How to apply flow table for Cement Mortar
The flow table test of cement mortar is accomplished in order to work out the amount of water necessary for performing strength test of masonry cement as well for drying shrinkage test of cement. Besides, this test provides some idea on the applicability of cement mortar.
The amount of water utilized for measurement of compressive strength test of masonry cement, should be in such manner so as to generate a flow of 110±5% with 25 drops in 15s.
The amount of water utilized for measurement of drying shrinkage test of hydraulic cement, should be in such a manner so as to generate a flow of 110 to 115% with 25 drops in 15s.
Test Impression: A particular amount of cement standard sand and water is amalgamated to form a mortar and facilitating it to flow by dropping from a particular height with time.
Method of test:
1. Consider 420 of cement & 1440 g of standard sand and a trial percentage of water.
2. Combine all the ingredients mechanically by applying a mixer.
3. Arrange all the mixing water in bowl.
4. Include the masonry cement to the water, then turn on the mixer and mix maintaining the slow speed (140±5 rev/min) for 30s.
5. Include the whole quantity of sand gradually over a period of 30 s, when mixing at slow speed.
6. Turn off the mixer, switch to medium speed (280±10 rev/min), and mix for 30 s.
7. Turn off the mixer, keep the mortar sustains one and a half minutes. Throughout the initial 15 s of this interval, instantly scrap down into the batch any mortar should be gathered on the side of the bowl, then for the remainder of this interval, cover the bowl with the lid.
8. Complete it by mingling for one minute at medium speed. If it is necessary to mix again, any mortar complying with the side of the bowl should be instantly scraped down into the batch with scarper before remixing that should be sustained unless a consistent mortar is produced.
9. Once the mixing is finished, shake the paddle to eliminate extra mortar into the mixing bowl.
10. Cautiously rub the flow table top clean, and dry and arrange the mould at the centre.
11. Arrange about 25 mm thick layer of mortar (mixed as above) in the mould and tamp 20 times with tamping rod.
12. Then fill the mould with mortar and tamp as indicated for the first layer.
13. Remove the extra mortar by drawing the straight edge of a trowel by applying a sawing motion across the top of the mould.
14. Raise the mould away from the mortar one minute as soon as the mixing operation is finished.
15. Instantly drop the table through a height of 12.5 mm, 25 times in 15s.