EXPANSIVE CEMENT - MANUFACTURE, PROPERTIES, TYPES AND USES

Expansive Cement

Expansive cement is a special type of cement when mixed with water,which forms a paste that, during and after setting and hardening increases significantly in volume.Shrinkage compensating concrete motor in an expansive cement concrete motor in which expansion if restained induces compressive stresses which approximately offset tensile stresses in concrete induced by drying shrinkage.

Manufacture of Expansive Cement

The process of manufacture of expansive cement is same as that of Portland cement,but the raw materials used for formation of clinkers are different.Firstly limestone and clay are heated together at a temperature of around 2600 ℉ and clinkers are formed and in the next batch limestone,calcium sulphate and buxite together heated  at a temperature about 2300 ℉,where sulfoaluminate clinkers are formed.These two clinkers are grounded together to form expansive cement, when this cement is exposed or mixed with water,sulfoaluminate expands in volume.

Types of Expansive Cement

There are three types of expansive cement:

1. K Type Expansive Cement

The raw material in this type of cement contains,Portland cement,anhydrous tetracalcium sulfate (C4A3S), calcium sulfate (CaSO4) and lime (CaO). which are grounded and expansive cement is formed.

2. M Type Expansive Cement

In this type of cement, the Portland cement clinkers are grounded with calcium sulfate.

3.  S Type Expansive Cement

In this type of cement a Portland cement containing a high computed tricalcium aluminate (C3A) content and an amount of calcium sulfate above the usual amount found in Portland cement.

Physical Properties of Expansive Cement

PROPERTIES	VALUE
Setting Time	75 min
Air Content	12 %
7 DAYS EXPANSION
Min	0.04 %
Max	0.10 %
COMPRESSIVE STRENGTH
7 Days	14.7 %
28 Days	24.5 %

Uses of Expansive Cement

• This cement is used in large continuous floor slabs without joints.
• In the construction of pre-stressed concrete compound.
• Used in the construction of water retaining structure.
• Used in repairing of damaged concrete surfaces.
• Used in grouting of anchor bolts.