Paving Onto Crusherdust

[SIMONLEWIS]

Hi Guys and Gals,
Just about to undergo a fairly big paving job. I have never paved before so a mate is helping me to get started. Just wondering - he has said we will be paving straight onto compacted crusher dust without the sand on top.
Can this be done - what are the problems that I'll have with this?
Using 200x200 x 50mm pavers on driveway and 200x200x40 on paths - he wants to put 50mm of crusher to lay it all on - will i need more than this?
CHEERS IN ADVANCE

[ozwinner]

Hi
If you pave for a driveway without putting concrete down first you will be ripping it up in 6 months and doing it again, for the pathways its fine with no concrete.

I did something similar years ago, laid 120 square meters of driveway without the concrete, I eventualy pulled it all up and just laid a concrete drive.:(

Al :)

[Bleedin Thumb]

I agree with what Al said re driveway unless you undertake a deep compacted subgrade, ie normal road construction details however on a small domestic driveway it probably cheaper to pour a blind slab.
As far as crusher dust vs paving blend sand.. queenslanders have been using crusher dust for years.. but theyre all weird.:p
I recon its easier to pull your screeding rod across sand. They both do the job. You probably have to allow around 7mm compaction of pavers on sand, with crusherdust I'd guess around 2mm again I prefer the extra give with sand it means your screed bed doesn't have too be too perfect but its really horses for courses.:rolleyes:

[ozwinner]

Sorry, I forgot to add it was all herring bone pattern, took me freakin ages to do.

Al :(

[SIMONLEWIS]

So basically dont pave staraight onto crusher dust??? use sand as well or a thicker base of crusherdust?

[Doughboy]

When I did my paving deck I laid 150 ml crusherdust base with 50 ml sand then pavers. Remember to haunch in on your edges and finally sweep in some fine sand after laying the pavers and then run a plate compactor with a carpet slide on it over the completed job just to sure the whole thing up at the end. And Voila one paver deck!!!

Sounds easy

Pete

[slipery]

Concrete straight on to crusher dust no worries. That is all I use not that I am a pro but I got the pros is to do my shed slab 9mx15m and they pored it straight on to crusher dust. Of course I am one of those crazy Queenslanders:cool: .

But if you are paving using paving stones or slabs etc then put the sand down over the crusher dust.

[woodsprite]

I do a fair bit pf paving of all sorts for a living. I have succesfully used crusher dust for domestic driveways underneath brick pavers and had no problems. First one I did was about 9 years ago, on a long sloping driveway and it has never shown any signs of shifting. I wil only use crusher dust now - we live a mile from a bluestone quarry and I can get a trailer load for 6 bucks - as I reckon because of its density ot packs down better and stays packed after it dries out.

On driveways, if there is a reasonablt solid earth base, I use about 50mm of dust, water it and whacker it to really compress it, then lay a thinner layer over that base for the pavers, and then whacker the lot.

Hope this helps - I reckon with crusher dust and clay pavers you will be fine.

Hope your knees ar in good nick! There's a HEAP of pavers in a driveway!

Jeff

[woodsprite]

I would think twice about using those big pavers - the bigger they are the more prone they are to cracking - and I would not use concrete pavers as I reckon at that size they are way too brittle - just my opinion. I know using smaller pavers is a heap more work, but I reckon it is worth using them instead of the big square ones.

[SIMONLEWIS]

Yeah its actually 4900 pavers - so hopefully I will survive... I was told by the paving place that 200x200x50 would be ok for a driveway - they seem pretty small???? Will be ordering first thing monday so want to make sure i guess

[namtrak]

IMHO,

50mm crusher dust with no sand will lead to dramas down the track, particularly a driveway.

50mm pavers are okay, however, I would be looking at 100-150mm of crusher dust, set down with a wacker. Then another 50mm of sand , screed out.

Whats your subsoil? Why only a 50mm of crusher dust with no sand? If your excavating down 50mm, then another 150mm shouldnt be a drama. There's no point trying to saving costs here - the crusher dust and the sand is neglible compared to the cost of digging it up again!!

Cheers

[Bleedin Thumb]

I would think twice about using those big pavers - the bigger they are the more prone they are to cracking - and I would not use concrete pavers as I reckon at that size they are way too brittle - just my opinion. I know using smaller pavers is a heap more work, but I reckon it is worth using them instead of the big square ones.

