Materials analysis of the masonry of the Hagia Sophia Basilica, Istanbul

Abstract

As part of an integrated structural investigation of the 1500 year-old Hagia Sophia Basilica in Istanbul, specimens of its historic brick and mortar are being analyzed. The materials analysis uses a suite of instrumental methods including neutron and X-ray diffraction, small angle neutron scattering, thermal analysis, and automated image analysis of SEM polished sections. Data from wet chemistry analyses have also been obtained. The results show that the mortar is pozzolanic rather than a traditional carbonated lime mortar as initially assumed. The pozzolana is ground up brick dust. Large chunks of brick are also found as coarse aggregate in the mortar joints. Comparison with modern lime-pozzolana mortars suggest that the Hagia Sophia could have tensile strengths on the order of 3.5 kPa. However, unlike Portland cement concrete, such pozzolanic mortars take longer to reach full strength. This could explain some structural problems such as the significant plastic deformations of the main piers.