Compression testing

Compressive strength is the primary mechanical property and is the one most used for quality control. The compressive strength of papercrete has been reported around 5.5 MPa.
The ‘concrete cube test’ is the most familiar test and is used as the standard method of measuring compressive strength for quality control purposes
Compression testing is widely used to determine the stress/strain behaviour of solids. It is defined as the compressive force per unit area that it can withstand. It one of the most important limiting factors of product development and it is necessary to be defined before the start of design phase because the results indicate if a material meets the requirements of the design element.
For the experimental determination of compressive strength of papercrete I used the 3M Laboratory in TU Delft (Zwick Z100 machines). The 21 specimens dimensioned 15x15x15cm were tested in the speed of 20 mm/min with a preload of 5 N
Before we started the test we had to prepare the specimens:
• Make the mix and pure it into plastic form
• Remove forms 2 weeks after
• Let the specimens dry until they take their finally properties (50 days)
• Specimens were measured again to get information about the physical properties.
• Put in the top and the bottom metal plates 15x15x0.5cm.
• Put the specimens in the machine
• Write down the maximum force and stress and study when the cracks started.
• Photographic charting for further analysis

Test specimens in compression

Papercrete compressive strengh

  • The curve has 3 different phases.
    • The elastic phase is until papercrete (until it reaches its practical limit)
    • The curvature become smoother in the plastic region. (Indication of creep)
    • After specimens start to crumble they become stiffer and the curve rise faster
    Studying the diagram I got information about the materials behaviour under compressive load.
    • The average compressive strength: σM= 1.12 MPa1 is very low. The value which will be used for safety reasons in the lowest 5% σ= 0.9 MPa.
    • Their is no relation between weight and compressive strength.
    • The specimen which had the max compressive strength (σM=2,36) was the specimen which shrunk during the production.
    • The deviation between min and max is big but we the results have consistent curves.

About Menelaos Kokkinos

Menelaos Kokkinos TU Delft
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