ASPHALT - BITUMINOUS MATERIALS

Asphalts are dark brown or black solids or semi-solids foimd in the natural state and are also produced by the refining of petroleiun. Raw asphalt is a eomplex mixture of bitumen and low-volatile organic chemicals that are recovered from petroleum refinery residues or natural deposits. Bitumen is ageneric name applied to various mixtures of hydrocarbon. The American Society for Testing and Materials has the following standard definitions for asphalt. 

1) Relating in general to bituminous materials Bitumen—a class of black or dark-colored (solid, semi-solid, or viscous) cementitious substances, natural or manufactured, composed principally ofhigh molecular weight hydrocarbons, of which asphalts, tars pitches, and asphaltites are t5 ical. 

2) Relating specifically to petroleum or asphalts Asphalt— a dark brown to black cementitious material in which the predominating constituents are bitumens which occur in nature or are contained in petroleum. 

Asphalt can be generally classified as natural or artificial. Natural asphalts include bituminous materials laid down in natural deposits, such as those in Trinidad, and as gilsonites and grahamite bitumens, which are completely soluble in carbon disulfide. Artificial asphalt includes mainly petroleum-derived asphalts and, to a lesser extent, coal tar, water-gas tars, and their pitches. There are types of asphalt products obtained from straight-run asphalt (refined naphtha-based crude oils) hot, cutback, and emulsion asphalt. 

Hot asphalts can be softened with heat and have good resistance to water and water vapor transmission when applied to dry surfaces under controlled heating, but have poor bond adhesion to wet surfaces. In addition, they have relatively poor flexibility, are brittle at low temperatures, and oxidize upon exposure to solar radiation. 

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For low slope commercial roofing, bituminous-based roof coverings are the most common systems in the United States. Asphalt-based materials predominate over coal-tar based materials in these systems. For residential roofing materials, various types of roofing products, including asphalt, wood, and tile, ate used for both new constmction and reroofing. 

Tar sand, also variously called oil sand (in Canada) or bituminous sand, is the term commonly used to describe a sandstone reservoir that is impregnated with a heavy, viscous black extra heavy cmde oil, referred to as bitumen (or, incorrectly, as native asphalt). Tar sand is a mixture of sand, water, and bitumen, but many of the tar sand deposits in the United States lack the water layer that is beHeved to cover the Athabasca sand in Alberta, Canada, thereby faciHtating the hot-water recovery process from the latter deposit. The heavy asphaltic organic material has a high viscosity under reservoir conditions and caimot be retrieved through a weU by conventional production techniques. 

Waterproof. Waterproofing barrier systems may be either hot- or cold-appHed. The hot-appHed generaUy involve a bituminous material such as asphalt used in conjunction with a reinforcing fabric such as roofing felt, cotton, or glass cloth. Cold-appHed can be bituminous or elastomeric materials either in Hquid or sheet form, with or without fabric reinforcement. Liquid elastomeric treatments include neoprene, polyurethanes, and blends of these or epoxies with bituminous materials. Among the commonly used precured elastomeric sheet materials are neoprene, polyisobutylene, EPDM mbber, and plasticized PVC. Polyethylene and PVC films and nonwoven plastic or glass fabric coated with bituminous materials also find use (78). Because these... 

ASTM (1) further classifies asphalts or bituminous materials as soHds, semisoUds, or Hquids. SemisoHd and Hquid asphalts predominate in commercial practice today. Prior to 1907, the principal portion of asphalt used occurred naturally since that time most asphalts have been produced from the refining of petroleum. Air-blown petroleum asphalts (5) of diverse hardness became available in the early 1900s, and as thek use increased, the demand for native products diminished. 

The concept of a photoresist is of great antiquity and has a number of features of interest relating to plastics. In Ancient Egypt mummies were wrappted in linen cloths dipped in a solution of oil of lavender containing high molecular mass bituminous material (Chapter 30) which was known variously as Syrian Asphalt or Bitumen of Judea. On exposure to light the product hardened and became insoluble. The evidence is that some form of cross-linking occurred. 

Bituminous materials Bitumen, asphalt Moulding materials, adhesive, pigment... 

Originally bituminous materials such as natural asphalt but now a by-product of petroleum refining - an air-blown petroleum asphalt. In rubber compounding it is a tack-producing softener in larger proportions it is classed as an extender. 

