Encyclopedia
Hydraulic lime
Hydraulic lime is produced at low temperatures by calcining limestone containing a sufficient amount of clay (although usually less than 20%) to allow the product to set in the presence of water. Hydraulic lime differs from natural cement in that it still contains some quantity of unslaked lime, which can in the presence of water turn into slaked lime.
Source: "Explanations to the Harmonized System of the Customs Tariff of the Russian Federation (HS Code of Russia)" (prepared by the Federal Customs Committee of Russia) (Volume 1, Sections I - VI, Groups 1 - 29)