Hi, what are your thoughts on using a mortar made of your lime putty and sand (say, in a 1:3 ratio) for a paving application, both as a bed and as grouting, probably bricks, something like this below (not the final layout, just playing around), on concrete? Is there a durability issue to think about there? It would be exposed to the elements, though thinking about a roof in the future… I want the traditional look of the lime, plus breathability because there will be some contact with timber probably. 
Thanks, I wasn’t previously familiar with that product, I will look into it, as far as I can see it has a small proportion of cement added, it sounds as if my suspicions are correct that regular lime mortar would not be up to the task. Maybe if the paving area was bordered, but even then…
Thank you for getting in touch. The products you’re suggesting would be much too weak. We would normally recommend Tradiblanc in this instance, it has similar porosity and vapour characteristics to St Astier NHL2/NHL3.5 and has the same aesthetic but is considerably stronger quicker. Tradiblanc would be a better option than NHL5 if its in contact with wood.