Bio-Modified Bitumen: A Comparative Analysis of Algae Influence on Characteristic Properties

Abstract

The main aim of this study was to identify and evaluate the characteristic properties of bitumen modified with algae. Two types of algae, each with distinct gradation and origin, were employed for this investigation. For each type of algae (noted as chlorella and microchlorella), three blends were created with varying algae contents (5%, 10%, and 15% by weight of bitumen), utilizing a 70/100 reference bitumen as the virgin material and a basis for comparison. The properties of the blends were investigated using the Penetration, Softening Point, Elastic Recovery, Force Ductility, Dynamic Viscosity, and Storage Stability tests, both before and after short-term ageing (TFOT). The test results were then used to calculate the Activation Energy (Ea), Viscosity-Temperature Susceptibility (VTS) Index, and Mixing Temperature (Tmixing), along with their respective Pearson Correlation Coefficient (PCC) and R2 and p-values. The main finding of the study was that the addition of a low algae content of 5% caused a change in the classification of the unaged bitumen from 70/100 to 50/70 according to EN 12591 and thus hardened the reference bitumen. Additionally, a strong linear statistical correlation was observed between Ea and the VTS index, suggesting that these values should be considered when characterizing the temperature susceptibility of algae-modified bitumen.