# Calcined clay arena surface



## Foxhunter (Feb 5, 2012)

Before you put any sort of surface down you need to put in something to aid the water to escape. 

French drains are the easiest and very effective. It is a trench about 2' deep and filled with stone and the solid put on top. A series of these across the area will make a big difference to the water getting away.


----------



## ObiWan (Jul 7, 2017)

I agree that that would be nice. I looked into doing a french drain around the lower edge where the water collects. It would have required almost 200' of drain to get the water away from the barn, and not the cheap stuff--I'd have to use the double wall tubing that you can drive & stand a horse on, and that costs 5x more. Total price tag would have been about $2000 if I did all the work myself, the next fact notwithstanding...

To make matters worse, our region has a severe shortage of gravel due to massive flooding this year that's required lots of road repair. My excavator was just notified by the quarry that nobody but government contractors are allowed to buy gravel between 1/4" and 3" in size. The nightly news has reported several times on the county road dept's shortage of both gravel and sand. So that kind of eliminates a french drain as an option.

Also, my excavator has seen french drains inside horse paddocks in the past. He said that it's only a matter of (not very much) time before the horses dig down to the landscape fabric that wraps the gravel and start pulling it up. Next thing you now, it's ripped open and flapping on the surface, and your sand/clay is running unabated into the gravel, which packs it solid and prevents it from draining.

What I'm really looking for right now is info & opinions about using calcined clay in a horse paddock.


----------



## QtrBel (May 31, 2012)

ObiWan said:


> Our 30x40' corral (into which our barn stalls exit) and the 25x40' entry area right outside it (between the corral and the pastures) is a constant mud bog. It doesn't slope enough to drain well, and any hoofprints dam up what little water flow there would be. Southeast Nebraska clay really sucks in a paddock.
> 
> My neighbor, who is a professional excavator and also owns horses, has recently started selling what he calls an "arena mix," which is 80% calcined clay and 20% sand. Calcined clay is the same stuff they put on the surface of baseball infields because it absorbs water without becoming muddy. It's not at all like what I think of when I hear "clay." He mixes in 20% sand to help it drain a little better and be just a little looser when used in either indoor or outdoor horse arenas. He charges about 40% more than for straight sand. A good friend of mine just spread about 250 yards of the stuff on his outdoor arena last month, and loves how it handles so far.
> 
> ...





Calcined clay is clay that has been heated (temps over 800C) to the point that the structure of the clay changes and agglutination occurs forming a very porous molecule. It drains only as well as what lies under it drains as water will move through it as well as be held within it. Since it doesn't completely trap the water evaporation can also take care of a small percent of excess (larger over time and in areas with "drying" winds). Since it holds its shape and is no longer plastic remaining water does not effect the footing. 



The difference between calcined clay and sand is the amount of movement and compaction when outside forces are applied. Sand can be round or angular and will shift readily. Round (think pebbled or river rock except teeny tiny) more so than angular (blocky). Both drain well but the shifting of the round particles can be unstable and effect footing adversely. Calcined clay is not only angular but it is a conglomerate of angled shapes making it even more resistant to shifting and due to the treatment of high heat resistant to breakage.


Calcined clay is a surface treatment. Not meant to be tilled in or covered. There are other products that work well but are constructed in layers to achieve the same/similar effect. The amount of drainage again is dependent on what underlies the area as well as how much water you receive. If the drainage layer is not deep enough to allow for a holding capacity large enough to compensate for the rate of drainage of the native base then you will still have issues. Depending on the slope, drainage capacity and water flow as well as use you may find that you have to employ several techniques to achieve an area that is relatively dry.


ETA - whether and how quickly it will eventually work its way into the layers under it or break down depends on what is under it and use.


Mixing it with sand IMO makes it easier to sell as he can lower the price accordingly. Whether it adds to the drainage capacity depends on size of the particle and how it moves in relation to calcined material. Correctly sized and added at a percentage to cause bridging and drainage is optimized. Too small and it fills the pores that are meant for the water to travel through. Too large and it separates out into layers.


----------



## QtrBel (May 31, 2012)

ObiWan said:


> I agree that that would be nice. I looked into doing a french drain around the lower edge where the water collects. It would have required almost 200' of drain to get the water away from the barn, and not the cheap stuff--I'd have to use the double wall tubing that you can drive & stand a horse on, and that costs 5x more. Total price tag would have been about $2000 if I did all the work myself, the next fact notwithstanding...
> 
> To make matters worse, our region has a severe shortage of gravel due to massive flooding this year that's required lots of road repair. My excavator was just notified by the quarry that nobody but government contractors are allowed to buy gravel between 1/4" and 3" in size. The nightly news has reported several times on the county road dept's shortage of both gravel and sand. So that kind of eliminates a french drain as an option.
> 
> ...





French drains are the most effective and quickest route for water to escape. Their success in your environment depends on how deep the drain can be placed. The more surface action the deeper it needs to go. If you don't have the slope that allows for a deep placement then you have to build up since you can't go down. Not saying it is a solution as there are so many factors that go into placement that it may well not be depending on what your limiting factors are. 



