Cube test | Compressive strength test of concrete

CUBE TEST( COMPRESSION TEST):-

Use:

Cube test is commonly used for determining compressive strength of concrete (or its ability to resist a crushing force).

The compressive strength of concrete is one of the factors, which controls the loads, which may be applied to a concrete structure.

In this test the concrete is filled in the square box and are taken in Laboratory for further completion of test.

Apparatus:

Compressive testing machine.

Tampering rod (dia 16mm and 60 cm long bullet pointed at lower end).

Square cube moulds.

Steps for Procedure:

1.) At site:

i. Preparation of cube samples:

The proportion and material for making these test specimens are from the same concrete in the field.

ii. Specimen:

6 cubes of 15 cm size (square).

iii. Sampling:

1.Clean the mould and apply oil.

2.Fill the concrete in the moulds in layers ( 5cm thick).

3.Compact each layer with not less than 35 strokes per layer using tampering rod.

4.Level the top surface at smoothen it with trowel.

iv. Curing of cubes:

The test specimens are stored in moist air for 24 hours and after this period specimens are marked and removed from the moulds and kept submerged in water until taken prior for test.

2.) In Laboratory:

i. Measurement: Measurement of 6- concrete specimen are taken (which are sent to laboratory) and calculation of cross sectional area of specimen (m㎡)

ii. The bearing surface of machine is cleaned.

iii. Start machine: Turn on machine and one concrete specimen is placed in the centre of the loading area.

iv. Lowering piston: Lower the piston against the top of the concrete specimen by pushing the specimen.

v. Applying Load: As piston is on the top of specimen, so load is applied and lever is pulled into the holding position.

Compressive Testing machine is placed by pressing zero button on display board.

vi. Increasing Pressure: By turning pressure increasing valve counter clockwise. The pressure on the piston is adjusted. So that it matches concrete compressive strength valve and load is applied without any shock.

vii. Test completed: concrete specimen is observed, when it begins to break stop applying load.

viii. Record the ultimate Load.

Calculation done in lab:

For calculating Compressive strength (C.S) of the concrete, it’s given as:

Compressive Strength = Ultimate load (N)/ Cross sectional area (m㎡).

Cross sectional area = 150 mm x 150mm

= 22500 m㎡

If any of the specimen Compressive Strength result Varies by more than 15% of the average results, the result is rejected.

Result obtained:

Average compressive strength determines its valve.

Observation Table of cube test :