Acoustic behaviour of 3D-printable cement mortars functionalized with recycled tire rubber aggregates

The incorporation of ground tire rubber into cementitious compounds has become a common ecosustainable practice to confer the materials improved physical-mechanical propertiesin terms of lightweight, durability, energy absorption, toughness, and thermo-acoustic insulation. Considering the current attention on more comfortable and low-energy structures, the acoustic performances of building materials play a decisive role in improving the quality of life in urban and household environments. This research work aims to reuse end-of-life tires as a granular product in 3D-printable cement mortars, taking advantage of its lightweight and viscoelastic properties to improve the sound attenuation behaviour of the material. Specifically, two grades of granulometry (0-1 mm rubber powder and 2-3 mm rubber granules) were used to replace 100% of the natural aggregates by volume and obtain three printable rubber-cement mixes. Comprehensive acoustic characterization, including sound insertion loss analysis, acoustic flow resistivity, and sound absorption coefficient measurements by impedance tube, was performed to evaluate the influence of rubber particle size on the sound attenuation performance of rubberized mortars. The addition of lightweight and elastomeric rubber particles increases the damping of the material. Indeed, all the rubber-modified mixtures shown comparable/superior insulation properties compared to the reference mixture (0 % rubber), which are modulated by the percentage of fine and coarse polymer fractions incorporated in the matrix. Besides, the rubberized mortars possess excellent sound absorption performances, which are governed by the influence of rubber particles on the microstructural features (porosity and tortuosity) of the cementitious media. The applicability of these mixtures in 3D printing methodologies implies the possibility of developing building-architectural elements with optimized designs for insulating purposes.