fresh concrete

Question 1

describes how
easily freshly mixed concrete can be
mixed, placed, consolidated, and
finished with minimal loss of
homogeneity

Answer 1

workability

Question 2

THREE TESTS TO CHECK CEMENT WORKABILITY

Answer 2

SLUMP TEST
COMPACTING FACTOR TEST
VEE-BEE

Question 3

One of the most common test for
workability of freshly mixed
concrete which can be performed
either at the working site/field or in
the laboratory.

Answer 3

Slump test

Question 4

Slump test aim

Answer 4

To determine the workability of
fresh concrete by slump test as
per IS*: 1199 - 1959.

Question 5

measure the workability of a fresh
concrete mix in accordance with
applicable ASTM and AASHTO
standards.

Answer 5

slump cone

Question 6

Use to eliminate
air voids in concrete when making
slump tests, concrete cylinders or
conducting concrete air entrainment
test.

Answer 6

tamping rod

Question 7

Hemispherically rounded on
both ends and plated for corrosion
resistance.

Answer 7

tamping rod

Question 8

slump test procedures

Answer 8

1. The internal surface of the
   mould is thoroughly cleaned and
   applied with a light coat of oil.
2. The mould is placed on a smooth,
   horizontal, rigid and non-absorbent
   surface.
3. The mould is then filled in four
   layers with freshly mixed concrete,
   each approximately to one-fourth of
   the height of the mould.
4. Each layer is tampered 25 times
   by the rounded end of the tamping
   rod (strokes are distributed evenly
   over the cross-section).
5. After the top layer is rodded, the
   concrete is struck off the level with a
   trowel.
6. The mould is removed from the
   concrete immediately by raising it
   slowly in the vertical direction.
7. The difference in level between
   the height of the mould and that of
   the highest point of the subsided
   concrete is measured.
8. This difference in height in mm is
   the slump of the concrete.

Question 9

results for slump test

Answer 9

The slump measured should be recorded in mm of subsidence of the specimen during the test. Any slump specimen, which collapses or shears off laterally gives incorrect result if this occurs, the test should be repeated with another sample. If, in the repeat test also, the specimen shears, the slump should be measured and the fact that the specimen sheared, should be recorded.

Question 10

designed primarily for use in the
laboratory but it can also be used in
the field

Answer 10

compacting factor

Question 11

It is more precise and
sensitive than the slump test and is
particularly useful for concrete
mixes of very low workability for
which slump test is not suitable.

Answer 11

compacting factor

Question 12

consists of
two conical hoppers having a hinged
trap door attached to the lower end
of each hopper, allowing the
concrete sample to flow freely into
the cylindrical mould

Answer 12

Compacting factor apparatus
Tamping

Question 13

Use to eliminate
air voids in concrete when making
slump tests, concrete cylinders or
conducting concrete air entrainment
test

Answer 13

tamping rod

Question 14

device used to measure mass

Answer 14

balance

Question 15

used for scooping fresh concrete

Answer 15

trowel

Question 16

compacting factor procedure

Answer 16

1. The sample of concrete is placed
   in the upper hopper up to the brim.
2. The trap-door is opened so that
   the concrete falls into the lower
   hopper.
3. The trap-door of the lower hopper
   is opened and concrete is allowed
   to fall into the cylinder.
   Palencia ra and Cutie Yahya
4. The excess concrete remaining
   above the top level of the cylinder is
   then cut off with the help of plane
   blades.
5. The cylinder is filled with a fresh
   sample of concrete and vibrated to
   obtain full compaction or it can also
   be done by using the tamping rod.
   The concrete in the cylinder is
   weighed again. This weight is known
   as the weight of fully compacted
   concrete.

Question 17

defined as the ratio of the weight of partially compacted concrete to the weight of fully compacted concrete. It shall normally be stated to the nearest second decimal place.

Answer 17

compacting factor

Question 18

Vee Bee Consistometer Test is
named after the

Answer 18

Sweden developer V
Bahrmer

Question 19

It is used to determine the
workability of concrete using
consistometer. It is usually performed
on dry and fresh concrete and it is not
suitable for very wet concrete. This test
gives results based on the mobility and
compatibility of the concrete

Answer 19

Vee Bee Consistometer Test

Question 20

It measures the relative effort and
time to convert the concrete mould
from one shape to another.

Answer 20

Vee Bee Consistometer Test

Question 21

The effort taken to convert the mould from one shape to another is known as

Answer 21

the remoulding effort

Question 22

The time that has been taken for
the concrete to settle down in
cylindrical shape is measured in
seconds, which is known as

Answer 22

vee bee seconds

Question 23

vee bee test apparatus required

Answer 23

Vee-Bee Consistometer Tamping rod 500 mm long & 20 mm dia.
The vibrator table should be 380mm long & 260mm width, which rests on elastic support at height 305mm above floor level.
The table should be mounted on a base which is equipped with an electrically operated vibrometer.
The sheet metal cone should be 30 cm height, and the diameter should be 20 cm and 10 cm at the bottom and top, respectively.
The graduated rod is fixed in a whirling arm. A glass disc is screwed at the end of the arm.
The division scale records the slump cone value of concrete in centimeters.

Question 24

vee bee test procedure

Answer 24

Step 1 – Place the slump cone in the consistometer machine.
Step 2 – Fill the cone with concrete in four layers.
Step 3 – Each layer should be tamped 25 times by the tamping rod.
Step 4 – Remove the excess concrete from the slump cone & level it.
Step 5 – Now, rotate the glass disc, which is attached to the whirling arm and place it over the slump cone concrete level & measure the initial reading from the graduated rod.
Step 6 – Rotate the glass disc to its original position. Then remove the slump cone slowly in a vertical direction. You can see the concrete slightly changed from its shape.
Step 7 – Now again, rotate the glass disc and measure the final reading.
Step 8 – Now turn on the electrical vibrator table & eventually switch on the stopwatch, continue the vibration until the concrete remoulded, and the surface of the concrete becomes horizontal.
Step 9 – Once the concrete surfaces come horizontal in the cylindrical pot, stop the vibration & the watch.
Step 10 – Record the time – Vee Bee Seconds.