To answer the initial questions sent by users of ArtificialRock.ca, yes we will be introducing the concepts of advanced sculpting technique as well as structural forms and steel.
I hope to be able to have this information available soon, but please feel free to begin asking any questions about the design and implementation of structural steel gridwork.
Essentially this is a poured concrete foundation with 10mm re-bar dowels protruding from the top. Using special re-bar bending tools you create a skeleton of steel that is able to be load bearing of its own accord. This step replaces the styrofoam used in the non-structural form building detailed on this website.
Hi Steve, Is there a Standard for the design and strength requirements for the rebar work? I'd be interested to know for reference, if there is such a thing. Though it's probably a case of applying general principles to the building of rock waterfalls or walls/boulders. - Would it be better to weld the pieces/sections together, rather than tying off? - In structural work like a waterfall, ( eg, about 6' high, and 10' long), is the base coat over the rebar cage the same mix as the sculpting coat, or does it have aggregate added to it, and if so in what proportions? I wouldn't want to go to all that work and expense and have it crack. - Does the sculpt coat have to be added within a certain time, and do you use a bonding 'slurry' for the top coat? Thanks for the help Steve, Stone
There is definitely a standard practice for the rebar design. Most inspectors will expect the entire formation to consist of a grid of "squares" which are between 6-8" center to center. I strongly do not recommend welding the overlaps, the tying is faster and strongler once you get the hang of it and allows much more flexibility in the future for redesign if you change your plans part way through the project.
Occasioanlly electrical inspectors insist that they want the joins to be welded for bonding purposes, but this is a result of not understanding the process properly. Definitely welding is not the way to go.
In your waterfall example - If you are experienced enough, the optimal building method is to gunite (shotcrete) the base coat providing uniform strength with a 35 MpA concrete mix which you should order from a batch plant. You will also need an air compressor and a pump truck operation and a few REALLY strong people to help out.
The most important step with the waterfall is the actual waterway. The shotcrete is not waterproof, and the sculpting mix is also not waterproof. To dispell any rumors - concrete itslef is pourus (sp?) regardless of how dense the mix is. This is why swimming pools have 8" thick concrete covered by 3/4" of plaster in a VERY specialized application. The plaster is extremely dense typically using quartz crystal as a main ingredient. The waterproof effect is achieved through a technique called a "hard trowel" which needs an experienced hand to do properly. If you have never done a hard trowel you will not be able to do this to build your waterfall.
You may like to finish the waterway of your waterfall in a torch on waterproofing agent which is VERY messy to work with, not to mention expensive. You can also try various other waterproofing compounds as a middle layer between your base shotcrete coat and the final sculpting mix which covers everything else.
Water retention is a mystery to most people and VERY few home builders can pull off constructing something that is completely waterproof.
In regards to your slurry question, If you are adding concrete to your project in different stages, you will want to add the next coat within three days if at all possible. After three days the concrete is still pulling moisture from wherever it can to aid with curing. Soak down the entire project before you start. If you are adding wet concrete to other wet concrete, no need for slurry. If you are adding fresh mixed concrete to hard concrete no matter how old, you really should use a slurry coat. The slurry must be applied in small doses because it dries very quickly. For example do not cover your entire concrete project in slurry and them begin adding fresh concrete. Cover a small section in slurry and then add your fresh concrete to it. Then add more slurry in another place and fresh concrete immediately overtop. Repeat this process until you have completely covered the old concrete with new concrete and you should NEVER have any problems with separation between layers.
Hi Steve, thanks for the reply. The reason I asked about aggregate in the base coat is that I'm looking at mixing it and applying it myself in a project at home. I realise it'll be a big job, but I have a cement mixer, and a mate to help. So, I was looking for a mix design for the base coat over mesh. I am a Tiler and Waterproofer, so I will do the waterproofing myself. Does the waterproofing membrane go only over the actual waterway? Of course I will waterproof the area further, past the actual water bearing surface itself. Yes, your answer was very helpful, much appreciated, Thanks, Stone ( Bruce)
Dont forget to account for the splash zone when adding the waterproof membrane. Any places where the water moves swiftly or breaks from the face you will have appreciable splashing which can add up to significant water loss over time.
Cheers.
Steve Goodale Green Pools www.ArtificialRock.ca www.GreenPools.ca 1-888-818-POOL