At this point it looks like your limiting factor is going to be availability of materials.



Depending on the depth of your clay you will likely have to dig out a fair amount to be replaced by this material and perhaps still do something to prevent the sides from now eventually collapsing in as well as making sure you have deep enough not to need additional drainage or some way to drain off excess. A perc test may be handy in your situation to help determine the thickness you'd need to place.


----------



## ObiWan (Jul 7, 2017)

Thanks, QtrBel.

I should clarify that my corral does have some slope, and does drain naturally if the surface is allowed to remain smooth. Of course, the horses don't allow that. At the moment, it looks like a miniature Bryce Canyon. I do grade it smooth with my blade whenever it dries out after a big rain, but it's been a month since I've been able to do that because it dries so slowly. Our theory is that if we grade the underlying native clay well (again) before we put down the new surface, then it should remain somewhat smooth underneath the clay. We're thinking that the calcined clay/sand mix should allow some lateral percolation so that the surface water should be able to drain through it and out of the fenced area even if the top is full of hoofprints. The key here is that we're not using straight calcined clay, but mixing it with normal arena sand.

Does anybody have experience to the contrary?


----------



## ObiWan (Jul 7, 2017)

QtrBel said:


> French drains are the most effective and quickest route for water to escape. Their success in your environment depends on how deep the drain can be placed. The more surface action the deeper it needs to go. If you don't have the slope that allows for a deep placement then you have to build up since you can't go down.


The barn can't go up, so we have to extend the drain's outlet until it reaches a low enough elevation that everything will drain. It has to drain really well to prevent freezing, which would render the entire drain useless (BTDT). Hence the 200' length that I mentioned earlier. Surface action in the horse corral is a problem, of course. My original estimate had the high end only 6" below the surface, which should be adequate since this isn't an arena, but a holding pen for two calm mares.



> Depending on the depth of your clay you will likely have to dig out a fair amount to be replaced by this material and perhaps still do something to prevent the sides from now eventually collapsing in as well as making sure you have deep enough not to need additional drainage or some way to drain off excess. A perc test may be handy in your situation to help determine the thickness you'd need to place.


I'm pretty sure our native clay goes all the way to China. It doesn't perc at all. All drainage has to be sideways, because none of the water will go downward. That's why nobody around here uses dry wells.


----------



## QtrBel (May 31, 2012)

The only company (Northern and Atalanta, GA area) I am familiar with that uses calcined clay uses it as one of several choice additives to be custom blended in and not a primary material. Your percentage would be flipped and likely closer to 90/10 or less of the additive. Due to amount needed, cost of material, weight and transportation I suspect it is not used as the primary portion of mixes for arenas and his application is unique. I also suspect it can be imported from China cheaper than it is produced here in the states but still not a cheap product to make or ship. So practical experience will be limited in use for the purpose you describe as well as comparable use. Something to consider documenting and following over time. It's been around forever time and it's properties are well documented so expanding the use is of interest. I suspect cost is a big factor as the amount you would need is going to be significantly greater than what you see used in other sports where it is a top dress and used in far thinner applications.


ETA Just like with adding sands to clay where you need to use a high enough percentage to allow for bridging I would suspect the same holds true here. Bridging would be where the sand particles actually touch to allow for space for the water to move through more quickly as well being held.


----------



## ObiWan (Jul 7, 2017)

QtrBel said:


> The only company I am familiar with that uses calcined clay uses it as one of several choice additives to be custom blended in and not a primary material. Your percentage would be flipped and likely closer to 90/10 or less of the additive. Due to amount needed, cost of material, weight and transportation I suspect it is not used as the primary portion of mixes for arenas and his application is unique. I also suspect it can be imported from China cheaper than it is produced here in the states but still not a cheap product to make or ship.


I'm not sure where my guy gets it, but I don't think cost is a big consideration. He charges $21/ton for pure washed sand, $25/ton for pure calcined clay, and $30/ton for an "arena mix" that's 80% clay + 20% sand. I suspect it's the labor to mix it that adds to the cost. I'm getting the mix for $25/ton as a "friends & family" discount, and because it's still a relatively new product for him and he wants to experiment a little with somebody who can give him detailed feedback.



> Just like with adding sands to clay where you need to use a high enough percentage to allow for bridging I would suspect the same holds true here. Bridging would be where the sand particles actually touch to allow for space for the water to move through more quickly as well being held.


My usage will be in two main areas: the enclosed corral where the horses will sometimes be detained, and the "foyer" (for lack of a better term) that leads from the corral to both of the pastures, and gets heavy horse traffic. The drainage swale that drains the corral & nearby ground runs through the middle of this foyer. We're thinking we'll go with an 80/20 clay/sand mix (his standard arena mix) inside the corral, because stable, non-mucky footing is our primary concern in there. Outside in the foyer, we'll go with a 50/50 clay/sand mix so that the water can drain more easily through the swale, but the footing still stays good as the horses tromp through that swale and climb a slight hill en route to the pastures.

