[dan deutekom]

Jeff

I too have relayed old jobs where the tops of the pavers have been disintegrated and the bottoms are fine when on limestone screenings. Every job that the bottoms were disintegrated the screenings were always saturated wet. That may have a lot to do with it. With poured concrete the water can't get through to the base like with pavers. Around here it is always the surface of the concrete that is a mess because of salt.

When I used limestone many years ago I hated the switch to sand. Limestone was so much easier to work with. Grade it level, pack it and lay stone. You could walk all over it when working without any ill effects.

I only use about 1/4" of sand to bed in my pavers. I feel if you use any more than this you increase the chance of failure. (use a grade rake and lie on my belly alot to check my grade for dips and high spots. Got to have patience and a bit of an eye for this)

All of your leveling should be in the gravel base not the sand. The sand is just to bed the paver and lock it.

[Turtle]

I wonder how different ones limestone is from one part of the world to another. I guess its possible that dans limestone becomes a high "caustic" when wet maybe or some other factor mixing with it A lot of drain cleaners are caustics not acids and they definitely can do some damage

I maintain a property where an old timer concrete engineer lives ill see him on wednesday and ask him. He developed putting air into concrete to make it stronger Long story ! He will definitely know the answer though

[davemac]

Limestone screenings is all we use around here. There maybe different grades of quality in different areas but here the screenings or stone dust are incredible. If you leave a 1/8" or 1/4" layer of soft screenings on top of your grade and tamp your pavers into this they will all tamp level. By spreading a layer of poly sand on top of the pavers and running th tamp over this the sand will fill the full gap top to bottom and lock the paversd in place. If the screenings are wet underneath there is a problem not with the screenings but with the grade. If there is a proper grade water should run off the pavers and not leach down to the screening base.

[EpicInterlock]

I find it incredible that the pavers can actually disintegrate just by sitting on limestone screenings as Dan Deutekom mentions. I wonder if the pavers he mentions are concrete pavers that we use nowadays or are they old clay pavers that were more commonly used 'back in the day'?

I certainly hope that limestone screenings are not the actual cause of the degradation, because 100% of my installations are all on a base of limestone screenings. Unilock and some local manufacturers recommend to install pavers on a base of brick sand, or concrete dust, not because it allows the stuff to migrate between the pavers after tamping, but to make it easier for amateurs (and some rookie landscapers/homeowners) to level the base easier before laying pavers.

I've been in the business for over 9 years, and I've NEVER seen any settlement in any of my installations. And that's coming from a frost climate (Toronto, Ontario).

[AZTLANLC]

I think manufactures are switching to concrete sand based on ICPI specifications, but some don't even have a certain clue on why not to use stone dust, I was on a hands on training seminar the other day for a new manufacturer in my area and when they talked about stone dust and concrete sand I felt it was absurd, they said because stone dust has more sharp end it will fracture pavers after final compaction, they even had a drawing to explain that and passed along samples of both the concrete sand and stones dust, some people were saying whoooa that is true!.
If stone dust is able to crack pavers I'm pretty sure it has more to seee with the quality of them, cause I have being using 1/4" gravel for my bedding base the last couple season and have not seeing pavers cracking unless there is a big enough stone underneath.

[Stonehenge]

If you guys would like, I could sneak back to pull a few pavers from the paver base test I did a few years ago (we left that shop on bad terms with the owner - that's why I'd have to sneak), to see if there's any difference in moistness of bottom of paver between the different preps, or if there are any signs of paver degradation.