I'm looking to use a brittle material that is easy to mix and pour into small moulds with a very low tensile strength to investigate cracking behaviour of brittle hollow discs when subjected to an internal expansive pressure.
I've tried using very weak concrete, but the irregularity in the material is undesirable. Dental plaster on the other hand seems to be too strong.
Any suggestions of something similar to dental plaster in texture and consistency, but much weaker, that I can mix and pour easily?
Hey Shobana,
how about a cementitious mortar? it has more homogeneous properties then concrete.
The link attached might be useful to read for the mix-design: "Strength of cementitious mortars: a literature review with special reference to weak mortars in tension."
Good luck with your experiments!
https://www2.warwick.ac.uk/fac/sci/eng/research/civil/dtu/pubs/rn/build/still_2004/still_11-2-04.pdf
do you mind saying more about the test you want to do?
For example, what kind of pressure and how will you apply the pressure.
My first thought was, can it be as simple as ice?
Dear Shobana, I think that a very easy way for you - to use gypsum. This material is homogenius, having enough low tensile strength, brittle and convenient for the quick molding in the form. So, you may fabricate a lot of samples for mechanical testing and physical modelling. Serge
Hi Bosco,
I'm trying to cast a small hollow disc of brittle material (internal diameter = 4mm, outer diameter = 12mm, height = 25mm), and impose an expansive pressure against the inside surface to see what pressure is required for cracking of this material to occur.
The tensile stress to break this material will ideally be between 0.5-2 MPa. I have tried dental plaster, but it is too strong (more than 3 MPa estimated tensile strength).
I think ice would be extremely difficult to handle - my loading set-up is fixed in the Structures lab so I need to cast my discs in-situ.
Hi Shobana, for the reducing of strength of dental plaster or other too strong compound you may introduce the inert (ballast) filler. The content of filler which allow to obtain desired 0.5-2 MPa is determined by experimental mixing.
Hi Serge, what sorts of fillers qualify as inert fillers? Would sand work?
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