Because of its fineness, Prompt natural cement adheres well to any type of construction material. The material must be damp, so that it doesn’t absorb the water from the mortar, which would compromise the strength gain and bonding of the Prompt natural cement mortar.

The bonding of Prompt natural cement mortar is optimised by the “skim layer” technique (cf. graph below). Bonding also depends on dosage: the higher the dosage, the better the bonding.

“Skim layering” instructions:

• dampen the surface,
• apply the mortar to the surface,
• skim with the edge of the mortar trowel, leaving a fine layer of binder on the surface,
• reapply wet-on-wet the excess mortar to the damp surface,
• apply successive layers (if necessary), wet-on-wet.

Figure 1: Example of bond on dry concrete after 28 days
(2 volumes of natural cement / 1 volume of sand)