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

984

2

1. Introduction In the past, "concrete restoration" was based on a concept that involved the replacement of the deteriorated parts with any cement-based product, without considering a very important factor, durability, which must be guaranteed to a structure, once it’s decided that it needs to be restored . Durability, as already mentioned, also blends perfectly with the scenario of environmental sustainability, a topic that is now of primary importance in all fields and especially in construction. Products related to the concrete restoration sector, fall under the guidelines dictated by the European standard EN 1504, which defines intervention procedures and minimum product requirements. The choice of materials must be based on a very important concept “the concept of system ”, in fact for the purpose of durability it is important not to rely on a single product but on a cycle composed of several materials, each specific to restore a problem. Below we want to present some tests performed on two different innovative materials, aimed at identifying their greater durability compared to more traditional ones. 2. Restoration of infrastructures with high fatigue strength mortars The experimental campaign conducted at the University “Federico II” of Naples on the mortar “ Mapegrout Easy Flow Zero ” (following “the mortar ”) is the determination of the fatigue behavior under flexural loads of concrete elements restored with this cementitious fiber-reinforced mortar. For this purpose, three different series of specimens were tested. The first and second series were composed by concrete elements having a characteristic compressive strength respectively of 30 MPa and 60 MPa, the third series by concrete elements having a characteristic compressive strength of 30 MPa and restored with the mortar. The resulting fatigue properties consist of experimental S-N curves which are represented by analytic curves in the logarithmic scale. To this scope, four-point bending tests are carried out; the specimens are first statically loaded up to failure in order to determine the ultimate flexural strength of the material σ u , and then dynamically by applying loading force steps (50250 cycles each) with increasing amplitude. For the determination of S-N Curves and of the estimated fatigue life of the concrete element subject to repair has been applied the Palmgren- Miner’s rule.

Figure 1 - Restored specimens under flexural test

Figure 2 - Graphic representation of S-N Curves of the 3 series

As described in the Figure 2, the RCK 30 specimens restored with the mortar shows an improved fatigue behavior than the one shown by the standard concrete element with a characteristic compressive strength of 30 MPa. Furthermore, this behavior can be assimilated to that of some concrete with a characteristic compressive strength of 60 MPa.