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Gel permeation chromatography (GPC), Corbett analysis, Heithaus test and other physical and chemical tests have been used to characterize asphalts and to relate chemical properties, physical properties and performance. The asphalts used in the present study consisted of periodic samples of virgin asphalt from various suppliers to Texas in the last two years, the test pavement asphalts in Dickens, Dumas and Lufkin, Texas from study 287, and a group of asphalts which had been rated according to tenderness.
In this project the researchers studied a correlation between molecular structure and corresponding compositional analysis of asphalt binders of conventional hot mix asphalt mixtures (HMA) as well as mixtures containing reclaimed asphalt pavement (RAP) and/or recycled asphalt shingles (RAS) with their cracking potential at intermediate temperature. The molecular size and structure of asphalt components of RAP and RAS undergo large changes during their exposure to environmental factors, which affects the physical properties imparted to their mixtures with conventional asphalt liquids. The composition of the mixtures prepared using a PG 70-22M binder was ascertained using thin layer chromatograpy/FID detection (Iatroscan), gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR). The distribution of species by molecular mass as determined by deconvoluting gel permeation chromatographs, emphasizing in particular, the amount of asphaltenes as they are related to the age hardening of asphalt materials. The extent of sample aging is apparent from the carbonyl oxygen content from FTIR measurements of the mixtures. Fracture resistance of laboratory produced mixtures was assessed using the Semi Circular Bend Test (SCB) test procedure; a minimal value of 0.5 kJ/m2 was considered acceptable. Mixtures containing up to 5% RAS, 15% RAP and 15% RAP/5% RAS met the SCB standard. Molecular fractionation through GPC of mixtures containing RAS confirmed the presence of highly associated asphaltenes in greater concentrations than mixtures containing recycled asphalt pavement (RAP). High concentrations of high molecular weight associated asphaltenes (mol wt > 20K Daltons) which are present in RAS samples decrease the fracture resistance of the asphalt mixtures. The use of recycling agents, Cyclogen-L, Hydrogreen, Asphalt Flux and Re-refined engine oil bottoms (REOB), did not reduce the concentration of the highly associated asphaltenes, further they failed to improve the cracking resistance of the asphalt mixtures evaluated in this study. However, the recycling agents effected quantitative extraction of the RAS asphalt component.
The urgent need for infrastructure rehabilitation and maintenance has led to a rise in the levels of research into bituminous materials. Breakthroughs in sustainable and environmentally friendly bituminous materials are certain to have a significant impact on national economies and energy sustainability. This book will provide a comprehensive review on recent advances in research and technological developments in bituminous materials. Opening with an introductory chapter on asphalt materials and a section on the perspective of bituminous binder specifications, Part One covers the physiochemical characterisation and analysis of asphalt materials. Part Two reviews the range of distress (damage) mechanisms in asphalt materials, with chapters covering cracking, deformation, fatigue cracking and healing of asphalt mixtures, as well as moisture damage and the multiscale oxidative aging modelling approach for asphalt concrete. The final section of this book investigates alternative asphalt materials. Chapters within this section review such aspects as alternative binders for asphalt pavements such as bio binders and RAP, paving with asphalt emulsions and aggregate grading optimization. - Provides an insight into advances and techniques for bituminous materials - Comprehensively reviews the physicochemical characteristics of bituminous materials - Investigate asphalt materials on the nano-scale, including how RAP/RAS materials can be recycled and how asphalt materials can self-heal and rejuvenator selection