Asphalt sulfur-

Highway Construction. The preparation and use of sulfur—asphalt (SA) paving materials have been reviewed (45,46). In the 1930s, asphalt (qv) was easily available and priced lower than sulfur. As of the 1990s, this is no longer the case. There are four different types of sulfur paving materials. 

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... 

During 1974—1985, about 200 sulfur—asphalt roads were constmcted worldwide, half of which were ia the United States. AH U.S. SEA experimental sections designed and constmcted according to standard practices usiag standard materials are performing as well as the control sections of conventional asphalt ia these experimental projects (49). 

D. Saylak and co-workers. Beneficial Uses of Sulfur in Sulfur—Asphalt Pavements, American Chemical Society, Washington, D.C., 1975. 

The most important use of sulfur is for sulfuric acid production. Other uses range from dusting powder for roses to ruhher vulcanization to sulfur-asphalt pavements. Flower sulfur is used in match production and in certain pharmaceuticals. Sulfur is also an additive in high pressure luhricants. 

A Review of the State of the Art of Sulfur Asphalt Paving Technology... 

SAYLAK AND conger Review of Sulfur Asphalt Paving... 

Figure 8. Typical settling of sulfur from a sulfur/asphalt (30/70) emulsion maintained at 285° F.

Figure 9. Relative sulfur settling in SEA blends with different sulfur/asphalt ratios maintained at 285°F (31). Key 20/80 , 30/70 A, 40/60 and M> 50/50...

Figure 17. Gulf portable sulfur asphalt module (SAM).

Figure 19. Texas Gulf portable sulfur asphalt emulsifier.

Table 2. Properties of Recycled Asphalt Pavement Using Sulfur/ Asphalt Emulsion Binder.

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. 

Garrigues, C. and Vincent, P., "Sulfur/Asphalt Binders For Road Construction", Adv. in Chem. Series 140, American Chemical Society, 1975, pp. 130-153. 

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. 

Sulfur-Asphalt Paying Materials (1J, ). Two different technologies are used to combine asphalt and sulfur into a binder that exhibits unique properties and often enhance the pavement performance as well as extend the supply of available asphalt. 

The current sulfur-asphalt technologies are the result of research and development carried out since the late 1960 s, but the sulfur-asphalt concept is far from new. The foundation was laid in the 1930 s by Bencowitz 9) and his co-workers who produced and patented sulfur-asphalt mixtures which had several advantages over regular asphalt. 

However, it was the availability of large quantities of byproduct sulfur combined with the energy crisis of the early 1970 s which stimulated the research and development needed to make sulfur-asphalt technology a commercial reality. The need to dispose of large potential tonnages of sulfur and the need to find alternative new materials to increasingly expensive petroleum-based asphalt spurred interest and research by many organizations. 

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. 

Early field trials were conducted in Saudi Arabia using this technology (22, 23). Considerable interest in sulfur asphalt pavements has been generated, but not projects of significance have been completed. Considerable research and development as well as demonstrations are continuing under the guidance of the Sulphur Development Institute of Canada. 

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