Full depth recycling
Encyclopedia
Full depth recycling or full depth reclamation (FDR), is a process that rebuilds worn out asphalt
pavements
by recycling the existing roadway.
Old asphalt and base materials are pulverized using a specialized machine called a reclaimer
. On top of the pulverized material, water is added to reach the optimal moisture content for compaction
and then a variety of materials, such as dry cement
, lime
, fly ash
, or asphalt emulsion
are incorporated for stabilization
. A reclaimer is used again to mix all the materials. After shaping and grading, the new base is compacted to produce a strong, durable base for either an asphalt or concrete
surface.
Since this method recycles the materials in situ
, there is no need to haul in aggregate
or haul out old material for disposal
. The vehicle
movements are reduced and there is no need for detours since it can be done under traffic
, making this process more convenient for local residents.
FDR with cement saves money while preserving natural resource
s by using existing materials and conserving virgin aggregate
s. The road performance is improved through better stabilization, building a stronger, low-maintenance road that will last for many years.
With proper engineering and testing protocols the FDR process provides a design life-cycle of 30-years. It is important to note that FDR is a manufacturing process and not an installation. Other pavement materials, such as concrete, asphalt, or aggregate base go through a rigorous quality control program that meets a qualified standard prior to site delivery and contractor installation. The FDR process requires the same level of understanding and product controls during lab testing and field verification to meet long-term performance goals.
Asphalt
Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...
pavements
Pavement (material)
Road surface or pavement is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway. In the past cobblestones and granite setts were extensively used, but these surfaces have mostly been replaced by asphalt or concrete. Such...
by recycling the existing roadway.
Old asphalt and base materials are pulverized using a specialized machine called a reclaimer
Reclaimer
A reclaimer is a large machine used in bulk material handling applications. A reclaimer's function is to recover bulk material such as ores and cereals from a stockpile...
. On top of the pulverized material, water is added to reach the optimal moisture content for compaction
Soil compaction
In Geotechnical engineering, soil compaction is the process in which a stress applied to a soil causes densification as air is displaced from the pores between the soil grains. When stress is applied that causes densification due to water being displaced from between the soil grains then...
and then a variety of materials, such as dry cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
, lime
Lime (mineral)
Lime is a general term for calcium-containing inorganic materials, in which carbonates, oxides and hydroxides predominate. Strictly speaking, lime is calcium oxide or calcium hydroxide. It is also the name for a single mineral of the CaO composition, occurring very rarely...
, fly ash
Fly ash
Fly ash is one of the residues generated in combustion, and comprises the fine particles that rise with the flue gases. Ash which does not rise is termed bottom ash. In an industrial context, fly ash usually refers to ash produced during combustion of coal...
, or asphalt emulsion
Emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible . Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion is used when both the dispersed and the...
are incorporated for stabilization
Stabilizer (chemistry)
In chemistry a stabilizer is a chemical which tends to inhibit the reaction between two or more other chemicals. It can be thought of as the antonym to a catalyst...
. A reclaimer is used again to mix all the materials. After shaping and grading, the new base is compacted to produce a strong, durable base for either an asphalt or concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
surface.
Since this method recycles the materials in situ
In situ
In situ is a Latin phrase which translated literally as 'In position'. It is used in many different contexts.-Aerospace:In the aerospace industry, equipment on board aircraft must be tested in situ, or in place, to confirm everything functions properly as a system. Individually, each piece may...
, there is no need to haul in aggregate
Aggregate (composite)
Aggregate is the component of a composite material that resists compressive stress and provides bulk to the composite material. For efficient filling, aggregate should be much smaller than the finished item, but have a wide variety of sizes...
or haul out old material for disposal
Waste management
Waste management is the collection, transport, processing or disposal,managing and monitoring of waste materials. The term usually relates to materials produced by human activity, and the process is generally undertaken to reduce their effect on health, the environment or aesthetics...
. The vehicle
Vehicle
A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....
movements are reduced and there is no need for detours since it can be done under traffic
Traffic
Traffic on roads may consist of pedestrians, ridden or herded animals, vehicles, streetcars and other conveyances, either singly or together, while using the public way for purposes of travel...
, making this process more convenient for local residents.
FDR with cement saves money while preserving natural resource
Natural resource
Natural resources occur naturally within environments that exist relatively undisturbed by mankind, in a natural form. A natural resource is often characterized by amounts of biodiversity and geodiversity existent in various ecosystems....
s by using existing materials and conserving virgin aggregate
Construction Aggregate
Construction aggregate, or simply "aggregate", is a broad category of coarse particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. Aggregates are the most mined material in the world...
s. The road performance is improved through better stabilization, building a stronger, low-maintenance road that will last for many years.
With proper engineering and testing protocols the FDR process provides a design life-cycle of 30-years. It is important to note that FDR is a manufacturing process and not an installation. Other pavement materials, such as concrete, asphalt, or aggregate base go through a rigorous quality control program that meets a qualified standard prior to site delivery and contractor installation. The FDR process requires the same level of understanding and product controls during lab testing and field verification to meet long-term performance goals.