Asphalt binder

Asphalt (bitumen) also occurs in various oil sand (also called tar sand) deposits which occur widely scattered through the world (17) and the bitumen is available by means of various extraction technologies. A review of the properties and character of the bitumen (18) suggests that, when used as an asphaltic binder, the bitumen compares favorably with specification-grade petroleum asphalts and may have superior aging characteristics and produce more water-resistant paving mixtures than the typical petroleum asphalts. 

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. 

A variety of materials has been proposed to modify the properties of asphaltic binders to enhance the properties of the mix (112), including fillers and fibers to reinforce the asphalt—aggregate mixture (114), sulfur to strengthen or harden the binder (115,116), polymers (98,117—121), mbber (122), epoxy—resin composites (123), antistripping agents (124), metal complexes (125,126), and lime (127,128). AH of these additives serve to improve the properties of the binder and, ultimately, the properties of the asphalt—aggregate mix. 

It has been shown that inclusion of fine mbber particles in asphalt reduces the cracking of pavement in adverse weather conditions [60,61]. There are two methods for introducing ground waste mbber into asphalt, namely, wet and dry processes. Wet process is carried out at 170°C-220°C for 45-120 min. Rubber particles absorb components with similar value of solubility parameter (5) from the asphalt, causing them to swell. The interaction between mbber and asphalt is mainly of physical nature. In the dry process, mbber is used as a replacement for part of the aggregate and is added to the mineral material before the latter is mixed with the asphalt binder. Addition of mbber greatly improves the elasticity of the binder and generally lowers its brittle point. Incorporation of GRT... 

Lewandowski, L.H., Polymer modification of paving asphalt binders. Rubber Chem. Technol., 67, 447, 1994. 

Sulfur is one of the four major commodities of the chemical industry. The other three are limestone, coal, and salt. Most sulfur that is produced is used to manufacture sulfuric acid (HjSO ). Forty million tons are produced each year in the manufacture of fertilizers, lead-acid batteries, gunpowder, desiccants (drying agent), matches, soaps, plastics, bleaching agents, rubber, road asphalt binders, insecticides, paint, dyes, medical ointment, and other pharmaceutical products, among many, many other uses. Sulfur is essential to life. 

The optimum or minimum allowable substitution ratio is then established by means of a series of justification tests at different binder contents. Figure 15 shows a comparison between the Marshall design properties of a conventional mixture using an asphalt binder and a 30 70 SEA binder. As indicated the optimum substitution ratio based on the maximum stability and equivalent air voids is about 1.7 1. Since minimizing the substitution ratio has a direct impact on the economic benefits to be realized by replacing the asphalt with sulfur these justification tests are to be recommended in all mix designs. 

Figure 15, Sulfur-extended asphalt (SEA) justification test data. Curve 1, asphalt binder and Curve 2, SEA binder (30-70) (33).

Kennepohl, G. J., Logan, A., and Bean, D. C., "Conventional Paving Mixes With Sulphur-Asphalt Binders", Proceedings of the Association of Asphalt Paving Technologists, 1975, 44. 

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., "Design of Open Friction Courses with Sulfur-Extended Asphalt Binders", Final Report on FHWA Contract No. DOT-FH-11-9588, May, 1981. 

Bakharevich (Ref 4) enclosed in a rigid casing (sheath) of compressed KC1 and asphalt binder (1.5%), Ammonits and Pobedits to obtain expls, known as Metanits, which did not ignite methane-air mixts and had deton rates of 46204900m/sec. The sheath protected the expls from dynamic compression, Another expl described by Bakharevich was Miporit... 

The volatile products from the soaking drum enter the fractionator where the distillates are fractionated into desired product oil streams, including a heavy gas oil fraction. The cracked gas product is compressed and used as refinery fuel gas after sweetening. The cracked oil product after hydrotreating is used as fluid catalytic cracking or hydrocracker feedstock. The residuum is suitable for use as boiler fuel, road asphalt, binder for the coking industry, and as a feedstock for partial oxidation. 

Antistripping agent an additive used in an asphaltic binder to overcome the natural affinity of an aggregate for water instead of asphalt. 

The asphalt binder used in both types of RUMAC is the same as that used in conventional asphalt. Therefore, conventional equipment is used for mixing the final product. A belt conveyor is used to feed the rubber into the mixer. 

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. 

Emulsification Method. Emulsified sulfur-asphalt binder was prepared by combining molten sulfur and liquid asphalt in a 2Vi -in.-diameter, vertical, Gifford Wood colloid mill (1) at a rotor-stator gap setting of... 

Figure 3. Viscosity of sulfur-asphalt binder vs. temperature...

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