Asphalt Recycling
Student’s Name
Institutional Affiliation
Asphalt Recycling
Of the recent past, heavy traffic and bad weather have been the leading causes of road damage. The fatigue of material propagates surface cracking as a result of heavy traffic. This material fatigue is due to the shear loadings for the vehicle tire. Another cause of surface cracking is the aging of bituminous materials. On the other hand, bad weather causes thermal cracking caused by tensile stresses. The changes in temperature are the cause of these stresses. These cracking roads have asphalt concrete content.
In a bid to rehabilitate the roads, governments spend a lot of money depending on the damage characteristics of the roads. Having it that these roads are made of asphalt concrete, there are several ways of recycling the asphalt pavements. This includes; cold in-place recycling (CIPR), full depth reclamation (FDR), hot in-place recycling (HIPR), cold planning, and hot recycling (Warren et al., 2002).
Cold in-place recycling (CIPR), involves rehabilitation techniques where pavement materials are reused in situ. For this technique, the asphalt materials are processed to a depth of 2-4 inches. No heat is applied in this process. The cold materials are mixed just as they are (Yongjoo & Lee, 2006). After pulverizing the pavement, an emulsified recycling agent with the reclaimed material is mixed, spread, and compacted hence producing a base course. On this bases, a new asphalt surface is required. For high traffic pavements, a modified emulsion surface is recommended. On the other hand, for low traffic pavements, standard asphalt emulsion may be used to treat the surface.
Just like the Cold in-place recycling, the full depth reclamation (FDR) is also in situ. This is used in solving the problem of continually deteriorating roads. In this process, the existing asphalt pavement is ground up together with the aggregate base course. These two are then mixed are replaced on the subgrade soil. To produce a base course, an asphalt emulsion is used (Santucci, 2007). FDR is a construction method applied in correcting base problems.
Hot in-place recycling involves pavement processing to a depth of a half to three-quarter inches. While on-site, the asphalt pavement is heated to soften it. It is then scarified to a thickness between ½ to ¾ inches. As a requirement, the usually applied asphalt emulsion is thus added. The hot in-place recycling (HIPR) process is further divided into three. These three methods are; repaving, heater-scarification, and remixing (Gardiner, 2011).
Cold planning involves the removal of a specific depth of asphalt pavement, and then the surface is restored to the desired grade. All surface imperfections such as humps and ruts are thus eliminated. One to two inches of the pavement is usually removed. In this process, a self-propelled rotary drum cold planing machine is used to mill/ remove the pavement. Trucks are then used to transfer the reclaimed asphalt pavement (RAP) and stock it for either cold or hot recycling.
In hot recycling, a hot mix asphalt (HMA) is produced by combining asphalt cement /recycling agent with reclaimed asphalt pavement (RAP) and new aggregates. Drum plants are used here to produce a recycled mix. Consequently, batch type hot mix plants are also used. Cold planning provides most of the reclaimed asphalt pavement that is used in this process. Generally, there are several factors that influence the use of reclaimed asphalt pavement. Of the elements, the two main ones are environmental benefits and economic savings.
References.
Chesner, W. H., Collins, R. J., MacKay, M. H., & Emery, J. (2002). User guidelines for waste and by-product materials in pavement construction (No. FHWA-RD-97-148, Guideline Manual, Rept No. 480017). Recycled Materials Resource Center.
Kim, Y., & Lee, H. D. (2006). Development of mix design procedure for cold in-place recycling with foamed asphalt. Journal of Materials in Civil Engineering, 18(1), 116-124.
Stroup-Gardiner, M. (2011). Recycling and reclamation of asphalt pavements using in-place methods (No. Project 20-05 (Topic 40-13)).
Santucci, L. (2007). Recycling asphalt pavements: A strategy revisited. Tech Topics, (8).