Geological Survey , National Minerals Information Center, compiled the following information on lime, an indispensable mineral material used in many ways. The world's largest limestone quarry, Calcite Quarry in Michigan, has been active since Lime is the common term for several chemicals in three major categories: quicklime, hydrated lime and refractory dead-burned dolomite. Lime is almost never found naturally.
It is primarily manufactured by burning limestone in kilns, followed by hydration when necessary. When crushed limestone is heated to temperatures between and 1, degrees Celsius, it breaks down into either high-calcium quicklime calcium oxide or dolomitic quicklime calcium-magnesium oxide ; the heating process also produces carbon dioxide gas, which is vented to the atmosphere.
Hydrated or slaked lime is a dry powder, putty or slurry produced in a hydrator by reacting quicklime with water. In the United States, most lime is produced as quicklime about 85 percent. Lime can also be produced from other calcareous materials — such as aragonite, chalk, coral, marble and shell — and as a byproduct in paper mills, carbide plants and water-treatment plants. Lime has dozens of uses. Dry-slaking is ideal for this: lumps of fresh quicklime are slaked with a limited amount of water and then immediately covered over with damp sand; then, after screening to remove any remaining particles of unslaked quicklime, the mixture of sand and lime is knocked up with water ready for immediate use, although it was probably 'banked' to allow the lime to mature for a few days first.
BAG LIME Most builders merchants supply a dry form of non-hydraulic lime which can be used like lime putty if allowed to soak in water for a while. Known as 'dry-hydrated' lime or 'bag lime', it is generally considered to be inferior to lime putty, not least because an unknown proportion will have reacted with carbon dioxide by the time it reaches the site. Limestone containing the lowest proportion of clay less than 12 per cent results in a feebly hydraulic lime with properties close to non-hydraulic lime, which is relatively weak, permeable and porous.
Higher proportions result in successively stronger and less permeable lime mortars. Because they react with water, hydraulic limes are usually supplied to site as dry powder. However, they can also be made by dry-slaking on site and may be knocked up with water and banked on site for a few days. Banking is not thought to harm the mortar despite the commencement of the set, as the bonds formed during banking are reformed later, after the mortar has been knocked up again.
Indeed, the process may actually result in a better set ultimately, as the lime is more mature. A similar effect can be achieved by adding pozzolanic additives to non-hydraulic lime as these additives contain highly reactive silica and alumina. However, the performance of a hybrid mortar was called into question by English Heritage following a number of spectacular failures, after which it banned the use of these mixtures on grant-aided work. The results of a study by the Building Research Establishment and English Heritage, which are now being prepared for publication, show that the addition of a small amount of non-hydraulic lime per cent improves workability but anything above this level significantly impairs durability.
Mixes containing and hydraulic lime:non-hydraulic lime:sand actually performed less well than a standard non-hydraulic lime:sand mix in their tests. This is to ensure that the new mortar performs in the same manner as the old and is similar in appearance. The original mix is best determined by analysis.
Several companies offer mortar analysis services - see The Building Conservation Directory or the Directory pages of this website for details. Selecting the most appropriate lime. How can you achieve this?
By comparing lime products through cost differences: When you compare lime products, make sure that you select the most economical product available in your region.
The value of limes of various types and from various sources can be compared by making the following calculations: First , gather quotes from suppliers for the total cost per tonne to have various limes applied to the paddock including the purchase price and the transport and spreading costs Second, obtain the effective neutralising value for the limes.
Most limes on the market have been tested to determine their ENV, and this information should be available from the supplier. Knowing these characteristics about lime including dolomite allows you to compare the cost-effectiveness of a variety of lime products and purchase the produce that will be most cost-effective for your farm.
However, you must also take into account other considerations, including the handling requirements of some products Use the following online lime calculators: Lime Comparison Calculator - Soilquality.
When taking the ENV into account, the unit cost of the products differ significantly. When and why should I need to apply lime? How do I manage the impact of sodic soils?
Brown Book content has been based on published information listed in the Resources and References sections below. Department of Primary Industries, Victoria. Clarkson T
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