Natural hydraulic lime is much less known than cement although it is much older. It has the same function but sand particles, bounded with cement form stronger parts than bounded with natural hydraulic lime (NHL). However a wall, made from bricks and NHL lime is able to deform after many years without developing a crack. Walls made with a cement mortar always generate a crack in case there is deformation due to insufficient foundation. Today, most people have forgotten that stable buildings can be made with bricks and NHL-mortar without using any cement. A very good book, written by the Prof. Dr. Ir. Koen van Balen, KU Leuven is an introduction in this matter, although written in Dutch. It handles about all kinds of lime in comparison with cement and remembers us that NHL-mortars without any cement are the only tool to renovate old historical buildings. Indeed cement mortars on old bricks are inducing cracks in these bricks.

Cement mortars on cellular glass are always a risk due to the very high drying stress exceeding the tensile strength of cellular glass. Organic additives can be added to cement mortars to induce some flexibility or the cellular glass surface cells can be filled with an organic flexible material like bitumen before applying cement mortar.  NHL-mortars have even in the dry state a kind of plasticity, probably generated by micro cracks, allowing deformation of the walls of old historical buildings and avoiding too much drying and thermal stress on cellular glass. Such a mortar could be the TD1320, produced by Tassulo in Italy.

Such a mortar has a compressive strength exceeding 2.5 N/mm². GLAPOR high density cellular blocks with compressive strength > 2 N/mm², sawed on the dimensions of typical bricks can be mounted on the foundation of one stock houses with this TD1320 mortar to insulate the foundation cold bridge and to avoid diffusion of soil water into the wall.

Another application could be to cover and strengthen the cellular glass with a NHL-based coating in order to have a hard surface with a minimal thermal expansion mismatch. GLAPOR, to our knowledge the only supplier of 3m x 1.5m cellular glass plates, can in that case replace wood and other materials when weight or / and combustibility are an issue. This is typically the case in ships, air planes and other places with a low fire loading.

But last but not least, NHL-based rendering products are a perfect solution for the finishing of non-combustible outside thermal insulation like GLAPOR cellular glass. This was already mentioned in a previous post.

It is my personal believe that the cellular glass world has to replace any organic accessory by a ceramic equivalent, where the flexibility comes from load distributing micro cracks like products with an NHL-bonding agent.