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Moorehead, David; Cummins, Anne
Georges Head 'Beehive' Fortification, Sydney Harbour Structure and Materials Investigations
Eleventh National Conference on Engineering Heritage: Federation Engineering a Nation; Proceedings
Institution of Engineers, Australia, Barton, Australian Capital Territory, 2001, pp. 63-70

The 'Beehive' Casemate was constructed between 1871-1874, under the direction of Colonial Architect James Barnet. The underground Casemate was one of the first locally designed fortifications built after the withdrawal of British troops in 1870. It consists of a series of three domed chambers of brick construction in excavated cavities in the sandstone bedrock. Their function was to fire on ships as they negotiated the passages around Sow and Pigs Reef, within the entrance to Sydney Harbour. The facility has suffered various degrees of degradation resulting from vandalism, the ingress of water and salt attack. The work reported in this paper is a summary of the investigations made on the brickwork, render, backing concrete and the sandstone embrasures to determine their composition and the causes of degradation. From this work we have been able to conclude that the primary degrading process in the brickwork was related to the crystallisation of salts within the bricks. The salts responsible for this spalling appear to have been sourced within the brickwork and not from adjacent ground waters. The main degrading process in the sandstone embrasures is due to the weathering of the clay seams that are fully exposed to the marine environment. A number of remedial options have been proposed to conserve the historic integrity of the structure by limiting the ongoing deterioration and to make the site safe for public visitation.

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