OBJECT TO DETERMINE QUANTITY OF WATER REQUIRED TO PRODUCE CEMENT PASTE OF STANDARD CONSISTENCY
IMPORTANCE This preliminary test forms base for other tests
APPARATUS • Vicat Apparatus
• Balance (capacity 1000 gms accuracy 0.1 gm)
• Gauging Trowel 100-150 mm long
TEMPERATURE • Dry Materials, Water and Laboratory : 27 + 2O C
& HUMIDITY • Relative Humidity in Laboratory : 65 + 5 %
PROCEDURE On non-porous platform ;
• Prepare cement paste of weighed quantity (300 gm) of cement mixed with weighed quantity of water (90 gm) using gauging trowel within 3 to 5 minutes before any sign of setting occurs.
• Immediately fill up mould by vicat apparatus with this paste and level up. Rest mould upon non-porous plate and shake to remove penetrated air. Level the top.
• Under plunger rod of vicat apparatus, keep the test block in the mould together with non-porous plate. Lower plunger needle together to touch top surface of cement block.
• Release plunger quickly and allow it to sink in test block.
• Prepare another sample from same lot by varying water contents and repeat the process till plunger needle remain embedded in test specimen 5 to 7 mm from bottom of vicat mould. Note water content at this stage. The sample is said to be of standard consistency at this water content.
CALCULATION Weight of water in sample
Water for standard consistency % = ----------------------------------------- x 100
Weight of dry cement in sample