Asphalt cement

The term bitumen is used in France to designate petroleum products, as in Great Britain and Germany. In the United States on the other hand, the equivalent material is designated by the expression asphalt-cement . In France, asphalt is a mastic, a mixture of bitumen and powdered minerals, poured in place. This mixture can be either natural or reconstituted by an industriai process. Asphait (French meaning) is utilized on roads, particularly in urban centers as well as for sidewalk surfacing. 

Asphalt retention is judged by how much asphalt cement is left in a geotextile after it is dipped in the cement and allowed to drain, and what change in area the geotextile undergoes. 

Sulfur as an Additive for Asphalt. Sulfur-extended asphalt (SEA) binders are formulated by replacing some of the asphalt cement (AC) in conventional binders with sulfur. Binders that have sulfur asphalt weight ratios as high as 50 50 have been used, but most binders contain about 30 wt % sulfur. Greater latitude in design is possible for SEA paving materials, which are three-component systems, whereas conventional asphalt paving materials are two-component systems. Introduction of sulfur can provide some substantial benefits. At temperatures above 130°C, SEA binders have lower viscosities than conventional asphalt. The lower viscosity enables the plant to produce and compact the mix at lower temperatures than with conventional... 

Preparation is accompHshed by simple blending of the diluent into the hot base asphalt. This is generally accompHshed in tanks equipped with coils for air agitation or with a mechanical stirrer or a vortex mixer. Line blending in a batch circulation system or in a continuous fashion (40) is used where the volume produced justifies the extra faciUties. A continuous, line-blending system is appHcable to the manufacture of cutback asphalts and asphalt cements (Fig. 8). 

As this ratio increases so does the gel character of the asphalt cement, and its coUoidal stabiUty increases. The properties of the asphalt (softening... 

For the asphalt cements produced at that time the adoption of the volatilisation and penetration tests provided some degree of control of excessive changes during plant mixing that might be reflected in more durable asphalts. The adoption of the method for bitumen was intended to provide a means for identifying Trinidad asphalt by observing the amount and color of the insoluble ash. 

During the 1920s the following three national specifications for asphalt cements were pubHshed (/) Federal specifications, adopted in 1925 (2) the American Association of State Highway Transportation Officials (AASHTO) specifications, adopted in 1924, revised in 1926 and (2) ASTM specifications, adopted in 1922 to 1926, withdrawn in 1939, and re-issued in 1947. 

Specifications for paving asphalt cements usually include five grades differing in either viscosity or penetration level at 60 °C (Table 8) (ASTM D496). Susceptibihty of viscosity to temperature is usually controlled in asphalt cement by viscosity limits at a higher temperature such as 135 °C and a penetration or viscosity limit at a lower temperature such as 25 °C. 

Table 8. ASTM Requirements for Asphalt Cement Viscosity...

If straight-mn asphalts are reduced to a hardness below 300 penetration (30 mm), they are termed asphalt cements. For hot-mix paving, either the AC-10 viscosity grade or the next harder AC-20 grade is commonly specified. 

This article discusses traditional hull ding and construction products, ie, not made from synthetic polymers (see Building materials, plastic), including wood, asphalt, gypsum, glass products, Pordand cement, and bricks. The article presents information about each basic material, the products made from it, the basic processes by which the products or materials are produced, estimates of the quantity or doUar value of the quantities produced or used in the United States, and some pertinent chemical or physical properties related to the material. More detailed chemical and physical property data can be found in articles devoted to the individual materials (see Asphalt Cement Glass Wood). 

The principal use of coal tar ia paviag is as a seal coat to bitumea paviag. Asphalt for paviag comes ia several forms deteroiiaed by the iateaded appHcatioa, ie, straight asphalts called asphalt cements (AC), asphalt emulsioas, cutback asphalts, and road oils. 

Chemical Designations - Synonyms Asphalt Cements Asphaltic Bitumen Bitumen Petroleum Asphalt Chemical Formula Not pertinent. 

