There is wide variety of lime, which have different uses and different states. Which can be supplied separately or supplied, ready to go. The main principle of their production is very similar but each one can used for separate requirements depending on their particular project, renovation, conservation and New builds. See below for the different types of lime.
Builders merchants supply a dry form of a non hydraulic lime that could be used with Lime putty; only if it’s soaked in water for a considerable amount of time. Dry hydrated or bag lime, is generally treated to be sub-standard to lime putty. Only because an unknown proportion will have reacted with carbon dioxide by the time it reaches the building site.
In the late 18th century towns and cities were growing at an exponential rate and required lime to be made on site; before it can mature. Dry slaking is perfect for this; where fresh quicklime are then slaked with a marginal amount of water added to the mix. This would be covered with damp sand, after which it would be screened to remove the un-slaked quicklime. The mixture of the sand and lime could be used immediately when water is introduced.
For historic conservation work, a non hydraulic lime is usually used with very soft bricks, due to the nature of its porous and brittle properities. Lime putty is usually in a saturated state and is usually delivered to site in air tight tubs and a small layer of water, to stop it setting. When the lime putty is matured, which can take months to set. The end product is the purest form of non-hydraulic lime, ideal to be used for plastering or limewash. Lime putty can also be used for pointing masonry and even rendering.
Non Hydraulic Lime
Is produced when limestone (or calcium carbonate) is used as the material. The lime sets will only set by the method of carbonation (See lime cycle diagram). Non-hydraulic limes have been used in the chemical and steel industries for an array of reasons. The modern building sector has a minor market for the main producers of it. To please modern consumers for conservation projects, non-hydraulic limes are known and only produced to the highest standards of purity. This is a not great asset for building use to keep the building’s integrity, but it means that modern non-hydraulic limes are not a direct equivalent for their historic ancestors.
Hydraulic lime is created by natural mixtures of calcium carbonate and clay are used as the starting material for producing the lime. A complex set of reactions between the calcium carbonate and clay whilst heated inside the kiln. The lime will set immediately when water is added to the mix. This will allow the lime to be used for harbour walls.
Feebly hydraulic Lime
Feebly hydraulic lime (NHL 2, Natural Hydraulic Lime 2) is used for internal work and external work on soft porous bricks and also in covered areas. Feebly hydraulic lime usually contains a small percentage of clay with other impurities. The setting process can take one week or even to the extent of a month if subjected to more water.
Ashlar Hydraulic Lime
Ashlar Hydraulic lime is traditionally made with fine sieved lime, this could be used with a non-hydraulic or hydraulic lime with crushed chalk. This is can be done with or without crushed stone or sand added to bulk up the masonry joints if required. This makes the mortar highly flexible, which is perfect for small joints of 6mm and 3mm. Primarily, Ashlar hydraulic Lime has been used for conservation buildings for renovation purposes, but in the last decade a large number of new build projects have used it for bespoke architectural building.
Moderately Hydraulic Lime
Moderate hydraulic lime (NHL 3.5, Natural Hydraulic Lime 3.5) can be used for external work in most areas. Moderate hydraulic lime contains clay in the range of 11% to 20%. This type of lime sets (assumes given shape) within a few days after the addition of water.
Mix proportion 1 : 2 1/4 Limetec® Moderate Hydraulic Mortar will reach HLM3.5 (class III) at 91 days (high resistance to freezing and thawing, high resistance to sulfates).
Eminently Hydraulic Lime
Eminent hydraulic lime (NHL 5, Natural Hydraulic Lime 5) is used for external work in exposed areas, such as chimneys and for floor slabs/underpinning.
Eminent hydraulic lime contains clay in the range of 21% to 30%. Properties of eminent hydraulic lime are close to those of cement. Eminent hydraulic lime sets within one day after the addition of water.
Mix proportion 1 : 2 Limetec® Eminent Hydraulic Mortar will reach HLM5 (class II) at 91 days (high resistance to freezing and thawing, high resistance to sulfate).