Argical M1000 Clay Pozzolan
A moderate pozzolan, best suited to retain the features of colour sensitive mortars
Produced from a fired kaolinite clay with the best pozzolanic index by far of any of the more standard pozzolans used in conservation. Argical was developed to combat the Alkali Silica Reaction (ASR) in concrete, it densifies concrete making it less permeable thus reducing associated concrete decay mechanisms. And because it is so good in the way it chemically bonds with calcium hydroxide (lime), we would advise its addition with some caution in a ‘traditional’ lime mortar, as it can negate quite significantly vapour permeability, one of the main reasons you would be using a lime mortar in the first place.
We absolutely recognise its quality as a pozzolan and sometimes use it within our dry mix blends to serve appropriate technical functions, but these are carried out under the controlled conditions of an ISO9001:2015 factory; completely different to site batched mortars. The addition rate in lime mortars is advised at 5 to 15% by volume of the binder