Physical-mechanical properties of new recycled materials with additions of padel-tennis ball waste

Around 320 million new padel and tennis balls are used worldwide each year, the game of padel also being known as padel or padel tennis. This level of use of padel-tennis balls is estimated to produce approximately 21,000 metric tons of waste from the balls, which are manufactured with a vulcanized natural rubber core covered with felt. Considering how plaster has been one of the most widely used materials in the construction sector, with excellent aesthetic and mechanical properties for indoor use, this research aims to assess the physical and mechanical properties of new recycled materials with the addition of padel-tennis waste. Several plaster mixtures were made using different residues from balls (felt and rubber), previously crushed, according to different ratios of water to gypsum and percentages. The statistical analysis indicates the representativeness and robustness of the results with a very high adjustment of the calculated models (coefficients of determination R2 greater than 98%). Also, it corroborates that density is a determining factor in the mechanical properties of plasters for the three types of residues studied and it is a key parameter in the design of those construction el-ements that require lightness properties. The results confirmed that the new recycled material complies with the minimum requirements established under the UNE-13279 building standard, and even the flexural strength increases by up to 20% when felt waste is used. Mechanical properties (flexure and compressive) increase more intensely when the surface hardness exceeds the value of 60 units. The water absorption and surface hardness also meet the standards, so the innovative material would be suitable for the manufacture of pre-cast panels, such as suspended ceiling plates or interior cladding walls, as well as any other construction element that is currently made from gypsum, thus optimising sustainability and the circular economy in the construction sector. The new innovative material includes the benefits of secondary raw materials and the problem of padel-tennis waste disposal.