Hard asphalt

Asphalt. This is a distillatioa residuum that can also be produced by propane deasphalting (Fig. 7) (33) and thereafter modified to meet specifications. For example, asphalt (qv) can be made softer by blending hard asphalt with the extract obtained ia the solveat treatmeat of lubricatiag oils. Oa the other hand, soft asphalts can be converted iato harder asphalts by oxidation (air blowiag). 

Cutback asphalts are mixtures ia which hard asphalt has beea diluted with a lighter oil to permit appHcatioa as a Hquid without drastic heatiag. They are classified as rapid, medium, and slow cuting, depending on the volatiHty of the diluent, which governs the rates of evaporation and consequent hardeniag. 

In this manner the predicted curve 6f Figure 7, showing the effect of varying petrolene viscosity at constant level of penetration, was obtained. Other asphalts were prepared and analyzed for the above variables. The experimental points were placed on Figure 7. Agreement between the predicted curves and the experimental points is seen to be satisfactory. Figure 7 illustrates that in this penetration range, gel-type asphalts are obtained only from crudes of low aromatic content at low petrolene viscosities. As the petrolene viscosity is increased, asphalts from all crudes tend toward the viscous type. At lower penetrations, the curves are shifted upward, so that hard asphalts from the more aromatic crudes have rather complex flow properties. 

Asphalt flux oil used to reduce the consistency or viscosity of hard asphalt to the point required for use. 

Usually determined by ASTM D 36, softening point determines the temperature at which hard asphalts reach an arbitrary degree of softening. 

Road oils are Hquid asphalt materials iatended for easy appHcation to earth roads. They provide a strong base or a hard surface and maintain a satisfactory passage for light traffic. Liquid road oils, cutbacks, and emulsions are of recent date, but the use of asphaltic soHds for paving goes back to the European practices of the early 1800s. 

For other recreational surfaces, such as mnning tracks, the installation techniques are quite different. Most are poured-in-place. An interlocking tile technique may be employed for tennis courts. In all cases, adequate provision for weathering and water drainage is essential. In general, the resiHent surfaces are installed over a hard base (see Fig. 4) that contains the necessary curbs to provide the finished level. Outdoors, asphalt is the most common base, and indoors, concrete. A poured-in-place polyurethane surface (14) is mixed on-site and cast from at least two components, an isocyanate and a filled... 

ASTM (1) further classifies asphalts or bituminous materials as soHds, semisoUds, or Hquids. SemisoHd and Hquid asphalts predominate in commercial practice today. Prior to 1907, the principal portion of asphalt used occurred naturally since that time most asphalts have been produced from the refining of petroleum. Air-blown petroleum asphalts (5) of diverse hardness became available in the early 1900s, and as thek use increased, the demand for native products diminished. 

Since the early 1900s most of the asphalts produced from the refining of petroleum have been used primarily in paving and roofing appHcations. The advent of motorized transportation led to increased asphalt manufacture from petroleum in order to provide binders for hard-surfaced pavements. 

Propane is usually used in this process although propane—butane mixtures and pentane have been used with some variation in process conditions and hardness of the product. Propane deasphalting is used primarily for cmde oils of relatively low asphalt content, generally <15%. Asphalt produced from this process is normally blended with other asphaltic residua for making paving asphalt. 

Colloidal State. The principal outcome of many of the composition studies has been the delineation of the asphalt system as a colloidal system at ambient or normal service conditions. This particular concept was proposed in 1924 and described the system as an oil medium in which the asphaltene fraction was dispersed. The transition from a coUoid to a Newtonian Hquid is dependent on temperature, hardness, shear rate, chemical nature, etc. At normal service temperatures asphalt is viscoelastic, and viscous at higher temperatures. The disperse phase is a micelle composed of the molecular species that make up the asphaltenes and the higher molecular weight aromatic components of the petrolenes or the maltenes (ie, the nonasphaltene components). Complete peptization of the micelle seems probable if the system contains sufficient aromatic constituents, in relation to the concentration of asphaltenes, to allow the asphaltenes to remain in the dispersed phase. 

Asphalts are usually specified in several grades for the same industry, differing in hardness or viscosity (95). However, with the changing nature and composition of cmde oil feedstocks over the past two decades, performance and supply factors are also an important consideration (95). 

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. 

Built-up roofing constitutes several pHes of a saturated roofing felt (low melt, flexible asphalt saturant) with each ply mopped in place and the stmcture covered by air-blown asphalts of from 60° to 105°C softening point, with the hardness selected depending primarily on roof slope. These roofs are usually surfaced with mineral aggregates. 

Thermal Asphalt. Thermal asphalt products are in low supply because the thermal process has been virtually replaced by catalytic cracking processes. Thermal pitches, because of their high viscosity temperature susceptibiHty, are very hard at ordinary temperatures (Table 9), but become quite... 

Linoleum, asphalted-fett-base, and other hard surface floor coverings, n.e.c. ... 

Generally, systems developed in the USA favour a combination of polyethylene with either butyl-rubber or hot-applied mastic adhesives, the latter consisting of a blend of rubber, asphalt and high molecular weight resins. In European and Far East coating plants, epoxy type primers and hard ethylene copolymer adhesives have been successfully employed. 

A fluid loss additive for hard brine environments has been developed [1685], which consists of hydrocarbon, an anionic surfactant, an alcohol, a sulfonated asphalt, a biopolymer, and optionally an organophilic clay, a copolymer of N-vinyl-2-pyrrolidone and sodium-2-acrylamido-2-methylpropane sulfonate. Methylene-bis-acrylamide can be used as a crosslinker [1398]. Crosslinking imparts thermal stability and resistance to alkaline hydrolysis. 

Process areas are normally provided with hard wearing surfaces, such as concrete or asphalt, which... 

Asphalt (referred to as bitumen in some parts of the world) is produced from the distillation residuum. In addition to road asphalt, a variety of asphalt grades for roofing and waterproofing are also produced. Asphalt has complex chemical and physical compositions, which usually vary with the source of the crude oil, and it is produced to certain standards of hardness or softness in controlled vacuum distillation processes (Barth, 1962 Bland and Davidson, 1967 Speight, 1999, and references cited therein Speight and Ozum, 2002). 

---