PSI - Issue 33

Fabrizio Pittau et al. / Procedia Structural Integrity 33 (2021) 630–645 Author name / Structural Integrity Procedia 00 (2019) 000–000

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In case of a real scale structure, the issue of gas tightness must be solved also for the construction joints. Each technology tested in this paper has its proper sealing cycle of the joints. This depends of course on the dimension of the joints. In the experimental campaign, the average dimension of the tested joints is 1 cm. The material is overstressed because of the displacement during the life of the construction, due to loading cycle and to thermal variation. The Polyurea was very effective in joints, ensuring tightness with elastic deformation. Although a small swealing appeared near the joint during the test, this disappear when the internal pressure decrease. This makes the material adequate also for local treatment of the cracking or for local defeats. The strip of the specimen C is a valid barrier for gas, but the tests highlights some problems in the sealing of this element. The excessive deformability of the strip produced cracks on the sealing and forced to stop the test. Stiffening element, as well as metallic shaped sheet, should be used as a protection on the joints or as stiffening element of the strip. 6. Conclusions This paper presented the experimental campaign aimed at testing four types of external coating applied to concrete boxes. The application of external coating aim to ensure tightness and to increase the durability of existing structures. This allows a separation of the functions of the mechanical resistance (carried out by the walls) and of the tightness (carried out by the external layers). If r.c. structure can withstand to relevant pressure, with the possibility to realize complex shapes, the tightness must be demanded to separate/independent elements. This consent also to overcome the physiological cracking of large concrete walls. The results of the experimental campaign show that the Specimen A and C can represent an effective solution to ensure gas tightness. Considering the limited thickness of the wall of the box and the poor quality of the concrete, the coating of the Specimen A and C shows a relatively good performance. None of the specimens exhibit an internal pressure but this result can be attribute by a very severe test condition. The possibility to inspect and to check the external coating of the walls is a significant strength point. The coating can be easily repaired in case of leaks or abrasion/scuffing with additional layers. This is a significant aspect to consider when it is necessary to choose an internal or an external coating application. The joints are critical element to control with care and attention. During the coating’s application, the preparedness of the worker and the initial state of the concrete surface play a crucial role. Other strategic aspects must be investigated, as the aging effects of the coating, also considering ultraviolet radiations, and the effect of aggressive atmosphere particularly in industrial plants. Acknowledgements The financial support is also given by Research Project PRIN 2017 (University of Cagliari) that is acknowledged by Mauro Sassu and “Monitoring of the structural and energy behaviour of existing constructions” (DR N.607 of the 3th July 2020) and is acknowledged by Mario Lucio Puppio. References ASTM C1202-19, Standard Test Method for Electrical Indication of Concrete’s Ability to Resist Chloride Ion Penetration , (2019) (testimony of AA. VV.). www.astm.org Alecci, V., & De Stefano, M. (2019). Building irregularity issues and architectural design in seismic areas. Building Irregularity Issues and Architectural Design in Seismic Areas , 13 (47), 161–168. Beconcini, M. L., Cioni, P., Croce, P., Formichi, P., Landi, F., & Mochi, C. (2018). Non-linear static analysis of masonry buildings under seismic actions. IMSCI 2018 - 12th International Multi-Conference on Society, Cybernetics and Informatics, Proceedings , 1 , 126–131. https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056494602&partnerID=40&md5=c1097f7bca076113355567673d42c508 BS EN 1992-1-1. (2004). Eurocode 2: Design of concrete structures - Part 1-1 : General rules and rules for buildings. British Standards Institution , 1 , 230. https://doi.org/[Authority: The European Union Per Regulation 305/2011, Directive 98/34/EC, Directive 2004/18/EC] Calvo, J. L. G., Moreno, M. S., Carballosa, P., Pedrosa, F., & Tavares, F. (2019). Improvement of the concrete permeability by using hydrophilic blended additive. Materials , 12 (15). https://doi.org/10.3390/ma12152384 Choinska, M., Al-Khazraji, H., Benkemoun, N., & Khelidj, A. (2018). Influence of tensile cracking and of aggregate size on concrete permeability. MATEC Web of Conferences , 163 . https://doi.org/10.1051/matecconf/201816302001