Gunite is a process involving a "mixture of Portland cement and sand thoroughly mixed dry, passed through a cement gun and conveyed by air through a flexible tube, hydrated at a nozzle at the end of such flexible tube and deposited by airplace of final repose." "When properly mixed and applied, Gunite is extremely strong, dense and highly resistant to weathering and many forms of chemical attack. It is heat resistant to a high degree and can be made more so by substituting refractory aggregates for part or all of the sand. Resistance to abrasion is extremely high. The bond to other Gunite, well cleaned masonry or other materials is equal to or greater than the shearing strength of the material to which it is applied." (from "Gunite and Shotrete" by the Gunite Contractors Association).