Restoration of Historic Buildings in Zanzibar

Abstract

Looking at current state of most repaired historic buildings in Stone Town of Zanzibar, it is quite clear that the repair attempts made have not been very successful. Modern materials and techniques introduced in the repair works have often proven to be incompatible with the original materials causing accelerated deterioration of buildings fabric. This shows that, there is no comprehensive study undertaken so far on identifying the appropriate materials and restoration techniques. To solve this problem, a study has been made with the main objective of developing the means of restoring historic buildings by using materials existing in Stone Town of Zanzibar. The study was conducted through visual investigation and laboratory testing of materials taken from existing historical buildings and those that are currently being used for repair. Laboratory test conducted includes chemical analysis, grading, compressive strength and water absorption. The results showed some similarities in both materials, however, the combination ratios are not the same resulting into different properties. It has therefore been established that sand of the same grading pattern as the one found in the historic building mortar must be sought and utilized in making repair mortar at a ratio of 1 part lime to 3 parts sand.

Exploration and Characterization of Dynamic Properties for Cultural Heritage Conservation: A Case Study for Historical Stone Masonry Buildings in Zanzibar

“…These modifications were necessitated by the adverse effects of excessive water leakage, resulting in material deterioration, structural damage, and fungal growth [37]. The mechanical properties of stone and mortar were investigated by Makunza (2017), who reveals that the compressive strength of the utilized masonry stones and mortar varied between 8.5 and 10 N/mm 2 and 0.65 and 0.95 N/mm 2 , with the density ranging between 1 and 1.2 kg/mm 3 and 1.5 and 1.95 kg/mm 3 , respectively [4].…”

“…In the past, the historical stone building in Stone Town experienced major disasters in the form of tropical cyclones, the Indian Ocean Tsunami in 2004, and extreme flooding in 2005, respectively, which inflicted multiple structural damages on the buildings. However, over the last 20 years, the United States Geological Survey (USGS) recorded several earthquakes within a 200 km circle radius centered around Stone Town [4][5][6]. Likewise, on 15 January 2005, a magnitude 5.0 tremor occurred 18 km north of Stone Town, inflicting damage on major buildings in terms of various crack openings and propagation, leading to material loss and even structural failures.…”