Hydraulic lime

Hydraulic lime is a type of lime that possesses the property of setting and hardening when exposed to water. It is produced by calcining (heating) limestone containing clay or silica impurities at a lower temperature compared to the process used for producing quicklime. This results in a lime product that retains a significant portion of its original clay and impurities, giving it hydraulic properties.

The hydraulicity of lime refers to its ability to set and harden through a chemical reaction with water, even when submerged or in damp conditions. This makes hydraulic lime an ideal material for applications where traditional non-hydraulic lime may not provide sufficient strength or durability.

There are several different grades or types of hydraulic lime, each with specific properties and recommended uses. The classifications include NHL (Natural Hydraulic Lime) and NHL-R (Natural Hydraulic Lime with a Prompt Natural Setting). These types are typically used in building and construction for applications such as mortar, plaster, and masonry repair.

Hydraulic lime offers several advantages in construction. It allows for the creation of breathable structures, meaning that moisture can pass through the material, preventing the buildup of trapped moisture that can lead to deterioration. This is particularly beneficial in historic preservation, where maintaining the breathability of traditional building materials is crucial.

Furthermore, hydraulic lime has self-healing properties, meaning that it can repair minor cracks and damage over time through the process of carbonation. This can contribute to the long-term durability of structures.

It's important to note that hydraulic lime should be used in accordance with appropriate guidelines and specifications, as the correct type and mix ratio will depend on the specific application and requirements.

In summary, hydraulic lime is a type of lime that sets and hardens when exposed to water, providing strength and durability even in damp conditions. It is commonly used in construction for applications such as mortar and plaster, offering benefits such as breathability and self-healing properties. Proper selection and usage of hydraulic lime are important for achieving desired results in various building projects.