PSI - Issue 64

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Available online at www.sciencedirect.com ScienceDirect

ScienceDirect Structural Integrity Procedia 00 (2023) 000–000 Structural Integrity Procedia 00 (2023) 000–000

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

Procedia Structural Integrity 64 (2024) 2141–2148

SMAR 2024 – 7th International Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures Assessment of Environmental-induced Degradation on Reinforced Concrete Tie Rods in a 70-Year-Old Arch Bridge Marco Carlo Rampini a,* , Nicoletta Russo b , Federica Lollini b , Tobia Zordan c , and Marco di Prisco a a Department of Civil and Environmental Engineering, Politecnico di Milano, P.za Leonardo da Vinci 32, 20133 Milano, Italy b Department of Chemistry, Materials and Chemical Engineering, Politecnico di Milano, P.za Leonardo da Vinci 32, 20133 Milano, Italy c Studio Bolina Ingegneria s.r.l., Via del Gazzato 20, 30174 Venezia-Mestre, Italy Abstract Given the present landscape of existing bridges in Italy, a significant portion of which dates back to the mid-20th century, the need to conduct detailed investigations on the current deterioration state and on the safety of these infrastructures becomes indispensable. This work, focusing on a case study involving reinforced concrete tie rods removed from a 70-year-old arch bridge and preserved for mini-invasive diagnostics, addresses the critical need of estimating the current condition of these elements while verifying whether the common non-destructive techniques can be used to monitor the progress of deterioration. Both electrochemical measurements (e.g. corrosion potential and electrical resistivity) were used to detect the current corrosion conditions of steel bars; small core samples were also extracted to assess the presence of carbonation. In addition, this study allowed to investigate the effectiveness of the past restoration interventions, determining whether they achieved the designed outcomes. This research questions the effectiveness of these diagnostic measures to propose their repetition in situ for reliable, non-continuous monitoring of the structural health of these elements over time. The next steps involve visual inspection and mechanical characterization of the reinforcement to demonstrate the effectiveness of the diagnostics presented. © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers Keywords: "Reinforced Concrete tie rods, mini-invasive diagnostic, corrosion state, structural health monitoring, restoration interventions." 1. Introduction The * knowledge of the corrosion conditions of a structure is of fundamental importance to guarantee the safety and functionality requirements during the designed service life, to properly plan the maintenance and to correctly choose the intervention strategies, see Bertolini et al. (2011). The evaluation of an existing structure is usually performed in two stages, a preliminary survey aimed at identifying the causes of degradation and the extent of damage, and a detailed investigation in which specific analyses can be carried out. The preliminary investigation starts with the collection of the available documents, such as data related to the design and construction phases, including the age of construction, the original materials (i.e. type of concrete and rebar in case of reinforced concrete structures) and technologies, as well as data on previous inspections and any maintenance intervention already carried out. At this regard, it is useful to understand if degradation phenomena already occurred in the past and which intervention was applied SMAR 2024 – 7th International Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures Assessment of Environmental-induced Degradation on Reinforced Concrete Tie Rods in a 70-Year-Old Arch Bridge Marco Carlo Rampini a,* , Nicoletta Russo b , Federica Lollini b , Tobia Zordan c , and Marco di Prisco a a Department of Civil and Environmental Engineering, Politecnico di Milano, P.za Leonardo da Vinci 32, 20133 Milano, Italy b Department of Chemistry, Materials and Chemical Engineering, Politecnico di Milano, P.za Leonardo da Vinci 32, 20133 Milano, Italy c Studio Bolina Ingegneria s.r.l., Via del Gazzato 20, 30174 Venezia-Mestre, Italy Abstract Given the present landscape of existing bridges in Italy, a significant portion of which dates back to the mid-20th century, the need to conduct detailed investigations on the current deterioration state and on the safety of these infrastructures becomes indispensable. This work, focusing on a case study involving reinforced concrete tie rods removed from a 70-year-old arch bridge and preserved for mini-invasive diagnostics, addresses the critical need of estimating the current condition of these elements while verifying whether the common non-destructive techniques can be used to monitor the progress of deterioration. Both electrochemical measurements (e.g. corrosion potential and electrical resistivity) were used to detect the current corrosion conditions of steel bars; small core samples were also extracted to assess the presence of carbonation. In addition, this study allowed to investigate the effectiveness of the past restoration interventions, determining whether they achieved the designed outcomes. This research questions the effectiveness of these diagnostic measures to propose their repetition in situ for reliable, non-continuous monitoring of the structural health of these elements over time. The next steps involve visual inspection and mechanical characterization of the reinforcement to demonstrate the effectiveness of the diagnostics presented. © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers Keywords: "Reinforced Concrete tie rods, mini-invasive diagnostic, corrosion state, structural health monitoring, restoration interventions." 1. Introduction The * knowledge of the corrosion conditions of a structure is of fundamental importance to guarantee the safety and functionality requirements during the designed service life, to properly plan the maintenance and to correctly choose the intervention strategies, see Bertolini et al. (2011). The evaluation of an existing structure is usually performed in two stages, a preliminary survey aimed at identifying the causes of degradation and the extent of damage, and a detailed investigation in which specific analyses can be carried out. The preliminary investigation starts with the collection of the available documents, such as data related to the design and construction phases, including the age of construction, the original materials (i.e. type of concrete and rebar in case of reinforced concrete structures) and technologies, as well as data on previous inspections and any maintenance intervention already carried out. At this regard, it is useful to understand if degradation phenomena already occurred in the past and which intervention was applied © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers

* * Corresponding author. Tel.: +39-02-2399-8792. E-mail address: marcocarlo.rampini@polimi.it * * Corresponding author. Tel.: +39-02-2399-8792. E-mail address: marcocarlo.rampini@polimi.it

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers 10.1016/j.prostr.2024.09.318 2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers 2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers