PSI - Issue 67

Gabriele Milone et al. / Procedia Structural Integrity 67 (2025) 90–106 G. Milone et al./ Structural Integrity Procedia 00 (2024) 000 – 000

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corrosion environments, 2% of NaCl by weight of cement was added directly into the mixing water until its dissolution. The reinforced bars, type D500SD (provided by Iturrino suministros industrials, Spain), were 6 mm in diameter. Some steel rebars were coated with a protective two-phase epoxy resin to limit the corrosion spread within predetermined sections of the bar. Finally, the sensors were installed on the mortar’s surface using a different two phase rapid-hardening epoxy resin, from Huntsman Advanced Materials (US) and supplied by RS components (UK). 2.2. Sample preparation The mortar beams subjected to accelerated corrosion had standard dimensions of 40 mm × 40 mm × 160 mm. They incorporated one steel rebar, ensuring a cover depth of 4.8 mm from the surface to facilitate targeted crack development. This cover-to-diameter ratio (c/ ϕ = 0.8) was critical in directing crack propagation along the mortar beam's surface, aiming to simulate real-world structural degradation patterns under accelerated corrosion conditions. The rebars were either fully exposed to corrosion or partially limited through epoxy coating. Hence, the corrosion test included specimens with both confined and unconfined rebars subjected to accelerated corrosion, as specified in Table 3. Table 3. Types of rebar setting subjected to accelerated corrosion test and related corrosion monitoring sensors applied. Steel exposure Sensor no. Epoxy confinement of steel [cm] Sensor distance from exposed rebar [mm] Applied sensors

Unconfined

#1, #2, #3

0 4 8

4.8

X, Y, Z

#4 #5 #6

36.3 76.2

Confined

Y

12

116.1

In agreement with UNE EN 196-1:2005, the mortar prisms were cured under controlled conditions (at 22 ± 2°C, RH = 98%) for 7 days. Such a short curing period was selected to give sufficient time for the cementitious matrix to harden and to limit its natural corrosion development. Afterwards, fully cured cement-based sensors were applied on top of 7-days old mortar prism. Figure 1 shows the sensors' encapsulation and subsequent application on the top surface of the substrate prism. These coatings were positioned transversally to the longitudinal axis of the rebar, each spaced 40 mm from the other (Figure 2), ensuring stable adherence and operational integrity throughout the corrosion testing phase. In unconfined rebar tests, the three sensors were named X, Y, and Z according to their distance from the rebar side directly connected to the corrosion equipment (Figure 2b).

Figure 1. Visual representation of sensing coating preparation and installation: (a) epoxy resin mixing; (b) sensor encapsulation; and (c) sensor application on mortar surface.