I have in my possession a copy of the Station Diary for RAF Ballyhalbert.
On 7th January 1943, a strong letter of complaint was sent to RAF HQ regarding the deplorable state of all brick buildings which were letting in water following heavy rainfall. The airfield had only been open for around 18 months, having opened on 28th June 1941. The following entry appears in the Station Diary in response to the above letter:-
26/1/1943:- Station Headquarters Building treated with "Gunnite" as an experiment to prevent rain penetrating the walls.
I can find no other entries in the Diary relating to this issue.
Can someone explain what exactly "Gunnite" is or was, and how it worked?
Gunnite is “mortar conveyed through a hose and pneumatically projected at High velocity on to a surface” *-ACI
Why is it different from conventional concrete?
Unlike conventional concrete, which is first placed and then compacted (vibrated) in a second operation, gunnite undergoes placement and compaction at the same time due to the force with which it is projected from the nozzle. Because of this it is more dense, homogeneous, strong and waterproof than any other process.
Gunnite is not placed in forms, it can be impacted onto any type of shape Of surface, including vertical or overhead.
Lamella Sheds (Hangars) were 'Gunited' externally during construction.
In modern day construction ann example of use is for large swimming pools where - as with Lamella Sheds - it is sprayed into bases and elevations formed with reinforcing bar mattresses. Used a lot in the USA.
Gunnite is “mortar conveyed through a hose and pneumatically projected at High velocity on to a surface” *-ACI
Why is it different from conventional concrete?
Unlike conventional concrete, which is first placed and then compacted (vibrated) in a second operation, gunnite undergoes placement and compaction at the same time due to the force with which it is projected from the nozzle. Because of this it is more dense, homogeneous, strong and waterproof than any other process.
Gunnite is not placed in forms, it can be impacted onto any type of shape Of surface, including vertical or overhead.
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