Asphalt-Rubber

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. 

Outdoor lead dust was found to be a more potent contaminant of children s hands than indoor lead dust at day care centers in New Orleans boys, in general, had higher hand lead levels than girls. The conclusions were based on lead analysis of hand wipe samples taken before and after children played outdoors at four different day care centers (a private inner-city site, a private outer-city site, a public inner-city site, and a public outer-city site). The private inner-city site had a severely contaminated outdoor play area with measured soil lead concentrations ranging from 287 to 1,878 mg/kg. The outdoor play area at the public inner-city site, where children exhibited the lowest hand lead measurements of any site in the study, had been completely paved over with concrete or rubberized asphalt and had well-maintained equipment (Viverette et al. 1996). 

If possible, make the construction forgiving to later appearing cracks in the concrete. If a slab is covered with a permanently elastic material, like rubberized asphalt or bitumen, future cracks in the concrete will not automatically result in a route of entry for soil radon. 

Polymeric Materials. The single-ply membranes are made from a wide variety of polymers. The following is a brief description of those polymers and their characteristics. There are three thermosetting-type elastomeric membranes as of this writing (1996) neoprene, CSPE, and EPDM. Neoprene is still used where oil resistance is needed. For instance, Hydrotech uses neoprene flashings, the base of which is hot-set in rubberized asphalt (see Elastot rs, synthetic-polychloroprene). 

Barriers to the increased usage of rubber in asphalt pavements are both economic and noneconomic in nature. The cost of installing roads of rubberized asphalt is greater than conventional asphalt, which is an economic barrier. On the other hand, several studies show that the total life cycle cost of rubberized asphalt is... 

The two forms of rubberized asphalt that have been tested the longest, asphalt-rubber and PlusRide , are patented. The required royalty fees increase the cost of these products. Although, initially, patents may have stimulated the growth of these products, they now appear to represent an economic barrier to increased scrap tire usage by these technologies. The patent for asphalt-rubber expires in 1991. After that more companies are expected to become involved, resulting in lower costs. Non-patented rubberized asphalt roadways are also being tested. 

There is a need to continue to perform research on methods of recycling tires, such as the use of crumb rubber in rubber products and plastics. Existing research on rubberized asphalt should be summarized, and a decision made regarding its feasibility for more widespread use, or if there are still technical or economic questions, determining exactly what additional research is needed to answer these questions, and then perform this research. States and Federal government, and environmental and transportation agencies, should coordinate research efforts so that fewer, more comprehensive research projects (particularly related to rubberized asphalt) can be performed. 

One of the concerns regarding both RUMAC and A-R highways is their recyclability. Old asphalt is typically heated and mixed with fresh material to create new asphalt. There is concern that when the rubber modified asphalt is reheated, it may catch fire or produce noxious smoke. The industry claims that this will not occur, and that recycling of rubberized asphalt has been successfully done in Sweden. However, many state highway departments are not yet convinced. 

The increased pavement life can be attributed to higher viscosity and impermeability of rubberized asphalt. These properties have decreased thermal cracking, potholing, deformation, and reflective cracking in most states in which tests were performed. Studies by the Alaska Department of Transportation showed decreased stopping distances as a result of rubberized asphalt being more flexible and preventing ice formation (37). 

Study Ratio of Rubberized Asphalt to Standard Costs Predictions of Life Extension... 

No national specifications for rubberized asphalt Patents can limit competition... 

Both technologies are commonly used in Europe, but rubberized asphalt usage in most of the United States is still in the testing stage. 

The economic barrier to the use of rubber in pavements is the high initial cost to the highway departments. It is difficult to obtain good data on the capital investment necessary to convert an asphalt operation to add rubber. But the consensus from the ARPG and several other sources is that the installation of rubber asphalt pavements will cost about 2 times as much as standard asphalt. Although the test results for asphalt pavements containing rubber are not yet complete, in many cases a factor of 2 or more in pavement lifetime is achieved. Therefore, if transportation departments evaluate costs over the life of the roads, the overall costs may be the same or less for rubber asphalt. The ARPG claims that rubberized asphalt roads cost less on a life-cycle basis. 

Some state government officials have expressed concern that, because the two most proven forms of rubberized asphalt are patented, prices for this material may be higher than they would be if the material were not patented. It is estimated that the royalty adds 35 percent to the cost of asphalt-rubber and 27 percent to Plus Ride The patent for asphalt-rubber expires in 1991. After that time ARPG expects more companies to become involved. The TAK process is not patented, but also has not been tested as long as the patented types of rubberized asphalt. 

Procurement guidelines for materials such as rubberized asphalt, products made from reprocessed rubber, and rubber railroad crossings are all potential means of helping to encourage these uses of scrap tires. 

Areas which appear ripe for further research include (1) research on the use of crumb rubber in plastic and rubber products, (2) research on environmental emissions from tire incineration, and (3) research on rubberized asphalt. 

While this book was in its final preparation stage, two additional types of adhered sheet linings for chemical exposures have come to our attention. One is a sheet with, as the exposed face, a Tedlar(sf film adhered to a layer of rubber-asphalt blend. The sheet is applied with rollers to a substrate surface that has been coated with an adhesive primer. Sheet edges are butted with an adhesive lap strip of Tedlar applied over the joint to protect it. This is a proprietary product presently available from only one source, which will supply particulars of the application procedure and chemical resistance tables upon request. 

Disposal and recycling of organic (polymeric) construction materials using plastics, rubber, asphalt, wood and paper. 

Decalin. [DuPont] Decahydronaph-thalene solvent and stabilizer far shoe creams, flotx waxes, paints, lacquers, resins, rubbers, asphalt... 

Rubber tires filler, paviors, mats (skid resistant), athletic tracks, dock systems, playground cover, slope stabilization, road fill, rubberized asphalt and concrete. 

The modified binder is commonly referred to as asphalt-rubber Asphalt-rubber binders are used primarily in hot mix asphalt paving, but are also used in seal coat applications as a stress absorbing membrane (SAM), a stress absorbing membrane interlayer (SAMI), or as a membrane sealant without any aggregate... 

Two processes are used in preparing the rubberized asphalt dry and wet. In both processes, the GRT particle size ranges from 6.35 mm to 40 mesh. In the wet process, asphalt is blended with GRT particles and then added into the hot mix. In the dry process, GRT is mixed with aggregate and the resulting mix is blended with asphalt. 

Uses Chemical intermediate solvent for greases, fats, oils, waxes, rubber, asphalt, coatings, phannaceuticals heat-transfer fluid substitute... 

Diphenyl sulfone Styrene diluent, rubber Asphalt Pyrophyllite diluent, slate pencil Pyrophyllite... 

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. 

---