Composition of asphalt

The influence of the composition of asphalt has been recognized, for many years, as being an important factor in controlling the performance of such materials. Furthermore, rheological properties have always been associated with composition but, in order to utilize compositional data effectively, more definitive correlations between composition and properties are needed (46—48). 

The foremnner of the modern methods of asphalt fractionation was first described in 1916 (50) and the procedure was later modified by use of fuller s earth (attapulgite [1337-76-4]) to remove the resinous components (51). Further modifications and preferences led to the development of a variety of fractionation methods (52—58). Thus, because of the nature and varieties of fractions possible and the large number of precipitants or adsorbents, a great number of methods can be devised to determine the composition of asphalts (5,6,44,45). Fractions have also been separated by thermal diffusion (59), by dialysis (60), by electrolytic methods (61), and by repeated solvent fractionations (62,63). 

During the summer after his sophomore year of college, Pauling (second from right) took a job testing the composition of asphalt being used to make highways. 

Determination of the composition of asphalt has always presented a challenge because of the complexity and high molecular weights of the molecular constituents. The principle behind composition studies is to evaluate asphalts in terms of composition and performance. 

Corbett, L. W., Composition of Asphalt Based on Generic Fractionation,... 

Tables 7.6 through 7.8 give the limiting wheel-tracking values recommended to be used in the United Kingdom to determine the target composition of asphalt concrete, hot rolled asphalt and SMA mixtures.

We obtained solubility parameter spectra of asphalt and asphaltenes for three different colloidal types of asphalt (AAM-1, AAA-1, and ABA-1). Figures 4-6 represent the solubility parameter spectra for asphalt, and Figures 7-9 represent that for asphaltenes. Comparing the solubility parameter of asphalt and asphaltenes, it can be found that the solubility parameters of asphalt and asphaltenes are around 7-10.5 and 8.5-10, respectively. Without a doubt, the composition of asphalt is more complex than that of asphaltenes. Therefore, the solubility parameter of asphalt has a wider range than that of asphaltenes. 

The conditions of pyrolysis either as low or high temperature carbonization, and the type of coal, determine the composition of Hquids produced, known as tars. Humic coals give greater yields of phenol (qv) [108-95-2] (up to 50%), whereas hydrogen-rich coals give more hydrocarbons (qv). The whole tar and distillation fractions are used as fuels and as sources of phenols, or as an additive ia carbonized briquettes. Pitch can be used as a biader for briquettes, for electrode carbon after coking, or for blending with road asphalt (qv). 

Asphalt Roofing Components. Asphalt (qv) is a unique building material which occurs both naturally and as a by-product of cmde-oil refining. Because the chemical composition of cmde oils differs from source to source, the physical properties of asphalts derived from various cmdes also differ. However, these properties can be tailored by further ptocessiag to fit the appHcation for which the asphalt will be used. Softening poiat, ductility, flash poiat, and viscosity—temperature relationship are only a few of the asphalt properties that ate important ia the fabricatioa of roofing products. 

The composition of montan wax depends on the material from which it is extracted, but all contain varying amounts of wax, resin, and asphalt. Black montan wax may be further processed to remove the resins and asphalt, and is known as refined montan wax. White montan wax has been reacted with alcohols to form esters. The wax component of montan is a mixture of long-chain (C24—C q) esters (62—68 wt %), long-chain acids (22—26 wt %), and long-chain alcohols, ketones, and hydrocarbons (7—15 wt %). Cmde montan wax from Germany typically has a melting point of 80°C, an acid number of 32, and a saponification number of 92. 

Trinidad asphalt has a relatively uniform composition of 29% water and gas, 39% bitumen soluble in carbon disulfide, 27% mineral matter on ignition, and 5% bitumen that remains adsorbed on the mineral matter. Refining is essentially a process of dehydration by heating the cmde asphalt to ca 165°C. The refined product averages 36% mineral ash with a penetration at 25°C of about 2 (0.2 mm), a softening point (ring and ball method) of 99°C, a flash point (Cleveland open cup) of 254°C, a sulfur content of 3.3%, and a saponification value of 45 mg KOH/g. The mineral matter typically contains... 

