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Posted: Tue Mar 28, 2006 8:22 pm
by david999
I have now paid for the job . They laid the block paving (200 by 100mm blocks from Wickes ) on a final bed of sand and cement - I believe it was about 4/5 of sand to 1 of cement .
They did lay and compact 100mm of No 1 hardcore - do you call it that ? - under the sand and cement .
What is likely to happen to the driveway in the near and medium term ?
Is there anything I can do , like using sealant ?
Help!
David
Posted: Tue Mar 28, 2006 10:46 pm
by Suggers
All you can do is pray -
Why write into a forum when - c'est un fait complete?
Sealant is neither here nor there in this case.
Posted: Tue Mar 28, 2006 10:46 pm
by colordrives
don't sound that bad to me mate, tho mot type 1 could do with being more like 150mm, looks like they made up for it by mixing the cement in, which is not really standard procedure with blocking on a diriveway. As long as sub-base was well compacted you should be ok. A sealant would'nt have any impact on the quality of the sub-base.
Posted: Wed Mar 29, 2006 6:00 am
by david999
Suggers wrote:All you can do is pray -
Why write into a forum when - c'est un fait complete?
Sealant is neither here nor there in this case.
Thank you Suggers .
"All you can do is pray -
Why write into a forum when - c'est un fait complete?
Sealant is neither here nor there in this case."
I wrote into the forum because I don't know much about driveway construction and I wanted to know what more experienced people thought about the method of contruction that was used for my driveway , and what the longer term prospects for it are .
I haven't read anywhere on this site that what the builder did was categorically wrong - forgive me if I have missed something .
Also , I wrote into this forum to find out whether there was anything I could do , like sealing it , which might improve its long term / short term durability .
Can anyone explain why such construction , with 100mm of compacted mot 1 and then about 50mm of sand and cement without the final course on sand - and on the sand and cement instead - will cause cracking or other problems ?
Thank you for your opinion .
David
Posted: Sun Apr 02, 2006 4:38 pm
by Tony McC
What the "builder" did was categorically wrong - there: you've read it now!
In Britain and Ireland, we use a flexible construction for block pavements. Adding cement to the laying course prevents it being flexible and turns it into a rigid laying course, for which the blocks were not designed. The loads imposed on the blocks will, over time, cause the laying course to crack but in the meantime, you have a pavement that is a bastard hybrid - a flexible sub-base with a rigid laying course and then a flexible paving layer. This is WRONG. The pavement cannot properly accommodate the forces to which it is subjected.
The way that a flexible pavement accommodates such forces is by being flexible, by having the ability to move slightly, to deflect and then bounce back when loads move across it. You pavement hasn't got this ability due to some halfwit "builder" thinking they know better than anyone else and that their method is superior to what we've learned from 60-odd years of experience of flexible block paving in Europe.
Sealants can't return flexibility to the laying course: nothing can. In the short term, there is a much higher risk of excessive efflorescence, and even of picture framing, which would be a permanent and irreversible stain on the blocks. In the longer term, the pavement could develop low spots due to variable settlement, especially if you have the type of driveway that has very definite traffic lanes.
If adding cement to the laying course was in any way beneficial, we'd all be doing it, believe me - but it isn't, so we don't.
The fact that this "builder" used a cement-bound laying course, combined with the fact that they used a budget block supplied by a DIY store rather than deal with a builder's merchant or a direct supply manufacturer, all suggests they were most probably of the cowboy persuasion.