HOW TO DO FLOW TABLE TEST FOR CEMENT MORTAR?

Flow Table Test for Cement Mortar

The flow table test of cement mortar is done only to calculate the amount of water required for gauging for conducting strength test of masonry cement and for drying shrinkage test of cement. It also gives us some idea on the workability of cement mortar.

The amount of water used for gauging in case of compressive strength test of masonry cement, shall be such as to produce a flow of 110±5% with 25 drops in 15s.

The amount of water used for gauging in case of drying shrinkage test of hydraulic cement, shall be such as to produce a flow of 110 to 115% with 25 drops in 15s.

Test Overview

A specified amount of cement standard sand and water is mixed to make a mortar and allowing it to flow by dropping from a specified height with time.

Apparatus

Measuring instrument

Name Range Accuracy
Balance 1000 g 1 g
Mixer IS:10890  
Flow table IS:5512  

Other accessories

Tamping rod

Environmental condition

Temp 27 ± 20 C
Humidity (Relative) 65 ± 5 %

Test Procedure

  1. Take 420 of cement & 1440 g of standard sand and a trial percentage of water.
  2. Mix all the ingredients mechanically with the help of a mixer.
  3. Place all the mixing water in bowl.
  4. Add the masonry cement to the water, then start the mixer and mix at the slow speed (140±5 rev/min) for 30s.
  5. Add the entire quantity of sand slowly over a period of 30 s, while mixing at slow speed.
  6. Stop the mixer, change to medium speed (280±10 rev/min), and mix for 30 s.
  7. Stop the mixer, and let the mortar stand for one and a half minutes. During the first the first 15 s of this interval, quickly scrap down into the batch any mortar that may have collected on the side of the bowl, then for the remainder of this interval, cover the bowl with the lid.
  8. Finish by mixing for one minute at medium speed. Incase requiring further remixing, any mortar adhering to the side of the bowl shall be quickly scraped down into the batch with scarper prior to remixing which is to be continued till a uniform mortar is obtained.
  9. Upon the completion of mixing, shake the paddle to remove excess mortar into the mixing bowl.
  10. Carefully wipe the flow table top clean, and dry and place the mould at the centre.
  11. Place 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 specified for the first layer.
  13. Cut off the excess mortar by drawing the straight edge of a trowel with a sawing motion across the top of the mould.
  14. Lift the mould away from the mortar one minute after completion of the mixing operation.
  15. Immediately drop the table through a height of 12.5 mm, 25 times in 15s.

Calculation

The flow is the resulting increase in average base diameter of the mortar mass, measured on at least four diameters at approximately equi-spaced intervals expressed as a percentage of the original base diameter

Flow = [(Davg – Do) / Do]*100

Where,

Davg=Average base diameter

Do=Original base dia.

Precautions

  • The material for moulding each batch of test specimen shall be mixed separately.
  • Tamping pressure must be sufficient to ensure uniform filling of the mould.

Test standard reference

IS:4031(Part-7):1988 – Methods of physical tests for hydraulic cement (Determination of compressive strength of masonry cement)

Add a Comment

Your email address will not be published. Required fields are marked *