CEMENT
Cement is a material that has cohesive and adhesive properties in the presence of water.
The standard density of cement is 1440 kg/m3 and 1 bag of cement is 50 kg.
Thus the volume of cement would be 0.0347 m3
- Hence the volume of 1 bag of cement can be approximated as 0.0347 m3 or 35 liters.
- Cement is a product obtained by pulverizing clinker formed by calcinating raw materials primarily consisting of Lime (Cao), Silicate (SiO2), Alumina (Al2O3), and Iron oxide (Fe2O3).
- It was invented by Joseph Aspdin of the UK in 1824. He named it Portland cement because the hardened concrete made out of the cement aggregate and water in definite proportion resembled the natural stone occurring at portland in England.
Pulverize: Make into a powder by breaking up or cause to become dust.
Clinker: A hard brick used as a paving stone.
Calcination: The process of heating a substance to a high temperature in the absence or limited supply of oxygen but below the melting or fusing point, causing loss of moisture, reduction in oxidation, and dissociation into simpler substances.
When cement is mixed with water it forms a paste that hardens and binds aggregates (fine and coarse) together to form a hard durable mass called concrete.
Cement used in the construction industry can be classified as hydraulic and non-hydraulic.
Hydraulic cement
- It set and hardens extremely fast in presence of water (Due to the chemical action between cement and water known as hydration) and results in a water-resistant product that is stable.
- This allows setting in wet conditions or underwater and further protects the hardened material from chemical attack. eg. Portland cement.
Non-hydraulic cement
- They are derived from the calcination of gypsum or limestone because their products of hydration are not resistant to water; however, the addition of pozzolanic materials can render gypsum and lime cement hydraulic. Thus, it will not set in wet conditions or underwater, rather, it sets as it dries and reacts with carbon dioxide in the air.
- It can be attacked by some aggressive chemicals after setting. Ex-Plaster of Paris.
Cement can be manufactured either from natural cement stones or artificially by using calcareous and argillaceous materials.
Examples of natural cement are Roman cement, Pozzolana cement, and Medina cement, and artificial cement is Portland cement and special cement.
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