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.
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 :
Final Result:
7th day test result- Average Compressive Strength of concrete = 22.33 N/m㎡
28th day test result - Average Compressive Strength of concrete = 31.42 N/m㎡
Differences between:
Whole Circle Bearing vs Quadrantal Bearing
Lintel level vs Sill level vs Plinth level
Construction Joint vsExpansion Joint
Site Engineer vs SiteSupervisor
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