Synergistic ethylcellulose/polyphosphoric acid modification of bitumen for paving applications

A lignocellulosic material, like ethylcellulose (EC), is assessed for bitumen modification, as a more sustainable alternative to polymers derived from non-renewable sources. However, ethylcellulose alone hardly enhances bitumen performance. This work studies novel bituminous binders prepared with ethylcellulose powder and polyphosphoric acid (PPA) as bitumen modifiers for paving applications. Rheological tests demonstrated that the addition of 0.5 wt% PPA to a binder containing 5 wt% EC, along with a thermal curing, leads to binders with improved rutting resistance at high in-service temperatures, compared to binders prepared solely with EC or PPA. TLC-FID chromatography, FTIR spectroscopy and modulated DSC were conducted on binders to shed some light on modification route. From them, it is possible to state that the rheological enhancement is related to a change in SARAs fractions (i.e., binder colloidal index), derived from the asphaltenes disaggregation and formation of new phosphorylated adducts. Therefore, the use of ethylcellulose as lignocellulosic raw material seems to be a promising alternative to design bituminous binders for paving applications with enhanced rheological properties at high in-service temperatures.