Another friend recently expanded his outdoor arena. His original portion has pure sand, while the new portion is 80/20 clay/sand. He says that the pure sand is noticeably more slippery because the particles don't lock together. After it dries out after a rain, the pure sand also becomes rock hard until it's harrowed, but the clay/sand mix is still very usable. He'll be mixing the surfaces together as time allows, of course.

We've had a dry week here, so I was able to flatten out the dry hoofprints in my corral tonight. The sand should arrive Thursday or Friday. We'll see how it all works!


----------



## ObiWan (Jul 7, 2017)

Well, we've had our new corral surface for a month now, so I thought I'd share my impressions. It's the dry season in southeast Nebraska, so we've gotten less than 1" of rain since then. Temps are consistently dipping below freezing at night now. 21 yards of clay/sand mix plus hauling & professional installation cost $1000.

Installation was straightforward. I flattened out the existing dirt with my tractor blade. My excavator then brought in a few yards of dirt to fill in the low spots that had become swimming pools with every rain. Once the drainage slope was established, he spread about 3" of calcined clay / sand mix throughout the corral and the entry/drainage area right outside. The lower part of the drainage swale got a 50/50 mix (a lighter gray color). The upper part and the inside of the corral both got a 80/20 clay/sand mix (a deeper brown color). It took about 2 hours to deliver 3 truck loads (21 yards) and spread it all around.

Previously, when the ground got muddy & then froze, it was terribly hard for horses to walk on. Because the footprints held water, I had to wait many days after it rained before it was dry enough to level it back down with my tractor blade. This new surface is far easier for the horses to walk on. It gets a little hard when wet & frozen, but even my 200+ lbs can still break through the crust enough to leave footprints in the softer sand below.

Picking manure is a breeze when the sand is dry, since it just falls through the fork. It does stick to the poop, though, so I'm losing a bit of sand with every pile I remove. When the sand is wet, picking gets harder, because the sand clumps more easily. Moreso when it's wet & frozen. Even then, though, it's still easier than picking poop off bare dirt/mud.

The horses love to roll in the 50/50 clay/sand mix more than the 80/20 clay/sand mix. I'm not sure if that's due to the consistency or the location. It makes the horses REALLY dusty, especially now that they're growing their winter coats. It's better than having them roll in the mud, though, so I'll take it.

Speaking of dust, that's my biggest complaint. This clay/sand mix lies right outside the south end of our barn, and our horse stalls open up right onto that corral. When the wind blows (especially from the south all summer), it blows dust from the sand into the barn, completely covering everything inside. It was bone dry for weeks after the sand was installed, so I don't know if this situation will improve after we get a good, heavy rain to wash the sand a bit.

We did finally get about 1/2" of rain a few days ago. The 80/20 mix in the corral absorbed all the water in the top 1" or so of the clay, leaving the lower levels of clay bone dry. It then froze that night, which left a decent crust on top of the clay, but not so much that my foot wouldn't break through it if I stomped. In the 50/50 mix outside the corral, there was no obvious absorption layer, so the rain must have run through a little deeper. In my pictures, you can really tell that the 80/20 mix turned a much deeper brown, while the 50/50 mix stayed grayish after a little rain. When wet, neither mix sticks to your shoes any more than you'd expect from beach sand.

I'm still curious to see how well this stuff drains when we get a really heavy rain or snow melt, but that will probably be a couple months away. Until then, I'm generally happy with it, except for the dust in the barn.


----------



## ObiWan (Jul 7, 2017)

Well, another month has passed. Last week, we got 2" of freezing rain, followed by below-freezing temps for a few days, so that was a pretty good test for the new corral surface.

The clay/sand mix doesn't drain very well. The 50/50 mix might drain just a smidge better than the 80/20, but it's barely noticeable. You can see from one of these photos that there were a few low areas where the water pooled without draining--I'll have to regrade that later. I still had to go out with a shovel and drag little drainage canals through the sand in order to let the water out. The good news is that doing so was much easier in the sand than it used to be in the native clay mud. Also, as long as the water was still liquid, the wet sand didn't really stick to my boots any worse than beach sand would. There was none of the boot-sucking glue that I used to get from the mud surface.

The more disappointing aspect is that, because the calcined clay holds in the water, it still freezes solid when the temps drop. This produces a clumpy, rock-hard surface that's quite hard to walk on and pick manure from. Unlike the mud, this hard sand softens up nicely as soon as the temps rise and the ice thaws. The 50/50 mix seems to freeze harder and sooner than the 80/20 mix, which surprised me. Perhaps that's just due to the horses walking around more on the 80/20.

I also found that the sand mix we spread onto the hill leading to the pasture seemed to mostly wash down into the drainage swale with that heavy rain. Given that water doesn't want to drain *through* that sand, I'll have to shovel some of that back up onto the hill.

So the short answer is that this calcined clay / sand mix isn't the panacea that I'd hoped it might be, but it's still a noticeable improvement over the mud that we used to have. Whether or not it was worth $1000 depends on who you ask.

Next time I spread something, I might try straight sand just to see how it compares.


----------



## QtrBel (May 31, 2012)

Thanks for the update!


----------

