[natural12]

When prepping a concrete paver patio/walkway who uses screening, aka stone dust, for the bedding between the gravel and the paver's. The specifications for Belgard pavers calls for concrete sand. The local Rep here also told me to use concrete sand.
I like to use concrete sand but for some reason a lot of landscape suppliers do not carry it. Mostly just mortar sand. I called three various suppliers recently asking if they have concrete sand. "Yup we got concrete sand". I show up and they only have mortar sand. Unbelievable!
Anyway, I like the screenings because you can use it to adjust for the dips and such in the ABC gravel base. Then use it for the bedding.

I guess my question is: is their any reason not to use it for bedding?

MIke

[davemac]

Screenings is all I use for a base for pavers. I find it easier to grade and it makes for a stronger base.

[Raj Venugopal]

We screed with crusher dust, which I believe is what you're calling screenings.

[mrusk]

You must have a redi mix plant by you? Thats where i get my concrete sand. Its all i will use.

[PaverDrew]

Screenings retain moisture and will eventually lead to the downfall of the install. Sand allows water to flow from the install, securing it's integrity. If you are using it to level your pad, any more than a 1/2" and it will show in time. Take the time to get your base right, and use the materials the manufacturers recommend. Check with your local aggregate yard, the same one where road guys get their stuff. Here they call it washed sand. Get onto the ICPI or Belgard site and get the sieve analysis for the sand and give it to them to match up. There is bound to be a proper material available.

[natural12]

Not a big problem finding concrete sand around here. I was just wondering - Why not screenings? There are several places that carry concrete sand around here. This difficulty in finding it has just been a recent frustration. I have been working a bit out of my area for the last couple of jobs and not wanting to travel far to get my sand I have lucked out at getting it at the suppliers near the job site. Everyone seems to carry screenings however, which led me to this post. In the past all I used was concrete sand and I just was curious why screenings was not recommended for use.

Thanks paverdrew for the insight. I used screenings on my last paver job for convenience but I guess it's back to concrete sand.
Just wondering what type of failure will occur by using screenings?

Thanks for all the replies

[Pelican]

What we see here for stone dust is too coarse for the leveling course. The idea behind the concrete sand is to allow the sand to migrate into the joints with final tamping to bond the pavers together through friction of the particles. The particles in our stone dust are too large to allow this to happen.

I don't purchase my aggregates from the paver supplier, his prices are inflated. I have several quarries in the area to choose from and all but one stock concrete sand.

[Raj Venugopal]

I am not convinced that final tamping causes any real interlock from below.

[Pelican]

At your next job do your final tamping and then pull up a few bricks. You will find there is indeed sand between the joints if you've used the proper sized material.

[Raj Venugopal]

But I don't buy that the amount of sand driven upwards due to tamping creates any effective interlock unless the space between the stones is rather large.

[Pelican]

OK then, another experiment. On that job I talked about, try pulling up some pavers before you've done the final tamping, and then again after. I think you'll find the bricks after tamping are harder to remove. The sand removes the ability for the bricks to move from side to side, and the granular friction to the sides of the bricks tends to lock them in place.

I've seen sand almost half way up the bricks after tamping.

[Fine Edge]

Screenings is all we've used and have NEVER had any install problems or downfall of the install even after 10 years.
I, too, don't believe that you can actually tamp ALL of the areas evenly especially if your pavers are in a corner or up against an area you don't want the tamp to touch.
You can't just leave those areas out, can you?

The best thing we have used is a fine sandblasting sand when we sweep in. It gets down through every crack and all of our paver jobs walk just fine. A liquid sealer after a cleaning works well with it also.
Our last couple of jobs were done with polymeric and even that was too coarse to get between the pavers ( Pavestone ) like we wanted.
Use the screenings and if your ever in the Charlotte area, let me know. I'll show you some old jobs that still look new.

[dan deutekom]

I always use sand ever since Unilock stopped honouring it's warranty on the stone if using limestone screenings. I find sand locks the stone in far better than screenings, makes for a much smoother finished surface after packing and has much less chance of failure. Every job that I have had for a relay over the years has been installed on limestone screenings. Also the limestone eventually disintegrates the concrete of the pavers. On very old jobs I have seen pavers that have decomposed on the bottom so badly that they were only 1/2 their original thickness.

[Stonehenge]

That's very interesting, Dan.

I wonder what's different about concrete pavers (over just plain concrete)? Concrete driveways, walkways and patios have been poured over crushed limestone here for decades, and I've yet to see any of them show the same degradation you mention.

I've never seen it with any concrete pavers, either, but I may not have had an opportunity to pull really, really old paver projects like you may have.

Limestone isn't acidic, either. So I have to wonder if it was the pavers and not the base material beneath it. I've seen the tops of concrete pavers degrade into a crumbling mess while the bottoms, sitting on limestone screenings, were fresh like new daisies.

As for all your relay jobs being over screenings - I've seen a lot of relay jobs that were over sand - a bed of a material with very small particle size just cannot resist forces acting on it like something of larger particle sizes can, meaning there are more often traffic pattern ruts where a bedding sand course was used.

My $.02, anyway.

[Stonehenge]

Originally posted by PaverDrew
Sand allows water to flow from the install, securing it's integrity.

Please describe for me where the water goes when it leaves the sand, and how that differs from other materials used as a base.

I have my own evidence that a sand bed reduces structural integrity of a segmental pavement.