Asphalt ductility

Asphalt—mbber is mixed and applied to roadways by several techniques. In one method, mbber and asphalt are mixed at ca 175—220°C for one to two hours. The hot mixture is applied to the roadway and covered with a layer of stone chips to form a chip seal. The mbber cmmb consists of scrap tires ground into particles less than 2 mm in diameter. Rubber-modified asphalt is also used for waterproofing membranes, crack-and-joint sealers, hot-mix binders, and roofing materials. The mbber improves asphalt ductility and increases its softening point. The aggregate adhesive bond is stronger, and the asphalt lasts longer. Production of rubber-modified asphalt has increased from 405 t in 1970 to 27,000 t in 1980 (41). Typically, about 2 t of mbber is used for 1 km of roadway. If it is assumed that asphalt—mbber contains ca 25% mbber and 75% asphalt, the potential demand for scrap mbber would be ca 40,500 t/yr, or ca 2% of the amount available. 

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. 

Blends with styrenic block copolymers improve the flexibiUty of bitumens and asphalts. The block copolymer content of these blends is usually less than 20% even as Httie as 3% can make significant differences to the properties of asphalt (qv). The block copolymers make the products more flexible, especially at low temperatures, and increase their softening point. They generally decrease the penetration and reduce the tendency to flow at high service temperatures and they also increase the stiffness, tensile strength, ductility, and elastic recovery of the final products. Melt viscosities at processing temperatures remain relatively low so the materials are still easy to apply. As the polymer concentration is increased to about 5%, an interconnected polymer network is formed. At this point the nature of the mixture changes from an asphalt modified by a polymer to a polymer extended with an asphalt. 

Sulfur, modified in its structure so as to become plastic, presents other problems as it can be a very ductile material. Reinforcement in the sense of load sharing may be effected by incorporating relatively ductile thermoplastic fibers. There is a commercial interest in using polypropylene fibers, and Bennett (10,11) has patented a process whereby woven polypropylene fibers are impregnated with asphalt or bitumen and then are coated on at least one side with a sulfur composition. The plasticized sulfur coating sticks to the base and makes the laminate flexible, weather resistant, and light reflecting. 

Rheology of SA Binders. Conventional test methods such as softening point, viscosity, penetration, Fraas break point, ductilities, etc. have been used to characterize the rheology of SA binders (11). The physical structure of SA binders is complex, and the sulfur-asphalt and sulfur-aggregate interaction make correlations to asphalt and to binder properties for aggregate rather difficult. 

Crete piping systems can be lined with special salt-glazed vitrified-clay liner plates, joined with a die-cast asphalt joint. Concrete pressure pipe is competitive with cement-lined ductile iron for underground plant water systems. 

Asphalt is a dark-brown to black solid or semisolid consisting of carbon, hydrogen, oxygen, sulfur, and sometimes nitrogen. It is made up of three components (1) asphaltene, a hard, friable, infusible powder, (2) resin, a semisolid to solid ductile and adhesive material, and (3) oil, which is structurally similar to the lubricating oil fraction from which it is derived. 

Stock. Propane deasphalting also has the ability to reduce a residuum even further and to produce an asphalt product with lower viscosity, higher ductility, and higher temperature susceptibility than other asphalts, although such properties might be anticipated to be very much crude oil dependent. Propane deasphalting is conventionally applied to low-asphalt-content... 

Brittle asphalt causes pavement instability. One particular test method (IP 80) is an approximate indication of the temperature at which asphalt possesses no ductility and would reflect brittle fracture conditions. 

The ductility of asphalt is a measure of the flexibility of the asphalt and is expressed as the distance in centimeters that a standard briquette can be elongated before breaking (ASTM D-113, IP 32). Ductility is a combination of flow properties and reflects homogeneity, cohesion, and shear susceptibility it is an indication of fatigue life and cracking. 

With minor exceptions the requirements for the physical and chemical properties of asphalt were essentially the same for the three national specifications and included penetration and ductility at 25 °C flash point % loss at 163 °C penetration of residue as a % of original solubility in carbon disulfide solubility in carbon tetrachloride specific gravity at 25°C and softening point. 

The naturally occurring asphaltic material gilsonite has proven effective in plugging fractures. It is introduced in a finely ground form, and behaves in a ductile manner in situ,... 

Natural and synthetic rubbers have been studied as additives to alter the viscosity, ductility, and flow properties of road building asphalts. Welbom and Babashak (23) added natural rubber and sulfur to asphalt and reported improved blending conditions, improved stability, increased toughness, and low temperature ductility. 