In tests (Ref 30) to determine the effect of liners and coating on the sensitivity of 50/50 Pentolite charges contained in bombs it was concluded that very little effect was obtained with a wax coating on the inner surface of the bomb, but an asphalt dip reduced the detonations considerably. The tests conducted were rather limited in the variety of waxes tested. Subsequent tests in 100-lb bombs were somewhat inconsistentwith the initial finding. Seven hundred-fifty lb general purpose bombs loaded in the 1970 s did use both a nose pad and liner of a bituminous material... 

Hoiberg, A.J. 1964. Bituminous Materials Asphalts, Tars, and Pitches. John Wiley Sons, New York. 

Rostler, F.S. 1965. In Bituminous Materials Asphalt, Tars and Pitches. A. Hoiberg (Editor). Interscience, New York, 11(1) 151. 

An additional approach which will result in the conservation of asphalt, which is under investigation by both the Bureau of Mines and Til, involves using sulfur in recycling old bituminous pavements (2,14). Sulfur can reduce the viscosity and hence improve the workability of age-hardened asphalt pavement material and can increase the stiffness of the recycled mix when it cools. 

Hoiberg, A. J. Bituminous Materials Asphalts, Tars and Pitches Interscience ... 

Analytical methods for some petroleum products are discussed in existing ATSDR toxicological profiles. The very volatile gases (compounds with 4 carbons or less), crude oil, and the solid bituminous materials such as asphalt are not included in this discussion of analytical methods. ATSDR profiles relevant to petroleum products are listed in Table 3-1. The TPHCWG also addresses some of these issues from a different perspective which includes, in some cases, more detail and references than provided here (TPHCWG 1998a). 

Asphalt is a black, bituminous material which is supposed to have been formed as the result of the evaporation and partial oxidation of petroleum. It consists of compounds of carbon and hydrogen, some of which contain in addition oxygen, sulphur, and nitrogen these are mixed with varying amounts of earthy material. Asphalt melts when heated on account of its physical properties it serves as an excellent binding material in making surfaces for roads, etc. The chief source of asphalt is Pitch Lake on the Island of Trinidad, which is 135 feet deep at the center and has an area of over 100 acres. 

Bituminous materials are dark brown or black, semi-solid or liquid, thermoplastic mixtures of hydrocarbons derived from natural or synthetic processes in which hydrocarbon mixtures have lost their volatile components leaving a denser residue. Natural bitumens come from exposed and weathered petroleum and rock deposits. Synthetic bitumens come from the residue remaining after the distillation of petroleum, coal tar, and other organic materials like wood and peat. The complexity of the high molecular weight hydrocarbon oils and resins bitumens contain make complete chemical characterization impossible. The terms bitumen, tar (8007-45-2), pitch (61789-60-4), and asphalt (8052-42-4) apply to any of these substances, although pitch and tar also describe the sticky resins that exude from various trees. 

Road oils, asphalts, roofing, and other bituminous materials are heated to aid their application on arrival. 

Recent inventions " are driven by product improvement needs and environmental aspects of application of these products. Janoski s patent describes a product which is an anhydrous blend of polymer and asphalt and is substantially solvent-free. This technology shows that it is possible for an ingenious designer to produce low viscosity materials without using solvents but by selecting the appropriate type and concentration of bituminous materials, polyurethane components, and plasticizers. 

Because of the variability of aggregate sources, aggregates should be tested to determine their suitability for use in asphalt (bituminous mixtures) or as material in base and subbase layers. Their suitability is defined in reference to geometrical, physical and chemical proper-ties/requirements. Table 2.3 summarises the main test methods. 

The addition of fillers to bitumen does not modify the properties of the bitumen. However, it is as an old and very economical way to increase the stability and stiffness of the asphalt (bituminous mixture) so as to improve resistance to deformation. Today, with the development of other modifiers and additives, their use is limited to the production of bituminous materials for water insulation, acting as a substance to increase volume. 

The tank of the delivery vehicle should always be clean, before loading bituminous materials. Small proportions of foreign matter, usually petrol, diesel, oils and so on, directly influence bitumen s properties and, hence, the bituminous mixture and the quality of pavement. Furthermore, safety is affected since the presence of these substances may lower the flash point of the bitumen substantially. It has been found that 0.1% of diesel in bitumen can decrease the flash point up to 28°C and increase the bitumen penetration by 10 units (Asphalt Institute MS-4 2007). In case of transporting bitumen emulsions, the presence of foreign substances will certainly affect the breaking time of the emulsion. 

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