concrete lab - cube test

2. This test measures the uniaxial compressive strength of concrete cubes which are
made, cured and tested to very specific requirements. It does not measure or
predict in any unique way the strength of the concrete in the structure. The test is
simply a quality control test which measures the consistency of the concrete in
terms of one particular property (“compressive strength”) using an arbitrary test
method. Testing the same concrete under different conditions, for example
specimen size, specimen shape, curing temperature, loading rate, etc. will give
different results.
INTRODUCTION :

3. OBJECTIVES
 Tests conducted to determine the strength of concrete.
 Compression strength test is carried out using cube test.

4. THEORY
 Two types of tests are carried out to determine whether
 the concrete produced does follow the specification given.
 They are compacting factor test, slump test and vebe
 consistometer test which are for wet concrete. Whereas for
 hardened concrete, they are cube compression test and
 flexibility compression beam test. Hardened concrete test is
 usually carried out when concrete is at age 3, 7, 14, 21, and 28.
 Concrete strength increases according to its age. In general,
 concrete would have acquired 70 % strength on the 7th day.

5. APPARATUS
 Concrete cube size 150mm × 150mm
 Compacting steel rod with size 25mm × 25mm
 Oil / Grease
 Compression test machine
 Trowel.

6. WORK PROCEDURE :
1. Concrete is prepared with the design mix of ( 1:2:4 ),weighed 26kg ( to make 3 concrete cubes ) and water
ratio pf 0.50 – 0.65.
2. Concrete cube mould was made from steel or cast iron with smooth inner surfaces. Every mould had steel
base plate to support and prevent leakage.
3. Mould and base plate was cleaned and applied with oil to prevent concrete from sticking to the sides of
the cube. Base plate was attached to the mould by using bolt and nut.
4. The cube was filled with concrete in three layers.
5. Every layer was compacted for 25 times. This process was carried out systematically and compaction done
uniformly to all surfaces of the concrete.
6. After the top layer has been compacted, a trowel should be used to finish off the surface level with the
top of the mould and the outside of the mould should be wiped clean.
7. The cubes was marked clearly after making the cubes immediately. The details of the cube was written in
ink on a small piece of paper and placed on the top of the concrete until it is demoulded.
8. Concrete cubes was left to harden for 24 before the moulds can be dismantled.
9. After remoulding, the concrete cubes was weighed before submerged in water for curing. The weight of
the cube was stated as ( M1 kg).
10. Compression strength test was carried out for concrete at age 7, 14, 21 and 28 days.

7. OPERATING PROCEDURE FOR THE UNIVERSAL
COMPRESSION MACHINE:
 The wet concrete was weighed and stated the weight as (M2 ).
 The volume of the cube was calculated as shown below :

 Volume of cube (V) = M2 – M1
1000
 The concrete cube sample was placed on the plate of the machine. The power
supply was switched on to operate the Control Box and the Universal
Compression Machine.
 Pressed “( star )” button and ‘Control SPA’ would appear on the screen. Wait
until the value of area appears. The standard cube area is 225.00 cm². Pressed
on to the same number and the date would appear. We did the same
procedure as for this area.

8.  After that, pressed “SET” button and “0 KN 000MPa” was appeared. “0 KN” would give
the value of loading and the “000 MPa” was converted value of loading to strength /
stress value.
 Switched on the Universal Compression Machine as showed above. Moved the first gear
from left to right follow by second gear from down to up. Wait until the “000 MPa”
increases to “999 MPa” then decreases back to “000 MPa” or until the cube failed or
when any form of destruction takes place.
 Then reversed the procedure for both gears and switched off the Universal Compression
Machine.
 The loadings reading was written down.
 Pressed the “SET” button followed by “ ” and the strength value in N/mm² could be
obtained. For the following test, just press on the “SET” button again followed by
 “ ” then “SET” again.
 Kept the workplace always cleaned.

9. RESULTS:
HARD CONCRETE
TEST
CUBE TEST DATE :
Experiment 8
No of cube
Cube
manufactured
date
Age
(Day
Cube
Weight
(M1)
Cube
Weight
(M2)
Volume (V) Compressio
n
Load (N)
Density Strength
(N/mm²)
Cube 1 13/8
20/8
7
7
7.786
7.843
7.324
7.740
-1.1×10−4
1.03×10−4
296.175
353.148
69.9×10³ 13.163
15.695
Cube 2 13/8 14 7.643 7.698 0.055 371.157 75.15×10³ 16.496
Cube 3
20/8 21 7.979 7.904 -0.134 395.201 10.54×10
17.564
Cube 4 13/8
20/8
28
28
7.846
7.845
7.905
7.795
0.059
-0.05
420.364
384.224
152.8×10
18.683
17.077
Concrete Average
Strength
( N/mm² )
46.942/6
=7.824
46.366/6
=7.728
-4.190/6
=0.698
2220.269/6
=370
163485050/4
=408712
98.678/6
=16.45

10. DISCUSSION
1. Why must the inner surfaces of the concrete mould greased with oil?
It prevent grease or dirt stick at the sides of cubes.
2. What is the meaning of characteristics strength of concrete and why it has to be
determine when the concrete age 28 days ?
Strength of the concrete below which is not more than 5% of the test results are
expected to fall and the proposed model has a good potential to predict concrete
strength at different age.
3. Why do concrete cubes need curing and how it is carried out in the
construction site ?
For concrete to develop strength, the chemical reactions need to proceed
continuously. Curing refers to procedures for the maintaining of a proper
environment for the hydration reactions to proceed and it is carried in places
where there is acute shortage of water.

11. 4. State the important steps taken when testing concrete cubes.
The cubes are generally tested at 7 & 28 days unless specific early tests are
required, for example to remove a concrete shutter safely prior to 7 days.
Usually 1 cube will be tested at 7 days and 2 cubes at 28 days, however this
may vary depending of the requirements, check the design first. The cubes
are removed from the curing tank, dried and grit removed. The cubes are
tested using a calibrated compression machine. This can be carried out
internally by competent personnel or by a certified test house.
5. Discuss the result obtained from the experiment.
The strength of concrete increases with age.

12. STAGES ITEM VALUE/CALCULATION UNIT
Materials Cement : Fine aggregate : coarse
aggregate ratio.
1:2:4 g
Water : Cement ratio 0.50 – 0.65 Ɩ
a.Fine aggregate ( Sand )
Experiment 1 -Sand Fineness Modulus 7420 g
Experiment 2 -Sand cleanliness 7420 g
-Sand contents 7420 g
b.Coarse aggregate
Experiment 1 -Aggregate maximum nominal size 36 mm
Experiment 3 -Aggregate impact test 8464 g
-Aggregate contents 14870 g
c.Cement
-Ordinary Portland Cement contents 82.1 g
d.Water
-Water content 1:2:4 Ɩ
Wet concrete test a.Slump test
Experiment 4 -Slump types True slump test
-Slump height 12 mm
-Mixing consistency
Experiment 5 b.Compaction factor test
-Compacted factor 0.5091 g
-Mixing consistency
Experiment 6 c.Vebe consistometer test

13. CONCLUSION:
This report introduced Cube Compression Test. We presented
information and the procedures about the Cube Compression
Test. First of all we would like to thank our lecture who thought
us to do this experiment. Through this activity we were able to
cooperate and able to finish it in required time.