I know a few people on here have experience of this product so was hoping you might be able to answer a query.
Bit late to ring their technical experts so just wondered if anyone could confirm that the 840 product cannot be used on slabs laid on a non-permeable mortar bed?
What was the outcome of your enquiry to NCC?
As we discussed yesterday , the issue of 'permeable' and 'non- permeable' does cause a little confusion. In reality all cement/mortar bedding used in paving is permeable ( as is concrete) unless it is specifically designed not to be via the use of various admixtures (plasticisers , waterproofing agents etc). You would not however use this type of mix design in the world of paving to my knowledge. More for basements , swimming pools etc that we encounter on the other side of our construction chemicals business.
The simple answer is that all our mortars are designed for use on sand/cement bedding in accordance with BS7533. These mortars are permeable though. 99% of projects we supply are laid on to a sand;cement mortar bed so you can carry on with confidence!
Does this help ?