Differences between air lime and hydraulic lime

Lime is a fundamental material in green building and restoration, but not all limes are the same. There are two main types: air lime and hydraulic lime, each with different characteristics and uses.

Air lime

• It is obtained by calcining pure limestone (calcium carbonate).
• It hardens only on contact with air, through the absorption of carbon dioxide (carbonation).
• It is ideal for interior work, plasters and finishes where humidity is not high.
• It offers great plasticity and breathability, but its mechanical strength is lower than that of hydraulic lime.
• It needs longer drying times.

Hydraulic lime

• It is produced from limestones that contain clays or silicas.
• It hardens both on contact with air and under water, thanks to a chemical reaction (hydration).
• It is suitable for damp environments, foundations and mortars exposed to water.
• It has greater mechanical strength and sets faster than air lime.
• It is less breathable than air lime, but more versatile in demanding conditions.

Summary

The choice between air lime and hydraulic lime depends on the type of work and the environmental conditions. Air lime is perfect for delicate finishes and restorations in dry interiors, while hydraulic lime is the right choice for structures subject to damp or for exterior masonry work.