 }

what is formwork in construction

Answer

Concrete formwork is the use of support structures and
moulds to create structures out of concrete which is poured
into the moulds.

There are many different types of formwork used in
construction, usually differing according to what the
building requirements and challenges are. Formwork is used
by creating moulds out of wood, steel, aluminium or
prefabricated forms into which the concrete is poured. This
is then allowed to harden and set after which it is
stripped, or in the case of stay-in-place formwork it is
left as part of the structure.

Formwork allows contractors to cast and construct the main
parts of a building which are required to be strong and
support the structure such as floors and walls, as well as
smaller parts of a building such as stairs relatively
quickly


Engineered formwork systems use prefabricated moulds made
from a metal frame, usually either steel or aluminum.
Engineered formwork is much cheaper and quicker to use than
traditional formwork. The frames are extremely strong and
rarely need replacing, reducing costs. Due to the formwork
systems being engineered, their construction is faster and
requires less manpower, again saving money. Simple
structures can be built with re-usable plastic formwork
systems (a type of engineered formwork), which consist of
strong, lightweight, interlocking systems.

Question { 8092 }

what is the different betweem expansion and construction joints

Answer

Construction joints . Construction joints are provided to
separate the areas of concrete placed at different times,
and may be
either longitudinal or transverse, as required .
(1) The spacing of longitudinal construction joints will
depend largely on the paving equipment . With most present-
day equipment, paving lanes 24 feet or more in width are
possible and may be used . Determination of the width of
paving lane to be used, that is, whether a 24-foot-wide
road or street should be paved in a single lane or in
two 12-foot-wide lanes, is left to the judgment of the
designer .
(2) When a longitudinal construction joint is used at the
center of two-lane pavements, a keyed joint with tie bars
similar to those required for longitudinal contraction
joints, or threaded split 5/8-inch tie bolt, should be
used . When a longitudinal construction joint is used at
the center of pavements having four or more paving
lanes, a doweled joint should be used .
(3) Transverse construction joints should be installed at
the end of each day's paving operation, and at other points
within a paving lane where the placing of concrete is
discontinued a sufficient length of time for the concrete
to start to set . All transverse construction joints in
nonreinforced rigid pavements should be of the doweled type,
and should be located in place of other regularly spaced
transverse joints . When paving is resumed, the regular
transverse joint construction should be used, beginning
with the first regularly Scheduled transverse joint . When
a transverse construction joint is required within a slab
in a reinforced rigid pavement, the reinforcing
steel should be carried through the joint and tie bars
added .
Expansion joints . Expansion joints are provided for the
relief of forces resulting from thermal expansion of the
pavement, and to permit unrestrained differential
horizontal movement of adjoining pavements and/or
structures . There are two types of expansion joints,
doweled and thickened-edge, both of which should be
provided with a nonextruding type filler metal . Usually a
preformed filler 3/4-inch thick will be adequate . The
expansion joint should be so designed as to provide a
complete and uniform separation between the rigid
pavements or between the rigid pavement and the structure
concerned .
1) Doweled expansion joints should be used for all
transverseexpansion joints within rigid pavements except at
the intersections of rigid pavements with structures or
with other rigid pavements . The designer is cautioned that
expansion joints within rigid pavements are difficult to
construct and maintain, and often contribute to pavement
failures . For these reasons, their use should be kept to
the absolute minimum necessary to prevent excessive
stresses or distortion in the pavement . Internal expansion
joints should be omitted in all rigid pavements 8 inches or
more in thickness, and also in pavements less than 8 inches
thick when the concrete is placed during warm weather .

Question { 15051 }

What is the density of cement?

Answer

The density of cement plays a significant role both in its
production and performance. The raw minerals are heated in
huge ovens to promote chemical changes and this
produces “clinker”. The final steps in cement manufacturing
involve grinding (milling) and blending that produce the
fine powder that is recognizable as cement. Every step in
the manufacture of cement is checked by frequent physical
tests, as is finished product, to ensure that it complies
with all necessary specifications.
The density of cement should be known in connection with
the design and control of concrete mixtures.
Density
Whether needed for the Blaine, or as a value in its own
right, density has historically been determined by liquid
displacement using, for example, kerosene or naptha. It is
necessary to thermostat the liquid to within +/- 0.2oC.
Disposal of used, wet sample is not usually considered in
standard methods and multiple measurements necessarily
incur a great deal of operator effort. Not so with
automatic gas pycnometers. Samples as large as 135 cc bulk
volume can be accommodated (thereby improving sampling
statistics), purged of air automatically, run multiple
times automatically and a printed report generated within
minutes. The sample is recovered unharmed and dry, and the
very same aliquot can be used for a subsequent Blaine
analysis or other test. This method has already been
adopted by a number of cement companies worldwide, and is
standard in applications such as petroleum coke, pitch,
coatings, carbon, cellular plastics, soils, ceramics,
catalysts, etc.

Question { UPPCL, 279217 }

How to calculate compressive strength of concrete?

Answer

Depending upon the quantity of concrete ,the nos of cube
mould is decided .first you finalised the set of cubes the
standard size of ( 150x150mm). after pouring the cubes
moulds , every cubes moulds is filled in required layer by
layer and every layer is tamping by 10 strokes.after
compacted the cubes moulds the following information is
noted on cubes / to maintain the site register for testing
data such as
1. Name of the structure were the cubes will be taken
2. Nos of sets
3. Date of casting
4. Time of casting
5. Grade of concrete
6. 7 days result
7. 28 days result
Then all the cubes moulds shall be pouring into the water
tank for 28 days curing.to calculate the 7 days result
required nos. of cubes mould are taken out and tested in
the COMPRESSION TESTING MACHINE.the same process are
carried out for 28 days.
Compressive strength of concrete = LOAD AT BREAKAGE ON DIAL
GAUGE

SURFACE AREA OF THE CUBES MOULDS

For 7 days test result the strength to be gain by
approximately about 70% of the grade strength of the
concrete and For 28 days test result the strength to be
gain by approximately 100 % of the grade strength of the
concrete. Normally the unit of compressive strength as
KG/SQMM , N/SQMM.
As per thumb rule , at the time of weighing the cubes the
minimum weight of cubes are 8.6 kg .

Question { 11140 }

what is the measure of slump

Answer

A slump test is a method used to determine the consistency
of concrete. The consistency, or stiffness, indicates how
much water has been used in the mix. The stiffness of the
concrete mix should be matched to the requirements for the
finished product.

All concrete is a combination of aggregate (gravel and/or
sand), cement, and water, but the proportions of the mix
can be varied. A larger proportion of water causes a
softer, wet concrete mix, which is easier to handle during
the pour and requires less care during curing. It also
results in a slightly softer and less durable finished
product. A smaller amount of water causes a stiffer, wet
concrete mix, which is harder to manage but makes a
stronger and more durable finished product, one with a
higher concrete pounds per square inch (PSI).