Post by matt on Oct 8, 2020 7:54:52 GMT
Hi Neil,
Too early to tell how well they hold up or whether the birds end up liking them, so I won't make any claims on those counts (yet), but happy to share what I learned so far when making them. The mix I ended up with was about 3-1-1 perlite/sand/cement, with addition of fibreglass strands for strength. No idea whether the fibreglass make much difference, but couldn't hurt I guess - I used some of these: www.ebay.co.uk/itm/Sika-Cim-No-Crack-Fibre-FIBRE-ADMIXTURE-FOR-ENHANCING-THE-STRENGTH-OF-CONCRETE/303315388429?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
Perlite is a bit pricey from garden centres, but quite cheap if you buy a hundred litre bag from eBay, which is what I did (also finds plenty of use in my garden so won't be wasted). The mix is not strong by concrete standards (very easy to drill, for example, even a few months after making), but should insulate pretty well, and perlite is inert so should be safe for the birds. I was leaving them 48 hours in the mold before removing, and didn't have any casualties, and concrete will continue to get stronger for a while after.
One of the key things with concrete is not to add too much water, as that weakens the final product. Mixing can be hard work to get everything evenly distributed when it is not too wet - I was using a paddle attachment on an SDS drill and it seemed to go OK.
I'll post some pics of the molds I made if you are interested.
Too early to tell how well they hold up or whether the birds end up liking them, so I won't make any claims on those counts (yet), but happy to share what I learned so far when making them. The mix I ended up with was about 3-1-1 perlite/sand/cement, with addition of fibreglass strands for strength. No idea whether the fibreglass make much difference, but couldn't hurt I guess - I used some of these: www.ebay.co.uk/itm/Sika-Cim-No-Crack-Fibre-FIBRE-ADMIXTURE-FOR-ENHANCING-THE-STRENGTH-OF-CONCRETE/303315388429?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
Perlite is a bit pricey from garden centres, but quite cheap if you buy a hundred litre bag from eBay, which is what I did (also finds plenty of use in my garden so won't be wasted). The mix is not strong by concrete standards (very easy to drill, for example, even a few months after making), but should insulate pretty well, and perlite is inert so should be safe for the birds. I was leaving them 48 hours in the mold before removing, and didn't have any casualties, and concrete will continue to get stronger for a while after.
One of the key things with concrete is not to add too much water, as that weakens the final product. Mixing can be hard work to get everything evenly distributed when it is not too wet - I was using a paddle attachment on an SDS drill and it seemed to go OK.
I'll post some pics of the molds I made if you are interested.