TM 5-822-10/AFM 88-6, Chap. 6
CHAPTER 1
INTRODUCTION
1-1.
Purpose and scope.
This manual contains guidance for preparing plans and specifications and for ensuring the quality of recycled
bituminous and portland cement concrete. In addition, this manual provides useful information to design engineers,
laboratory personnel, and inspectors concerning the mix design, plant production, and laydown of recycled pavement
mixtures. The emphasis is on airfield pavements; however, the concepts also apply to other pavements.
1-2.
References.
Appendix A contains a list of references used in this document.
1-3.
Recycling pavement development.
Recycling pavement materials has proved to be a feasible process to rehabilitate worn-out pavements. Since recycled
pavements will not always be cost-effective, recycling should be considered when repairing or rehabilitating existing
pavements. The use of recycled materials in pavement maintenance and rehabilitation has increased for the following
reasons:
a. Environment. Prior to the inception of recycling techniques, the reconstruction of old pavements often consisted
of removing, stockpiling, or disposing of old pavement materials. Recycling of these pavement materials uses an
inexpensive, available material and eliminates the disposal problem.
b. Material cost. In the last several decades the public and Government have recognized that there is not an
unlimited supply of natural materials. The amount of asphalt and high-quality aggregate available for construction is
limited. This fact, along with an inflated economy, has caused a substantial increase in the cost of pavement materials and
thus encouraged the use of recycle materials. The rising cost of fuel and equipment required to haul the asphalt and
aggregate to job sites has encouraged recycling, especially as the haul distances become longer.
c. Technology and equipment. The increased interest in recycling pavements has brought about the development
of technology and equipment for recycling that results in an overall reduction in cost when recycled materials are used.
There still exist problems that are peculiar to recycling; however, the number and the complexity of these problems have
been reduced significantly in recent years.
1-4.
Bituminous pavement recycling.
Bituminous pavement recycling methods can be divided into the following three categories: surface recycling, cold-mix
recycling, and hot-mix recycling. Table 1-1 lists the advantages and disadvantages of the various methods. Many types
of distresses can be corrected by one of the three pavement recycling methods identified in figure 1-1.
a. Surface recycling. Surface recycling, heater-planing-scarifying, cold milling, and rejuvenating are methods of
surface recycling that are used to increase skid resistance, decrease permeability to air and water, and improve properties
of the asphalt binder. Depending on the process used, surface recycling may modify the top to inch of pavement.
However, surface recycling does not increase the strength of the pavement. The cost to scarify and rejuvenate pavement
is approximately the same as the cost of an additional 1 inch of overlay, but the benefits of the additional 1 inch of overlay
usually exceed the benefits obtained from the scarification and rejuvenation.
b. Cold-mix recycling. Cold-mix recycling is a process which reclaims most or all of the existing bituminous
pavement by breaking it to a maximum particle size of 1 to 1 inches, mixing it with virgin materials, if needed, and
reusing the mixture as a pavement material. Cold recycling material can be used to surface secondary roads, if a seal coat
is applied, and as a base course for high-quality pavements.
c. Hot-mix recycling. Hot-mix recycling is a process which involves removing the existing asphalt concrete,
crushing it if necessary, and mixing it in a hot-mix plant with new aggregate, asphalt, and recycling agent, when required.
The hot-mix recycled asphalt concrete can be designed for use in all types of pavements. Crushed portland cement concrete
has also been used as aggregate for hot recycled mixtures.
1-5.
Portland cement concrete recycling.
Portland cement concrete recycling involves reclaiming existing portland cement concrete pavements and structures
by crushing them to produce construction aggregate for reuse. Table 1-1 lists the advantages and disadvan-
1-1
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