How are asphalt emulsions used in recycling applications?

Cold in-place recycling (CIR), hot in-place recycling (HIR) and full depth reclamation (FDR) are three of the most common applications that use asphalt emulsion as the binder that mixes with pulverized and reclaimed pavement to create a new level base course.

What is cold in-place recycling?

Cold in-place recycling is a treatment used to rejuvenate flexible hot mix asphalt roads. Initially, a milling machine processes 2 to 6 inches of the existing surface layer. The milled material is further crushed and compacted into the desired size for the project during the gradation control process. Virgin aggregate can be added during this process if necessary. Afterwards, a binding additive is mixed with the graded material, and the resulting mixture is placed over the remaining pavement structure. The recycled mix is then compacted to the specified density.

What is hot in-place recycling?

Hot in-place recycling is a rehabilitation treatment for deteriorated bituminous pavements. HIR is a continuous process that can be completed in a single pass. It works by heating the top 1 to 2 inches of existing asphalt until it is pliable, scarifying the pavement, removing the material and supplementing it with a small amount of new hot mix or binder, then placing the mix over the remaining roadway structure. The recycled material is then compacted using traditional roller operations.

What is full depth reclamation?

By addressing the entire pavement section, full depth reclamation is able to correct delinquent cross sections, increase the load-bearing strength of the base, and utilize 100% of the existing materials. Substantial savings can be realized while meeting environmental goals. Equipment for the process includes traveling hammer-mills, crushing units, stabilizers, or a combination of these types of machines. Critical to the success of this process is the preliminary testing to establish design criteria for gradation, residual asphalt content, and the possible use of additives. This reconstruction technique requires a wearing surface of a thickness to be determined by an analysis of traffic data.

What is the difference between CIR/HIR and FDR?

Cold in-place recycling pulverizes the existing pavement to a depth of 2 to 6 inches. Hot in-place recycling processes the top 1 to 2 inches of the surface. Full depth reclamation pulverizes to a greater depth than either of these other treatments, reaching below the existing pavement into the underlying material to produce a stabilized base course.

What are the advantages of recycling?

Energy is conserved as the construction is completed in-place/on-grade, and little or no fuel is required forheating. Reflective cracking can be reduced with CIR/HIR and eliminated by FDR. Additionally, the pavement crown and cross slope can be restored, and loss of curb height is reduced or eliminated.

Are there benefits to using asphalt emulsion?

Yes. In fact, there are significant benefits when using asphalt emulsion as the stabilizer, including a faster return to traffic, and the creation of a crack-resistant flexible base, which can help reduce highway maintenance costs. Specifically for FDR, further benefits include less water use and the creation of much less dust. This results in significant environmental impact reduction and greatly increases project safety issues relating to construction workers and the traveling public.