What is hydrolic lime?

Answer 1

Hydraulic lime is a type of lime made by burning limestone containing clay (a source of silica and alumina), which results in a lime that will harden underwater. It is a very old type of lime that has been around at least since the time of the Romans. It can be difficult to find an impure limestone that meets the necessary raw material specifications, so it can also be manufactured by combining high-calcium lime (made by burning high-purity limestone) with a source of pozzolanic material (materials containing reactive silicates and aluminates). Roman builders utilised volcanic deposits from Pozzuoli near Naples, as well as crushed clay tiles. Chemically, it can be broadly classified as being between lime and Portland cement. It has almost entirely been replaced by Portland cement, although it is still produced in some European countries (Italy, France, Germany, the U.K.). It is only used for structural purposes--mortars, plaster, and concrete. In the U.K. it's use is largely restricted to conservation and restoration work.

Answer 2

Hydraulic lime is a type of lime that sets and hardens by reacting with water to form calcium silicate hydrate and other compounds. It is used in construction for mortar, plaster, and stucco because it can set under water and is more durable than non-hydraulic lime.