# Decomposed Granit for Track Bed ??



## Pjhinde (Mar 11, 2013)

All,

I have received very good feed back on track bed. So I took some shots of some of my current useage of the stuff and thought I would get some feed back if you have any. 

http://pj-pjphotos.blogspot.com/201...ar-12.html

Pj


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## chuck n (Jan 2, 2008)

Pj, that looks a lot like the stuff I collected in the hills in back of Denver. If the stuff has some larger than 1/4 inch fragments you can get some 1/4 or1/2 inch hardware cloth and make a screen and pass the material through it to remove the larger pieces. In your pictures it looks as if the granite has set up. Did you add a binder? If so, I would recommend leaving it loose. That will allow the track to move a little with temperature changes. What you do may be effected by where you live and your regional climate. We might be able to give you better advice if you you tell us what region of the country you call home. Chuck


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## Pjhinde (Mar 11, 2013)

Chuck,

As for the setting up of the granit, it does that naturally, I added nothing. As for the area I live, I am in Dallas Forth Worth Texas, not much snow, lots of rain normally during spring and fall, but we have been far from normal these last few years, heavy drout conditions, very hot in summer with humity of about 30-40% average. When it rains at times its like a cow peeing on a flat rock so I am very cognoscente of looking for any drainage issues which I do not have any major issues where the track might/will meet the ground. As for flexibility with track, I will need to see how that works out, the very top layer is often somewhat loose. When it gets wet it becomes very plyable. 

Thanks
Pj


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## Stan Cedarleaf (Jan 2, 2008)

PJ..... All my ground level track work is ballasted with 3/8 minus DG... It's super easy to work with, looks great and packs in very nicely when wet. 

Check the link to my website in the signature line...


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## chuck n (Jan 2, 2008)

Pj:


I lived in Dallas for three years while I was getting my PhD in geology at SMU, so I am familiar with your weather. I have been trying to figure out why you are getting your granite to self cement. If your local water supply comes form wells, it is possible that your water is hard (a lot of calcium carbonate and other dissolved minerals). As I think that the major aquifer in north Texas is a limestone. If you spray this out on the lawn and your decomposed granite some of it will evaporate and leave calcium carbonate as a residue. This could bind the grains together. As an experiment take a small piece of your cemented granite and put it in a bowl and cover it with vinegar. If it fizzes, you have calcium carbonate cement, that most likely came from your water.

Since you are interested in trains, I suggest that you go over to SMU and visit the Degrolier (spelling?) Library. He left an extensive collection of model trains and railroad books and photographs to the university. It is well worth a visit.

Chuck


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## Greg Elmassian (Jan 3, 2008)

I live in San Diego, we have DG here too, reddish brown. It will set up close to cement once watered down.. we do have a high calcium and magnesium content. 

Greg


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## Pjhinde (Mar 11, 2013)

We get city water but I will try your experiement to see what happens Chuck. One of these days I will check out SMU Degrolier Library. 

Thanks for your time.

Pj


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## chuck n (Jan 2, 2008)

I think some cities use well water, water from the Trinity River, or both. Do you get scale in your coffee maker and other appliances that boil or heat water? Chuck


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## Pjhinde (Mar 11, 2013)

Chuck,

No I do not get any scale anyplace. I actually live in the City of Euless TX in between Dallas and Ft Worth and we have our own water bladder. I get the granit from Home Depot so who knows where they get it. Just thought about that. 

Pj


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## chuck n (Jan 2, 2008)

Just some thoughts. Chuck


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## NYC Buff (Sep 21, 2008)

Gentlemen: 

Is the decomposed granite that you are using for roadbeds washed or as crushed? If it is washed decomposed granite, there will be little or no decomposition ultra-fines mixed with the spread of sizes you are using. If it is unwashed decomposed granite, there are decomposition ultra-fines (dust to the layman). The decomposition ultra-fines act in a manner very similar to that of cement and when water is added (hard or otherwise) a concrete is formed. If you do not want the decomposed granite to set in a manner similar to that of concrete wash the decomposed granite well and it will not set into a pseudo-concrete. 

Hopefully, these comments will have some positive bearing on this discussion and will be received as they are meant as infomative rather than directive. I will attempt to provide additional insight into the use of crushed stone later in this thread when I have had a chance to find some chemical and materials engineering texts in my library on crushed materials. 

Respectfully, 

NYC Buff


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## Pjhinde (Mar 11, 2013)

NYC,

All comments are appreciated by me and never will I take them wrong. I am not even sure how to answer your questions, but I am guessing they are unwashed as they are meant for sidewalks, roadbeds, etc. 

Thanks to you, Chuck, and everyone else who has commented in response to my rookie - ness. 

Anyway, once my new track gets here I plan to lay down the third set, this will be a small one kind of inner circule to track #2, so if I try the granit gig and it does not work out no big deal on the re-due. I do not consider re-due work as to be perfectly honest, I find more fun in the engineering, construction, and testing more then just watching the trains go around on the track. I view it all as a hobby with a never ending goal. LOL.. 

Thanks Again,
Pj


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## Totalwrecker (Feb 26, 2009)

Good to know Mr. Buff.


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## Stan Cedarleaf (Jan 2, 2008)

NYC Buff... 

All the DG in our area is crushed with a great amount of dust.... Locks in right nicely when watered... Then loosens when drenched...


