7 Ingredients and Composition of Cement and Test

Cement ingredient, composition and tests on cement

Cement ingredients, composition and Test on cement

Cement is one of most important construction material, because it provide strength and durability to the structure, so Right choice of it is greatly affect the structure quality and life.

Cement can be define as fine powdery form of mineral. When it mix with water, hydration of it is occure and it get start gaining strength. 

Before proceed ahead, We should know difference between below terms.

What is Ingredient and Composition of cement?
Ingredient means raw materials use in manufacturing of cement. Strength and setting time of cement is greatly affected by this, so proper quantity of each raw material is require.
There are enlisted ingredient use in manufacturing of cement.
  • Lime
  • Silica
  • Alumina
  • Iron Oxide
  • Magnesium Oxide
  • Sulphur Trioxide
  • Alkalies

Composition is nothing but compound form after the chemical process and heating of raw material.

Composition of cement is listed below.
  • Tricalcium silicate (C3S)
  • Dicalcium silicate (C2S)
  • Tricalcium Aluminate (C3A)
  • Dicalcium Alumino Ferrite (C2AFe)

Ingredients of Cement and their function:

Proportion of each Ingredient:
Cement ingredient proportion pie chart







Lime as construction material
Lime :

Lime is one of main and most important ingredient in manufacturing of cement. Cement consist almost 63% of lime. 

it is responsible for strength and soundness of cement. Excess amount of lime makes cement unsound.

Here what is Soundness?
Soundness can be define as gaining strength in Cement within acceptable expansion.

So excess lime cause excess expansion in cement, which cause disintegration of cement.

Silica as construction material
Silica:

Cement consist 22% of silica. Silica provide strength to cement. It make dicalcium silicate and tricalcium silicate. Surplus amount of silica cause slow setting of cement.

Alumina:


6% of Alumina is use in production of cement. Alumina is responsible for formation of foam in cement. It produce TricalciumAluminate, Dicalcium Alumino Ferrite. This two compositions are responsible for quick setting to cement and development of temperature during hydration.

Iron oxide as construction material
Iron oxide:

Cement consist 3% iron oxide. Iron oxide deliver colour, hardness and strength to cement. It also very useful during kiln process of manufacturing of cement.

Magnesium oxide:


Cement comprise 2.5% Magnesium oxide. Small amount of Magnesium oxide gives hardness and colour to cement, But excess of it make cement unsound.

Sulphur trioxide:

1.5% of sulphur trioxide present in cement. It's function is almost same as Magnesium oxide, because small quantity of it make cement sound and high cause unsoundness in cement.

Alkalies:


There are 1.5% Alkalies in cement. It should be very less in quantity because it cause efflorescence.


Composition of Cement:

During the kiln process in manufacturing of cement, this chemical composition is produce. Which are in following composition.
Cement compositions pie chart graph


Tricalcium silicate:

Cement consists 40% tricalcium silicate in clinker. Tricalcium silicate is responsible for the rapid hardening of cement.

Due to Tricalcium silicate hydration of cement taken place rapidly, so it is responsible for early strength of cement, and due to quick hydration more heat will be generate in cement.

Disadvantage of tricalcium silicate is that due to high hydration heat, there are more chances of development of crack. It consist less resistance against sulphate attack.

Dicalcium silicate:


There are 32% dicalcium silicate in cement clinker. Dicalcium silicate provide ultimate strength to cement. It hydrate at slow pace. It harden slowly, due to it there are less hydration heat.
It consists high resistance against sulphate attack.

Note: up to here, we have understood that tricalcium silicate and dicalcium silicate are responsible for early strength and production of high hydration heat in cement.

By increasing tricalcium silicate and reducing in dicalcium silicate, we can make rapid hardening cement. Which suitable for cementing in cold region

At high percentage of dicalcium silicate and low percentage of tricalcium silicate in cement get harden slowly, less hydration heat, more resistance to sulphate attack.


