PSI - Issue 62

Federico Laino et al. / Procedia Structural Integrity 62 (2024) 983–989 Barile S., Laino F., Muzzupappa E./ Structural Integrity Procedia 00 (2019) 000 – 000

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In addition to this experimental campaign conducted on a small scale, cyclic flexural tests on real scale beams, unrepaired and repaired ones, were performed. These tests were designed and executed according to the state of the art and implemented through an ad-hoc experimental procedure based on: • accelerated corrosion; • structural repair with the mortar; • application of dynamic loads; The resulting cyclic properties and cracking behavior of the structural elements have been related to the level of corrosion achieved through the accelerated test and the effectiveness of the structural repair made with the mortar. For the cyclic tests at the structural scale, four reinforced concrete beams were fabricated. The first beam was named B1_R, where “R” stands for “reference” because it is the only beam that has been tested without any application of repairing mortar after accelerated corrosion (3%). The remaining beams, named B2_8%, B3_6% and B4_3%, have steel rebars with different levels of corrosion; the percentage number denotes the level of corrosion which ranges from 3% to 8% expressed in terms of (theoretical) steel mass loss. All beams have been designed according to NTC2018. Once the accelerated corrosion test was completed, the concrete cover of B2_8%, B3_6% and B4_3% was removed by chiselling to prepare them adequately for structural repair. The exposed surface was subsequently cleaned, and the concrete cover has been restored through a layer of 5 cm of the mortar. All specimens were loaded in four-point loading configuration. The flexural load was applied using a large-scale steel testing frame equipped with a servo-hydraulic actuator with 200 kN load capacity. The schematic representation of the testing setup and of the designed specimens are shown in Figure 3.

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Figure 3 - Fatigue test set up

Figure 4 - Fatigue curves envelope of the four beams

Figure 4 represents the comparison of the results made in terms of recorded force vs displacement, by overlapping the envelope obtained from the fatigue curves for the four beams having three different corrosion rates. B1_R beam and B4_3% beam, characterized by a lower theoretical rate of corrosion, reached higher force’s values at first cyclic cracking whereas B3_6% and B2_8% are characterized by a lower cracking moment although they show similar

behavior to the reference beam despite being affected by a much higher corrosion rate. Other important considerations were made about how cracks propagated during the tests.

• In the cases of similar low-to-moderate corrosion levels, the restoration of the damaged cover with the mortar tends to increase the first cracking load of the beam in comparison with the non-repaired counterpart; the