Asphalt physical properties

There have been a number of not particularly successful attempts to correlate asphalt physical properties to chemical properties, including SEC (10,19,35-40). Chollar et al. (41) attempted to relate a number of chemical and physical properties, including percentage LMS, with poor results. Huynh et al. (42) divided asphalt into a number of fractions by preparatory SEC and showed that the glass transition temperature (not precisely defined for asphalts), in moving from one fraction to the next, first decreased with increasing molecular size and then increased. Beazly et al. (43) used SEC and nuclear magnetic resonance (NMR) to estimate asphalt yields and viscosity from crude oil Woods et al. (44) used SEC fractions to study differences in maltenes from tar sand bitumens. 

Attempts to correlate asphalt physical properties with chemical properties have not been particularly successful. This no doubt is primarily the result of the lack of uniqueness in the chemical properties that are used. For instance, a Corbett fraction from one asphalt may have very different physical properties from those of the same fractions from another asphalt. Also, two asphalts with similar physical properties can have radically different SEC chromatograms. 

The products could be classified as a function of various criteria physical properties (in particular, volatility), the way they are created (primary distillation or conversion). Nevertheless, the classification most relevant to this discussion is linked to the end product use LPG, premium gasoline, kerosene and diesel oil, medium and heavy fuels, specialty products like solvents, lubricants, and asphalts. Indeed, the product specifications are generally related to the end use. Traditionally, they have to do with specific properties octane number for premium gasoline, cetane number for diesel oil as well as overall physical properties such as density, distillation curves and viscosity. 

Asphalt Roofing Components. Asphalt (qv) is a unique building material which occurs both naturally and as a by-product of cmde-oil refining. Because the chemical composition of cmde oils differs from source to source, the physical properties of asphalts derived from various cmdes also differ. However, these properties can be tailored by further ptocessiag to fit the appHcation for which the asphalt will be used. Softening poiat, ductility, flash poiat, and viscosity—temperature relationship are only a few of the asphalt properties that ate important ia the fabricatioa of roofing products. 

The physical properties of elemental sulfur can be modified by its reaction with various organic and inorganic compounds. Many of the resulting sulfur products tend to have properties similar to paving asphalt (49,50). 

Durability. The term "durable" has several meanings, but in the present context it is used to describe an asphalt that possesses the necessary chemical and physical properties required for the specified pavement performance, being resistant to change during the in-service conditions that are prevalent during the life of the pavement. 

This article discusses traditional hull ding and construction products, ie, not made from synthetic polymers (see Building materials, plastic), including wood, asphalt, gypsum, glass products, Pordand cement, and bricks. The article presents information about each basic material, the products made from it, the basic processes by which the products or materials are produced, estimates of the quantity or doUar value of the quantities produced or used in the United States, and some pertinent chemical or physical properties related to the material. More detailed chemical and physical property data can be found in articles devoted to the individual materials (see Asphalt Cement Glass Wood). 

Modified Bitumen Membranes. These membranes were developed in Europe during the late 1950s and have been used in the United States since the late 1970s. There are two basic types of modified asphalts and two types of reinforcement used in the membranes. The two polymeric modifiers used are atactic polypropylene (APP) and styrene—butadiene—styrene (SBS). APP is a thermoplastic polymer, whereas SBS is an elastomer (see Elastomers, thermoplastic elastomers). These modified asphalts have very different physical properties that affect the reinforcements used. 

Styrene—butadiene—styrene modified bitumen is an elastomeric material mixed into an asphalt between 10 and 15%. By using high energy mixing, the SBS is uniformly dispersed throughout the asphalt to form a network, referred to as phase reversal because the minor component s (SBS) physical properties are displayed by the final mixture. A properly formulated SBS asphalt blend has an elongation of 100% or greater and is flexible down to temperatures below —6°C. 

Of the data that are available, the proportions of the elements in petroleum vary only slightly over narrow limits (Chapter 1). And yet, there is a wide variation in physical properties from the lighter more mobile crude oils at one extreme to the heavier asphaltic crude oils at the other extreme. The majority of the more aromatic species and the heteroatoms occur in the higher boiling fractions of feedstocks. The heavier feedstocks are relatively rich in these higher boiling fractions. 

Early in the development of solid propellant, the asphalt composites were found to have poor physical properties, such as cracking under normal temperature cycling, poor tensile characteristics, etc. They were replaced with the elastomeric polymers which have become the present-day binders. The first of these was Thiokol rubber, a polysulfide rubber, whichgives the propellant with good physical properties. The presence of the sulfur atom in the Thiokol rubber decreases the performance compared to a CHO polymer thus the most frequently used binders are polyurethane, polybutadiene acrylic acid (PBAA), epoxy resin, etc. The choice of the latter binders is made with regard to physical properties rather than performance. 

Table I. Physical Properties of Sulfur-Asphalt Binders...

The physical properties of several sulfur-asphalt blends were determined in the laboratory and are illustrated in Table I. The softening points and penetration of the asphalt were relatively unchanged. The viscosity of the sulfur-asphalt blend is generally lower at all temperatures and is significantly less at 135 °C. The aggregates used in the trial are described in Table II. 

The use of higher amounts of sulfur, above a sulfur/asphalt weight ratio of 1.0, yields pourable mixes with a marked change in physical properties. For example, the sand mixes in Figure 8 exhibit negligible stability without sulfur addition of sulfur permits mix designs to high stability levels at a variety of asphalt contents. Other mix properties are affected in a similar fashion. 

Petroleum asphaltenes are commonly viewed as an undesired component of crude oil that creates serious difficulties in upgrading of petroleum heavy ends. However, it is not often recognized that processing of petroleum residua also includes production of asphalts where asphaltenes are not only a very desired component but the component that determines, to a great extent, the physical properties of an asphalt. 

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