Premixed hot lime mortar developed to mitigate the potential health and safety risks that hot mix mortars pose when mixed onsite. Mix ratio 1:3 and available in many different sands. Supplied cool in 1 tonne bags.
Quicklime is limestone that has been fired in a kiln during which time the carbon dioxide and water present is liberated, chemically altering it from calcium carbonate to calcium oxide, a very unstable material that is desperate to reacquire its lost properties and when added to water initiates an exothermic reaction getting very hot, very quickly.
Quicklime is the base component for both lime putty and hot mixed mortars. When slaked with water it is stored for a prolonged period of time to produce lime putty, and when combined with water and sand creates the mortar referred to as hot mixed mortar.
A hot mixed mortar can offer a very workable 'plastic' material due to its high lime content. It is very sticky and this can help stop the mortar from being washed out. It offers good water retention during the mix. Hot mixed mortars (under lab testing) offer an extremely high vapour permeability, especially when compared to some NHL mortars, which can be beneficial to historic fabric, conversely in areas of high exposure this can allow the penetration of too much water.
There are health and safety risks when working with quicklime, it is chemically unstable and produces a violent reaction that poses risks when working on site. For this reason, we supply a range of ready mixed hot lime mortars where some of these risks have been mitigated.