Chemical Nature of Asphalt in Highway Engineering
Explore the chemical composition of asphalt used in highway and transportation engineering, including the predominance of hydrocarbons, sulfur, and nitrogen compounds. Learn about the structural models proposed for asphalts and various analytical techniques like chromatography for studying asphalt properties.
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First Stage Lecture2 Lecture. Rana Amir Yousif Lecture. SadyAbd Tayeh Highway and Transportation Engineering Al-Mustansiriyah University 2017-2018
References: Edwin J. Barth. Asphalt Science and Technology , 1st Ed. ,1962. James Speight Asphalt Materials Science and Technology , 1st Edition 2015.
Chemical Nature of Asphalt Predominately hydrocarbon Carbon 82-88% Hydrogen 8-11% Sulfur 0-6% Oxygen 0-1.5% Nitrogen 0-1% Trace amounts of metals Ni, Fe, V, Mg, Ca Acid value 0-4.5 mg KOH/g High MW (Molecular Weight) naphthenic acids Small base value Nitrogen compounds Nitrogen compounds Salt SARA fractions
Some Structural Modelsfor Asphalt Pfeiffer and Saal (1940): Asphalts are visualized as colloidal system, with asphaltenes forming the centers of micelle and having a more pronounced aromatic nature, the asphaltenes were assumed to be surrounded by lighter constituents of less aromatic nature, and there were no distinct interphases between the micelles and the medium surrounding it
solvent precipitation, chemical precipitation, adsorption liquid chromatography, ion exchange liquid chromatography, coordination liquid chromatography, thin-layer chromatography, gas-liquid chromatography, size-exclusion chromatography, high pressure gel permeation chromatography, vapor pressure osmometry, mass spectrometry, electrophotometric spectroscopy, nuclear magnetic resonance spectroscopy, electron spin resonance spectroscopy, spectrochemical analysis, elemental analysis, distillation fractionation, wax content determination, photochemical reactions of asphalt, acid number determination, internal dispersion stability, titrimetric/gravimetric analysis . .
a) Relating in General to Bituminous Materials: Bitumens: Mixtures pyrogenous origin, or combination of both, frequently accompanied by their nonmetallic derivatives, which may be gaseous, liquid, semisolid, or solid, and which are completely soluble in carbon disulfide. b) Relating Specifically to Petroleum Asphalts: of hydrocarbons of natural or Asphalt: A dark brown to black cementitious materials, solid or semisolid in consistency, in which the predominating constituents are bitumens which occur in nature as such, or are obtained as residue by refining petroleum.
Asphalt is found in widely scattered parts of the world in one or another of the following forms: a) Laid down in geologic strata and occurring both as soft bituminous material and also as hard, friable, black bitumen in veins of rock formations, or impregnating various limestones, sandstone formations, and the like. The soft bituminous material, almost like heavy petroleum, is typified in the Trinidad Lake deposit on the Island of Trinidad, in Bermudez Lake, Venezuela, and in the extensive "tar sands" area near LakeAthabasce, Canada. b) Colloidally dispersed asphalt petroleum (petroleum asphalts). hydrocarbons in crude