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## jfrank (Jan 2, 2008)

I use it here in Houston also, simply because there is nothing else that works. It is not washed. They just dig it up around Marble Falls and truck it into Houston. I usually have to screen out the big chunks for the ballast, but I use them else where. One time, when they had some big rains and floods up there you couldn't even get it and when it finally was available again it was full of chunks of mud. We do have a few that use chicken grit, but that is expensive, around $12 a bag.


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## Charles (Jan 2, 2008)

Posted By chuck n on 12 Mar 2013 04:52 PM 
Pj:


I lived in Dallas for three years while I was getting my PhD in geology at SMU, so I am familiar with your weather. I have been trying to figure out why you are getting your granite to self cement. If your local water supply comes form wells, it is possible that your water is hard (a lot of calcium carbonate and other dissolved minerals). As I think that the major aquifer in north Texas is a limestone. If you spray this out on the lawn and your decomposed granite some of it will evaporate and leave calcium carbonate as a residue. This could bind the grains together. As an experiment take a small piece of your cemented granite and put it in a bowl and cover it with vinegar. If it fizzes, you have calcium carbonate cement, that most likely came from your water.

Since you are interested in trains, I suggest that you go over to SMU and visit the Degrolier (spelling?) Library. He left an extensive collection of model trains and railroad books and photographs to the university. It is well worth a visit.

Chuck

Chuck

Memories-Back at the home place in the Hill Country of Texas, one of the family landmarks was "Spy Rock" a huge pink granite outcropping of many, many acres that we would have family picnics. It was grand to climb to the top (required rock climbing skills to scale the smooth sides along using the crevices and deep crevasses)and see for miles or entire the caves with old Indian symbols- a hidden treasure. The unstable and porous granite (no good for commercial use) would wash down the rock slopes into a stream. I cannot remember at any time the grains binding together, always loose. So, I agree that it must be something in the water.


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## jake3404 (Dec 3, 2010)

As a former rock quarry engineer, what you guys are calling Decomposed Granite is a form of Base Course. Base Course is a gravel that has fines (average person calls dust) in it. It is used as a base on roads, foundations, concrete work, gravel roads and anything that needs a solid base. What you have discovered is the main reason it is used, the ability it has to set up, like concrete, and form a solid base. The names of materials is very dependant of region, what someone calls a certain material in Pennsylvania does not mean it is the same stuff in Arizona. 

This setting up happens when you wet down the material, the fines will settle in between the large rock. The rock makes up the strength of the material and the fines stabilize the rocks so they dont move around. As far as using this material as a base for your track, is a good idea. It will set up very good and provide a solid base. At times it can wash out like anything, but it will do a good job of resisting it. 

If you wish to have a more prototypical look after you have installed your base, you can look at some of the washed materials. A 1/4" works out to about ~5" in 1:20.3 scale, and bigger if you go with a smaller scale such as 1:29 or up. However, it still looks just fine. The top layer is really just for looks, it does not provide much of a stability to your track, the base does that. 

I use on my layout a material we call "-4 +6" this is a clean rock that screens out all material that is larger than a 4 sieve (This is a number for a size opening of a screen, which equals 0.187") and smaller than a 6 sieve (0.132"). For me this scales out to around a 3"-4" nominal size (1:20.3) which is the size most railroads use for ballast on their railroad. Now I dont know if you can get this stuff in your area of not, at my quarry we made it for special asphalt and concrete mixes. It cant hurt to ask at a local quarry. And I would venture to say that it will be considerably cheaper to buy from the quarry instead of bagged product from the hardware store. As a comparison, I paid about $20 for 400 lbs of my material at the quarry. I have seen this stuff bagged up at the local hardware store and they were charging $20 for a 50 lb bag. 

Anyways, good luck. And I can answer anything you need when it comes to rock products.


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## Pjhinde (Mar 11, 2013)

Thanks Jake,

I also noticed that when you get the stuff wet again, you can mess with it (remold it). I discovered this when I had half a bag in a bucket in my barn. It set up like concrete and for grins I applied some water and whala, I was able to use it again. I think this goes with your "like anything, it will wash away eventually" (not exact quote I do not think) statement. 

Pj


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## Totalwrecker (Feb 26, 2009)

Actually Charles your description matches with Mr. Buffs explanation above. 
What you saw was freshly washed with no locking fines present. 
It is not the water, it takes a fair amount of time for minerals to leach out of water.... how long does it take for your shower head to clog? Same 'miracle gluing' minerals.... tic toc.... months or years? 

If we are to mimic the bigboys, we should be washing our ballast to remove the 'locking fines' and improve drainage... 
I have seen my track grow in heat, my ballast holds firm enough, but has plenty of give. I have coarse sand deposits on site that I use. 
My speculation of locking ballast is it could lead to buckling track during heat waves... my clime is 4 -114 degrees F. 

See ya down the line, 

John


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## jake3404 (Dec 3, 2010)

Just to add to what I was talking about, here is a picture of the material I used as the ballast.










Keep in mind I am only using this material for looks. It does not provide any stabilization of my track. I have a ladder roadbed.


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## toddalin (Jan 4, 2008)

Drag a magnet through the material and see if it/how much sticks. If the material is magnetic, it has a high iron content and will "bleed" off current in moist conditions. The extent of the "bleed" will determine if you can run track-powered, HIGH CURRENT, trains after sunset when the dew point drops, if you have dew in your area.


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## Pjhinde (Mar 11, 2013)

Using the ladder style track very little bed is actually in contact with the track and our dew is very low. On a morning after I run the sprinklers at night I do not fire things up until it all dries out. So no worries there. 

Thanks
Pj


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