Hello,
We are doing a driveway installation with Permacon pavers. We put down 12 of 0-3/4 crush compacting every 3 inches and then 1 inch of stone dust, compacted this layer once and then installed most of the stones (560 sq ft.). The manufacturer says not to compact the stone dust layer. It appears to be about 90% compacted.
The stones are not rectangular but are kind of T shaped - such that 4 of them fit together to make a rectangle. We also have a colored polymer sand to fill the joints.
I tried sprinkling some stone dust over the top of the pavers and recompacting. This fills the voids between the pavers but the paver still does not sink into the stonedust layer. Will we have to remove all of the stones and loosen the material for a proper installation? Or will the stone dust spread over the surface do just as well?
Paul
People here disagree on wether the stone dust should be compacted or not before laying the pavers. I've seen it done both ways and my opinion is that compacting the stone dust first is wrong. I've done a lot of paver work and have never done it that way and have never had a problem.
If you used sand you would not compact that first, you would screed it smooth, set the pavers, then compact the pavers into the sand. The stone dust should be done the same way.
When I see guys use your approach, they sit with a trowel, rubber mallet, and extra dust and basically hand set each paver to get it level and smooth. If you properly screed uncompacted sand or stone dust and set the pavers carefully, it's much faster and you will likely get a flatter finished project.
Also, although others have disagreed w/me here on this, interlocking pavers are called such because they interlock with the bedding material, not because the shapes mechanically fit together. Pre-compacting the bed won't let that happen.
I like doing things right the first time and never touching them again. I would say take up the pavers (you don't have much), loosen up the stone dust, screed, set, and then compact.
I also like polymer sand to fill the gaps, but many people won't spend the extra $$ up front.
Good luck!
I have the sinking feeling that you are right. I'll remove them all and proceed as you suggest...
Thanks very much,
Paul
ps - I noticed while compacting the pavers using the jumping jack that some of the pavers (t shaped with cobble appearance)
http://www.permacon.ca/products.html?product_id=422
cracked and broke loose from its form. (No visible crack on the surface.) Does this matter or am I compacting with too much force?
If the pavers are level enough for your purpose, you could leave them as is. Just make sure you have an excellent edge restraint system.
As Syakoban says, the proper way is to screed the bedding material and then compact the pavers into the bed, but I have done it both ways with no issues.
You do not use a jumping jack on pavers, you use a plate compactor.
Actually, after looking at that product, I would compact the bedding material first (assuming that each paver consists of several cobbles).
Yes - each unit is made up of 5 cobbles. I am (just looked it up) using a plate compactor - not a jumping jack.
Why do you recommend compacting first? Should I add some additional stone dust on top...otherwise I'm afraid that there will not be stone dust between the 5 cobble units.
My edge restraint is good but perhaps not excellent.
Paul
Because the amount of bedding you will get with that unit is minimal, and the large size will make it difficult to avoid lipping (adjacent pavers at different levels). I would also add stone dust to fill the joints to near the top, then finish with the polymeric sand.
Would you compact after putting the stone dust between the joints, add the polymeric sand and compact again?
Should we clean out the excess stone dust from the valleys between the cobbles since the manafacturer of the polymeric sand says not to layer it with stone dust...
If yes - any suggestions on do this?
If they say not to layer it, don't layer it. Blow out the dust, cover with ploymeric sand and then compact. After compaction, sweep the sand into the joints and finish it however it says to.
OK. We've found a reasonable way to get out the XS stone dust...
We've also noticed that many of the pavers are rocking when we step on them (curved surface) ...would you expect this to disappear once we've added the stone dust and compacted? Shud I also assumme that during compaction some of the cobble pieces will break away from the unit but that this is ok/expected....?
paulhar -
Don't worry too much about the differing methods you hear about. What works for you using the pavers you have, is important.
Because the units you are laying are much larger in comparison to the thickness, your instructions may be somewhat different from traditional units. The units may crack during installation or use, but that would not adversely effect the performance. They are made in that manner for manufacturing and consumer installation ease.
In general, stone dust may not be acceptable. Virtually all specifications (domestic and international) reccommend a clean sand. Because of the angular shape of stone dust particles, those that do permit it, have different size requirements for stone dust. The shape of the particles do not permit the movement desired during installation.
The best material to use for setting is a clean, natural sand. For setting a concrete sand meets the requirements. For sanding and filling, a fine concrete sand or a masonry sand would meet the requirements. Some local creative people feel stone dust works, but they are in the U.S. where major interlocking paver construction is relatively new (30-40 years) so the real life has not been tested. Internationally, where paver installations are much more advanced, there is a wealth of experience and testing that form the basis for the long life and high level of paver performance.
The U.S. use of pavers is slowly catching up to the rest of the world. In some countries, paver projects covering 10 to 20 acres are common. These are generally for very, very heavy loads (airplanes, ship unloading, etc.).
Your project will work out very well for the intended purpose.
Dick
I assumed stone dust WAS sand. What is it?
Where I have lived, it was a local term for semi-clean fines from the crushing process. It was angular and difficult to compact without effort and a good amount of water, but it can be compacted well (not always good). It can contain quite a bit of fines, which hinder drainage. It didn't move into place as easily as natural. rounded sand particles.
Not to be confused with crusher run, which is coarser and contains enough fines to fit betewwen the larger particles.
Soils and aggregates have too many different local names. That is why a gradation report is good to look at.
Dick
I see; in this area, that is called limestone fines, and it works well for bedding material, but not at all for joint filling.
The Interlocking Concrete Pavement Institute www.icpi.org only recommends sand for the issues coming into discussion here: the term stone dust varies w/region. The stone dust Concretemasonry describes is what we have in my area and it works fine for bedding. The ICPI is totally against limestone dust for bedding - their tech director specifically told me that once.
I still follow their methods and don't vary:
compacted 3/4 QP base
1 loose screeded sand (or stone dust)
set pavers by hand
compact pavers w/plate compactor w/rubber membrane attached
sweep in joint sand (polymeric preferred by me)
compact again
blow off excess sand
gently wet polymer sand if used
I have never cracked or chipped a paver w/this method and they don't move over time.
Oh yeah, I always use a geotextile under the QP if the ground is questionable like clay. It's cheap insurance in the long run.
The use of the proper base really has more to do with the strength of the pavement system and ability to maintain stability in wet periods. Chipping and cracking is are installation problems, not a material problems. Granted, the compressive strength probably should be something more than 8000 psi for 60 mm pavers, but not as important on 80 and 100 mm pavers.
In the short term and for minimal strength applications like patios there is a wide range of materials than can work. For more critical applications like poor bases, heavy duty driveways, streets, taxiways and industrial applications, the choice of materials is more critical.
Your short term experience may not cover the wide range of uses. Canada did not start using a considerable amount of pavers until the 1970's with the U.S. following much later. The rest of the world is a little more advanced and sophisticated in the application and selection of materials. The cementing action of limestone fines can prevent the uniform distribution of loads to the base.
The ICPI has done good a job technically despite the non-technical influences exerted by some members Their technical notes usually refer to the U.S./Canadian terms such a concrete sand and masonry sand because they are readily identified and universally available.
Dick
Tags: driveway, pavers, stone dust, bedding material, then compact, compact pavers, concrete sand, have never, jumping jack, plate compactor
