Innovative application of steelmaking slag from ladle furnace as filler for recycled nitrile butadiene rubber industrial scrap

This research explores the valorization of ladle furnace (LF) slag as a functional filler in recycled nitrile butadiene rubber (NBR) industrial scrap, addressing waste management challenges in both the steelmaking and rubber industries. A comprehensive characterization of the LF slag was conducted, including its leaching behavior, chemical composition and mineralogy. Notably, the slag exhibited self-pulverizing properties, with 60 % of particles measuring below 90 μm. XRD and SEM analyses revealed the presence of γ-dicalcium silicate, β-dicalcium silicate (larnite), gehlenite, and MgAl 2 O 4 spinel, with their distribution varying according to particle size. Comparative evaluations were performed on virgin NBR, recycled NBR, and recycled NBR reinforced with 10 % v/v LF slag in two distinct particle size ranges (0–50 μm and 50–100 μm). The key properties evaluated included crosslink density, hardness, tensile strength, and dynamic mechanical behavior. The incorporation of LF slag promoted devulcanization during calendering, increased hardness and elastic modulus, and enhanced dynamic mechanical performance. Furthermore, leaching tests demonstrated that the NBR matrix significantly reduced the release of hazardous elements from LF slag, bringing leachate concentrations well below regulatory thresholds. These findings highlight the potential to develop sustainable rubber composites entirely from recycled materials, exemplifying the principles of the circular economy. • Innovative recycling of NBR scrap via calendering with LF slag filler. • Valorisation of LF slag as functional filler in recycled NBR composites. • LF slag improves devulcanization, hardness, and elastic modulus in NBR. • Incorporation of LF slag reduces hazardous leaching via polymer shielding. • Sustainable industrial symbiosis advancing circular economy goals.