Concretes Modified with Insulation Wool Recovered from Recycled Heating Pipes

This study evaluated the potential use of waste mineral wool recovered from heating pipe insulation as a functional additive in cement concrete. The research aimed to determine the effect of this fibrous recycled material on the mechanical, physical, durability, thermal, and microstructural properties of concrete. One reference mix and three modified mixes were prepared, incorporating waste mineral wool at 12%, 16%, and 20% by cement mass. All mixes were prepared using CEM I 32.5R cement, 0/2 mm basalt aggregate, 2/8 mm granite aggregate, and a superplasticizer. After 28 days of sample curing, compressive strength, splitting tensile strength, density, water absorption, frost resistance, and thermal parameters were determined. Microstructural observations were also performed on concrete fracture surfaces. The results showed that the addition of mineral wool reduced the compressive strength from 84.9 MPa for the reference concrete to 63.8–53.3 MPa for the modified concretes. At the same time, moderate dosing improved the splitting tensile strength, reaching a maximum of 3.93 MPa with a 16% addition. The most favorable thermal effect was achieved with a 12% addition, for which the thermal conductivity coefficient decreased from 1.3461 to 1.1988 W/(m·K). The results indicate that waste mineral wool can be used in concretes with limited structural function; however, its dosage requires optimization due to increased water absorption and decreased compressive strength.