Asphalt evaluation

Although distillation and elemental analysis of the fractions provide a good evaluation of the qualities of a crude oil, they are nevertheless insufficient. Indeed, the numerous uses of petroleum demand a detailed molecular analysis. This is true for all distillation fractions, certain crude oils being valued essentially for their light fractions used in motor fuels, others because they make quality lubricating oils and still others because they make excellent base stocks for paving asphalt. 

Sohd materials, such as gilsonite and asphalt, and partially soluble sulfonated asphalt may also be added to plug small fractures in exposed shale surfaces and thereby limit water entry into the formation (105,124). The asphalts are oxidized or treated to impart partial solubiUty. These materials may be softened by the downhole temperature, causing them to deform and squeeze into small openings exposed to the borehole. Laboratory tests designed to evaluate shale-stabilizing muds have confirmed the beneficial action of these materials (125) (see also Soil STABILIZATION). 

Determination of the components of asphalts has always presented a challenge because of the complexity and high molecular weights of the molecular constituents (6,44,45). The principle behind composition studies is to evaluate asphalts in terms of composition and performance. Such studies are always suspect when this is not the overriding goal of the work. 

The composition data should always be appHed to in-service performance (64,65) in order to properly evaluate the behavior of the asphaltic binder under tme working conditions. 

Laboratory experiments have been conducted with a chromium lignite-chromium lignosulfonate mud system both without and with solid lubricants. These studies include filtration loss, cake quality, and their impact on the formation. A comparative evaluation has led to the conclusion that Gilsonite is a better additive compared with sulfonated asphalt as it results in less filtration... 

Source From Noureldin, A.S. and McDaniel, R.S., Evaluation of Steel Slag Asphalt Surface Mixtures, presented at the 69th annual meeting, Transportation Research Board, Washington, January 1990. 

Asphalt concrete is properly proportioned to resist the potentially damaging effects in the road. Asphalt concrete paving mixtures should be evaluated for the following properties stability, flow, air voids, stripping resistance, resilient modulus, compacted density, and unit weight. Table 4.18 provides a list of standard laboratory tests that are presently used to evaluate the mix design or expected performance of fresh and hardened asphalt concrete. 

This test (ASTM D529) evaluates the relative weather resistance of asphalt used for protective-coating applications, especially for roofing. No direct measure of outdoor life or service can be obtained from this test. Methods for preparing test panels (ASTM D1669) and failure-endpoint testing (ASTM D1670) are available. 

Macado ML, Beatty PW, Fetzer JC, et al Evaluation of the relationship between PAH content and mutagenic activity of fumes from roofing and paving asphalts and coal tar pitch. Eundam Appl Toxicol 21 492-499, 1993... 

Table 4. Degrees of evidence for carcinogenicity in humans and experimental animals and overall evaluation of carcinogenicity to humans for agents to which asphalt workers and roofers may be or may have been exposed, as evaluated by lARC as of 1993 ...

Field development and evaluation of sulphur extended asphalts has been going on since the mid-seventies. The first commercial placements of sulphur extended asphalts under competitively bid contracts took place in North America in 1980. Of the approximately 160,000 tonnes of hot mix involved, over half used the additive technology mentioned above, the remaining projects used a number of different approaches. 

The kind of test that is appropriate in the two cases is different in the first case, load should be increased until failure while in the second, some sort of deformation (or strain) control is appropriate. (A practical case of the latter is the Marshall stability test for evaluating the performance of asphalt concrete). In reality some combination of stress and strain capacity is required. 

The Texas Transportation Institute has just completed a very extensive two year FHWA sponsored program to look into other aspects of safety and environmental impact of sulfur-asphalt construction [53]. A number of typical sulfur-asphalt and sulfur-concrete paving systems were evaluated to assess their potential environmental impact and establish safety considerations relative to their formulation, construction and maintenance. The environmental impact was investigated from the formulation stages, through weathering, and included considerations of simulated fires and chemical spills. 

A large number of structural materials were evaluated for possible attack by run-off from a sulfur-asphalt pavement. Of the ten materials studied, copper and steel appeared to indicate a vulnerability. The former or its alloys should never be used in equipment or structures which could bring them in contact with sulfur due to the high probability of producing the sulfates of copper. Steel reinforcing rods would be susceptible to attack by H SO produced by moisture on contact. 

The results of this study also produced a Field Evaluation Document (Volume II) and an Annoted Bibliography (Volume III) containing over 500 relevant sources. The Field Evaluation Document was designed for use by contractors and state agencies to establish the relative safety and for identification of potential hazards at the various locations and work elements on a sulfur-asphalt construction project. Recommended clothing and first aid procedures were included in this document. 

Saylak, D., Gallaway, . M. and Noel, J. S., "Evaluation of a Sulfur-Asphalt Emulsion Binder Systems for Road Building Purposes", Final Report, Texas A M Research Project - RF 3146, January, 1976. 

The success of SWRI in formulating Sulphlex binders wtih promising laboratory properties prompted FHWA to construct a small pavement section to evaluate the use of such materials with conventional asphalt construction equipment and practices. The goal was to determine if the Sulphlex binders might present unrecognized problems which would argue against their further development ... 

Terrel, R L. "Evaluation of Wood Lignin as a Substitute or Extender of Asphalt" Report FHWA/RD-80/125, November 1980. 

From adsorption analysis data, it is possible to calculate theoretical yields of deoiled wax, asphalt, resins, and solvent extraction yields of waxy raffinate. Nearly 100 different stocks have been so evaluated by California Research Corp. during the past few years and many of these data have been correlated with operations in refinery equipment and with pilot plant operations. 

One of the major noneconomic barriers to the use of rubber in asphalt pavements has been the lack of consensus on the results of long-term testing. Many long-term tests have been performed, but they were performed in over a dozen states, and as yet these tests have not been brought together and evaluated in a cohesive study. 

The economic barrier to the use of rubber in pavements is the high initial cost to the highway departments. It is difficult to obtain good data on the capital investment necessary to convert an asphalt operation to add rubber. But the consensus from the ARPG and several other sources is that the installation of rubber asphalt pavements will cost about 2 times as much as standard asphalt. Although the test results for asphalt pavements containing rubber are not yet complete, in many cases a factor of 2 or more in pavement lifetime is achieved. Therefore, if transportation departments evaluate costs over the life of the roads, the overall costs may be the same or less for rubber asphalt. The ARPG claims that rubberized asphalt roads cost less on a life-cycle basis. 

Emissions. An environmental assessment has been carried out to evaluate the effects of sulfur-asphalt during and after construction. Ambient air samples were taken from points around the pugmill and paver and analyzed for hydrogen sulfide (H2S), sulfur dioxide (S02), carbon disulfide (CS2), carbonyl sulfide (COS), mercaptans (RSH), and total hydrocarbons. The results indicated that no problems exist in terms of current health standards during construction or after. Typical test results obtained at the pugmill and methods used are given in Table II. 

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