Characterisation and Contextualisation of Mortars from the 19th and First Half of the 20th Centuries in Muharraq, Bahrain

Within the context of the restoration projects at the buildings of the Pearling Path in Muharraq (World Heritage Site), interdisciplinary research has been conducted to determine the composition and historical context of the various mortars present in these historic structures. Some previous analyses carried out on historic mortars indicated a predominant use of gypsum, although lime was also frequently identified. However, the lack of details about the analysed samples did not allow estimating the possible composition of the local traditional mortars through their dating or location. To understand the use of historic mortars, an in-depth historical research and data analysis were conducted. This focused on the chronological sequencing of the buildings' construction which was combined with petrographic analysis performed on a group of samples. Their selection was based on a pre-classification made according to the dating and the visible appearance of the mortars. The new data also enabled fresh conclusions on previously published studies. The obtained result is a mineralogical characterisation of the mortars used in Muharraq during the 19th and the first half of the 20th centuries, supported by historical data, including information about the provenance, the application criteria, and an explanation of changes in material trends. This information will assist heritage professionals in gaining a deeper understanding of buildings from this period in Bahrain, enriching the knowledge of materials used in the region. It will enable them to predict the composition of historic mortars based on dating, location, and visible physical features such as colour, type of aggregates, and binder-to-aggregate ratio.