Q.
What is Flow Test for fresh concrete?
A.
The flow table test or flow test is a method to determine the consistence of fresh concrete.
Application When fresh concrete is delivered to a site by a truck mixer it is sometimes necessary to check its consistence before pouring it into formwork.
If the consistence is not correct, the concrete will not have the desired qualities once it has set, particularly the desired strength. If the concrete is too pasty, it may result in cavities within the concrete which leads to corrosion of the rebar, eventually leading to the formation of cracks (as the rebar expands as it corrodes) which will accelerate the whole process, rather like insufficient concrete cover. Cavities will also lower the stress the concrete is able to support.
Equipment
Flow table with a grip and a hinge, 70 centimetres (28 in) square.
Abrams cone, open at the top and at the bottom - 30 centimetres (12 in) high, 17 centimetres (6.7 in) top diameter, 25 centimetres (9.8 in) base diameter.
Water bucket and broom for wetting the flow table.
Tamping rod, 60 centimetres (24 in) long
Conducting the test
The flowtable is wetted.
The cone is placed in the center of the flowtable and filled with fresh concrete in two equal layers layers. Each layer is tamped 10 times with tamping rod.
Wait 30 seconds before lifting the cone
The flowtable is then lifted up 40mm and then dropped 15 times, causing the concrete to flow
After this the diameter of the concrete is measured.
