John's Alu Profile build

[Evengravy]

Initial test mix is done, the testing here is designed to judge bonding strength when using a simple UHPGRFC mix as a replacement for mortar. This might be unnecessary but mixes like this are said to be good for 12,000psi or so, so I'd like to try it.


UHPGFRC mixes (in my very limited experience) are approached differently than regular cement type mixes, insofar as the cement to aggregate (sand) proportions are quite different. With regualar cement mixes you would generally be 1:3 cement to sand ration, here we are 1:1 roughly.

I have a simple mix and a more exotic one, the simple mix is approached here as I'll need to source some other part for the latter which I'll detail later.

Here we have:




+200g Sharp Sand (quartz I believe) I live near several quarries and this stuff costs me roughly 25 euro per tonne, give or take, and makes great concrete.

+200g Portland Cement (regular cement). Generally this will be mixed with other elements such as 20% CSA or Silica Fume, I'll fill you in on that later, those can be hard to source.

+6g of Glass Fiber (From mbfg.co.uk added to the mix last, strand length is 13mm in this case, probably too long but it'll do the job)

+0.6g of Plasticiser (FLUP PCE 104 from moertelshop.de) I went with the manufacturers recommendation in this case of 3g/kg, it probably needs to be doubled in reality though, so I'll have to order another 1kg tub for the table to be sure.

Don't take anything I say as gospel, this is what works for me so far, I'm very new to this so take everything with a pinch of salt and as 'in testing'.
The mixing procedure used was pretty straightforward, mix sand and cement together dry first, add a small amount of water to make an overly dry mixture that is just starting to clump a little. Add super plasticiser, continue to mix for a minute or two (vigorously) and add more water to bring it to field capacity being careful not to overdo it. When the consistency was where I wanted it, I mixed in the glass fibers last.

I ended up using a little more water than I would have liked or predicted from my calculations (65g), but I think I'll double the plasticiser next time and test again to see if I can further reduce the water input.



I used some small 'soap bar' bricks which are almost identical in nature to the larger versions to test it out, at the moment I'm mainly concerned with bonding strength if I use it as a mortar between the blocks. If it fails to bond, I plan to make another custom mortar mix using standard mortar mix with sand, cement lime and mortar plasticiser with some added glass fiber reinforcement to beef it up as I know that will stick well to the blocks.

One thing I've noted is that the mixture consistency becomes noticeably more 'dry' when adding the Glass Fiber, so I'll have to balance that out. Also the working time is short, around 20 minutes, so I'm going to have to be on the ball when doing this but I have a cement mixer so it should be doable.

The mixture is curing very fast, so in a day or two I should have an idea how the bonding is.