Another gap in our knowledge is the diflSculty of relating the properties of asphalts and specific test results to performance in each application (29). Penetration, viscosity, ductility, and elasticity properties are related to performance. However, the problem of correlating results from many of these empirical tests with the development of additives to increase asphalts durability has created diflBculties in interpreting the results (30, 31,32,33,34,35). 

CKD can be added to asphalt binder to produce a low ductile mastic asphalt Mastic asphalt is a mixture of asphalt binder and fine mineral material When mastic asphalt is produced using CKD mixed 50/50 with an asphalt cement binder, a potential exists for a relatively large volume replacement of asphalt cement... 

The European use of mastic asphalts, with low ductility, for bridge deck waterproofing and protection is well documented, and this could represent a potential application for kUn dusts in the United States... 

Utilization of scrap tire rubber in asphalt has advantages in the performance of roads and their longevity. This includes enhanced ductility, crack resistance, skid resistance, and noise reduction. Disadvantages of the rubber-modified... 

The penetration grade, softening point, and ductility of the GRT-modified bitumens were studied as a function of rubber selection, temperature, rotational speed, shearing time, order of rubber, and oil addition (Li et al 2009). It was established that a shearing time of 40 min, a temperature of 180" C, a rotational speed of7000 rpm, and a rubber concentration below 25 wt.% with oil content below 4 wt.% were optimal for carrying out the technological process for preparation the GRT-modified asphalts. 

During the testing, the water bath temperature must be kept constant and any water oscillations or undulations resulting in early fracture of the created asphalt thread must be avoided. A typical ductility apparatus, known as a ductilometer, and moulds are shown in Figure 4.3. 

AASHTO T 51. 2009. Ductility of asphalt material. Washington, DC American Association of State Highway and Transportation Officials. 

The fracture energy can be utilised as a parameter to describe the fracture resistance of asphalt concrete, and the fracture energy parameter is particularly useful in the evaluation of mixtures with ductile binders, such as polymer-modified bitumen. It has been shown to discriminate between these materials more broadly than the indirect tensile strength parameter determined by AASHTO T 322 (2011) (Wagoner et al. 2006). 

There have been objections to this approach (16), partly because of the arbitrariness of the procedure in which the percentage of LMS is very much an artifact of the SEC operating parameters. It is also thought that it is the mechanical properties that cause failure, and these do not correlate well with chemical properties, such as SEC thus if ex post facto measurements are to be used, they may as well be the physical properties of the old asphalt. There are several studies that indicate that there is a limiting ductility below which all roads fail (84,85). It has been suggested (86) that penetration at 4X, a good predictor of the limiting stiffness temperature, be used to predict the tendency to crack. 

Jennings has also done some work with asphalt recycling. In this process old road material in bad condition is stripped from the roadway, mixed with a softening agent, and relaid. Sufficient new material is generally added to restore viscosity and ductility to levels approximating those of new asphalt. This does... 

Utilization of scrap tire rubber in asphalt has advantages in the performance of roads and their longevity. These include enhanced ductility, crack resistance, skid resistance, and noise reduction. Disadvantages of the rubber-modified asphalt are its cost and a possibility of toxic emissions into the air. Tests indicated that rubber-modified asphalt increases the cost of road construction by about 50% in comparison with conventional asphalt [192]. The requirement for an additional step of hot mixing during processing of the rubber-asphalt mix may possibly cause toxic emissions into the air. 

Hot-applied polymeric sealants are formulated with a carefully balanced blend of polymer with certain compounds, like asphalt, plasticisers and inert reinforcing fillers to produce a hot-pour point sealant with excellent bonding properties, high resiliency, ductility and resistance to degradation from weathering, to provide a positive seal during expansion and contraction of the joint. 

Superabsorbent polymer can be used as a water-blocking construction filler with cement and asphalt emulsion (155). The main benefit of the fill material is its high ductility compared to conventional construction backfills such as gravel or sand. These fillers can be delivered in low viscosity, which aids in the complete filling of the space. Similar principles are employed in making and using sealing compounds for electrical and optical cables. 

I and II, type III asphalt is thin enough to penetrate masonry, wood, and paper to provide a bond for other bitumen applications. It is also used to wet surfaces (e g., metal). Depending on requirements, type III can be made from soft, ductile asphalt as well as harder-base asphalts for application to dense, metal, or porous surfaces. 

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