Physical and morphological properties of polyurethane modified bitumen under ageing conditions

The aim of this research is to evaluate the effects of ageing on 60/70 penetration grade bitumen modified with polyurethane (PU). Effects of ageing were evaluated by performing consistency test through ageing index and morphology evaluation. The results of these tests show that adding 3 wt% of PU stiffens the bitumen in comparison to base bitumen. A very high increase in viscosity was observed due to the hardening effect of PU. The computed ageing index shows that this alternative material reduces ageing effects on the physical properties of the bitumen, as indicated by the lower ageing index value of physical testing subsequent to ageing. Therefore, the addition of PU results in improved bitumen resistance to oxidative ageing. Optical microscopy shows the sample was homogeneously blended. Atomic Force Microscopy (AFM) was conducted to evaluate the catana phase, peri phase, and para phase topography images of P U modified bitumen. Topography image from AF M test indicates that the inclusion of P U and ageing conditions has decreased the bee-like structures of the bitumen, showing larger dispersion in the sample.