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Asphalt cutbacks can be used to treat dense-graded/open-graded aggregate mixes, and for cold-in-place recycling asphalt pavement. These cutbacks typically were formulated with 15% to 20% “cutter” (cut stock). The high amount of cutter is important for treating dense-mix aggregates since the cutter allows the asphalt to disperse and coat the fine particles in the mixture.

Dense-graded mixtures contain aggregate with a good representation of all particles sizes that include fine material and filler. When compacted, a dense-graded mixture has low air voids and is essentially impermeable to water. In contrast, open-graded mixtures contain aggregates that range from large to small, usually containing little or no mineral filler. The void spaces in the compacted open-graded aggregate are relatively large, containing high voids and are permeable to water.

The down side to using asphalt cutbacks is the high amount of cutter used in their formulations. The cutters used vary on the type of cutback and the list includes naphtha, gasoline, kerosene, jet fuel, diesel oil, or fuel oil. Most of the cutter’s used in asphalt cutback were eventually deemed to be harmful for the environment and therefore their use has declined across the United States over the last few years.

Three types of cutbacks are named based on their rate of curing. Medium Curing, CMS-2 and CMS-2s.

Medium Curing asphalt cutbacks (MC) contain a less volatile substances such as kerosene or jet fuel. Upon exposure to the atmosphere, the cutter evaporate, leaving the asphalt remaining to perform the cementing and waterproofing.

Because of this, alternative asphalt emulsions such as CMS-2 and CMS-2s was then substituted for asphalt cutbacks. However, since CMS-2 and CMS-2s has a reduced cutter content in the 8 to 12% range, they are used for open-graded mixes and not used in dense-graded mix.