[badhabit]

Hi Thomas - How are you going to pressurise the sample to 8bar? do you have an autoclave? 8 bar is 80 tonne per sqm.. or do you have a big pressure pot? or a big steel tube I suppose.... I don't think eliminating internal bubbles will make a measurable difference? but you will find out... You can compress bubbles but then you trap micro bubbles at pressure in the concrete and they break out eventually. In aerospace laminates they are compacted at 6-8bar but the air goes into the resin as a saturated gas. Then as the part is cured at 120C it desorbs out, plus there is a vacuum system to remove gases....So you will need a plastic bag around the concrete part with a breather layer then 7 bar applied to the outside of the bag to pressurise the part....???? Regards Peter

at 8bar a 2mm bubble will be compressed to a 1mm bubble so is this a difference? will be interesting to find out...

I was going to build a chamber for this. Some Ø150mm steel tube with flanges on the ends and then compressed air. And before the internet police arrest me, yes, i know it is "a bomb", but heavy duty seamless structural pipe(like 8-10mm wall) and with a good penetrating weld on the flanges it'll be just fine...

I'm not convinced it is going to do a whole lot to the EM, but maybe the final strength. I did some test-casting and my EG was somewhat "brittle" in small sections. Not sure if "brittle" is the correct term though...but it seemed like the test-pieces broke "through" all the trapped air-bubbles and i wanted to see if i could get rid of them somehow...this is one of those samples:
Attachment 468324
...as you can see, a ton of small bubbles....

I read somewhere, i can't recall where(was it a qoute from you, Peter?) that "someone" raised the pressure to above 6bars and the gas dissolved into the epoxy eliminating the bubbles. Like you describe above. This was actually the main reason why i wanted to try to cure it under as high pressure as i could...to try to dissolve the gas into the resin to avoid the bubbles...if i just reduce the bubble size it will not have any significant effect....but if it does dissolve, do i then need to put it under high temperature(like 70c i used for post-cure) vacuum afterwards to pull out the gas from the cured epoxy afterwards? I would use the same pressure-champer for this. It would be easy to wrap the cylinder in heating wire and isolation material to heat up the sample during the vacuum process...

/Thomas