Relegated Lime is one of the most claimed from bio for its great advantages compared to Portland cement materials.
Until the industrial revolution and the discovery of cement in 1824 in Portland, England, lime has been the main binder construction mortars, coatings and paints.
It is responsible for the soundness of the ancient and medieval buildings and has participated in prestigious works as the frescoes and stucco decorate.
The builders then applied limes available in quarries and lime kilns closer.
That is, the quality of the rediscovered limes varies rock extraction, because of the limestone, the purest come limes more fats, ie, air and limestone more clay, because richer in silica (loam) were from lean lime is said hydraulic.
resulted denominations number for lime, typical places of origin.
Due to the limited portability, builders applied the local material but knew a wide range of tricks to correct the effects of each of the limes found for bring to their mortars qualities required in each application, such as control of speed in hardening, hardness and waterproofing grade.
From this we conclude that all kinds of lime lived from all time.
I say this because in Today we tend to value at the first traditional and mythical class purest limes; while disqualify as second impure limes with hydraulic properties as these are not mentioned in the literature before about two centuries past.
The choice of our limes heritage restoration and new construction today should follow a more technical aspects and less doctrinaire.
Off quicklime on site. Photo © EcoHabitar
20% of the land surface is covered with limestone.
Depending on the type of limestone used, cooking allows the manufacture of various types of lime:
- Air lime, from a pure limestone
- Dolomitic lime, limestone from rich in magnesium carbonate
- The natural hydraulic lime, from a loam (clayey limestone).
Air Calcination occurs Cal by cooking pure limestone (calcium carbonate or bột đá) about 900 degrees and is accompanied by a loss of 45% by weight, corresponding to the loss of carbon dioxide.
After the extinction quicklime (calcium oxide), resulting from cooking, suitable for application in building (calcium hydroxide) is obtained slaked lime. By producing much heat, the extinction process is done at the factory or by trained personnel.
The water added in the preparation of lime-based mortar and sand, makes the start of carbonization, a slow reaction requiring several months the presence of water and carbon dioxide from the air at once. Once the water had evaporated, the following calcination with water vapor present in the air that has an affinity for carbon dioxide (carbonic acid form). The calcination then feeds this carbonic acid gas in this.
dolomitic limestone In the carbon is associated with the calcium magnesium carbonate.
After firing at temperatures below 900 degrees is obtained an air lime.
Natural hydraulic lime
are rare pure limestone. Almost always appear mixed with clay, rich in chemical elements such as iron and especially aluminum and silica which comes natural hydraulic lime. Between 800 and 1,500 degrees (usually about 900 degrees), calcium limestone combined with those forming silicates, aluminates and calcium aluminate ferro-elements.
On contact with water these bodies want to form insoluble carbohydrates which give the binder a hydraulic character.
On contact with moist air, lime and hydrates thus formed char with carbon dioxide from the air. This reaction lasts several months and is the aerial part of the process.
The scientists of the nineteenth century attempted to classify the hydraulic limes according to their level of rainfall, depending on their clay content (between 5 and 30%).
At present hydraulic limes are produced low and high water resistance forming 3 classes of which the most frequent are the NHL 5 (the strongest among natural hydraulic limes, with a minimum compressive strength 28 days = 5 MPa class and clay content Limestone from 15-20%) and NHL 3.5 (minimum compressive strength 28 days = 3.5 MPa, clay content of the limestone from = 8-15%) and less frequent class 2nd class NHL with a very low clay content and end in little higher than that of an air lime compressive strength.
The Limes rainfall somewhat higher than that of natural hydraulic limes are called Artificial Hydraulic Limes (hydrated lime) because they contain added substances before or after cooking, such as, among others:
- Clinker, are hydrated silicates and aluminates, being cooked above the sintering (1500 degrees).
- Naturally occurring pozzolans (volcanic) or artificial well (mixture of silica, alumina and ferric oxide).
- Fly ash, which come from burning oil.
- Steel slag.
- Filleres limestone.
Artificial hydraulic limes
Speaking of artificial hydraulic limes and enter the world of “natural” (cooked under the sintering cement) cements as their constituent elements are the same.
