**2. Experimental Program**

#### *2.1. Materials and Specimens*

A mortar mix with Portland cement CEM I 52.5R [19] and quartz sand [20] was prepared. A total of 400 g of cement (density 3.1 kg/dm<sup>3</sup> and 4500 cm2/g Blaine specific surface) and 1350 g of sand was used. The w/c was 0.6. The cement mortar component proportions ensured an increase in open porosity and prevented the segregation of composition.

The specimens with the steel rebar were cast. The steel rebars, S235JR, with a diameter of 6 mm (according to EN 10025-2 [21]) were used. The chemical composition of steel, as declared by the producer, was given in [18]. Wet polishing with SiC paper (4000 grit) followed by sonication was performed before the steel bars were coated with epoxy resin. For each bar, 10 cm<sup>2</sup> of smooth steel surface was left for electrochemical measurements, according to PN-86-B-01810 [22]. Standard curing conditions before irradiation were used (temperature of 20 ± 2 ◦C, duration 28 days).
