Today we will see how to make project on ' project on setting of cement' this project is only for class 12th student and this project is belongs to 'chemistry' in this project we will see how can we make this project .
Experiment – 1
Aim: To
study the setting of mixtures of cement with lime, sand, fly ash etc.
Requirements: Beakers, glass rod, weights, small wooden boxes
or empty match boxes. Lime, pit sand, river sand, cement, fly ash, rice husk…
Introduction:
Cement is essentially
a finely ground mixture of calcium silicates (3Cao.SiO2) and aluminates
(3Cao.Al2O3) which sets to a hard mass treated with water. This property makes
cement capable of joining rigid masses like bricks, stones, tiles etc. into
coherent structures. The cements have property of setting and hardening under
water due to certain physicochemical process and are, therefore, called
hydraulic cements. During setting of cement, the physical changes taking place are
gel formation and crystallization and chemical changes are hydration and
hydrolysis. The process of solidification of cement paste involves: (i) setting, and (ii) hardening.
Setting is stiffening
of the original plastic mass into initial gel formation. After setting,
hardening starts due to gradual start of crystallization in the interior of the
mass. The strength developed by cement at any time depends upon the amount of
gel formed and the extent of crystallization. A mixture of cement, sand, small
pieces of stone (gravel) and water is known as
concrete and sets to an extremely hard structure.
When cement is used
for construction purposes, it is always mixed with sand and little water to
make a pasty material called mortar. Here
cement or lime forms the binding material and function of sand is to prevent
shrinking and cracking and to increase the bulk, thereby reducing the cost of
the mortar. When cement is used as the binding material it is called cement mortar and when lime is used as the binder it is called lime-mortar. Sand in addition to its other functions also
increases the adhesive qualities of the binding material. Effect of quality of sand on setting of cement mortar. Sand
obtained from different sources has
different qualities. For example, sea sand obtained from sea contains some unwanted salts and retards the setting of cement and is unsuitable for making mortar. On the other hand, pit sand obtained
from pits in the soil and river sand obtained from river bed are considered excellent
for preparing mortar and concrete.
Effect of time on setting of cement mortar. Time has an important role
on the strength developed by cement mortar. When a cement sand paste in the
ratio 1:3 in water is allowed to dry, the strength of the solid mass keeps on
increasing with increase in the time given for setting. It acquires nearly full
strength in 28 days.
Procedure
1.
Prepare the sets of mixtures of various
compositions as given in the observation table.
2. Take each of the
mixtures in different beakers and
prepare their pastes
by adding minimum quantity of
water.
3. Take 10 empty match-box
inner cases and mark them from 1 to 10.
4. Transfer the
prepared pastes immediately into the
matchboxes and
compact them by pressing with hand.
5. Spray water from
time to time over the pastes so
that they are always
moist.
6. Take out the slabs
after three days and test for its
strength. For that
hold a weight of 10g on the hand at a fixed height (say 50 cm above the ground)
and drop
the weight on the
slab. See if the slab breaks or not. If
it does not break
then take 20g weight and drop it
from the same height.
This way keeps on increasing the weight and note down the minimum weight
required to break the slab.
Observations:
Setting time allowed = 3 days.
Note: - The slab
should be of 0.5 cm thickness, 2 cm
wide and 10 cm long.
Experiment – 2
AIM: To
study the setting of mixtures of cement with sand, lime and fly-ash with
respect to time and
strength.
Requirements: Beakers,
glass rod, weights, small wooden boxes or empty match boxes. Lime, pit sand,river
sand, cement, fly-ash, rice husk.
Procedure
1. Prepare mixtures of the various compositions as given in
the following observation table.
2. Take each of the mixtures in different beakers and prepare
their pastes by adding minimum quantity of water.
3.Take 9 empty match-box
inner cases and mark them from 1 to 9.
4.Fill three cases
with paste of each composition.
5. Spray water from time to time over the pastes so that
they remain moist all the time.
6. After three days take out one slab of each composition
and test for their strength by the method described in previous experiment.
7. Similarly,
take out a set of three slabs after 7 days and then after 30 days and test for
their strengths.
Observations
Note: - The slab should
be of 0.5 cm thickness, 2 cm wide and 10 cm long.
Conclusion:
- The strength of the slab increases with increase in the
setting time allowed…!
Bibliography
1.
PRACTICAL MANUAL
2. www.wikkipidia.com
4. NCERT textbook class 12
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