Portland cement is the result of cooking of these elements with much higher (up to sintering) temperature. Thus a binder for rigid and high resistance to compression due to a mortar hardening process and equivalent to only hydraulic loss bioclimatic qualities, good workability and water retention and good appearance is obtained compared to a lime mortar.
Besides being incompatible with all kinds of materials that make restoring heritage buildings, cement mortars, besides use case for the foundation, are absolutely unnecessary to erect a building or multi-family housing with few plants.
The Cal depending on application
• Mortars for foundations and settlements of natural stone blocks Factory
. The air lime provides most workability and flexibility due to greater finesse against natural hydraulic lime
But it is preferable hydraulic lime since apart from good has greater flexibility workability and compressive strength and a higher initial resistance, with the advantage of the rapid advance with time and money saving work.
Moreover transfers moisture tolerant and minerals.
Thanks to the higher initial hardening hydraulic lime naturally allows the builder working on the outside year round, even in the winter months, provided protection against heat, ice and rain water during the first 72 hours of cure is provided.
• Construction of natural pools and ponds (storage of rainwater, etc.):
Natural hydraulic lime (NHL 5) as it is more waterproof, more resistant to compression, more resistant to mineral salts and capable of curing even under water without the presence of air.
• Exterior and interior Coatings
. The mortars for exterior cladding in any case would be based on natural hydraulic lime, since it has the greater strength, greater impermeability and better resistance to environmental stress and maritime influences
could innerliners be composed of a base coat of natural hydraulic lime mortar and a fine finish (in one or more layers) based on aerial lime mortar, with or without pigment which in its entirety is a plaster of lime.
The high fineness and maximum workability of air lime, which can be increased further by working with fat lime paste, is necessary for a good final result of the finish.
Its high porosity is responsible for maximum effect compensation water vapors in housing and excellent thermal insulation.
• Grouts and paintings:
To secure an area with poor adherence, could apply one or more layers of air lime slurry or natural hydraulic lime. To fix sandy surfaces is advisable hydraulic lime.
To increase the adhesion of a stand just before coating gives more effect air lime slurry, the more fat as possible.
The paintings would be based on aerial lime (color plus white) preferably fat lime paste, diluted with water and if anything capable pigments mixed with lime. The lime putty, paint, must be made of the upper layers (with no fat particles without turning) Lime that has rested under water for a period of months or years.
It is advisable to add to paint a natural stabilizer which enters into reaction with the lime casein such as thus increase in its resistance to the touch.
The humidification of the support and control of the drying of the film of paint is of great importance because lack of water is incompatible with the carbonization of lime.
The scope of lime paints are rather interiors as lime paints are sensitive to climatic variations (ice, sun, wind and humidity). As demand a high degree of maintenance outdoors.
• Fixing tiles, marble (interior and exterior) and pieces of decoration and murals:
Tiles and flooring with natural hydraulic lime as interested strength and high impermeability. For fixing of decorative ceramic tiles or natural stone on vertical surfaces and draw up a mortar with high lime content and optimal grain size, you could apply a mortar based on hydraulic lime (strength and good adherence) and lime paste fat (increase in adhesion). The support, if necessary, could be prepared with a fat lime slurry.
• Stabilize soil with lime:
It can stabilize the soil to manufacture bricks or mud and get increase its mechanical strength and water resistance.
The heavy clay soils (40% or more) are better stabilized with hydrated lime.
The soils very sandy better stabilized with hydraulic lime to gain more strength.
In addition to mix well, to ensure proper curing process, soil mixtures and hydraulic lime should be put into work early, avoiding rapid drying because, if you can not easily lose 50% resistance.
The lime powder can be used to stabilize but has the disadvantage of producing much heat can damage the skin pelirosamente. Because of heat of hydration tends to dry quickly the ground with the risk of dilation.
In general applies stabilizer 5% since less lime almost means means a loss of resistance. Stabilization is not an exact science therefore depends on the technical or constructor is best to test blocks for testing. The purpose of these tests is to find the smallest amount of stabilizer that satisfies the requirements.