Non-hydraulic and Hydraulic
Hydraulic limes set under water, and non-hydraulic limes need air to carbonatate and set. For hydraulic lime mortars, the lime is obtained from lime stone containing impurities. A non-hydraulic lime is produced from high purity calcium lime stones.
In the past, countless lime kilns all over countries, such as Britain, burnt lime stones of varying qualities - many of these lime stones containing impurities. The lime thus having varying degrees of hydraulicity, making them unsuitable for today’s industrial processes but due to its water resistancy suitable for building. Most of those kilns ceased production as portland cement gained widespread use replacing hydraulic lime. Today mainly non-hydraulic limes for lime plasters are produced and a very small number of kilns are still producing hydraulic lime for the building industry to standards which are now expected of any building material.
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