2522.30.00.00 - Hydraulic lime

This HTS category, 2522.30.00.00, specifically covers hydraulic lime. Hydraulic lime is a type of lime that possesses the ability to set and harden under water. This property is due to the presence of specific clay impurities, primarily silica and alumina, within the limestone from which it is produced. Unlike common lime, hydraulic lime undergoes a chemical reaction with water that results in a stable, cementitious bond, making it suitable for applications where exposure to moisture is expected.

It is crucial to distinguish hydraulic lime from its sibling categories. Quicklime (2522.10.00.00), also known as calcium oxide, is produced by calcining limestone and is highly reactive with water, generating significant heat. Slaked lime (2522.20.00.00), or calcium hydroxide, is the product of reacting quicklime with water and is essentially a powder or paste that also hardens in air but not effectively underwater. Hydraulic lime, while derived from similar processes, contains sufficient siliceous and aluminous materials to develop hydraulic properties, meaning it can harden even when submerged.

As a leaf node, this classification has no further subcategories. Therefore, classification within 2522.30.00.00 relies on confirming the hydraulic properties of the lime. Key indicators include its ability to set and harden in the presence of water, its chemical composition (presence of silica and alumina), and its intended use in construction where water resistance is paramount, such as in mortar for underwater structures or in certain types of plaster.