LIME (CaO) : –

• Lime imparts strength & soundness control.
• In excess cement become unsound.
• In deficiency strength will reduce.
•  

SILICA (SiO2): –

• Silica also imparts strength of cement
• In excess strength of cement increases with prolong of the setting time.

ALUMINA (Al2O3) : –

• Alumina imparts Quick setting of cement and reduces the temperature of clinkers.
• In excess, cement becomes weak.

IRON OXIDE (Fe2O3) : –

• • It imparts hardness, colour and Helps in fusion.
  • It gives ‘graphite grey’ colour to cement.

GYPSUM (CaSO4.2H2O) : –

• • Gypsum increases the initial setting time of cement.
  • If gypsum is not mixed in cement, cement will set very quick (in 5 minutes) after mixing water, which is called flash set.
  • Gypsum is used as Retarder.

MAGNESIA (MgO) : –

• • In excess cement become unsoundness.
  • It also impart Yellow colours and strength of cement.
  • MgO ≯ 5%

SULPHUR (S): –

• • It also imparts soundness of cement.
  • S ≯ 2.75%

ALKALIES/SODA POTASH (Na2O, K2O) : –

• • These are the undesirable component of cement.
  • They give efflorescence and staining to cement.
  • Line → efflorescence
  • Spots → staining

IMPORTANT NOTE : –

• • Lime + Silica = 70 to 80%
  • Soundness is given by three component of cement.
  •              → Lime               → Sulphur              → Magnesia

                  (Lechatlier Apparatus)                        (AutoClave Test)

• • For sulphur – No test available.