## 2 Materials and Methods  
This study aims to predict the open porosity of an industrial mortar based on the mortar's bulk density, water absorption by capillarity, drying index, compression strength, and substrate characteristics (bulk density, open porosity, and water absorption by capillarity). This study used Orange software version 3.36.2, developed by Bioinformatics Lab at University of Ljubljana, Slovenia, in collaboration with the open source community [24].  
The selected pre-dosed cement-based mortar is suitable for various substrates, indoor and outdoor use, can be applied manually or by spraying, and includes cement, aggregates, admixtures, and synthetic fibers. The mortar used has the following characteristics, according to the manufacturer's declaration based on EN 998-1 [25]:  
* Bulk density of the hardened product: 1400 to 1500 kg/m\({}^{3}\);
* Compressive strength: \(>\)1.35 N/mm\({}^{2}\);
* Adherence: \(\geq\)0.25 N/mm\({}^{2}\);
* Water vapor permeability (\(\upmu\)): \(\leq\)35;
* Water absorption: Wc0.  
The product's technical data sheet does not disclose the proportions of the mortar components or the binder's chemical composition. However, the manufacturer advises using 4 to 5 L of water for each 25 kg bag of mortar. The experimental campaign used 4.5 L of water for every 25 kg mortar.  
The substrates selected for this study comprised hollow ceramic brick measuring 300 \(\times\) 200 \(\times\) 70 mm\({}^{3}\), solid ceramic brick at 215 \(\times\) 110 \(\times\) 55 mm\({}^{3}\), concrete block sized 500 \(\times\) 200 \(\times\) 100 mm\({}^{3}\), lightweight concrete block also at 500 \(\times\) 200 \(\times\) 100 mm\({}^{3}\), and concrete plate with dimensions of 300 \(\times\) 200 \(\times\) 40 mm\({}^{3}\), all of which were chosen due to their prevalent application within the construction sector.  
To facilitate the application of the mortars to the substrates, wooden molds were constructed to ensure a uniform thickness of 15 mm. Moreover, a fiberglass mesh was incorporated at the interface between the mortar and the substrate to aid in the detachment process following curing. The utilized mesh exhibited resistance to alkaline conditions, possessed a mesh opening of 5 \(\times\) 5 mm\({}^{2}\), and had a specific weight of 158 g/m\({}^{2}\). The mortar detachment was ultimately executed manually.  
According to the specifications provided by the mortar manufacturer, the substrates must be pre-moistened exclusively under elevated temperature conditions; however, this condition was not met, leading to the decision to refrain from pre-moistening the substrates.  
Preliminary tests conducted on the employment of fiberglass mesh at the interface between the substrate and mortar demonstrated that the mesh does not substantially affect the properties of the mortar applied [26].  
For the curing conditions of the mortars applied to the substrates, they were stored in a sheltered environment without regulation of relative air humidity or ambient temperature. Consequently, the average relative air humidity and ambient temperature recorded were 66% and 17 \({}^{\circ}\)C, respectively, over 28 days. After detachment, the samples had dimensions of 40 \(\times\) 40 \(\times\) 15 mm\({}^{3}\).