Investigating the applicability of storage stability test for waste plastic modified bitumen: Morphological analyses

• Published in: Construction & building materials Vol. 441; p. 137451
• Main Authors: Haji Seyed Javadi, Nioushasadat, Hajimohammadi, Ailar, Heydari, Soheil, Kien Chung Ng, James Jeremy, Kypreos, John Emmanuel, Khalili, Nasser
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 30.08.2024
• Subjects: Bitumen; Bitumen modification; Cross-contamination of plastics; Phase separation; Recycled plastics; Storage stability; Cross-contamination of plastics; Storage stability; Recycled plastics; Bitumen modification; Phase separation; Bitumen
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2024.137451

Plastics have proven as effective modifiers for asphalt binders; however, significant knowledge gaps exist around appropriateness of standard method of storage stability test and phase separation mechanism. These gaps are even more critical when using waste plastics containing polymeric cross-contamination. This study addresses these gaps through the application of asphalt tests, fluorescence microscopy (FM) and image processing techniques. The FM and image processing results showed that there is a relationship between elevated plastic swelling rates and plastic dispersion in bitumen matrix. Quantitative analysis of the images indicated that LDPE and LLDPE modified binders exhibited the lowest level of phase separation (5 %), followed by HDPE modified binder (13 %), and PP modified binder showed the highest level (20 %). Furthermore, cross-contamination of LDPE, LLDPE, and HDPE with PP notably worsened the storage stability of the resulting modified binders by approximately 10 %. The findings from FM and image processing indicated that the softening point test conducted through the storage stability tube test is insufficient for assessing the storage stability of plastic modified binders. To further validate this point, asphalt performance was examined for asphalt mixtures made with the binders before and after storage stability test. The findings demonstrated a substantial influence of phase separation of binder on key properties of the resulting asphalt mixture. •This research provides new insights into the swelling rate and dispersion of plastics in bitumen.•Cross-contamination of plastics with polypropylene exacerbates the compatibility with bitumen.•LDPE and LLDPE cross-contamination have limited effects on the compatibility with bitumen.•The common storage stability test is ineffective for measuring phase separation for some plastic-modified bitumen.•This study introduces a novel method for measuring phase separation in plastic-modified bitumen using image processing.