the true characteristics of
the original;
many of the thin skins are backed up in concrete, brick or other inappropriate ma- terials, or with significant voids behind the new veneers. Therefore, a highly invasive intervention is carried out in what was an otherwise stable structure. In most cases,
the mortar used for
repairs, restoration or conservation con- tains cement. In these buildings, the use of cement mortars promotes condensa- tion build up, salt reactions, and generally the long term survival of the building. In general, surface repairs are required to provide a good visual match for
the
existing masonry. The physical properties of the masonry may vary from one part of the building to the next and the ability to vary the properties of the repair mortar is an advantage. For surface repairs to be successful, the
materials employed need to have certain characteristics. They should: • Have characteristics similar to the host masonry
• Have adequate bond strength • Have a good modulus of elasticity
NOVEMBER 2014
• Be vapour permeable • Be durable • Be capable of being dressed with similar tools to the original masonry
• Remain workable to allow details to be fashioned
• Match in colour and texture • Adsorb water sufficiently in wetting and drying periods to match adja- cent masonry.
• They must always be reversible They should not: • Become significantly stronger than the surrounding masonry
• Have a significantly lower rate of absorption or adsorption than sur- rounding units
• Create a barrier to diffusion St. Astier natural hydraulic lime mortars
provide a valid alternative to cement mor- tars or cement/lime mixes and, if applied correctly, they will have a much longer life. Environmentally, they offer far greater efficiency than cementicious mortars by reabsorbing CO2 and not compromising the recyclability of the building materials. Lithomex is a very cost effective, ver-
satile mortar widely used for repair, restoration and stone simulation. Stone colours are precisely matched. Tonalities and surface finishes are easily achieved by trained masons. The UK is one of the largest users of
Lithomex, as colour matching services and training are available. St. Astier Limes specialists, when required, actively work with the specifier, giving technical advice to establish the most appropriate mortar for the proposed intervention. If mortars are not dosed or mixed prop-
erly, if they are not cured and protected correctly, if the application surfaces are not properly prepared, if suction is not controlled,
if salt movements are not
taken into consideration and so forth, the result will be a failure.
For more information, clarification or for any query, please contact:
technical@stastier.co.uk
WWW.PREMIERCONSTRUCTIONNEWS.COM
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