Property of cement in chemistry - physical properties of cement And Chemical Properties of cement 


 Explain: various properties of Cement.

(1) Quality of cement:


Quality of cement is expressed as Silica modulus and Alumina modus = percentage of sio2 / percentage of fe2o3+ percentage of Al2O3



(2) Setting time:

When cement is mixed with water, it starts hardening. This occurs by hydration

followed by crystallization.

Cement

+

Paste

1 day

Hydration of

 C3A

 & C4AF

7 days Gelation of

 C2S

28 days Gelation of

 C2S &

 C3S

C2S and C3S provide full strength in one year.

(3) Shrinkage:

-During setting of cement, volume first increases due to hydration.

-After that, volume decreases due to crystallization of different components.

-This shrinkage of volume is 5 to 10%.


(4) Soundness:

-Resistance to disintegration (cracking etc.) by cement in different harsh

conditions is called soundness.

-Cement is sound if it does not undergo change in volume and disintegration

(cracking etc.) under harsh weather conditions.

(5) Colour:

Colour of Portland cement is due to iron.

-White cement is obtained by using proper raw materials.

(6) Heat of setting or hardening:

-Setting takes place due to hydration of components in cement.

-Hydration is exothermic and large heat is released which is called heat of setting

or hardening.

-Heat of hydration can be decreased by using high % of Fe2O3 to lower C3A.

-Fe2O3 combines with Al2O3 and forms C4AF so decreases C3A.

-Cement having low C3A is useful for making dams due to high crack resistance

capacity.

(7) Strength:

-Quality of hardening of cement is measured by tensile strength and compressive

strength.

(8) Acid corrosion:

-All acids are harmful to cement.


(9) Dissolved CO2 corrosion:

-Dissolved CO2 from water dissolves free lime to give calcium bicarbonate.

-This decreases the strength of cement.

(10) Sulphate corrosion:

-Dissolved sulphates (MgSO4 & Na2SO4) from water disturb the balance of free

lime, silicate and aluminate in set cement.

-This decreases the strength of cement.


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✪ AUTHOR: SAHIL SIR 

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