Compatible Restoration Mortars For HagiaSophia Earthquake Protection

Abstract

Structural studies to determine the earthquake worthiness of Hagia Sophia in Istanbul have proved that the monument's static and dynamic behavior depends very strongly on the mechanical, chemical and microstructural properties of the masonry mortars and bricks. The results show a decrease of 5-10% in the natural frequencies, as the amplitude of the accelerations increases and returns to their initial values, due to the non-linear nature of the masonry (Cakmak et al 1 ). The analysis of the historic mortars has indicated that the amorphous C-S-H gel-formation between the crystalline phases of the calcite and the dispersed ceramic fragments allows for energy absorption by the structure during an earthquake, without affecting the materials properties irreversibly, while the compatibility of the mortars to the original building units allows for continuous stresses and strains. In the present work the synthesis of restoration mortars has been performed, following the methodology of reverse engineering, i.e. to evaluate and simulate their physico-chemical and mechanical characteristics to the historic ones. During setting and hardening, thermal (DTA-TG), porosimetric analysis and mechanical tests (compressive, flexural strength) were performed. The results indicate that mortar syntheses with hydraulic lime as binding material and being admixed with crushed brick, present a better behavior to those made with aerial lime, or lime-cement, or lime-pozzolanic additives, confronting the criteria set by the analysis of the historic mortars, which have proved to be earthquake resistant.