10 REASONS TO PROMOTE THE USE OF LIME PUTTY.
1) THE LIME ALLOWS BREATHABILITY.
The crystals of calcite generated during the carbonation of lime-based products are of size much bigger than those created during the hydration of hydraulic binders. Their growth in the pores coated from solution supersaturated of hydroxide lime, besides producing a very gradual increase of resistance in time, confers high permeability to mortars.
Vice versa, especially in the case of plasters, dense mortars and impermeable materials of cement nature can trap moisture in the masonry that very often triggers and / or catalyzes various mechanisms of degradation.
2) THE LIME ENSURES A GREATER COMFORT AND SALUBRITY TO THE ENVIRONMENTS
Exterior and interior plasters, when are properly hygroscopic as those based on slaked lime, absorbing and releasing moisture, regulate the optimal room humidity, increasing the comfort level of the premises, reducing condensation and preventing the onset of moulds. The lime, strongly alkaline, is caustic and thanks to this characteristic, that confers good antiseptic and disinfectant properties, has been and is still used to sanitize the environments.
3) THE LIME HAS AUTO-SEALING CAPACITIES
When the mortars made of non-hydraulic lime are subject to vibrations and small movements tend to develop many fine cracks, but when the water enters in the cracks can dissolve the calcium hydroxide still present, and in the presence of carbon dioxide also the calcium carbonate (as bicarbonate) is transported and distributed. As soon as the water evaporates, the carbonate precipitates again and hydroxide is deposited and subsequently carbonated, inducing the sealing process. Phenomenon known as: autogenous self sealing of cracks or fissures.
4) THE LIME PUTTY HAS A GREAT ADHESION CAPACITY
The ultrafine particles (nano-sized) present in slaked lime of quality and sufficiently seasoned, are able to penetrate more deeply into the tiny gasps of the surface, gently binding themselves, and developing an excellent adhesion.
5) NON-HYDRAULIC LIME-BASED MORTARS CAN ALSO PROTECT ADJACENT MATERIALS
The high porosity and permeability of slaked lime-based mortars, controlling with their correct hygroscopicity the passage of moisture through the masonry, provide the optimal protection of brick and / or stone masonry, on which they are applied.
6) THE MIXES OF LIME PUTTY HAVE A GOOD WORKABILITY
The ability of a mix to maintain cohesion and plasticity, even when subject to suctions by porous materials and to be easy to apply without undue effort, is said workability. This property is excellent especially in seasoned slaked limes and is of great help to get easy and optimal execution of joints, plasters and stucco works, etc.
7) CONSTRUCTIONS MADE OF NON-HYDRAULIC LIME-BASED BINDERS ARE MORE DURABLE
The absence of potentially harmful chemical components makes the mortars of lime and hydrated lime immune from the destabilizing expansive action of sulphates and the deleterious alkali-silica reaction. Consequently, the works that employ non-hydraulic lime-based binders are extremely durable, demonstrating how the lime is able to pass the test of time.
8) LIME PUTTY-BASED FINISHES HAVE A GREAT DECORATIVE VALUE
The double refraction of calcite crystals gives the lime putty-based finishes a unique effect by combining a soft surface texture with a sheen that gives vivacity and aesthetic pleasure to the walls. The lime putty-based finishes nobly seasoned do not have a tendency to detach and peel off, but they consume and degrade in harmony with the substrate.
9) THE LIME IS ECOLOGICAL, ECONOMIC AND ENHANCES THE REGIONAL IDENTITIES
The non-hydraulic lime, cooking at lower temperature compared to hydraulic binders, requires a lower fuel consumption and consequently gives rise to lower emissions of carbon dioxide into the atmosphere. The different types of limestone that differ from region to region, will produce non-hydraulic limes with colors, textures and properties that will characterize and enhance local identities. The lime is a product economically advantageous thanks to the excellent coverage property (in volume): used in plaster, to cover the same surface unit, its dosage is up to 50% lower than the ordinary binders.
10) LIME PUTTY IS THE IDEAL BINDER FOR HISTORICAL-ARCHITECTURAL AND ARTISTIC RESTORATIONS
The binders of non-hydraulic lime are the only ones known to be compatible with the building materials characteristic of historic-artistic building: they do not react chemically with the existing materials and do not give rise to the formation of unstable compounds, inconsistent or generally harmful, from the point of view of the physical behavior they have values of elastic modulus, mechanical strength, thermal expansion and porosity less than or equal to those of ancient materials. The breathability of mortars based on lime putty allows the walls to “breathe” ensuring the durability of all its components. The natural color of lime mortar and the whole range of colors that can be achieved with the addition of sand and earth are integrated in harmony with the appearance of traditional materials, both natural (stones) and artificial (bricks).
Since ever we hear talking about lime, but not always the appropriate terminology is used to talk about it in a proper way, distinguishing first of all non-hydraulic lime from hydraulic lime, thus avoiding confusion.
The argument concerning non-hydraulic lime is extensive and much has been written about it, but what is more important is its use, millenniums of buildings that went down to history, arrived from antiquity to the present day, handing down a high quality material for the buildings of today, while respecting the traditions of yesterday. Therefore I decided to summarize the key points in ten voices about the importance of slaked lime.
Di Albiz Ermacora – some concepts are taken from the book by Andrea Ratazzi “Conosci il grassello di calce?”