Asphalt cutback

Customblen Cut-and-paste plot plans Cutback asphalt Cutback asphalts Cuticle removers Cutin... 

The main uses of petroleum naphtha fall into the general areas of solvents (diluents) for paints, etc, dry-cleaning solvents, solvents for cutback asphalt, solvents in mbber industry, and solvents for industrial extraction processes. Turpentine, the older, more conventional solvent for paints, has been almost completely replaced by the cheaper and more abundant petroleum naphtha. 

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. 

The hquid cutback asphalts are prepared in a number of viscosity grades, ranging generally from 70 to 6000. The grade number indicates the viscosity at 60°C. 

Preparation is accompHshed by simple blending of the diluent into the hot base asphalt. This is generally accompHshed in tanks equipped with coils for air agitation or with a mechanical stirrer or a vortex mixer. Line blending in a batch circulation system or in a continuous fashion (40) is used where the volume produced justifies the extra faciUties. A continuous, line-blending system is appHcable to the manufacture of cutback asphalts and asphalt cements (Fig. 8). 

Fig. 12. A viscosity-temperature chart, mm /s = cSt ----, iadustrial asphalts ---cutback asphalts ...

Distillation (ASTMD402). Approximate amounts of volatile constituents are deterrnined by this test which is particulady appHcable to cutback asphalt and road oils. 

Liquid Asphalt. Liquid asphalt products comprise cutback asphalts and emulsions. A number of grades of different viscosities are available, which permit appHcation from ambient temperatures to 150°C. The lower viscosity products are used for dust-laying purposes and as tack coats, prior to laying asphalt surface courses. The heavier grades are used for mix-in-place road mixes. 

The principal use of coal tar ia paviag is as a seal coat to bitumea paviag. Asphalt for paviag comes ia several forms deteroiiaed by the iateaded appHcatioa, ie, straight asphalts called asphalt cements (AC), asphalt emulsioas, cutback asphalts, and road oils. 

The use of cutback asphalts has increased remarkably from 130,000 tons in 1929 (39) to about 2,390,600 tons in 1949 (126). Since these consist of paving asphalt, temporarily liquefied by means of a volatile petroleum solvent to facilitate application and manipulation in construction, control of the rate of hardening by solvent evaporation is necessary. Normally, hardening characteristics have been determined and specified by means of a distillation test, but this procedure has come to be considered inadequate. Martin (68) has suggested the evaporation index, as an improved method, and other methods are under consideration by Committee D-4 of the American Society for Testing Materials. 

Hubbard, P., Cutback Asphalts, Their Characteristics and Use, Tenth Annual Asphalt... 

Pensky-Martens dosed tester-apparatus used in determining the flash point of fuel oils and cutback asphalt, under conditions prescribed by test method ASTM D 93. The test sample is slowly heated in a closed cup, at a specified constant rate, with continual stirring. A small flame is introduced into the cup at specified... 

SBR—see styrene-butadiene rubber. SC asphalt—see cutback asphalt. 

Cutback asphalt asphalt liquefied by the addition of a volatile liquid such as naphtha or kerosene that, after application and on exposure to the atmosphere, evaporates leaving the asphalt. 

State of Pennsylvania regulations for cutback asphalt are given below. Note that a 20% offset indicates that the ratio of actual emission reductions to new emissions is equal to or greater than 1.2 to 1. 

VOC regulations vary from state to state. The following is an excerpt from the regulatory provision provided by the state of Pennsylvania regarding VOC usage in cutback asphalt paving ... 

After April 30, 1980, and before May 1, 1982, no person may cause, allow, or permit the mixing, storage, use, or application of cutback asphalt for paving operations except when ... 

Note that cutback asphalt contains VOCs, but the waterborne mix has no VOCs. The above result indicates that, if this conversion is adopted (using the 75% vaporization adopted in the solution), a new source could operate that emits a maximum of 180,000 Ib/yr. 

Oxidized Asphalt Vacuum-Reduced Asphalt Cutback Asphalt... 

Asphalt is prepared from a distillation residuum, and therefore the need for distillation data is limited. Vacuum distillation data (ASTM D-1160) will be valuable for composition purposes if the asphalt is prepared from an atmospheric residuum. Approximate amounts of volatile constituents can also be determined by test methods developed for other products (ASTM D-20, ASTM D-402, ASTM D-3607, ASTM D-4893) but that are particularly applicable to cutback asphalt. 

The Pensky-Martens closed tester (ASTM D-93, IP 34) and the tag closed tester (ASTM D-56) are normally used for determining the flash point of fuel oil and similar products. The Cleveland open cup method (ASTM D-92) is most commonly used, although the Tag open cup (ASTM D-3143) is applicable to cutback asphalt. As noted above, the flash point of asphalt is an indication of fire hazard and is frequently used to indicate whether asphalt has been contaminated with materials of lower flash point. 

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