Shotcrete is pneumatically applied portland cement mortar made with an intimate mixture of Norlite and either portland cement or Lumnite cement. The material is shot into place by means of compressed air. For fireproofing structural steel members, proportions shall be in the 1:4 range for cement/aggregate.
All mixes containing Norlite/Lumnite hydrate to produce an alumina gel in the concrete or mortar that make it resistant to the corrosive effects of many industrial wastes and certain mild acids. It is also highly resistant to sulfate attack. The Norlite aggregate as well as the cement must be resistant to corrosion.
Because of the rapid strength development of Norlite/Lumnite, it is often used to produce concrete or grout for maintenance applications such as setting machinery, repairing industrial floors, etc., where downtime must be minimized. With a properly proportioned mix and good concrete construction practices, Norlite/Lumnite concrete can achieve a strength level in 24 hours which normally can only be obtained with a similarly proportioned Type 1 portland cement concrete in 28 days.
Norlite/Lumnite is also used to produce concrete for structural applications such as the construction of fire training towers, waste heat flues, chimneys, floors, ash bins, etc.
Since the hydration of Norlite/Lumnite mixes is an exothermic reaction, a rapid evolution of heat takes place during the first 24 hours. It is vital that this heat be dissipated and evaporation be prevented until the concrete is 24 hours old.