Rapid-Curing Asphalt

There are two main hazards associated with asphalt Fire and explosion hazards and health hazards associated with skin contact, eye contact, and/or inhalation of fumes and vapors. Most of the fire and explosion hazards associated with asphalt come from the vapors of the solvent mixed into the asphalt, not the asphalt itself The hazard is determined by the flammable or explosive nature of the solvent used and how fast it evaporates. The flash point (FP) of the asphalt and solvent mix will be higher than the FP of the solvent alone. Asphalt is combustible, typically with a FP of 204-288°C (400-550°F).The flash point—and therefore, the fire or explosion hazard— can be determined, in part, by the type of asphalt used.There are three types of cut asphalts. Rapid-curing asphalt (RC) is blended asphalt that has been cut with a low-flash (highly flammable) petroleum solvent. This low-flash solvent quickly evaporates, allowing the RC mixture to rapidly set and harden. Examples of solvents commonly used in RC mixtures include Benzene (FP=-11°C (12°F)), Dioxin (FP=27-32°C (81-90- F)), Naphtha (FP=42°C (107°F)),Toluene (FP=4°C (40°F)), and Xylene (FP=27-32°C (80-90°F)). Medium-curing asphalt (MC) is blended asphalt that has been cut with a solvent with a flash point over 170°F. Slow-curing asphalt (SC) is blended asphalt that has been cut with a low-flash oil having a flash point of over 12 PC (250 F). 

AASHTO M 81.2012. Cutback asphalt (rapid-curing type). Washington, DC American Association of State Highway and Transportation Officials. 

ASTM D 2028/D 2028M. 2010. Standard specification for cutback asphalt (rapid-curing type). West Conshohocken, PA ASTM International. 

The ASTM has published at least 30 specifications for the numerous types of petroleum asphalts and road oils. The most fluid road oils of the RC, MC, or SC grades are designated as No. 0 and the heaviest as No. 5. The rapid curing (RG) grades contain a cutback of kerosene or distillate-like material, whereas the slowest curing (SC) grades may condst of asphalt and the heavy distillates that are naturally associated with asphalt in crude oil. 

Cutback asphalts are mixtures in which hard asphalt has been diluted with a lighter oil to permit application as a liquid without drastic heating. They are classified as rapid, medium, and slow curing, depending on the volatility of the diluent, which governs the rate of evaporation and consequent hardening. 

Low modulus polyester resin mortars have also been developed. They too cure rapidly. They are principally used to fill cable slots cut across asphalt runways and also to fill over PVC cable ducts installed in concrete runways and taxiways (Shaw, 1993b). 

Other uses - Diatomite is used as a nonscratching abrasive in polishes and cleansers, in concrete, mortars, grouts, plasters, and stucco for improved plastic and cured properties, in asphalt products to decrease cracking caused by rapid temperature changes, in catalyst carriers, in chromatographic supports, and as a silica source in the production of synthetic calcium and magnesixun silicates. 

As seen in Fig. 12-16, the unmodified asphalt emulsion was made with a PG64 asphalt and the rutting resistance temperature increased slightly from 66 °C to 68 °C after one month. The sample with Portland cement shows a gradual increase in to 71 °C within three weeks. This increase in is mostly due to stiffening of the asphalt as the phase angle of the residue increases from 82° to 88° at T. The value of showed a rapid increase to 76 °C within the first 3 days of curing when 3 % of the... 

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