Tricalcium aluminate:


There are 10.5% tricalcium aluminate in cement. It is first composition in cement to react with water. It is responsible for the initial setting of cement. As it react very fast with water so there are high hydration heat.

Tetra calcium alumino ferrite:


Cement comprise 9% tetra calcium alumino ferrite. It can not react easily with water, so it produce very low hydration heat.

Hint: according to upper both composition we can say that initial setting time of cement is depend upon it. By increase tricalcium aluminate in cement clinker, we can reduce initial setting time of cement.


Tests on cement:


Quality of cement greatly affects on quality of construction, so to decide best quality some tests on it should be conducted.
This test can be divided in two parts. Test conducted in lab and second one on site. In this part we will focus on test conducted in lab in detail.

Tests in Lab

Fineness test:

Cement should be well grind. To check it this test is adopted. Fine cement have more surface area per unit weight and fast gaining of strength. It can be perform two way either sieve method or air permeability method.

Sieve method:

This method is rarely use now a day. In this method cement is sieve through 90 micron sieve by shaking horizontal and vertical direction. For well graded cement residue should not more than 10% by sample weight.

Air Permeability method:

Blaine's apparatus is use for air permeability method. In this method fineness is define in specific surface term. Here specific surface means total surface area per unit weight in gram. It is measure in cm²/ gm.

For good ordinary Portland cement specific surface should be 2250 cm²/ gm.

Consistency Test:

This test is adopted for determination of consistency of cement, initial and final setting time.
To conduct this test vicat's apparatus is use. Plunger of it is 10mm dia and consist 40mm to 50mm length. 

In this test plunger is allow to penetrate through freshly mix cement mortar up to 33mm to 35mm depth at 25°C to 29°C temprature and 20% humidity. This test is conducted for three times.

Consistency of cement can be define as amount of water content, which allow plunger to penetrate in cement mortar at 33mm to 35mm depth within 3 to 5 minute of mixing.

Consistency of cement should be 25% by weight of cement.

Initial setting time:

To decide initial setting time vicat's apparatus is use. In it time require by cement past to penetrate plunger to depth of 33mm to 35mm is counted.
It must be greater than 30 minutes.

Final setting time:

To decide it cement is allow to hard until plunger can not penetrate more than 0.5mm in cement paste. This hardening time is known as final setting time.
Final setting time should not more than 10 hour.

Soundness test: 

We have discussed soundness of cement already. To decide it Le Chatelier apparatus is use. This test is conducted to decide amount of lime and magnesium in cement, because excess amount make cement unsound and cause expansion. 

Expansion of cement should not more than 10mm to avoid cracking and disintegration.

Tensile strength of Cement:

This test is conducted on briquettes in tensile testing machine. Mortar for it is made in 1:3 ratio. Which should be well cured for 3 to 7 days at 25°C tempreture.

Tensile strength of briquettes are measured at 3rd and 7th day after curing. Which are not less than 2 N/mm² after 3 day and 2.5N/mm² after 7 days.

Compression test:

Compression test is carried out on universal testing machine on cement mortar cube of 1:3 proportion.
Total six cube are being tested in it. Three cubes are tested after 3 days of curing and remaining after 7 days of curing.

Compression strength of cement should not less than 11.5 N/mm² after 3 days and 17.5 N/mm² after 7 days.

Field Tests


 Following tests should be adopted on cement on field to check suitability of it for construction.

Manufacturing and expiry date: 

cement lost it's strength with passing of time. It must be use within 90 days of manufacturing.

Colour: 

colour of cement must be evenly light brow.

Presence of Lumps:

Cement bag with lump must be rejected because it indicate reaction of cement with atmospheric water. Lumpy cement resolve less strength.

Rubbed test:

Cement should smooth, when you rubbed it between fingers. If it is not, than it indicate impurity in it.

Floating test:

Cement should float on water for some time before sinking in water.

We will publish more detail blog on tests on cement.

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