Softening point of asphalt

The softening point of asphalt may be defined as that temperature at which asphalt attains a particular degree of softness under specified conditions of test. 

Several tests are available to determine the softening point of asphalt (ASTM D-36, ASTM D-61, ASTM D-2319,ASTM D-3104, ASTM D-3461, IP 58). In the test method (ASTM D-36, IP 58), a steel ball of specified weight is laid on a layer of sample contained in a ring of specified dimensions. The softening point is the temperature, during heating under specified conditions, at which the asphalt surrounding the ball deforms and contacts a base plate. 

D3461 Test Method for Softening Point of Asphalt and Pilch (Meltler Cup-and-Ball Method) ... 

The softening point of the modified asphalt was higher than 60°C at concentrations above 5% of LDPE/GRT at a ratio of 30/70 and POE-g-MA content of 8% under shearing speed of 3000 rpm for 20 min. In addition, these blends showed good storage stability at high temperatures. 

It is noted that the European practice on using R A for the production of recycled asphalts requires the penetration or softening point of the binder in the resulting mixture, calculated from the penetrations or the softening points of the added binder and the recovered binder from the RA, to meet the penetration or softening point requirements of the selected grade, as if the works had to be conducted with virgin bitumen. 

ATLASTIC 31 is a hot-melt asphaltic compound with a ball-and-ring softening point of 200° to 225°F (93° to 107°C). ATLASTIC 40 is a corrosion-resistant membrane system consisting of a layer of ATLASTIC 40 textile in the center of two layers of ATLASTIC 31. ATLASTIC 50 is a textile-reinforced, hot-melt asphaltic membrane with a ball-and-ring softening point of 250° to 275°F (121° to 135°C). 

Take no more than 2 h to heat an asphalt sample to its pouring temperature in no case shall this be more than 110 C (2(X) F) above the expected softening point of the asphalt. 

Trinidad asphalt has a relatively uniform composition of 29% water and gas, 39% bitumen soluble in carbon disulfide, 27% mineral matter on ignition, and 5% bitumen that remains adsorbed on the mineral matter. Refining is essentially a process of dehydration by heating the cmde asphalt to ca 165°C. The refined product averages 36% mineral ash with a penetration at 25°C of about 2 (0.2 mm), a softening point (ring and ball method) of 99°C, a flash point (Cleveland open cup) of 254°C, a sulfur content of 3.3%, and a saponification value of 45 mg KOH/g. The mineral matter typically contains... 

Temperature is the most important variable and preheating is generally necessary to 200—230°C. After air has been introduced, there is a gradual temperature rise because of the exothermic reaction, until some means is appHed to hold the temperature such as a water or steam spray on the asphalt surface to maintain a temperature of approximately 260°C. The end point can be predicted by periodic testing of the softening point. 

Many agents have been proposed and patented including copper sulfate (34), zinc chloride (35), ferric chloride (36), aluminum chloride (36), and phosphoms pentoxide (37) ferric chloride, zinc chloride, and phosphoms pentoxide have been most widely used. The addition of these agents may vary from 0.1 to 3%, depending upon the feedstock and the desired characteristics of the product (Table 5) and all asphalt feedstocks do not respond to catalysts in the same way. Differences in feedstock composition are important qualifiers in determining the properties of the asphalt product. The important softening point-penetration relationship, which describes the temperature susceptibiUty of an asphalt, also varies with the source of the feedstock. Straight-reduced, air-blown, and air-blown catalytic asphalts from the same cmde feedstock also vary considerably. 

This equation is based on the approximation that the penetration is 800 at the softening point, but the approximation fails appreciably when a complex flow is present (80,81). However, the penetration index has been, and continues to be, used for the general characteristics of asphalt for example asphalts with a P/less than —2 are considered to be the pitch type, from —2 to +2, the sol type, and above +2, the gel or blown type (2). Other empirical relations that have been used to express the rheological-temperature relation are fluidity factor a Furol viscosity P, at 135°C and penetration P, at 25°C, relation of (H—P)P/100 and penetration viscosity number PVN again relating the penetration at 25°C and kinematic viscosity at 135 °C (82,83). 

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 ductiUty at 25 °C flash point % loss at 163 °C penetration of residue as a % of original solubiUty in carbon disulfide solubiUty in carbon tetrachloride specific gravity at 25°C and softening point. 

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. 

Type 1 asphalt is the softest type of mopping asphalt with softening points between 68°C and with penetration at 25°C between 18 and 50 mm /10. It is for roof slopes of less the j in. per ft (0.25 per 12). It is also called dead level asphalt and is not commonly used today because of the porosity of the fiber-glass ply felts and the industry recommendation that roof slope a minimum of j in. per ft. 

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. 

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