Environmental Benefits of Cold-in-Place Recycling

Abstract

The conventional highway resurfacing technique of mill and overlay (M&O) partially removes the existing pavement and replaces it with asphalt derived from some recycled but mostly virgin materials. Cold-in-place recycling (CIR) is an alternative highway resurfacing method that partially mills the existing pavement and uses it beneath a thinner layer of new asphalt. CIR has become widely used for convenience and cost benefits, but the environmental impacts are poorly quantified. The objective of this study was to quantify the environmental life cycle benefits of using CIR for highway resurfacing instead of M&O. Material quantities and equipment used for CIR and what would have been used in M&O for the same project were provided by contractors for nine highway resurfacing projects in Wisconsin. With this information, a life cycle assessment (LCA) tool was used to determine the relative environmental impacts of the two methods, with energy consumption, water usage, and carbon dioxide emissions chosen as the metrics of the LCA. Results show average environmental savings of 23% in energy consumption and carbon dioxide emissions and 20% in water consumption when using CIR instead of M&O for highway resurfacing. Additionally, CIR reduced virgin aggregate consumption by 37%. Environmental savings achieved by using CIR were found to be directly related to the reduction in volume of new hot mix asphalt (HMA) used, and to the reduction in transportation of materials to and from the site. Linear correlations that can be used to estimate savings of future CIR projects were projected.

%100 Geri Dönüştürülmüş Asfalt Kaplamanın Türkiye'de Soğuk Karışım Bakım Malzemesi Olarak Kullanılabilirliğinin Deneysel Olarak İncelenmesi

“…Sustainable use of RAP as part of asphalt pavements has been investigated by many studies especially as part of regular HMA (Rinkal et al, 2021;Nazaal et al, 2015), as an aggregate substitute in cold in place asphalt pavement technologies (Dughaishi et al, 2022), or as an embankment material (Soleimanbeigi and Edil, 2015;Plati and Cliatt, 2018;Al-Shujairi et al, 2021). Some other studies partially or fully used RAP as an aggregate as part of conventional In-Plant Recycling (CIPR) and Cold In-Place technologies; these technologies use RAP along with asphalt emulsion so that they could be constructed in lower temperatures (Giani et al, 2015;Turk et al, 2016;Pakes et al, 2018). However, there are very few numbers of studies investigating the use of RAP as part of CPMs (Kwon et al 2017).…”

Assessment of two laboratory design methods for CIR mixtures with bitumen emulsion based on static and gyratory compaction

“…CIR mixtures have earned global recognition in the last few years, primarily because of their significant environmental and economic benefits [8] compared with traditional methods. CIR mixtures can be manufactured using 100% milled RAP, which results in the efficient use of resources and construction materials and reduces the amount of transport operations.…”

“…This technique not only reduces the consumption of aggregates and bitumen, but also reduces the emission of greenhouse gases (i.e. CO 2 ) into the atmosphere by 40%, as it is not necessary to heat the mixture [8][9][10][11][12]. Consequently, the fossil-fuel consumption during pavement rehabilitation is minimised, and the technique has a minimal impact on climate change [11,12].…”