AsphalNkitt, m. asphalt cement, asphalt mastic, lack, m. asphalt varnish, mastiz, rn. Asphaltkitt. -mehl, n. asphalt powder, papier, n. asphalt paper. pappe, /. asphalt board, pech, n. bituminous pitch, pflaster,... 

Asphalt concrete is primarily used as a structural pavement surface constructed over a subgrade and a subbase. It is designed to support the traffic load and distribute the load over the roadbed. Asphalt concrete pavements can be constructed using hot mix or cold mix asphalt. Hot mix asphalt is a mixture of tine and coarse aggregate with asphalt cement binder that is mixed, placed, and compacted in a heated condition. Cold mix asphalt is a mixture of emulsified asphalt and aggregate, produced, placed, and compacted at ambient air temperature. Cold mix asphalt pavement usually requires an overlay of hot mix asphalt or surface treatment to resist traffic action. 

Air-cooled blast furnace iron slag, however, is more absorptive than conventional aggregate and therefore has a higher asphalt cement demand. It also has a lower compacted unit weight than conventional mineral aggregates, which results in a higher asphalt pavement yield (greater volume for... 

Pendrys, J. P., Biodegradation of Asphalt Cement-20 by Aerobic-Bacteria. Applied and Environmental Microbiology, 1989. 55(6) pp. 1357-1362. 

The application of lignosulfonate-chromium derivatives in oil well drilling mud has already been mentioned as a typical example of the above effects in combination with crosslinking. The use of lignosulfonates as active extenders in concretes is a further example of the applicability of the above effects (61). Another is the use of lignins as extenders for asphalt cement (70). 

The prime impetus for this wide spread activity was the "energy crisis" which produced considerable uncertainty about the future availability of asphalt cement for road building purposes and as a consequence caused bid prices to soar over the past eight years. 

Extension And Replacement Of Asphalt Cement With Asphalt Cement with Sulfur", FHWA Report No. FHWA-RD-78-95, March, 1978. 

Elemental sulfur has been modified In an exothermic reaction with commercially available hydrocarbon compounds to produce a pavement binder material that has been successfully utilized to construct several experimental pavement sections on public highways. The engineering properties, the formulation, and the methodology for producing and utilizing this chemically modified sulfur pavement binder, intended as a substitute for asphalt cement, are discussed. 

The worldwide disruptions in crude oil supply in 1973-74, 1978-79 and 1980 have illustrated the tenuous nature of imported crude oil supplies. The United States annually consumes approximately 30 million tons (2.7 X 10 kg) of asphalt cement refined from crude oil 93 percent of the total mileage of surfaced highways and streets, or close to 1.6 million miles (2.6 million km), has been constructed with asphalt materials. Thus, the highway industry is very vulnerable to asphalt price and supply problems if crude oil imports again suffer severe disruptions. 

Their penetration decreases with age, but at a considerably faster rate than experienced with asphalt cements. Unlike asphalt, which hardens primarily through oxidation, Sulphlex binders can under certain circumstances be brought back to near their original penetrations by heating to approximately 120C. 

The results of this program are contained in reference (10) Table II presents a comparison of the selected physicochemical properties of Sulphlex-233 and an AC-20 grade asphalt cement used in the FHWA study. The table indicates that their properties are generally quite different, particularly the specific gravity, penetration, viscosities, and flash and fire points. However, from a practical standpoint, as the materials are used in the field, these differences are not highly significant. 

These results accentuate the differences between Sulphlex-233 and the AC-20 asphalt cement, and the realization that Sulphlex-233 is not a strictly one-for-one replacement for asphalt. Failure to keep the differences in mind could have serious consequences in field use of the Sulphlex material. 

Table IV presents a comparison of the Marshall design parameters for mixtures of Sulphlex-233 and AC-20 asphalt cement under three conditions 1) equal weight percents, 2) equal...

Marshall Design Results Sulphlex—233 and AC-20 Asphalt Cement ... 

Table V presents the "optimum" binder content for the Sulphlex-233 and the AC-20 asphalt cement and selected mixture properties obtained at these optimum values.

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