Durability of interlayer connections in external walls in precast residential buildings

Abstract The work concerns the procedure of examination and assessment of the condition of external curtain walls used in typical prefabricated residential construction systems at the end of the 20th century in Poland. External partitions were formed from a concrete structural layer, thermal insulation made of expanded polystyrene or mineral wool with variable thickness and a layer of textured concrete. The insulating and texture layers were attached to the structural panel through connectors known as “hangers”. The durability of the exterior barrier, planned at the design stage for 50 years, is determined by the effectiveness of the execution of both concrete layers’ connections. The technical condition of more than one hundred buildings assembled in the large-panel technology was carried out after 35–50 years of operation, usually prior to the thermo-renovation of the buildings planned by the users or before the end of the designed period of use. Various research techniques were used, non-destructive testing has allowed to limit the required number of destructive tests. The test results, assessing actual physical and mechanical parameters of the materials used for the construction of connections, permitted to build calculation models and verify the effort state of structural elements. As a result of the research, calculations and analyses, a concept of effective reinforcement of threatened connections was developed. In addition, recommendations regarding effective testing of interlayer connections that are difficult to reach were formulated.