Effect of ethylene-vinyl acetate and rubber waste on asphalt concrete performance

The performance of asphalt concrete under increasing traffic loads and varying climatic conditions necessitates the development of enhanced bituminous binders. Some additives used as asphalt modifiers are polymeric materials. Examples of these polymers are styrene-butadiene rubber latex (SBR), diblock styrene-butadiene (SB) and triblock styrene-butadiene-styrene (SBS). The use of crumb rubber from worn-out tires can be considered as polymer-modified bitumen. This study investigates the effects of ethylene-vinyl acetate (EVA) granules and crumb rubber waste as modifiers on the physical, mechanical, and chemical properties of asphalt concrete. An ever-increasing pressure on waste resources and environmental protection leads to clear transition to a regenerative circular economy. The research aims to address the limitations of conventional bitumen, such as thermal instability and susceptibility to aging, particularly in regions with high traffic loads and extreme temperatures, by incorporating these polymer additives at 20% and 25% dosages relative to the binder mass. Laboratory-prepared asphalt concrete mixtures were evaluated for key performance indicators, including compressive strength at 0, 20 °C and 50 °C, water saturation, moisture resistance, crack resistance, shear stability, and rutting depth. Results demonstrated that EVA granules significantly improved thermal stability, with crack resistance at 0 °C doubling from 3.0 to 6.9 MPa. Compressive strength also increased to 2.2 MPa compared to the control sample (0.9 MPa). Rutting resistance was notably enhanced, with EVA-modified mixtures exhibiting an 85% reduction in rut depth (0.77 mm) compared to the unmodified mix (4.9 mm). Crumb rubber, while less effective in thermal performance, improved water resistance by reducing water saturation from 2.7% to 2.4% and demonstrated moderate gains in deformation resistance. Fourier-transform infrared spectroscopy (FTIR) revealed distinct chemical interactions between the modifiers and bitumen. EVA introduced polar functional groups (e.g., C=O at 1738 cm^-1 and C-O-C at 1,242 cm^-1), indicating chemical integration, whereas crumb rubber primarily influenced physical structure, evidenced by polyisoprene-related bands (966-970 cm^-1). Economic analysis highlighted that EVA would be more cost-effective, due to lower material costs and superior performance. Both modifiers support sustainability by repurposing industrial waste. It turned out that both modifiers can contribute to environmental sustainability by repurposing industrial waste.