Paving materials, asphalt

Keyword paving material, asphalt mixture, waste plastics, recycling, Marshall test, wheel tracking test, dynamic stability, bending test. 

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... 

Petroleum refining and related industries Manufacture of paving and roofing materials Asphalt and tars, felts, paper, cloth, fiber... 

T. A. Subivan, W. C. McBee, and K. L. Rasmussen, Studies ofSand-Sulphur--Asphalt Paving Materials, RI 8087, U.S. Bureau of Mines, Washington, D.C., 1975. 

Construction, maintenance, and rehabilitation costs for pavements have risen sharply during the past decade, while revenue for these purposes has leveled or declined. In an effort to offset these rising costs and reduce dependence on uncertain asphalt supplies, increased research and development activity throughout the world has been devoted to the development and implementation of new and improved materials for use in pavement construction and maintenance. The use of sulfur in asphalt paving materials has proven to be one of the more promising developments to come from these activities. 

On the basis of the results of extensive laboratory and field studies of SAS paving materials, it can be concluded that, when prepared and placed using established recommended practices, they can be expected to perform as well as, if not superior to, conventional asphaltic concretes. Three major drawbacks appear to hinder the general acceptance of SAS materials for greater usage in the paving industry. 

Studies of Sand-Asphalt Paving Materials", U. S. Bureau of Mines Report of Investigations 8087, 1975, 19 pages. 

A major application now under very active research is the use of SC as a road paving material. This technology is considerably different from the use of sulfur as a potential substitute for asphalt which was discussed earlier. Paving with SC can be regarded as a total substitution of sulfur for asphalt, or as an... 

It has been known for many years that sulfur can modify the properties of asphalts (38). With the recent dramatic increases in oil prices and hence the price of asphalt, the use of sulfur in flexible paving materials is being examined with renewed interest (39-45), particularly in areas where sulfur is available and is less expensive than asphalt. In addition to the possible economic benefits, if asphalt can be partially or completely replaced by sulfur in flexible pavement concretes, other benefits in terms of improved material properties might also accrue. 

U ecently, interest in sulfur utilization in asphalt paving materials has been rekindled. One of the foremost reasons for this is the potential availability of surplus sulfur recovered from secondary sources in connection with meeting environmental pollution standards (I). These sources include sulfur recovered from sour gas, from refining of petroleum, and from smelter and powerplant stack gases. Another potential saving of energy and petroleum is possible by replacing part of the asphalt binder with sulfur (2). 

A test program to determine the feasibility of direct substitution of sulfur for asphalt in preparing sulfur-asphalt concretes was conducted. Properties of the resultant materials were compared with those of emulsified sulfur-asphalt binder materials and conventional materials. In addition, a test program was conducted to determine if direct-substituted binders could be used to upgrade marginal aggregates for use in paving materials. 

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