Tests On Concrete: How To Do Slump, Compaction Factor & Crushing Strength Tests
Various tests may be carried out on concrete to ascertain the properties of concrete. The following are some of the tests that may be carried out on concrete:
- Slump test
- Compaction Factor test
- Crushing Strength test
Slump test: slump test is conducted to determine the workability of concrete it needs a slump cone for test. Slump cone is a vessel in the shape of a frustum of a cone with diameter at the bottom being 200 mm and the diameter at the top is 50 mm, the cone itself is 300 mm high. The cone is kept over an impervious platform and filled with concrete in four layers. Each of the layer is tamped with a 16 mm pointed rod for 25 times. After filling completely, the cone is gently pulled up. The decrease in the height of the concrete is called slump. The higher the slump, the more workable is the concrete.
Compaction Factor test: this is another test to identify the workability of concrete. This test is conducted in the laboratory. The test equipment consists of two hoppers and a cylinder fixed to a stand, the dimensions and the distances between the three vessels being standardized. vessel A and B are having hinged bottoms whereas cylinder C is having fixed button.
The top vessel A is filled with the concrete that is to be tested. As soon as it is filled, the hinged door is opened. Concrete is collected in vessel B. Then the hinged door of vessel B is opened to collect concrete in cylinder C. The concrete in cylinder C is weighted. Let it be W1.
Again the cylinder is filled with the sample of concrete in 50 mm layers, which is compacted by ramming and vibrating. Then the weight of compacted concrete is determined. Let this weight be W2.
The ratio W1 over W2 is termed as compaction Factor. The specified values of compaction factor for different works are known.
Crushing strength test: in the crushing strength test, moulds of size 150 mm by 150 mm by 150 mm are used for carrying out the test. Before filling mould, it is properly oiled on its inner surfaces, so that the cubes can easily be filled with concrete and cubes could easily be removed from the moulds later on. The mould is filled with concrete to be tested in three layers and kept in the room afterwards it is removed from the mould and kept under water for curing. After 28 days of curing, it is tested under the compression testing machine. The crushing load is noted and crushing strength test is determined.