However, for the past 30 years fractional separation has been the basis for most asphalt composition analysis (Fig. 10). The separation methods that have been used divide asphalt into operationally defined fractions. Four types of asphalt separation procedures are now in use ( /) chemical precipitation in which / -pentane separation of asphaltenes is foUowed by chemical precipitation of other fractions with sulfuric acid of increasing concentration (ASTM D2006) (2) solvent fractionation separation of an "asphaltene" fraction by the use of 1-butanol foUowed by dissolution of the 1-butanol solubles in... 

Asphalts are usually specified in several grades for the same industry, differing in hardness or viscosity (95). However, with the changing nature and composition of cmde oil feedstocks over the past two decades, performance and supply factors are also an important consideration (95). 

EmulsffiedAsphalts (ASTMD244). This standard covers a variety of tests for the composition, handling, nature and classification, storage, use, and specifying of asphalt emulsions used primarily for paving purposes. 

A variety of materials has been proposed to modify the properties of asphaltic binders to enhance the properties of the mix (112), including fillers and fibers to reinforce the asphalt—aggregate mixture (114), sulfur to strengthen or harden the binder (115,116), polymers (98,117—121), mbber (122), epoxy—resin composites (123), antistripping agents (124), metal complexes (125,126), and lime (127,128). AH of these additives serve to improve the properties of the binder and, ultimately, the properties of the asphalt—aggregate mix. 

Concrete is a particulate composite of stone and sand, held together by an adhesive. The adhesive is usually a cement paste (used also as an adhesive to join bricks or stones), but asphalt or even polymers can be used to give special concretes. In this chapter we examine three cement pastes the primitive pozzolana the widespread Portland cement and the newer, and somewhat discredited, high-alumina cement. And we consider the properties of the principal cement-based composite, concrete. The chemistry will be unfamiliar, but it is not difficult. The properties are exactly those expected of a ceramic containing a high density of flaws. 

The composition of crude oil may vary with the location and age of an oil field, and may even be depth dependent within an individual well or reservoir. Crudes are commonly classified according to their respective distillation residue, which reflects the relative contents of three basic hydrocarbon structural types paraffins, naphthenes, and aromatics. About 85% of all crude oils can be classified as either asphalt based, paraffin based, or mixed based. Asphalt-based crudes contain little paraffin wax and an asphaltic residue (predominantly condensed aromatics). Sulfur, oxygen, and nitrogen contents are often relatively higher in asphalt-based crude in comparison with paraffin-based crudes, which contain little to no asphaltic materials. Mixed-based crude contains considerable amounts of both wax and asphalt. Representative crude oils and their respective composition in respect to paraffins, naphthenes, and aromatics are shown in Figure 4.1. 

Asphalt (referred to as bitumen in some parts of the world) is produced from the distillation residuum. In addition to road asphalt, a variety of asphalt grades for roofing and waterproofing are also produced. Asphalt has complex chemical and physical compositions, which usually vary with the source of the crude oil, and it is produced to certain standards of hardness or softness in controlled vacuum distillation processes (Barth, 1962 Bland and Davidson, 1967 Speight, 1999, and references cited therein Speight and Ozum, 2002). 

Wang, J., Lewis, D.M., Castranova, V., Frazer, D.G., Goldsmith, T., Tombl3m, S., Simpson, J., Stone, S., Afshari, A., and Siegel, P.D. Characterization of asphalt fume composition under simulated road paving conditions by GC/MS and microflow LC/quadrupole time-of-flight MS, Anal Chem., 73(15) 3691-3700, 2001. 

The chemical composition of vapors and fumes from asphalt products is variable and depends on the crude petroleum source, type of asphalt, temperature, and extent of mixing. Therefore, the adverse effects from asphalt may also vary considerably depending on the source of exposure. 

Gulf Canada Limited (20, 2T). The process developed by Gulf consists of a pumping system wfnch continuously delivers measured volumes of sulfur and asphalt to a mixing device which disperses the molten sulfur in the liquid asphalt. The composition of the emulsion is typically in the range 25-60 parts sulfur to 75-40 parts asphalt. The temperatures of the sulfur, asphalt and S/A emulsion are maintained in the ranges 121-154 C, 121-177 C, and 121-154 C, respectively. 

---