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Characterisation of heritage cementing materials has become a topic of great importance in the protection of culture and history for future generations. The original cementing material analysis helps to achieve compatible and long-term restoration of heritage buildings. The analysis is done for different purposes - research, compatibility assessment prior to restoration and/or documentation. There are several analytical techniques that many researchers use for analysing the composition of original cementing materials. However, until the present time, the choice of the analytical method depended solely on the researchers' discretion and personal preference. The common methods include microscopic, wet chemical and x-ray analyses. The purpose of this paper is to review the technical literature pertaining to the characterisation (physical, chemical, mineralogical and mechanical) of original heritage cementing materials and its application in proposed restoration work. The knowledge of originally used materials and types of binder, aggregates and additives (in some cases) is considered a useful tool in the search of the compatible repair materials by the construction industry, especially in South Africa where the standard procedure for heritage cementing material characterisation has not been well documented.

The history of the South African construction industry dates as far back as the Castle of Good Hope (1666), Slave Lodge (1679), Robben Island (1700), Union Buildings (1913, memorials and cathedrals, among many others. These structures represent the political, slavery, liberation and religious history of South Africa and its development throughout the years, while also contributing towards economic growth through tourism. Historical buildings stand out from the rest of the modern constructions as they portray marvellous architectural designs and unique materials used for their construction. However, due to ageing and environmental conditions, they often show critical signs of deterioration, which threaten the existence of some. In attempts to rescue these national treasures, the use of Portland cement, which is considered incompatible with the original materials, has become a common practice, not only in South Africa but abroad. To avoid disparity in materials during repair of historic structures, original material characterization is therefore recommended. This paper investigates the effects of Portland cement used on the repairs of historical masonries of the Castle of Good Hope, Cape Town and buildings on Robben Island, in South Africa. The mortar samples were collected from the Castle and analyzed using the techniques such as the visual investigation, cohesion test, microscopic and titration test. It is observed that the original limebased mortars are not compatible with the Portland cement produced mortars. It was evident on the masonry, as the repairs are repelling from the original surfaces on these two structures.