I have 220 new gallons to fill (Al is the man) and can’t afford Tonga branch rock. I figure if I made some up soon, it could cure through the summer and be ready by say, August. Anyone up for a group project? I missed the last one, how is that rock holding up?
I’d be interested in giving a hand and seeing the whole process and maybe taking a few pieces home.
I would, as well.
I might be interested in lending a hand, but I dont really need any rock.
I’m in. I don’t need any though. I would love to learn 
so how does this work? can we make the rock into any shape we want? i could use some specific shapes to fill the rest of my tank. if we can do stuff that’d look like branching coral or thin ledges, yeppers for me. just fist shaped rocks, i do not need, but i’d still like to learn how to do it for the next tank [wife says in 2010].
Moliken,
Here is some info I put together 2 years ago on the topic. You are only limited by your imagination and time. The more time you have to layer the rock the more detailed it can become. Lumps, caves, arches, Branching, and anything can be made in concrete.
would be pretty sweet for “custom shaped” pieces. just not sure if time plus material prices would really be cheaper than just buying base and curing it in a live system… (what i did when i set up my 90)
im looking to set up my 90 or 75 in the next few months so this would be great 4 me. ide be interested. it would be alot faster then drilling rock and i could make custom hole. would be great.
Sounds like fun but got more rock then I know what to do with now.You defiantly come out way ahead on cost compared to even base rock but it does take a lot of time. For the concrete to cure with standard cement takes 28 days and then you have to cure it in water for up to 4 weeks to reduce pH. There are methods/products to reduce the time but using the basic material it will be about 2 months min. This will vary based on size and density of the rock.
The biggest benefits would be:
no impact to the reef
Create unique shapes
Cost
no unwanted Hitchhikers
Ability to say I DIY the rock
ya i will help. so count me in was at last one with al and cd angel0 Al may have alot of scrapes laying around.
I can bring them no problem if needed
i think some diy rock would be neat so count me in
I was reading on GARF that Leroy switched from regular portland cement to some sort of white grout cement. says its less alkaline and cures faster and looks a bit more natural too. whiter than the portland gray. i think they have it in 5 lb boxes at HD. has to be one without sand, additives or polymers added. just straight white grout.
he mentioned the change in some other articles i cant find right now. but this looks like a cool way to make branching finger rock.
That is neat
I missed that before and have always made branches by digging my fingers in to the sand then adding more sand and repeating the procedure. I have seen the grout used but it has to be plain grout without the anti-bacteria additive. The main reason to use cement is cost. Grout does add to the cost.
Al, did you guys use sand last time for aggregate?
I used cement, old coral, old cement chunks, sand and crushed coral as aggregate.
[quote=“a1amap http://delreefclub.org/index.php?option=com_content&task=view&id=27&Itemid=38”]
Appropriate Aggregate
All aggregates should be washed to remove any small particles and free silica. If there is a question as to the whether the aggregate contain phosphates or silica give the aggregate a acid bath and then soak in fresh water.
Sand - Sand makes cement stronger. You may also find that sand is a great casting medium and that you can get crazy shapes with damp sand. Any “clean†sand will work but avoid sands that are dark in color as they may contain metals
Aragonite – preferred sand but is the most expensive.
Limestone Sand/Pulverized Limestone – used in sand beds and DSB with success.
Play sand - most play sands will be made of quartz and so basically inert.
Play box sand – works well same as play sand.
Any white Sand – Avoid dark grain sands as the may contain heavy metals.
Sand Blasting sand - (casting sand) sugar fine, can be used for filtration, 99% pure Industrial Quartz.
Plastic shavings - PVC, Plexiglas and Lexan drill shavings.
Sodium Bicarbonate or Sodium Carbonate.
Perlite – Lightweight and inert.
Glass Sand - recycled product.
Calcium Carbonate, Aglime, Dolomite – Large grain size preferred, Comes in calcium based (preferred) and granite based.
Hydrated Lime – Reduces alumina content, boosts calcium, rocks more resistant to sulfate.
Vermiculite – Bulk insulation, also an aggregate in insulating and plaster and in insulating concrete.
Crushed Coral – Makes realistic rock and is coral so has a high over-all calcium content.
Oyster Shell – Common Koi canister filter media. It removes phosphate through both chemical composition, and structure. Morton Salt
Salt – Discovered by Travis Stevens (RC) – Solar Salt Crystals (Water Softener Salt). Side effects of salt use: salt acts as a set retarder and if excess amounts are used or overworked into the mix; the cement gets weakened.
