Curing

Curing is the process of maintaining adequate moisture and temperature in freshly placed concrete so that cement hydration can continue and the material develops its intended strength and durability. Hydration stops when the water available in the pore system falls too low, and strength gained is not recovered later by re-wetting.

In practice

Printed elements are more exposed than cast ones. There is no formwork holding moisture in, every layer is open to the air from the moment it is deposited, and the ribbed geometry gives a high surface area for the volume of material, so drying begins immediately and continues over the whole element. Printable mortars are also binder-rich and fine-grained, which increases both the water demand and the sensitivity to early drying. Practical measures are covering with sheeting once printing is finished, curing compounds, controlling air movement across the workpiece, and avoiding printing in direct sun or in a draught. Curing conditions should be recorded alongside the print, because strength tests are only interpretable against them.

Related terms

• Shrinkage cracking — the usual visible consequence of poor curing.
• Green strength — early stiffness during printing, a separate property from cured strength.