You are correct about the small size pavers because most of the strength of you paving comes from the joints not the base.:eek:
Its true the idea of sweeping sand in the joints isn't to make the paving lokk good it is to aid in gaining "LOCK UP" . That is why commercial segmented paving (on container terminals etc) used to be those squiggly patterned pavers. These created more edge and hence more strength. Lock up usually takes around 2 weeks or more to start happening however there are now a couple of commercially available products that you sweep/ pour over the new pavers that will help speed things up.
As far as the thickness of the pavers IMHO I think 50mm is too thin.
As far as the base .. Crusher dust is not the same as road base so if you are creating a subbase use roadbase to gain the best compaction then use crusher dust or paving blend sand for your screed bed. As your creed bed will compact slightly (as it must) your ideal thickness of the bed is usually around 25 - 50mm if you have to build it up anymore than this once again roadbase to 98% general compaction or a blind slab - thats if you want it to look smooth in a couple of years time.;)

[woodsprite]

I probably ought to clarify the crusher dust bit - as mentioned, I live only 2 minutes from the local bluestone quarry, so the crusher dust I am talking about is actually basalt fines that fall sdown from the main crushing rigs and conveyors. This is the stuff I have success with. In other states or regions, crusher dust may be similar fine material but from a different type of rock.
Jeff.

As an aside, the crusher dust from this particular quarry, - because of the age of the basalt and and the peculiarities of the basalt in its molten state 5 million years ago - also makes an excellent slow release fertiliser! It is full of trace elements. Mixed with soil it makes for a great lawn bed, and people in this area have been known to grow their vegies in it and it is great as a top dressing for fruit trees! I made a lawn for a customer about 5 years ago with good quality soil - it died within 12 months. 2 years ago she asked me to redo the lawn - this time I added about a cubic metre of crusher dust to the lawn bed, rotary hoed it into the old soil, and she has the BEST lawn in the area - stays green and moist even in long dry spells.

[Bleedin Thumb]

Jeff,
I wish I could get crusherdust at the cost you get it for. It probably does vary a bit from quarry to quarry. I did a job about 1.5 years ago and used a cheap blue metal (basalt) as a gravel mulch in biological drainage channels, its now decomposing and turning to dust - I knew it would but it was an economic thing at the time:o
I saw on Country Wide once how cane farmers were turning to gravel as a fertiliser- makes sense but sound weird!:eek:

[SIMONLEWIS]

IMHO,



50mm pavers are okay, however, I would be looking at 100-150mm of crusher dust, set down with a wacker. Then another 50mm of sand , screed out.

Whats your subsoil? Clay/red dirt
Why only a 50mm of crusher dust with no sand? -
the crusher dust and the sand is neglible compared to the cost of digging it up again!! Couldn't agree more - a mate is helping and he has suggested this - I am trying to convince him I need 100mm at least and then 30mm of sand. The last thing I want to do is do it all twice.....

Cheers

[Smiley Guy]

Just caught onto this thread - I'm still not sure if people are saying it's OK to lay straight onto crusherdust. Providing the layer of crusherdust is thick enough, and ignoring the issue of diffuculty of screeding; will crusherdust (crushed blue metal) be OK to lay straight on top of. My paver is doing a job for me outside right now - paving straight onto 100mm of crushed blue metal/crusherdust. Is this just as stable as using sand? It's for foot traffic only.

[Bleedin Thumb]

Hi SG,
There seems to be a couple of opinions here. I've done a bit of paving in my 24 years - one job alone was 4500 sq.m. so IMHO:-
You can use crusherdust instead of paving sand, ideally no thicker than 50mm this is called your bedding layer.
Under your bedding layer is your subbase layer. This should be be a compacted thickness of 75mm min for pedestrian or 150mm vehicular made from DGB 20 roadbase (or recycled). Compaction for pedestrian by flatplate or vehicular by vibrating roller to 98%.
Under that layer is your subgrade layer. Most of the time in a domestic sence this gets ignored but on a commercial vehicular paving job this may need modifying to acheive longevity and strength.

The other opinions expressed on this thread dont seem to differenciate between bedding and subbase. Whilst for most domestic, pedestrian jobs this may be OK, if your subgrade has a poor load bearing capacity,ie sandy or plastic clay soils then I would feel better if the subbase was roadbase at the very least.

Crusherdust does compact better than pavingsand but the point I'm trying to make is it doesnt compact anywhere near as good as roadbase and that is what you should use as a subbase.
SG What your pavior is doing is probably fine for domestic paths. My signiture used to read "If its worth doing, its worth overdoing" which is my philosophy on commercial projects.:p
Sorry for the long winded answer.:o