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Posted: Thu Mar 09, 2006 6:12 pm
by dak uk
I’ve laid 6" of dolomite on my proposed block-paved drive, compacted at 2" layers. The problem is the dolly is very fine dust with hardly any hard stone mixed (should be 25mm-30mm) it rain all the next day and my quite firm base has gone spongy 
.
If left to dry-out will it be ok to use after another compaction as there is 7 ton used with *2 ton left still to be used (*area not yet completed, still need to purchase 3 more ton of stone ).
My thoughts were:-
1: leave the stone to dry out before the laying of blocks.
2: spred spongy stone out and sandwich a geo-tex fabric between this and a dry top coat.
3:spred the spongy stone out and compact stone chippings of the 3 ton still needed into it to try to firm up a bit.
Posted: Sun Mar 12, 2006 1:10 pm
by Tony McC
The dolomite should firm up like concrete as soon as it dries out.
If you had reservations regrading the consitency of the dolomite (ie: all fines and not enough lumps), you should have either...
1 - reject it on delivery and send it back to the supplier
2 - used a geotextile between sub-grade and sub-base
Item 1 warns of the importance of checking stone and other materiual deliveries before they are unloaded. All too often we implicity accept that "it'll be alright" and instruct the driver to unload on trust. However, with aggregates, once they are tipped, it is very, very difficult to get them sent back, as the supplier (quarry or BM) will usually claim that the instruction to unload is an acknowledgement of acceptability, that is: if you tell the driver to toip the load, you're effectively saying that the load is suitable and all responsibility passes on to you.
On one or two ocassions when we've been able to argue that the load was tipped without being sanctioned by the ganger/engineer (we usually had signs on our sites stating that all deliveries MUST report to the site office), and it then turned out to be a pile of crap, the agg supplier wanted us to re-load the material at our own expense. When you've a 20 tonne tracked machine on the job, this might not be a major problem, but when you've just had 20 tonnes of dusty sub-base dropped on a job where it was being spread by hand, the prospect of throwing all that back onto a 3m high wagon is just not worth thinking about.
Item 2 is an "emergency" solution for dusty sub-base materials laid on uncertain sub-grades in wet conditions. It won't help the sub-base drain any faster, and it won't prevent it holding on to any of the water, but it will elimnate any pumping of slushy sub-grade and it will significantly stiffen the sub-base as soon as the material starts to drain.
So: your sub-base should be OK as soon as it dries up, but, in future, check each and every delivery before unloading. 