Heritage Conservation and Restoration
Building limes solutions

Restore - Repair - Consolidate - Grouting
Saint-Astier Genuine Natural Hydraulic Limes

In Restoration and Conservation Projects, it is of the utmost importance that mortars are compatible, chemically and mechanically, with the existing mortars and with the building materials present. This is especially the case in interventions involving the placing of mortars within a structure (rebuilding, injection, grouting, re-pointing) as potentially damaging chemical or organic components in the binders and the aggregates adopted will cause the deterioration of the structure itself.

Mainly because of the main damaging component detailed below it is by far preferable to adopt pure hydraulic lime mortars in the restoration or conservation of our built heritage (vernacular or monumental).

The main damaging components are:

Soluble salts. Sulphates are the main ones). Represented mainly by SO3, SO4, CaSO4 (gypsum).

Aluminates. Mainly tricalcium aluminate (C3A). The presence of sulphates and aluminates will cause, in a relatively short period, a sulphate attack when these components are exposed to rain water.

Alkalis (K and Na). Their presence, even if generally in small percentages, can cause a reaction with the silica content of the sands (Alkali-Silica reaction) with similar effects to a Sulphate attack.

Organic content. It must be below 1% of the binder content. Organic matter is subject to deterioration in time and can also promote biological growth.

Why use Saint-Astier Genuine Natural Hydraulic Limes ?


As the “only” Maître Chaufournier producing only Natural Hydraulic Limes, Saint-Astier has acquired since more than 100 years of exploiting its underground quarry, the control of its quality and a constant regularity on the production process which enable a production of Genuine Natural Hydraulic Limes.


Qualities of Saint-Astier genuine natural hydraulic limes

No addition of any kind is made to Saint-Astier Natural Hydraulic Limes to enhance their performance

The Saint-Astier range of Genuine Natural Lime Binders allows the selection of the most suitable binder for the work at hand without having to add pozzolans, cement, plasticisers, water retainers, waterproofers… Blending introduces considerable risks, added costs and short and long term results that are uncertain and therefore potentially costly

The availability of a range of binders with different performance characteristics ensures the compatibility of Saint-Astier Natural Hydraulic Lime based mortars with existing mortars whatever their age.

Responsible for workability and self healing in NHL mortars

The low bulk density of all Saint-Astier Genuine Natural Lime binders products will produce more mortar as they are purchased by weight but mixed by volume

Versatility of use

For Building
For making lime mortars
For pointing
For rendering and plastering mortars
For preserving
For grouting & injection
For Lime concrete & paints

Frequently Asked Questions

NO – Saint-Astier NHL products are burned at temperatures between 900-1000°C. At this temperature it is chemically impossible to develop Tricalcium Silictate (C3S) and high levels of Tricalcium Aluminate (C3A) which are formed at much higher temperatures and are the main components of cement.

NO – These reactions are common when materials have high content of C3A sulphates (SO3) and additions such as Gypsum (CaSO4) all present in Cement. Saint-Astier NHLs contain none of these potentially damaging components or only naturally occurring insignificant traces.

Saint-Astier Natural Lime Binder’s content of these components is below 0.3% and totally safe to us.

NO – Gypsum added to cement and to some ‘Hydraulic limes’ and C3A above 3% will react with the sulphates contained in sea salt. It is not possible for Saint-Astier Natural Hydraulic limes to react as they do not contain the necessary agents.

YES – This is due to the absence of gypsum or additions of cement and the low content of aluminia in the raw materials. Re-worked mortars ensure less wastage.

Not if one uses the correct grade and mix.

YES BUT WHY?? – As there is a range of products available we do not see any necessity for blending. Furthermore, blending will affect the performance of the mortar which potentially undesirable results.

Natural Hydraulic Limes is a sustainable and natural building material from Earth!