Outdoor grouting using clay and lime?

Hi all

Anyone know what I can use on my outdoor paving stones as `natural`waterproof grout?
I have clay, river sand, straw and lime. Can any of this work and survive rain or will it just become mud again (which Im guessing)

Thanks
Sebastian

Sebastian, how big are the joints?  If big joints (over 1/8"), I would recommend Type S masonry cement with a Laticrete additive.

You could make a lime based mortar with lime and the sand. Its properties will vary a bit depending on how the lime is made though.

Limecrete may work for you.

Limecrete is a mix of natural hydraulic lime (NHL5) and sharp sand.
Sometimes glass fibres are mixed in to give a more durable surface.
Test have shown that physical characteristics in terms of compression strength are more than adequate to meet Building Regulations requirements,
and products from companies such as Eco Lime, Tŷ Mawr Lime and The Limecrete Company have Local Authority Building Control (LABC) approval.

thanks amigo, appreciate it.