Development of new specifications for bituminous mixtures with reacted and activated rubber from recycled tires

Description

Development of new specifications for bituminous mixtures with reacted and activated rubber from recycled tires
Luís Quaresma, Margarida Gonçalves, Filipa Marques, Eugénia Correia, Anabela Martins, Maria Conceição Machado, Hélder Lourenço, Carlos Sousa, Paulo Valentim

ABSTRACT
Technologies for using crumb rubber from recycled tires as a modifier of neat bitumen have been successfully used in crack sealing, spray applications (chip seals) and hot mix asphalt for at least 50 years, notably the wet method technology, being recognized as a practical means of providing environmental, economic, sustainable, and safety of using crumb rubber, leading the Portuguese Road Administration to publish specifications both for the rubber modified bitumen and its use in bituminous mixtures. New innovative technologies were developed both concerning asphalt rubber production and hot mix asphalt production, leading to a new material consisting of pre-treated and pre-reacted rubber (RAR) that can be used directly in a mix plant just like a “filler” thus it is easy to handle and requires no special equipment for blending crumb rubber and asphalt and no additional heat source. Laboratory testing and experimental construction sites using RAR have demonstrated a product capable matching and surpassing the performance of traditional hot mix asphalt and the traditional crumb rubber method asphalt.
To ensure the quality and take advantage of the unique nature of RAR hot mix asphalt new specifications are being developed by Portuguese Administration for National Roads (Infraestruturas de Portugal). These specifications encompass a broad range of quality measures to better enable a wide use in road works. The specifications were applied for the maintenance of the national road EN 10, near Setúbal, chainage 48,000 to 52,700. The RAR will be used in a Stone Mastic Asphalt surface layer and will be compared with other surface layers, namely a traditional asphalt concrete AC 14 surf with neat bitumen and a gap-graded asphalt concrete AC 10 surf with polymer modified bitumen.
The pavement structural and functional performance were evaluated, including noise measurements for RAR hot mix asphalt surface layer and other traditional hot mix asphalt surface layers located nearby. The results will contribute to a revision of the RAR hot mix asphalt new specifications and to prepare recommendations for the use of the new materials in road maintenance.

Keywords: reacted and activated crumb rubber, specifications, performance requirements, noise emissions.