Quicklime – Calcium Oxide (CaO)
Quicklime products:
Kibbled 2mm or 5mm – Used for making Hot Lime Mortar Mixes
Extra Fine – Used for Hot Limewash and slaking Lime Putty
What is Quicklime?
It’s limestone (a rock rich in calcium carbonate) which has undergone a chemical change in a kiln, liberating it of all the carbon and water it holds, creating a very unstable material (calcium oxide) which needs to hydrate. Quicklime will do so very energetically with any moisture it comes into contact with, resulting in a strong exothermic reaction and the production of lime. The addition of water (slaking), has the potential to produce temperatures exceeding 250C very quickly. However, when creating a mortar the quicklime can reach these high temperatures as hot spots only, and the overall temperature of the mortar should not exceed 100C – the temperature at which the water turns to steam.
Quicklime is available in two forms, ‘kibbled’ which is granular (2mm or 5mm), or finely powdered. Both of these are chemically identical, but kibbled is more dense than an equal volume of powder, and as mortars are usually mixed by volume not weight, mix proportions should be varied accordingly. (Kibbled expands to approximately 2.7 times its original volume, while powdered expands approximately 2.1 times.)
Quicklime can be used to make Hot Mixed Mortars which are very vapour permeable with a good ‘sticky’ consistency. It’s also used to make Lime Putty which has been slaked with water.
Quicklime (Calcium Oxide) is a highly reactive and quite dangerous material, please make sure you understand the risks and have taken suitable safety precautions before ordering. This material must be stored in a cool dry environment away from direct sunlight.
See our Technical Data Sheets section for more information, and in particular the Product Data Safety Sheet
Lime Terminology
• Calcium carbonate – also known as: chalk, limestone, agricultural lime chemical formula: CaCO3
– Calcium oxide – also known as: quicklime, burnt lime chemical formula: CaO
• Calcium hydroxide – also known as: hydrated lime, slaked lime chemical formula: Ca(OH)2
