St. Astier Natural Hydraulic Lime is truly a unique and rich exterior finish. Unlike the cold, urban look and feel of cement, natural hydraulic lime is a time-honored, old-world finish, enjoying a modern comeback due to its soft, rich, and velvety texture. Its ability to absorb multi-nuances of color is enhanced by the varied angles of sunlight reflected throughout a day. This is a finish that improves with age, always evolving, deepening, and taking on a character of its own. Its warmth lures one to touch and invites one to linger. Not only is St. Astier Natural Hydraulic Lime a pleasure to live with, but it is also healthy to live with. With no chemical additives whatsoever, St. Astier Natural Hydraulic Lime is the ultimate safe, natural, green building finish product—a throwback to the old world, rediscovered to help the environment of our new world.
What is Natural Hydraulic Lime?
Lime comes basically in two forms: Hydrated and Hydraulic.
Hydrated Lime (or calcium lime, air lime, high calcium lime): This is the most commonly used and known lime. It comes in powder form, like Type N, NA, S or SA, or in a paste form, known as Lime Putty. Although it has wonderful physical and aesthetic qualities, hydrated lime has very strong limitations in the construction industry. Hydrated Lime sets only by carbonation (the re-absorption of CO2) and thus, thicknesses are very limited. It is not suitable or practical for scratch or brown coats in a plaster, but can do wonders as a finish coat but requires blending most of the time. The application requires very highly skilled labor and that special care must be taken to avoid physical harm, such as burns when in the form of quicklime. Consequently, it becomes a specialty with associated costs.
Hydraulic Lime: Although basically of the same chemical composition as hydrated lime, hydraulic lime has its initial set with water, much like cement, and a second set by absorption of CO2. This allows for simplicity of application although basic care is required, such as minimizing the amount of water, good sand and tarping. The cost of labor is comparable to normal stucco installation. Hydraulicity for St. Astier lime is achieved by the nature of the raw material.
Hydraulicity of Hydrated lime may be obtained by the addition of cement, pozzolanes, etc. In such a case, the introduction of foreign chemical elements may have immediate or long range inauspicious consequences and the sensitive user should stay away from these hybrid products.
Why Use St. Astier Pure and Natural Hydraulic Lime?
St. Astier pure and natural hydraulic limes (NHL) have been in production for over 150 years. The characteristics of the raw materials are unique and consist of an undisturbed layer of calcareous rock infiltrated mainly by silica with only traces of other minerals. Millions of tons have been used successfully on a global scale, in the most diverse climatic conditions. During this time the uninterrupted experience of the manufacturer has generated a wealth of technical information both scientific and practical which is always available to the user.
NO ADDITION of any kind is made to the St. Astier Natural Hydraulic Limes to enhance their performance.
No Need For Blending
The St. Astier range of Natural Hydraulic Limes allows for the selection of the most suitable binder for the work at hand without having to add pozzolans, cement, plasticisers, water retainers, waterproofers etc. Blending introduces considerable risks, added costs and short and long term results that are uncertain and therefore potentially costly.
Compatibility & Suitability
The availability of a range of binders with different performance characteristics ensures the compatibility of St. Astier NHL mortars with existing mortars whatever their age.
Free Lime Content (available lime)
Responsible for workability and self-healing in NHL mortars.
The low bulk density of all NHL products will produce more mortar as they are purchased by weight but mixed by volume.
Versatility Of Use
Building and plastering mortars, grouts, injection, lime concrete and paints are all possible with NHL products.
Important in minimizing shrinkage and cracking.
Allows for minor movements.
Good vapor exchange qualities allow for condensation dispersion. Great benefits to the living environment.
Resistance To Salts
The absence of any potentially damaging component or additions (i.e. gypsum or cement) make sulphate attack and alkali-silica reactions impossible. Existing salts in the building fabric will pass through and eventually wash off. Excellent performance in marine environment.
Suitable Compressive Strength
Unlike cement or cementitious mixes (1:1:6 etc.) the compressive strength will be achieved gradually, allowing for movement. The availability of a range will permit the making of mortars with the required strength without having to add or blend.
Resistance To Weather
Early setting means less time for protection from adverse weather.
The available lime provides this benefit.
Resistance To Bacteria & Vegetation Growth
The long lasting alkalinity of the binder inhibits their development.
The excellent vapor permeability of NHL mortars reduces moisture in walls, therefore significantly improving insulation levels.
Sand Color Reproduction
The whiteness of the NHL binders will reproduce the color of the aggregate used.
All St. Astier mortars can be reworked (8-24 hours), reducing waste and increasing work rate. This is due to the absence of cement, gypsum, pozzolans or high aluminates.
Materials built with NHL mortars can be reused.
Probably the most eco-friendly feature of using limes. CO2 is re-absorbed during the carbonation of the free lime.
What Makes NHL Green?
- The amount of energy used at the production stage is one-quarter of what is needed to produce cement. Consequently, the release of CO2 into the atmosphere is reduced considerably. Furthermore, NHL reabsorbs most of the CO2 during the curing process, while cement reabsorbs none.
- St Astier products have received the LABELVERT EXCELL or "Green Label" in France. This label guarantees the total absence of contaminants and any risk of pollution. It also authorizes the use of this product in chemically sensitive areas such as living spaces, wine cellars, etc. The total absence of aromatic or polycyclic elements in NHL are proof of its purity.
- The absence or lower concentration of detrimental chemicals like tri-calcium aluminate, potassium and sodium oxides, (which are ever-present in cement), protect NHL mortars from chemical reactions such as sulfate or alkali attacks.
- The total absence of Chromium VI, eliminates the risk of skin cancer associated with clinker cement.
- Material used in construction with NHL may be reused or recycled. In addition, the NHL mortar itself may be recycled in a number of ways, such as an aggregate for new lime mortars, fertilizer, (NHL is calcium carbonate), or it can be used for water purification or hazardous waste treatment.
- Breathability, elasticity, plasticity, gradual development of strength, low shrinkage, longevity, CO2 absorption, self-healing, are all highly desirable. These traits, along with sustainability and greenness, are only some of the qualities of St. Astier Natural Hydraulic Lime (NHL).
- The change-of-use of older buildings through adaptation or preservation and restoration maximizes the need for the environmental recovery of materials. It is essential to ensure the long-term survival of these structures with compatible materials. Some buildings have been in use for centuries; there is no logical reason that this cannot continue. Preservation, adaptation and restoration can have significant environmental advantages over new construction. Aside from the environmental impact, there is the aesthetic value in preservation. Natural Hydraulic Limes have a significant part to play in this process.
- Material longevity is unsurpassed when applied and maintained correctly and its life will span over several generations.