🕑 Reading time: 1 minuteExpansive cement is special type of cement when mixed with water, which forms a paste that tends to increase in volume to a significantly greater degree than Portland cement paste after setting. The expansion of the cement mortar or concrete is compensated for the shrinkage losses. In this article we study about the manufacture, properties, types and uses of expansive cement.
Manufacture of Expansive CementThe process of manufacture if this type of 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 to a temperature of around 2,600 degrees Fahrenheit and clinkers are formed and in the next batch limestone, calcium sulphate and bauxite together at a temperature of about 2,300 degrees Fahrenheit, 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.
Physical properties of Expansive CementTable 1: Properties of expansive cement
|Setting Time||75 min|
|Air Conctent||12 %|
|7 Days expansion|
|7 Days||14.7 Mpa|
|28 Days||24.5 MPa|
Types of Expansive CementDepending upon the type of expansive compound used in the cement, expansive cement is divided into 3 types,
1. K Type expansive cementThe raw material in this type of cement contains, portland cement, anhydrous tetracalcium trialuminate sulfate (C4A3S), calcium sulfate (CaSO4), and lime (CaO), which are grounded and expansive cement is formed.
2. M Type expansive cementThe Portland cement clinkers are grounded with calcium sulfate.
3. S Type expansive cementIn this type of expansive 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.
Uses of Expansive Cement
- This cement is used in large, continuous floor slabs without joints
- It work well to fill holes in foundations and to create self-stressed concrete that is stronger than conventional portland cement concrete.
- Pre-stressed concrete components for bridges and buildings are made using this material.
- Used for construction of water retaining structures and also for repairing the damaged concrete surfaces.
- Used in grouting of anchor bolts.