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- Air Lime.
- Another word for pure lime putty. The name implies that the lime sets in the presence of air, in contrast to hydraulic lime which will set in the presence of water.
Batching.
- A name used to describe the careful control of the ratio of lime to aggregtes during mixing. Proper batching ensures that the properties of the mix remain consistent. Variations in the 'batches' will create differential strength, flexibility, durability and permeability which may cause premature failure in the material.
Calcination.
- The process by which raw limestone is converted to quicklime by heating at temperatures between 900 - 1000 degrees C. During the process CaCO3 splits into calcium oxide (CaO) and carbon dioxide (CO2).
Eminently hydraulic
- A term established in the 1820's by a frenchman named Louis Vicat to describe the rate at which hydraulic lime would set in the presence of water. The other terms used were 'feebly' and 'moderately'. Eminently was the fastest setting of the three. This system of rating lime has been replaced by the terms NHL 2, NHL 3.5 and NHL 5 although these newer terms do not directly match Vicat's terms. (see the diagram on the Lime page).
Fat Lime.
- Another word for pure lime putty. The term 'fat' implies that the lime is pure and has a high calcium carbonate content, with low clay, minerals or other impurities.
Feebly hydraulic.
- A term established in the 1820's by a frenchman named Louis Vicat to describe the rate at which hydraulic lime would set in the presence of water. The other terms used were 'moderately' and 'eminently'. Feebly was the slowest setting of the three. This system of rating lime has been replaced by the terms NHL 2, NHL 3.5 and NHL 5 although these newer terms do not directly match Vicat's terms. (see the diagram on the Lime page).
Fly Ash.
- A solid residue left over from the burning of coal. It contains large amounts of silicon dioxide and calcium oxide and is added to lime and cement to accelerate setting and increase strength and hardness. Similar to 'pozzalans'.
Hydrated Lime.
- Calcium hydroxide - Ca(OH)2 - created by the hydration of quicklime. Hydrated lime is a dry powdery material. It is turned into lime putty by the addition of a little more water. Pure hydrated lime is much more stable than quicklime. It can be handled safely and stored for a while as long as it is kept dry.
Hydration.
- The process of combining quicklime with water to create hydrated lime or calcium hydroxide. CaO + H2O = Ca(OH)2. This process is called 'slaking'. Due to the extremely hydrophilic nature of quicklime hydration is a volatile process which gives off large amounts of heat. To avoid a potentially violent reaction, quicklime should be added to the water, and not the other way round.
- Hydraulic Lime.
- The group of limes which, due to their clay content, have the ability to set in the presence of water. The group includes Hydraulic lime (HL) and Natural hydraulic lime (NHL). HL has clay added. NHL contains naturally occuring amounts of clay.
Hydraulic Quicklime.
- Similar to pure quicklime, hydraulic quicklime contains clay which allows the lime to set in the presence of water. See 'quicklime' for definition.
Lime Mortar.
- Also referred to as stucco or render, made by mixing lime putty with different aggregates such as sand or gravel, and fiber such as straw or horse hair for tensile strength. Fly ash or other pozzalans can be added to provide added strength and faster setting. Mortar is used in place of cement in the construction of foundation walls and applied to walls as the protective and finish layer. The ratio and grade of aggregates are determined by the specific application. Mortars tend to be more course in nature with larger agregates and more fiber. The ratio of aggregates to lime is important and should not exceed 3 : 1 as the lime must fill the 'spaces' between the aggregate prticles in order to provide a good bond. Too little lime will results in voids which will weaken the mortar. Aggregates should have sharp (jagged) surfaces which increase the bond strength.
Lime Plaster.
- Similar to lime mortar. Lime plaster is typically used as a top or finish coat on walls. The size and ratio of aggregates is usually less than for mortars in order to produce a finer and smoother surface.
Lime Putty.
- Chemically the same as hydrated lime, ie: calcium hydroxide. Lime putty is the consistency of stiff pottery clay and is produced by the same slaking process as hydrated lime, except that a little more water is added. Lime putty is the principle ingredient of pure lime mortars or plasters. It is highly beneficial to keep lime putty for several weeks or months before it is used as this ensures that all the lime has been fully hydrated. It must be kept wet during storage as it will start to set if allowed to dry. Hydraulic limes cannot be stored as putty since they will set in the presence of water.
- Lime Wash.
- A diluted solution of lime putty used to paint and protect walls. Washes can be combined with pigments and other additives, such as caseine, to colour and protect lime plasters.
Moderately hydraulic.
- A term established in the 1820's by a frenchman named Louis Vicat to describe the rate at which hydraulic lime would set in the presence of water. The other terms used were 'feebly' and 'eminently'. Moderately comes between feebly and eminently. This system of rating lime has been replaced by the terms NHL 2, NHL 3.5 and NHL 5 although these newer terms do not directly match Vicat's terms. (see the diagram on the Lime page).
Natural Hydraulic Lime (NHL).
- Hydraulic lime that has naturally-occuring clay in the source material. The ratio of clay determines the rate at which the lime sets in the presence of water, as well as its strength and hardness. The higher the clay content the stronger, faster setting and harder the resultant material.
NHL 2. / NHL 3.5 / NHL 5.
- The three modern classifications of hydraulic lime. The differences include; the rate at which the lime sets in the presence of water; the relative hardness and 'flexibility' of the material; and its strength. NHL 2 is the slowest setting and weakest, and NHL 5 is the fastest and strongest.
Non-hydrated Lime.
- Another name for quicklime.
Pozzolans.
- The word comes from Pozzuoli, a town in Italy, near which the Romans mined a volcanic sand which was used to make the first effective cement. The name 'pozzolan' is now used to describe any lime or cement additive which has a high silicate content. These minerals combine with calcium hydroxide to speed up the setting time and also create a crystaline structure within the lime which increases its initial strength.
Pure Lime.
- Usually another word for pure quicklime, although it is should more accurately be used to describe the group of limes that are not hydraulic.
Quicklime.
- The product of calcination. Quicklime should, more accurately be divided into pure and hydraulic, although it is common for the word to be used to mean pure quicklime on its own.
Slaking.
- Another term for hydration. The process of re-combining quicklime with water to produce hydrated lime or lime putty. The word means to quench a thirst. In this case the attraction of quicklime to water.
Void test.
- A way to establish the ratio of lime to aggregates. Place a carefully measured quantity of your chosen aggregate into a clear container. Place the same quantity of water into a second measuring container. Pour the water into the aggregate until the level of water is exactly the same as the aggregate. Measure the quantity of water remaining in the second container, subtract this from the original volume of water and this gives you the volume of lime required to fill the voids in the aggregate.
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