NATURAL HYDRAULIC LIME


Natural Hydraulic Lime in New Construction


There is an increasing interest from specifiers in the reintroduction of lime as a mortar for new construction projects. For masonry, particularly where porous stone or brick is selected, the lime is a suitable material whether working in thick joints or thin. The extraction of any moisture that penetrates into the façade is assured as soon as it comes into contact with the mortar joint ensuring that damage from salts and staining cannot occur. Fine stonework and brick suffer no contamination, staining or bleaching from Unilit Natural Hydraulic Lime mortar.


Natural Hydraulic lime is particularly suited to building without expansion and movement joints which are prevalent in modern day construction. Leading research has been undertaken in to the performance of hydraulic lime mortars in compression and axial loading. The open pore structure of the mortar promotes the ability of each individual unit of the masonry to move as an independent element, rather than as a mass as occurs with cement and concrete. This tolerance of movement allows construction without unsightly movement joints to mirror the style and continuity of our historic buildings.


Harmful CO2 emissions acknowledged as being a major cause of the greenhouse effect occur during the production of both cement and lime. However with lime burnt at temperatures of circa 900°C and cement exceeding >1450°C, more energy is required for the production of cement. Additionally, a study of the lime cycle indicates that an equal amount of CO2 is retained during the carbonation/setting process as is released by the limestone during burning. As a consequence lime mortar is by far the more ecologically preferable product.


Base mortars are supplied pre-bagged, in hydrate form for site mixing or in a pre-blend manufactured in the UK with limestone sand of an appropriate grade. Natural earth ochre mortars are pre-mixed to produce coloured finishes that weather and perform similarly to natural stone. The assured bond of lime to lime enables thickness to be built up without risk of delamination between the layers. Feature rendering in ashlar, cornices and raised bands is particularly suited to Unilit. The low salt content and control of free lime in the mortars ensures the façade is resistant to lime bloom.


Masons and bricklayers view natural hydraulic lime favourably due to the excellent workability achieved without the addition of synthetic plasticisers, together with its ease of application and mixing.


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