1.Crushing Strength Test: Metallic moulds of size 150 mm × 150 mm × 150 mm are used for
casting concrete cubes. Before filling mould, it is properly oiled on its inner surfaces, so that cubes can
be easily separated. Fresh cube is filled with concrete to be tested in 3 layers and kept in the room. After
24 hours, cube is removed from the mould and kept under water for curing. After 28 days of curing
cubes are tested in the compression testing machine. In this test cubes are placed over the smooth
surface which is in contact with side plates of mould. The crushing load is noted and crushing strength
is found as load divided by surface area (150 × 150 mm2).
Code specify the desirable strength of concrete
2.Slump Test :This test is conducted to determine the workability of concrete. It needs a slump cone for test (See fig).
✓ Slump cone is a vessel in the shape of a frustum of a cone with diameter at bottom 200 mm and 50 mm at top and 300 mm high.
✓This cone is kept over a impervious platform and is filled with concrete in four layers. Each 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. Higher the slump, more workable is the concrete. The desired values of slumps for various
works have been shown in fig.
3.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 bottom. [Ref. Fig. 👇👇]
✓Top vessel A is filled with the concrete 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 B is opened to collect concrete in
cylinder C. The concrete in cylinder C is weighted. Let it be W1.
✓Now cylinder is again 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/W2 is termed as compaction factor. The specified values of compaction factor for
different works are already listed in fig.
Ultrasonic Pulse Velocity Test-
✓Ultrasonic testing of concrete or ultrasonic pulse velocity test on concrete is a non-destructive test to assess the homogeneity and integrity of concrete.
Procedure-
✓Ultrasonic pulse velocity test consists of measuring travel time, T of ultrasonic pulse of 50 to 54 kHz, produced by an electro-acoustical transducer, held in contact with one surface of the concrete member under test and receiving the same by a similar transducer in contact with the surface at the other end.
✓With the path length L, (i.e. the distance between the two probes) and time of travel T, the pulse velocity (V=L/T) is calculated.
✓Higher the elastic modulus, density and integrity of the concrete, higher is the pulse velocity. The ultrasonic pulse velocity depends on the density and elastic properties of the material being tested.
Concrete quality based on UPV test
Hope you enjoyed it.👌
CIVILIANS 