Cement
CEMENT
is a grey powder used in buildings which become very hard when it is mixed with sand
and water.
➢ Cement compound and water molecules form chemical bonds resulting in a chemical reaction
known as hydration.
➢ This hydration process determines, for the most part, how strong cement will ultimately be as
concrete.
➢ If you do not use pure water during this process, cement and ultimately the concrete made from
it later will be compromised and not as strong due to potential side reactions.
PROPERTIES OF CEMENT
• Mobility
– term used to describe the ability to move cement around once it has been mixed
– Water hydration and air, as well as other aggregates in a cement mixture, impact cement's
place ability.
• Permeability
– ability of cement to be porous and allow water to be absorbed.
– pertains to the ability of cement to be porous and allow water to be absorbed.
– if the cement mixture has too much water in it, structure might not harden as quickly as it
should. If the cement is too dry, it will be difficult to place or mold.
• Strength
– Cement is strong enough to withstand elements like strong winds, rain, sleet and snow when
combined with other strong components used to turn into concrete.
INGREDIENTS OF CEMENT
• Gypsum
Control hydration and control setting time - prevents the concrete
from hardening almost immediately after adding water.
• Lime
It makes the cement sound and provides strength to the cement.
✓ Soundness of cement- ability to retain its volume after it gets hardened
• Silica
it gives strength of the cement due to the formation of dicalcium
and tricalcium silicate
• Alumina
It acts as a flux and it lowers the clinkering temperature.
• Calcium Sulphate
its function is to increase the initial setting time of cement
• Iron Oxide
imparts colour, hardness and strength to the cement.
• Magnesium
This ingredient, present in small amount, imparts hardness and
colour.
MANUFACTURING PROCESS OF CEMENT
Dry process
Wet process
1. Mixing of raw material in dry state in
blenders.
1. Mixing of Raw materials in wash mill with 35 to
50% water.
2. The dry materials exiting the mill are called
“kiln feed”.
2. Materials exiting the mill are called “slurry” and
have flowability characteristics.
3. Fuel consumption is low i.e., 100 kg of coal
per tonne of cement produced
3. Fuel consumption is high i.e., 350 kg of coal per
tonne of cement produced
4. Cost of production is less.
4. Cost of production is high
5. Capital cost is high due to blenders.
5. Capital cost (Cost of establishment) is
comparatively less
6. Size of the kiln needed for manufacturing of
cement is smaller.
6. Size of the kiln needed for manufacturing of
cement is bigger.
7. Difficult to control mixing of Raw materials,
7. Raw material can be mixed easily, so a better
so it is difficult to obtain a better homogeneous
homogeneous material can be obtained
material.
TYPES OF CEMENT
• Ordinary Portland Cement (OPC)
– is the most widely used type of cement, which is suitable for all general concrete construction. It is
the most commonly produced and used type of cement around the world, with annual global
production of around 3.8 million cubic meters per year.
– This cement is suitable for all kinds of concrete construction.
TYPES OF CEMENT
• Pozzolan Cement
– An inert silicious material which, in the presence of water, will combine
with lime to produce a cementitious matter with excellent structural
properties.
Advantages of Pozzolans
1. Improved workability
2. Economy
3. Reduced alkali-aggregate reaction
4. Increased sulphate resistance
TYPES OF SPECIAL PURPOSE CEMENT
OPC-based
• Rapid hardening Portland Cement.
– It is high in Tricalcium Silicate (C3S) content and must be finer grinding. A high fineness of cement
particles provides greater surface area for water action.
• Sulphate-resisting Cement.
– This type of cement content high silicate due to resisting the sulphate attack on the concrete.
Sulphate attack is where water containing dissolved sulphate penetrates the concrete.
• Waterproof Portland Cement.
– is manufactured by adding a waterproofing substance to ordinary Portland cement during mixing
• Coloured Portland Cement.
– Pigment is added to this cement in quantities up to 10 per cent during the process of grinding the
cement clinker.
TYPES OF SPECIAL PURPOSE CEMENT
Non-OPC cement
• High Alumina Cement.
– High alumina cement is very reactive and produces high early strength. Generally no additives are
added to alumina cemen
SUITABILITY OF CEMENT
• Weather.
– Each and every type of cement gives different reaction towards the temperature. Some of the
cement can restrain the heat and some of them cannot retrain a high temperature
• Environmental condition.
– Different types of cement give different strength. Some of the places need a high strength
cement to make the concrete last long
• Speed of construction.
– Some parts of the construction need short time to be constructed. Therefore, use cement
which can harden in a short time.
• Type of construction.
– Mass concrete is any volume of concrete with dimensions large enough to require that
measures be taken to cope with generation of heat from hydration of the cement and
attendant volume change to minimize cracking. Some of the cement is suitable for the mass
concrete and some might be not.
TESTING OF CEMENT
FIELD TESTING
– It is sufficient to subject the cement to field tests when it is used for minor works.
The following are the field test.
• 1. Open the bag and take a good look at the cement. There should not be any visible
lumps. The color of the cement should normally be greenish grey.
• 2. Thrust your hand into the cement bag. It must give you a cool feeling. There should
not be any lump inside.
• 3. Take a pinch of cement and feel between the fingers. It should give a smooth and
not a gritty feeling.
• 4. Take a handful of cement and throw it on a bucket full of water, the particles should
float for some time before they sink. Take about 100 grams of cement and a small
quantity of water and make a stiff paste. From the stiff paste, pat a cake with sharp
edges. Put it on a glass plate and slowly take it under water in a bucket. After 24 hours
the cake should retain its original shape and at the same time it should also set and
attain some strength.
LABORATORY TESTING
• Consistency
https://www.youtube.com/watch?v=PlbCpJqWqwU
• Setting time
• Soundness
• Fineness
• Compressive Strength
• Heat of hydration - defined as the quantity, in calories per gram of
hydrated cement liberated on complete hydration at a given
temperature.