# grout background question



## postskunk (Jul 19, 2009)

once again looking to the masters for answers. I know that you have to keep grout backgrounds wet to leach out the PH in a wet or heavy misted type set up but what about in a dry set up. I'm doing a background for my knob tailed gecko out of foam and grout but its going to be a very dry set up so do I have to worry about keeping the grout wet for a few weeks before I use it or can I just let it dry the first time/ maybe mist it for a few days instead? and if it's safe to use sooner will skipping the wetting step make it more vulnerable to cracks and flaking? you guys know this stuff better then anyone else so I thought I'd ask. And I promise I'm going to get some dart frogs one of these days and then I'll be able to put up relevant threads .
Thanks guys
-Matt


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## melas (Oct 24, 2007)

You can skip the neutralization step (the vinegar etc) but you will most certainly want to keep it wet to ensure proper curing of the cement. The first three days are the most important but if you can keep it submerged/wet for 5-7 days you'll get the highest strength out of it. You are correct - skipping this step will cause your cement to flake, crack, and never properly cure.


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## postskunk (Jul 19, 2009)

Thanks for the quick reply and the info, very much appreciated and useful of course. Maybe I'll sneak a pic of it in this thread when I'm done.
thanks again
-Matt


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## VivariumWorks (Feb 27, 2008)

I make concrete backgrounds on a weekly basis. You don't need to worry about curing the grout with water for a couple of days. If its a thin layer on foam its going to crack no matter what. You've got a thin layer of a solid rigid material in front of a flexable less dense material. Your going to get some cracking, however if you layer it up enough times it will make it irrelevant. Point is that you don't need a full cure for desert reptile applications. Its only when there is water that the calcium hydroxide concentration is an issue.

By doing the submersion curing you do get better strength out of the layers but its not going to be enough to ward off the clawing action of many desert herps.

I would just add enough layers, at least two good ones, probably three. And not worry about it. I've got a 6 foot tall, 3 foot wide and 2.5 foot deep desert viv done with three grout layers over foam. In a waterfall area I designed, I coated in epoxy to seal and waterproof it to not worry about this impartial cure of the grout, but it still leaked after three coats of epoxy so I said F it and filled it in with desert grasses instead.

If you havn't carved your background yet, make a few thin, deepish holes in it with a slight upward angle. Then get a cheep dense flexable foam and cut a hole in it. Go out and collect some dry grasses or they have some at Hobby Lobby/Michaels and stuff them into the flex foam that then gets stuffed into the hole. It looks pretty good if you do it right. I'll post pics of my setup when I get around to clean it up. The 6 lizards I keep in there sure make a mess of the place pretty quick.


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## melas (Oct 24, 2007)

I can assure you that the proper curing of concrete is essential to its performance. I'm currently working on my 4th vivarium utilizing the technique outlined in my signature and have yet to have any cracking. Please see the threads below where I discuss in detail the hydration process. I also discuss the difference between curing (hydration) and pH neutralization (which many people tend to confuse).

http://www.dendroboard.com/forum/parts-construction/35790-concrete-curing-method.html#post322797

http://www.dendroboard.com/forum/parts-construction/34636-fake-rock-questions.html#post308465










Also - per the OP this viv will be for Knob-tailed geckos. I've personally never kept them but I'm sure they will be unable to do damage to a properly cured background. I typically end up with a 1/4" thick layer of cement which is incredibly strong. 

If you use some sort of cement modifier (polymer, latex, etc) you may be able to reduce the curing time down to hours rather than days. I used liquid latex to make the rock wall background in this 10' x 4' x 2.5' python enclosure. I made a 3/4" thick "platform" in each of the doorways which I crawl on to get in and out of the enclosure for maintenance. I'm around 230lbs and have put my full weight on these platforms.



















Please note that two 80lb+ pythons share this enclosure (for now) and have not caused any damage.

I do like the idea of the dried grasses etc. 

FYI - I worked for a GeoTechnical Engineering Firm as a concrete\soils field engineer. I was in charge of making sure the foundations and floors of large commercial buildings (Lowes, Walmart, Kohls, Target, etc) were installed properly and met the compressive strength required by the design.


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## VivariumWorks (Feb 27, 2008)

All-right well your concrete experience well surpasses mine. I would listen to Melas then.

However I stand by the idea that it is not necessary for most of our applications as we don't have the need for super strong concrete. In most herp applications, your 10' masterpiece aside, I argue that we don't need the hardness to be equal to that of a grade required for structural applications. We just need it as an aesthetic veneer. And if one layer of grout water cured over time is equal in durability to animal claws as three layers quickly cured and dried, then I'll follow your method, as I loose detail every time I add a layer. 

I guess you'd also be the one to ask, what is the chemical difference between grout, mortar, and concrete anyways? I know, from unfortunate experience, that grout has a higher level of caustic material in it than quickcure concrete does, but I'm not certain why. I'm assuming it’s that the grout contains something to retard the cure to make it not setup too fast, but from a chemical standpoint what’s the difference? I ask because I like to use the fast hardening quickcrete for rock casting applications because it sets up fast and also causes less of a pH spike. I’d like to use the grout, as it comes pre-colored, but I don’t like the pH issues from it. I’ve thought this was due to lye concentration differences but I don't know if that’s true. I probably need to talk to concrete chemist, but you know a lot about this so maybe you've got some insight.


