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Basic Knowledge
8.7 Compressive strength testing device
  • Detailed description

1. The application of compressive strength testing device
This device is mainly used to test the compressive strength of set cement. It also can be used to test the compressive strength of construction materials such as concrete, brick and stone. The biggest strength the set cement withstood when it is broke can be tested in accordance with the constant loading rate given.


2. The function of compressive strength
The compressive strength testing device adopts the hydraulic pressure loading and electronic force measurement methods. It has the functions such as loading digital displaying, loading rate displaying, the biggest loading value keeping, overload protection and power-off protection etc. according to the API specification, the loading rate should be constant. The loading rate can be controlled in a constant speed scope by adjusting the oil-delivery speed. This testing device has high precision, high reliability and conversional operation. The biggest testing force can come to 300KN.


3. The test procedure of compressive strength testing device
a. Make sure the oil-delivery valve and oil-return valve is turned off, start the oil pump, pre-heat for 5 min.
b. Press the “Area no.” button, the meter displays P0001, press the “Enter” button, the meter displays S0004, press the “Enter” button; input the section area which is 25.8 cm2(50.8mm×50.8mm), press “Enter” button. The unit of the biggest load the set cement can withstand and the loading rate is MPa and MPa/S separately. (Note: the side length of set cement is 50.8mm; S0004 is suitable for any size set cement.)
c. Put the set cement into the compressive fixture. The testing sample should be aligned to the fixture. The sample should not point to the tester in case of hurting people when it is broken.
d. Unscrew on the oil-delivery valve slowly, make the piston up 1~4mm and contacting with the sample. Screw on the oil-delivery valve.
e. Press the “reset” button on the digital display.
f. Unscrew on the oil-return valve slowly, increase the loading rate slowly. Keep the loading rate between 0.4 and 0.44MPa/S until the testing sample being broken.
g. The loading rate comes to zero, when the testing sample is broke. Screw on the oil-return valve, unscrew on the oil-delivery valve for several second and then screw on it. Take down the broke testing sample, write down the value on the digital display which is the biggest pressure the testing sample can withstand.
h. Repeat the above mentioned procedure, and do the next compressive strength testing.
i. After the experiment, clean the cement particles on the table and turn off the power.


4. The maintenance of compressive strength testing device
a. Start the oil pump and pre-heat it for 5 min before test. If the device is not prolonged use, it should be circulated unloaded for several times in order to empty the air in the oil-line.
b. After the test, clean up the table.
c. Open the host back cover at regular intervals; observe the oil level of oil tank.
d. The new device should change the hydraulic oil after one year usage, and then the hydraulic oil can be changed for ever two years.

Breakdown maintenance
a. Big noise, and unstable pressure
Cause: 1. there is air in the oil-line. 2. The oil in the oil tank is very little.
Solution methods: 1. start the oil pump, shut off the oil-return valve, unscrew on the oil-return valve and make the piston up 1~4mm. then shut off the oil-delivery valve, open the oil-return valve and make the oil returning to the oil tank. Do it like the above mentioned for several times, and the air in the oil-line can be emptied.2. Add hydraulic oil into the oil tank.
b. In the same group, the “zero point” of fist sample is different from the second one.
Cause: it is not reset after lifting the piston before loading.
Solution methods: shut off the oil-return valve, open the oil-delivery valve to make the piston up1~4mm and then press the “reset” button.