2

I am trying to make garden spheres. First attempt was concrete..no success too much aggregate need a smooth mix. 2nd attempt was cement, much smoother but doesn’t come in quickset so Bunnings staff sold me bondcrete additive, no idea really how to use I just don’t get the whole Picture on what it does and how to add as in water cause if I add too much it ruins my builders mix. Also builders sand and cement mix I’m only using 3 cups of mix at a time and I’m adding water to the ratio for bondcrete...I get air bubbles which is a sign of weakness in the mix once dried, I just can’t get a happy medium at all it’s stressful. i just need to know How much water to add to the builders sand and cement Mix- I’m using 3 cups at a time, for a consistent mixture. Then I need The same Formula but Now adding In the bondcrete to help it set quicker. I’m noticing that it crumbles once it has set...and bubbles in mix as it sets. I’ve never attempted to make anything out of cement or concrete but I really want to make a garden orb/sphere. I don’t want to give up but I read your page a lot and I get great tips so I just thought I’d put it out there see if anyone can advise me.

For my spheres I’m using blowup beach balls-medium and A gym ball-lge, sadly I only have made a 1/2 of a beach ball.

Gigi
  • 21
  • 3
  • This is more of a "decorating" question (which is off-topic) than a "home improvement" question. In either case, some formatting would be _really_ helpful in terms of making this readable. – FreeMan Oct 07 '20 at 13:26
  • It sounds like you may not be mixing the concrete properly. It's possible you have some concrete that's still dry, and was never mixed completely. If you're getting air bubbles, you need to vibrate the concrete to remove air bubbles. Just a simple orbital sander would work, pressed up against your forms. This will both remove air bubbles, and encourage the cream (higher portion of cement) to go to the sides. I'm not sure why you care about cure time. AFAIK boncrete is a bonding agent, not something that decreases cure time. –  Oct 07 '20 at 16:01

1 Answers1

0

The question is on how to build a sphere not how to decorate.

Are you using a medium to hold the concrete in place? We built reef balls using a similar procedure. (Reef balls are concrete balls dropped on the ocean floor to create artificial reefs for fish to hide)

We would wrap chicken wire around the ball making openings for the fish and pack about 1” thick of mortar with some fine rock called Turkey grit. We mixed until it felt right not runny at all but wet enough to be able to push the mix into the layers of wire. we would do 1/3 to 1/2 the ball at a time depending on size and let it cure for 2-3 days then do the next section or finish it.

We eventually found that 18” worked the best for our project the larger ones got two heavy and the beach balls did not hold up well. The smaller 12” ones worked but would disappear from the area?

There are all kinds of methods, molds and doing 1/2 shell at a time. we found the wire and mortar mix worked well but using that same method you could build your sphere without the holes once it is completed if the surface is two rough you could give it a finishing coat to make it smooth (we wanted rough surfaces for plant and animal life to attach to).

There are all kinds of examples on line not many do the balls like we did but last time I dove the area. There was a lot of life in that area that was a “desert” before.

Ed Beal
  • 101,306
  • 4
  • 72
  • 150
  • Ed thank you. It must be rewarding once you see what security your reef balls bring to our ocean. Your response has helped me a lot and yes I’ve googled everyday and it becomes confusing to say the least. Enjoy your day. – Gigi Oct 07 '20 at 22:16