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## postskunk (Jul 19, 2009)

Thanks both of you, 
he is a pretty tiny like 15 grams so I don't think he'll damage it but I'm not good enough at it yet to get a good application under a quarter inch anyway. I wasn't really worried about how long it would take, if I had to I would wait and do it right I just didn't want to take all that time if it wasn't necessary. 

also that Python cage is unbelievable it's always cool to see different background techniques used on a large scale.

I'm gonna start carving it out tonight if I can muster up the energy. 
thanks again 
Matt


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## melas (Oct 24, 2007)

I meant no disrespect. 

I agree that most applications do not require concrete to have a high compressive strength but I'm not sure why you wouldn't aspire to getting the concrete as hard as you can? You would not need to submerge the piece - you just need to have water available for the hydration process throughout the curing period. Wet towels work well for that. I built my last rock wall as a removable insert. It is attached to a piece of egg crate so that it is easily removed if necessary. Were it not properly cured it may have crumbled by the tensile forces exerted with me moving it around. 

As far as the difference between Grout, Mortar, and Concrete: The main difference between the three is the water/cement ratio and the size of the aggregate used. 

Concrete has the lowest water to cement ratio, with mortar coming next, followed up by grout. This is of course when mixed to the designed ratios for each product - you could certainly change the ratio, thus altering the usefulness of each for your application.

Here's an image depicting the results of a typical slump test on each type of material:









Now individual BRANDS and specific designations of each product may greatly affect the composition of what you are using.

I'm certainly no chemist - I always struggled with that stuff in college - Organic Chem kicked me up and down the aisle! I do know that grout and concrete have essentially the same ingredients. Cement, aggregate, and water. Commercially available grouts may have polymer admixes in them to help with the elasticity. This would vary by the brand and type. As far as being more caustic . . . I'm not sure on that. It should have essentially the same carbonate content (source of the alkalinity) but perhaps it is, as you say, related to another reagent in the mix. Perhaps it is from the increased water content that causes more of the cement to go into solution with the water thus causing the unspecified problems you are encountering. Also - I do know that mortar and possibly some grout mixes add lye which would have a profound impact on the pH of the resulting product. Hard to say . . . 

I'm just going to be using straight Portland cement and sand in the future. It's REALLY cheap (Like $4.00/50lb bag) and it's really the same thing. This would allow you to play with the aggregate/cement ratio to get different textures etc. I've been working on documenting a new process that I have developed utilizing latex, portland cement, and fiberglass . . . maybe I'll do a simple test run to demonstrate the process this weekend. 



VivariumWorks said:


> All-right well your concrete experience well surpasses mine. I would listen to Melas then.
> 
> However I stand by the idea that it is not necessary for most of our applications as we don't have the need for super strong concrete. In most herp applications, your 10' masterpiece aside, I argue that we don't need the hardness to be equal to that of a grade required for structural applications. We just need it as an aesthetic veneer. And if one layer of grout water cured over time is equal in durability to animal claws as three layers quickly cured and dried, then I'll follow your method, as I loose detail every time I add a layer.
> 
> I guess you'd also be the one to ask, what is the chemical difference between grout, mortar, and concrete anyways? I know, from unfortunate experience, that grout has a higher level of caustic material in it than quickcure concrete does, but I'm not certain why. I'm assuming it’s that the grout contains something to retard the cure to make it not setup too fast, but from a chemical standpoint what’s the difference? I ask because I like to use the fast hardening quickcrete for rock casting applications because it sets up fast and also causes less of a pH spike. I’d like to use the grout, as it comes pre-colored, but I don’t like the pH issues from it. I’ve thought this was due to lye concentration differences but I don't know if that’s true. I probably need to talk to concrete chemist, but you know a lot about this so maybe you've got some insight.


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## VivariumWorks (Feb 27, 2008)

Hmmm that helps acutally. That slump test pic is great. From what I have heard lye is added to concrete to reduce the curing time to allow for a longer working time before it becomes too hard to sculpt/mold/pour. Grout definetly has a larger caustic content than the fast cure mortar as I've had no issues with reinforcing polyester resin ontop of the quickcure mortar and MAJOR issues with doing the same method onto grout. I talked with a chemist who makes epoxy and polyester resins and he said it was due to the polyester resin not being able to withstand caustic substances like epoxys can. That and I've noticed that unless I seal my grout designs well with epoxy it will affect the pH much more than the quickcure mortar.
Now what I've tried already with some success is the addition of a plazzoian, fumed silica (sp?). This sems to increase the strength and is supposed to increase the cure rate and reduce the pH spike. I'll have to do some tests on what ratios are necessary but it seems to work thus far.
I'm casting out concrete into silicone molds for production of vivarium backgrounds like this:


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## melas (Oct 24, 2007)

Bigger picture please!


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## VivariumWorks (Feb 27, 2008)




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## postskunk (Jul 19, 2009)

Another question or two:
I can only find the color I want for the top part of the background as unsanded grout, do I have to add sand to it or can I use it as is? I'm guessing I have to add sand which I could do cause I can get sand in that same color but if I can use it without the sand (hopefully making it even smoother) that would be nice?

second question it there any particular paint that works well and is safe to add detail? type/ accessible brand maybe?

-Matt


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## postskunk (Jul 19, 2009)

figured out the grout thing, didn't take much digging. sorry about that guys
-Matt


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