Natural Hydraulic Lime (NHL) comes from limestone containing natural impurities of clay and other minerals.
Natural Hydraulic Limes (NHL) are made from limestone containing impurities which enable a hydraulic set. They are supplied as dry powders, and begin to set through a chemical reaction known as hydration, when water is added. Natural hydraulic limes (NHL's) are used to create breathable mortars and plasters which are more sympathetic to solid wall constructions than sand and cement.
Natural hydraulic lime is supplied in three European classifications: NHL 2, NHL 3.5 and NHL 5. These grades are based on the compressive strength of laboratory mortars at 28 days.
They are also often termed ‘feebly hydraulic’, ‘moderately hydraulic’ and ’eminently hydraulic’.
Roundtower natural hydraulic limes gives first class results, full breathability and vapour permeability, great flexibility, minimal shrinkage and, most importantly, stability over time. This lime is unblended and has been a critical element to the success of thousands of projects throughout Ireland and the world.
Roundtower Natural Hydraulic Limes are natural products. They contain no additives and are not blended. Roundtower Natural Hydraulic Limes are suitable for building restoration and conservation. Equally, they are very suitable for new construction and engineering works. Roundtower Natural Hydraulic Limes are recommended for mortars, plasters, concrete and grouts.
All Roundtower NHL's are certified to EN459-1.
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Feebly Natural Hydraulic Lime - Used for internal plastering and externally where the masonry is made up of a soft material.
Otterbein NHL 2 is a feebly hydraulic lime suitable for the production of plaster and mortar in ecological, biological building construction, in the restoration and preservation of historic buildings.
Moderately Natural Hydraulic Lime - Another NHL 3.5 with the exception that it has a higher 'whiteness' and is useful when colour matching mortars.
Eminently Natural Hydraulic Lime - This material is used in areas of high exposure such as in marine environments, wall copings, lime concrete, etc.
Otterbein NHL5 is an eminently hydraulic lime. For the production of plaster and mortar in ecological, biological building construction, in the restoration and preservation of historic buildings.
Otterbein NHL 3.5 is a moderately hydraulic lime suitable for the production of plaster and mortar in ecological, biological building construction, in the restoration and preservation of historic buildings.