A New Pressure Water Saturation Method for Assessing Accessible Porosity of Recycled Tire Rubber Panels

The increasing use of recycled tire rubber in construction products requires reliable methods for characterizing its internal structure, particularly porosity, which significantly affects material properties. In composite panels made from rubber granulate and polyurethane binder, porosity is important because of its influence on density, water absorption, thermal and acoustic properties, yet sufficiently adapted and standardized test methods for such materials are currently lacking. This paper proposes a simple pressure-assisted water saturation method for estimating the accessible porosity of panels made from recycled tire rubber. The method is based on saturating the specimen with water under pressure and gravimetrically monitoring mass increase until stabilization. A total of 27 specimens with densities ranging from 585 to 1100 kg/m3 were tested, divided into three groups according to granulometric composition: fine, coarse, and mixed granulation. The results showed a general inverse relationship between density and accessible porosity, whereby lower-density specimens exhibited a higher proportion of pores, while denser specimens showed a smaller volume of water-accessible voids. The highest mean porosity was determined for a density of 585 kg/m3, at 29.832%, while the lowest mean value was recorded for a density of 915 kg/m3, at 16.664%. The proposed method represents a simple and cost-effective application.