CUBE TEST

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 :

OBJECTIVES

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

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.

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

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. 

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.

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.

RESULTS:HARD CONCRETE TEST

CUBE TEST DATE :

Experiment 8No of cube

Cube manufactured date

Age (Day

Cube Weight (M1)

Cube Weight (M2)

Volume (V) CompressionLoad (N)

Density Strength (N/mm²)

Cube 1 13/820/8

77

7.7867.843

7.3247.740

-1.1×1.03×

296.175353.148

69.9×10³ 13.16315.695 

Cube 2 13/8 14 7.643 7.698 0.055 371.157 75.15×10³ 16.496Cube 3  

20/8 

21 

7.979 

7.904 

-0.134 

395.201 

 10.54×10

17.564

Cube 4 13/820/8

2828

7.8467.845

 

7.9057.795

 

0.059-0.05

420.364384.224

  

152.8×10 

18.68317.077 

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

DISCUSSION1. 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. 

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.

STAGES ITEM VALUE/CALCULATION UNITMaterials 

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 gExperiment 2 -Sand cleanliness 7420 g  -Sand contents 7420 g  b.Coarse aggregate    Experiment 1 -Aggregate maximum nominal size 36 mmExperiment 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 ƖWet 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      -Vebe time 20 - 30 second  -Mixing consistency    

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.