Micro-silica - AKA Silica fume (used by Reef Balls) Use a Max of 10% silica fume by volume or 5% by weight. The concrete used to make Reef Balls features W.R. Grace’s Force 10,000 micro silica to create a super high strength, abrasion resistant, concrete that has a pH similar to natural sea water.
Styrofoam – Lightweight and inert
Great Stuff Foam – Lightweight and inert[/quote]
I use gutter guard as rebar for larger pieces or to make tubular arches. I chop up clean styrofoam in to small pieces and mix in with the dry ingredients to lighten the finish cement.
[quote=" a1amap http://delreefclub.org/index.php?option=com_content&task=view&id=27&Itemid=38"]
Reinforcement and Rebar
· Fishing line, Weed trimmer line
· Structural Support Rods / PVC / Acrylic (drill ½ inch holes throughout PVC)
· “Concrete fiber” (nylon hair strands), Fiberglass strands
· Gutter Guard
· Felt cloth strips
· Thin plastic hangers
· Plastic or acrylic rods – Available as bike flag holders or standard scrap acrylic.
· Nylon or plastic window screen
Great Casting materials
· Rubber fish lure worms
· Salt
· Sand
· Oyster shell
· Crushed coral, Old corals can be crushed up to give texture to the new rock.
· Balloons – Water filled or air filled. Leave some of the balloon exposed for easy removal.
· Latex gloves filled with air or water.
· Silicone / Plastic – Rubber bait worms.
Do Not Use
Wood Dowels – Splits when trying to remove from cast concrete. Pain
Pasta – Wet Pasta is nasty and Dry pasta should only be used on the outside as it becomes hard to remove and may crack the concrete as it hydrates.
Tip: If you dampen the casting material most will not stick to the rock. This helps went you want to add layers to the rock. Additional concrete will adhere very well to fresh concrete but not to the dry casting material.[/quote]
Things I would consider:
If you want to reduce time but still keep cost down use a quick set cement such as quickcrete brand type V
Type V Resists chemical attack by sulfates. Seawater contains 150 to 1500 ppm of sulfates.
If the cement is the standard portland type I or II cement I would add some (5% max) sugar (See article)
If you use salt to act as casting material fold it in at the last minute. Do not over mix into the cement as it will weaken. The idea of the salt is that with warm water soaks it will dissolve and leave the rock porous. I broke open the rock in my tank and live rock; most of the activity in the live rock that took millions of years happens within an inch of the surface. The concrete I made when broken open after 6 months had activity about 1/4" into it. The more porous the better. The styrofoam will reduce the weight in the middle of the rock with out having salt that needs to be purged. I did like the look of the rock that was cast in the solar salt so I would consider layering rock to have a light center and a salt cast outside.
The sand in this region is infamous for “alkali silica reactivity”, it weakens concrete pretty severely. To the point that there is a specific mason sand that has to be used in mortar/concrete in order to ensure a strong product. I think the oyster shell is the way to go. Have you heard anything negative about its use? Way less expensive than the others.
Also, when you mixed yours before did you use an air entrainment agent? In commercial mixes this is usually some sort of detergent. I would think that the curing/soaking period would remove the phosphates left by the soap, but I’m not sure.
How well did the rock hold up? Is it still around?
Silica and phosphate can leach from oyster shell but It is not proven. I think mixing it with concrete bonds the available phosphate and most of the available phosphates are (forget the term but means not available or usable). Some things I have read say the exact opposite and the oyster shell absorbs phosphates. Wash it to remove any loose particles and it should be fine. More people have used oyster shell then any other aggregate without problems.
The air entrained I read about use machines to infuse air in the mix or “chemicals”. I didn’t see any reference to the chemicals being standard detergents but it would be interesting to use something like drift (used for babies clothes) as it is dye and perfume free. I would doubt you could remove it easily. Water does move through the rock and I can prove it. When I made the first batch I used solar salt throughout the rock and after soaking the new concrete for 2 months I broke open some of the rock and the salt was gone.
Most of my first batch of rock fell apart after 1 year because I over mixed the salt and it weakened the rock. Fissures appeared after 6 months and they eventually broke. My third batch was hard and solid Some of those batches are in a bucket of water outside to nuke. The remainder that I didn’t need is fill under my shed. I can bring a few pieces. The more you play the better the rock looks. I started playing with small batches to see how different mixes worked.
Using only aggragates makes a solid lump rock I liked using salt, old PVC shavings and styrofoam to lighten the concrete and leave holes. These aggregates worked well.
What I was planning for the larger tank was to make odd shaped doughnuts with a pvc tube in odd shapes to stack smaller rocks, see rough image below. It leaves lots of places to mount frags and fills in great.
nuts.bmp (100 KB)
