Chemical Composition of Raw Materials | Construction Materials | Cement | Part II

Chemical Composition of Raw Materials | CEMENT

CEMENT | Civil Engineering | Engineer Ji | Er. Neeraj Gosain

• The three basic constituents of hydraulic cements are Lime, Silica-alumina and Iron-oxide.
• The relative proportions of these oxide compositions are responsible for influencing the various properties of cement.
• An increase in lime content beyond a certain value makes it difficult to combine completely with other compounds.
• Consequently, free lime will exist in the clinker and will result in the unsound cement. An increase in silica content at the expense of alumina and ferric -oxide makes the cement difficult to fuse and form clinker.
• The approximate limits of chemical composition in cement are given in table.

Constituents of Portland cement (Raw Material)

Oxide	Function	Composition (%)	Average
Lime, CaO	Controls strength & soundness. Its deficiency reduces

Cement | Introduction | Construction Materials | Part I | Engineer Ji

Introduction to Cement | Civil Engineering | Part I 

• Cement is a material which has cohesive and adhesive properties in the presence of water.
• 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 UK in 1824. He named it Portland Cement because

i) Point to be Noted | Important Points of | Construction Materials

Good Verity of cement contains higher % of:

Tricalcium Silicate (C3S): 3CaO.SiO2

• Supposed to be the best cementing material & well-burnt cement.

Dry Rot:

• Reduces the timber to powder. 
• Dry rot is decomposition of felled timber. It is caused by the action of various fungi.
• The fungus reduces fiber to a fine powder and the timber losses its strength.