Abstract

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 lime- based 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.

Abstract

This paper explores a novel restoration approach for consolidating historic structures using structural glass to substitute for the missing elements, preserving at the same time the structural integrity of the structure. A restoration design is proposed for thehypothetical consolidation of the remaining tower of Schaesberg Castle, in Limburg, The Netherlands. The masonry walls suffer from a significant loss of material and a temporary steel structure currently prevents the tower from collapsing. It is proposed to use stacked float glass to fill the missing parts of the wall. The connection between the old masonry and new glass is the most challenging aspect given the different physical and mechanical properties of the materials, which need to work together in a coherent way. Shear tests of various connecting materials are carried out in order to evaluate the performance of this connection with respect to aspects of compatibility and feasibility.