lutonlagerlout wrote:lay and compact your subase to levels
lay 50 mm of screed 5:1 grit sand cement, screed this off then lay your mats directly onto it while it is still plastic,I.E. has not gone hard
then point ASAP
LLL
Don't take this as gospel, as you need a composite solution here. IMO the setts are too thin, and so instead of having a flexible installation, you might have to end up with a rigid installation. LLL's advice here is good. Because you are only going to get one shot at this, you can't cock up. The 150mm
sub base of MOT1 is critical to a sound base and compact this hard as hell. The Screed layer must be soft enough to compact your setts into, yet must be damp enough and strong enough to cure to form a combined pavement thickness i.e. about 70mm thick of solid drive. I hope this make sense. As an aside, to lay individual cobbles (110 x 110 x 50mm units (see my web, or ask ScottKerb if he still exists) is easily as fast, we are doing 270sqm in 5 days from start to finish, the cobbles go down in 2 days.
Thank you very much for your input.
Do you think that the 5:1 screed mix is ok or should it be 4:1 to achieve a harder, stronger set product?
Should I get fibre into the mix to make it stronger and less likely to crack?
Do you think that an SBR slurry should be used?
Can this be applied to the screed rather than the back of the tile mats?
Should the setts be consolidated soon after laying with a plate compactor?
If so, should a neoprene mat be used to prevent damage to the setts?
Will a product such as Rompox drain or the like make this installation considerably stronger than traditional methods and as such would you deem it essential?
Sorry for number of questions but I really need to get this right and feel that I have to advise the 'lucky' contractor that gets this job as to how I would like him to proceed.
Matthewt, to be honest, for this size of job, and the ramifications if you get it wrong, I would pay for Tony's guidance on this, with no aspersions on LLL or any other. You need a detailed step by step procedure with clear technical specs. (As a matter of interest, Do you know what Mpa the setts are made to?)
IF, and this is a big IF, I was doing this job, with your limitations of product, I would go 4:1 damp and compacted screed laid 75mm before compacting. Fibre adds maybe 20% extra strength but the slab is going to crack anyway, I would limit sections to 4 x3m sections and add an expansion joint. The setts have to be consolidated BEFORE the Screed hardens, and I would definitely use a mat. Having said all that, email Tony.
At 1mPa equaling 10.2 kg/cm2 I get 144 mPa, but I've always been iffey with converting. I can only assume they are compressing the complete mat section, as opposed to a 6" cube (normal test procedure) but even so, far more likely to be 14mPa. I know bricks could be as low as 11 mPa and they work OK so not trying to scaremonger, it's the 30mm thickness that concerns me, I suggest you get the supplier to confirm that these will take domestic vehicular traffic.
(Our cobbles are made to 30 - 40 mPa after 28 days cure)