The Vaults of the Subotica Synagogue after 114 Years: Condition Assessment and Repair Recommendations

This paper presents an original contribution with assessment of the current state in exploitation safety and usability of thin concrete domes of the beauteous Subotica Synagogue, built in 1902. The authors are analyzing the condition of the materials used in the Subotica Synagogue, on extracted samples of concrete and steel reinforcement with a binder which was used instead of cement, a gypsum - CaS[O.sub.4]x0,5[H.sub.2]O. The source of the problem, according to the author, is the lack of lime -Ca[O(H).sub.2] from the mixture of gypsum and pozzolanic aggregates made of baked clay. This is the main reason for poor concrete strength of only 7.6 MPa and the present significant corrosion processes in the steel reinforcement of that concrete, which far from the recommended values of pH [greater than or equal to] 12, have a measured value of only pH = 7.55. These results advise a need for repair of the part of the building that has not been analyzed or investigated yet, partially due to difficult access and also apparently good condition, since cracks, larger deformation or collapse have not appeared yet. The condensation on the domes is damaging the painted decorations with gilding which is falling and reduces the exploitation safety and the mood of the visitors and believers, who came to the synagogue. The authors are proposing a method for rehabilitation of the vaults and ribs of the beautiful Subotica Synagogue domes by simultaneously satisfying the exploitation safety and avoiding the occurrence of condensation and damaging of the painted and gilded ceilings. We believe that the article will inspire and have a positive effect in the professional and scientific society so in other synagogues in Europe and around the world the exploitation usability of vaults will be inspected and if necessary, possible repairs can be made in the same or any similar way as proposed in this scientific work.