## 2 Materials and Methods
### Conceptual Measures and Analysis  
The methodological framework for data collection and analysis is shown in Figure 6. The main problem with the assessment of the deflection indicators D\({}_{0}\) and D\({}_{1800}\) is the lack of internationally available benchmarking values, which is somewhat justified due to the variety of parameters that affect pavement performance, such as pavement layers, material properties, etc. Wherever thresholds are developed, they have limited validity for the pavements under consideration. In addition, the test load for concrete pavements is not clearly defined and is usually chosen during the assessment based on case-dependent conditions. Based on limited available information, [PERSON] et al. [18] specified the limit value D\({}_{0}\) = 127 \(\upmu\)m at a load of 45 kN to distinguish structurally sound pavements for the case of continuously reinforced structures.  
A critical issue in this study was that there were no previous deflectometric measurements that could be used as a reference. Therefore, it was not possible to assess the evolution of the performance of the pavement over time. For this reason, it was necessary to establish threshold values (i.e., control values--Figure 6) that would apply to the pavements in question depending on their condition at the time of assessment. The procedure to achieve this objective was first based on the determination of characteristic values through a distribution-fitting analysis considering the whole sample of D\({}_{0}\) and D\({}_{1800}\) values. Then, a critical engineering judgment was made to increase the characteristic values by a certain percentage to obtain the threshold values. The latter values were evaluated on the basis of the theoretical response of the pavement structure, considering the thicknesses and properties assumed in the design but under the in situ test load.  
As already mentioned, durability tests are mainly recommended for airfield pavements. Nevertheless, this type of assessment was also performed here, following the Federal Aviation Administration (FAA) guidelines for condition assessment based on durability. The FAA [28] specifies ISM thresholds for the quantitative assessment of durability problems. ISM values above 3 may indicate poor durability at a corner or edge of the pavement slab. Values between 3 and 1.5 indicate questionable durability, while ISM values  
Figure 6: Analysis procedure.  
below 1.5 guarantee good condition. These values were retrieved from the international literature [28] and were also used for this study.  
In relation to the LTE assessment, this indicator lies between 0% and 100%. High values indicate complete cooperation between adjacent slabs, which can be enhanced by the presence of dowels that improve the performance of the pavement. Dowels were present in the tested slabs. Low LTE values indicate poor joint condition and increased susceptibility to faulting or corner breaks. In general, values falling below the threshold of 60-70% have been reported to indicate poor performance that may require action to rehabilitate the joints [3,4,29]. It should be noted that LTE is subject to daily variation depending on the surface temperature, which may cause the slab to expand and the joints to close. For this reason, LTE measurements are recommended at ambient temperatures of around 20-25 \({}^{\circ}\)C [4]. In this study, a value of 60% was conservatively used as a warning threshold for LTE at both joints and cracks.