Sand as Pre Road Base

JimMorrissey · Oct 20, 2005

Anybody have any reason why/how compacted sand might cause problems as a pre-base material for a new road? I want the surface smooth and even before I put the fabric down. It makes for a nice surface for the fabric too. I can get the sand delivered for a pretty good deal ($120 per tandem / 16 yards). I also think the sand would be a good way to sculp the crown prior to the crushed gravel which is much more expensive. I'm also looking for it to be a fill material to bring the whole excavation up to the same grade.

PineRidge · Oct 20, 2005

Jim there is a lot of useful information here camp roads

beenthere · Oct 20, 2005

I think it would cause lots of problems.

Toiyabe · Oct 20, 2005

Should work fine. I'm not sure I know what you mean by "tandem", but you may not get 16 yards per load. If it's a standard three-axle dump truck, it will be overweight with 16 yards of sand. 10 yards is closer to reality.

You may have difficulty with compaction unless you hire a roller. If you can leave the sand exposed for a while and let vehicle traffic compact it, that will help. It will also help if you dump from the access road outwards to get the most compaction out of the delivery truck itself.

With a clean sand subbase you ought to be able to do away with the geotextile. The sand itself is pretty good at preventing the fines from the subgrade from pumping into the base.

JimMorrissey · Oct 20, 2005

Like what?

A friend of mine used sand a few years ago and it has worked great so far. The sides of my road are cut down into the soil so the sand doesn't have anywhere to squirt out to. I'll still use fabric to keep the road from compressing under heavy loads from cement trucks and delivery vehicles.

Toiyabe · Oct 20, 2005

Why are you excavating, rather than building on the surface?

Removing topsoil is good, but there's no reason to go any further unless you can get down to a good material. If you backfill into what is essentially a trench with impermeable materials on three sides you can be sure that the sand will stay wet year round. It would be best to provide some way for the sand to drain either by building above grade, cutting a ditch or installing perforated pipe.

JimMorrissey · Oct 20, 2005

I'm "excavating" in order to get down to something other than black topsoil! I'm not going to build a road on topsoil, and there's lots of topsoil; over 20 inches in places. It's impossible to get a perfected excavated surface with a backhoe, so I'm looking to even the surface out with the sand. As far as moisture goes, I have no doubt the sand will be moist most of the year. It won't be "wet" due to the fact that it will have heavily compacted crushed limestone with a 4" layer of compacted crushed stone on top of it. Rain will eventually run off this surface like asphalt. If it does get wet from below the water will be able to permeate the subsoil where it came from. Not sure why moist sand is an issue.

rswyan · Oct 20, 2005

In hindsight, one thing I wish I had done was spread some sand, or crusher run for that matter, on top of the geo-textile before I had put down the No.2 gravel. Some of the No. 2 had some pretty sharp edges .... using a layer with alot of fines first might avoid any issues with the sharp edges chewing up the geo-tex.

Toiyabe · Oct 20, 2005

Wet sand is certainly better then wet topsoil. Not as good as dry sand. Providing a way for the sand to drain will give you more structure, but it sounds like you'll have plenty.

JimMorrissey · Oct 21, 2005

Yeah, I agree. I intend to sandwich the geo in sand. I think you'll be fine though. The woven fabric is incredibly strong.

JimMorrissey · Oct 21, 2005

Definitely won't be "wet" because it will be so well protected from above. The moisture it gets will be from below and sides of the native soils. Dry sand seems to be too loose and sloppy, while damp sand holds and packs better. The right amount of moisture is key for compaction. Remember, I live in VT, not Nevada (it's been raining for two weeks straight) and it would be impossible to keep it dry. On average, I'd expect it to get about as damp as a wrung out spung. I think compacting it before the fabric goes down will help too. I'm going to rent a vibrating compactor to get the firmest surface I can before the crushed stone shows up.

keeney · Oct 21, 2005

The bad thing about sand is that it can wash out easy. Larger stone or a graduated mix tends to stay more where you put it, even with some water flowing through. The fines may go, but the larger stone will stay. With sand, once a channel of water starts flowing, the surrounding sand just keeps erroding as well.

Even under my concrete driveway, I was hesitant to use sand and instead used what they call up here in MN a "Class-5" road-base mix of crushed limestone and fines.

- Rick

Kyle_in_Tex · Oct 21, 2005

Don't do it. Sand displaces easily under uneven loads.

Most people put down 3" rock first, cover with screened 1" gravel, and then you can put a little sand over it for filler if your screened doesn't have enough. Usually, it does and sand is not needed. I put down the geotextile cloth first and have put down a rough mix straight out of the pit. I have some large rock that has kicked off to the side. I now need to buy some more 1" screened gravel to shore up and smooth what I have...Kyle

have_blue · Oct 21, 2005

Jim,

You don't need to compact sand. It's not compressible. There is no better base for a road that I can think of. It also makes a great road itself! Perhaps you should lay down the sand and use it for a few months before installing the fabric and gravel. You may like it!

I love my sand roads. I can drive on them right after a rain, because they drain instantly. No muddy tracks ever. Another good thing is that sand self levels. A good shower knocks down the ridges and deposits them into the low places and makes the smoothest road you can ever have.

Only downside to sand roads is the sand eventually mixes with the underlying soil. This makes re-sanding necessary every few years. Mine is 3 years old and could use re-sanding. Next application will probably last 5 years. I grow bremudagrass on mine because I like the look of a country lane.

Farwell · Oct 21, 2005

Sand is great until it turns to sugar. I have several patches of sugar sand on my place and it is almost like quick sand. When it is wet it is great. A sand, clay, and gravel mix seems to work well for a while on the Michigan back roads. Not sure of what the ratios are but if mixed right it is almost as good as black top.
In late Summer I have to carry water with me if I want to dig post holes due to the constant sand slides in the holes.
Farwell

rswyan · Oct 21, 2005

( I think you'll be fine though. The woven fabric is incredibly strong. )

Yeah ... was pretty funny looking at some single stones (fist-sized) that were laying on the fabric after the dump truck had run over them .... the fabric was sucked down below grade along with the stone .... some serious pucker. /forums/images/graemlins/grin.gif

Toiyabe · Oct 26, 2005

( Remember, I live in VT, not Nevada (it's been raining for two weeks straight) and it would be impossible to keep it dry. )

I agree, it will be impossible to keep water away from it which is why you'll need to provide a way to drain it if you care about it being dry. Since you seem to be thinking about this material more as a subgrade improvement then as part of the road structure, I guess that's moot though.

Compacting before placing the fabric and using a vibratory compactor are both good ideas.

How important compaction is depends on the gradation of the sand. A poorly graded sand (one size material) won't compact much, and compaction is not very sensitive to moisture content. A well graded sand, with over 10% fines will compact a great deal and compaction is very sensitive to moisture content. I don't know much about VT soils, but glacial tills are more likely to be well-graded, and sediments are more likely to be poorly-graded. This may account for the regional variation in the responses to your question.

JimMorrissey · Oct 26, 2005

Instead of the sand I fell back on the more expensive "dolomite". It's basically crushed limestone....packs extremely well and makes an excellent base. Some people use the 1 1/2 minus material for a finished road, but it's too coarse and it's too light in color (almost white) for me. I'll cap it with some 3/4 minus in a dark grey and that'll look and drive pretty nice.