Question

How much water is added in cement mortar to determine compressive strength of cement?
1. Equal to \(\left(\frac P 4 + 3\right)\) percent of total mass of cement and sand, where P is water required for standard consistency
2. Equal to 0.85 P percent of total mass of cement and sand, where P is water required for standard consistency
3. 0.28 times the mass of cement mortar
4. 0.4 times the mass of cement

Answer 1

Correct Answer - Option 1 : Equal to \(\left(\frac P 4 + 3\right)\) percent of total mass of cement and sand, where P is water required for standard consistency

Concept:

Consistency: Vicat’s Apparatus is used to find out the consistency, initial setting time and final setting time of the cement. In the normal consistency test we have to find out the amount of water to be added to the cement to form a cement paste of normal consistency.

Type of test	Water to be added (Consistency)
Setting time  (both initial and final)	0.85P
Compressive strength test	(P/4 + 3) %
Soundness test	0.78 P

Important Point:

Standard consistency is the consistency of the cement paste that permits the Vicat’s plunger of diameter 10 mm and height 50 mm to penetrate in to the mould up to depth of 33 to 35 mm from the top.