Concrete Cube Testing to determine the strength of concrete can be done in both Destructive and Non-Destructive Methods of Testing. In Civil Engineering Jobs, Civil Engineering Construction Practice Cube test is one of the vital test which is performed to determine the strength of concrete which has been already used in the construction. Cube Testing is a Destructive Testing Method of Concrete Testing, as the cubes are crushed in Compression Testing Machine. The mostly tested cubes in practice are of 150x150x150 size in mm.
Here is How to Do The Cube Test Of Concrete.
|150x150x150 mm. CUBE MOULD|
- 150x150x150 mm. cube moulds 6 Nos.
- Slide wrench 1 No.
- Trowel 1 No.
- 600mm long and 16mm Dia. Temping Rod 1No.
- Nail 1 No.
- Water Tank 1 No.
- Steel Rule 1 No.
- Compression Testing Machine
- Soft Cloth 1 No.
- Mallet 1 No.
- Lubricating agent.
Raw Materials :-
Freshly prepared concrete that is Green Concrete which is to be tested.
- First of all measure the mould for its Length, Breadth and Height all inner to inner dimensions accurately with the help of the steel rule.
- If there is any dimensions which deviates from Length x Breadth x Height = 150x150x150 mm. then loosen the nut bolts of the mould with the help of slide wrench and adjust it to the perfect 150x150x150 mm and tighten the nut and bolts again.
- Now lubricate the inside of the mould thoroughly with lubricating agent, which may be engine oil or Grease.
- Then pour the green concrete to be tested into the mould with trowel in Three Layers of each having height approximately 50mm so that three layers fulfill the cube mould as 50+50+50 = 150 mm. after pouring each layer, compact that layer with the help of the Temping Rod with the bullet ended side stroking into the concrete for 35 Strokes.
- After Pouring each layer into the mould, struck the mould from outside on all four wall moderately with the help of mallet so that no honeycombs forms at the contact surface of the Concrete and the mould.
- After pouring all three layers according to the step 4 and 5, now trim of the top of the mould and finish it smooth with the help of trowel.
- Prepare 6 moulds filled with concrete in the same manner.
- Leave the moulds about 1 hour, then write the cube nos. as cube 1 cube 2……cube 6 and date on which they have prepared on the top surface of the concrete with the help of nail.
- After 24 Hours open the moulds by opening the nut bolts with the help of slide wrench and release all the 6 cubes from there moulds, and immerse completely all of these cubes under water in water tank at room temperature that is 28C +/- 2C.
CUBE BEING TESTED ON COMPRESSION TESTING MACHINE
- At 7th day from the date of preparation of cubes take 3 cubes of the 6 cubes and soak the water on them with cloth and test them in compression testing machine, crush the cubes one by one and note the results on the compression testing machine.
- Do the same for the remaining 3 cubes at 28th day form the date preparation of the cubes, and note the results on the compression testing machine.
- Now calculate the Crushing strength for all cubes from the obtained results in terms of N/mm^2 by the following :-
The top surface area of each cube at Top is 150×150 = 22500 mm^2
suppose a cube tested at 7 days crushed at a loading of 310 KN then the Calculation will be as follows
30 KN = 310×1000 N = 310000N
Hence the Crushing Strength of that cube is
( Load at Crushing/Surface Area of Cube in Contact) = (310000/22500) = 13.78 N/mm^2