Hello everyone. I'm currently working on conductive/piezoresistive concrete with carbon black addition. Previous experiments on 40x40x160mm samples (column shape) gave good, and expected results, ie, the decrease of the electrical resistance over the increase of the axial compression.
Nevertheless, new experiments on 100x100x60 samples (slab shape) showed an unexpected behaviour under compression. The resistance initially increase and only after a certain compression level, starts decreasing. The attached picture ilustrates the phenomena with a plot.
Any idea for such behaviour?
Thank you all in advance.
Hi
A guess - could it relate to differences in precompression, i.e. if your first sample did not have precompression and your 2nd sample has precompression, then the reversed slope would make sense until you hit zero precompression and start loading the sample again?
In any case, it should be easy to toy with added precompression and confirm/reject this hypothesis.
Cool - I did not even know piezoresistive concrete exist.
Out of curiosity
- What is it used for?
- How high temperature before you hit the Curie temperature?
I imagine, you can make smart concrete and embed sensors this way?
Sincerely
Claes
Dear Claes,
Thanks for the suggestion. It was actually because the jack was not applying the load uniformly in the sample at the beginning of the loading .
This could be used for traffic monitoring in roads. The attached picture shows our last results, if you're curious. The material is pretty reactive to the static/dynamic compressions.
Sincerly,
André
Hi
OK, good to hear that you identified your system Gremlins.
I imagine your material, if it holds mechanical properties similar to that of ordinary concrete, being ideal as built in load cells in large structures. Then, low frequency matters and piezoresistive is better than piezoelectric.
What is your Gauge Factor?
Any known limits wrt to the Curie temperature for your material? I imagine there is a market, in particular if you can go beyond 250 C and the material is low cost.
All the best
Claes
Experiments were done in mortar mixes, and the mechanical properties got even better.
We've got gauge factors between 30 (45°C) and 40 (10°C). I've still no idea about the Curie temperature. What we saw, in fact, is a reduction of the GF when increasing the temperature. We did experiments considering temperatures between 10°C and 45°C.
Cheers,
André
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