Understanding Full Depth Reclamation in the Construction Process

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Full Depth Reclamation (FDR) has started to gain popularity over the years.

Many construction experts are beginning to see its benefits, and it is becoming more and more popular. There are chances that most road constructions that have been carried out in recent times have been carried out by full-depth reclamation. 

There are a lot of benefits of using this process, even though the process can be stressful. We can understand that nothing good comes easy, but this process, as stressful and tedious as it may seem, will guarantee you quality in the end.

This website has some of the basic principles of road construction you should f

amiliarize yourself with.  

Suppose you want to replace your asphalt pavements that have been worn out by working on the existing roadways. In that case, you are reading the right article because here; we will be discussing what it takes to understand the term “Full-depth reclamation fully.” Before we continue, we need to ask ourselves; 

What Exactly is Full Depth Reclamation?

This can be defined as a recycling method where predetermined amounts of underlying materials and all or parts of an asphalt pavement section are treated and conditioned to produce a standardized base course.

Others may describe it as a technical process of blending and pulverizing all or some layers of asphalt pavements and base materials to get something homogenous for a surface course.

The treatment of these asphalt pavements and underlying materials can be carried out by different additives like asphalt emulsions, chemical agents, calcium chloride, lime, fly ash, and Portland cement. 

These can be added to get a solid and improved base surface. There are usually five main steps implemented in the process, and they are listed below in the correct order;

  • The method of pulverization.
  • An introduction of the additives listed above.
  • The way of shaping the mixed material.
  • The process of compaction.
  • The application of a wearing course or a surface.

There are many advantages to this process, or it would not be widely used as it is today. But what are those advantages?

  • A massive improvement of the surface structure without having to alter its shoulder construction and pavement geometry.
  • The construction process can be used to restore those old pavements to their desired or initial profile while eliminating any wheel ruts, potholes, rough areas, and irregularities.
  • It can also restore the slope and crown of the surface.
  • It can terminate transverse, reflection, alligator, or longitudinal cracking, improving the pavement’s ride quality.
  • It can significantly improve frost susceptibility.
  • Its production cost is relatively low and what may be required is only a chip seal or thin overlay for most of these projects.
  • There is also the advantage of the low cost of engineering.
  • The energy and materials are conserved, and there is little risk of dust, smoke, and fumes contaminating the whole area, making it environmentally friendly and desirable.
  • There is also no much worry about disposal as there is little waste from the process.

 

The full-depth reclamation process is usually recommended for load-associated cracks, deep-rutting, reflection cracks, non-load-associated thermal cracks, and other pavements that have maintenance patches such as skin, spray, deep hot mix, and pothole. If your pavement has a subgrade or base problem, you definitely need FDR.

Explaining the Construction Process

The first step is usually to pulverize, scarify, or rip the existing pavement down to a particular depth in four different processes.

The second step would involve the presence of a central plant or the other three processes, which are called in-place methods. 

The materials from these processes are now processed further to reduce the size, are mixed with newer materials and recycling agents, and become ready for use. The choice between using a central plant and an in-place plant would depend mainly on economics, roadway condition, and equipment availability.

The in-place method is known to be more economical than the method of the central plant. Different mixing methods in this process include flat type, blade, hopper type, and window type. There are also four types of in-place mixing and sizing operations being used. They are the multiple-step sequence, single machine, single-pass equipment train, and the two-step sequence.

 

Recycling Additives 

To improve the recycled base’s mechanical property, some liquid additives need to be added. These additives are mostly asphalt products, and they are recycling agents best suited for cold recycling. Examples of these include cutback asphalts, emulsified recycling agents, and emulsified asphalts (either medium or slow settings). 

Water is also essential because it helps disperse the asphalt modifier during the process of mixing.

Portland cement in small quantities can be added to the emulsified asphalts to stabilize the mix and reduce the time taken to cure. You can check this link https://howmonk.com/how-long-does-asphalt-take-to-dry/ for speeding curing time for asphalt mixes. 

Making the right choice of stabilizing agents depends on various factors, including the existing structure composition, the recycling objective, and the type of subgrade soil. If the base material is mixed with untreated subgrade soil, then additives for soil stabilization need to be added. There are other construction considerations to be made for better results which are;

  • The unbound base course should be free of tree stumps, rocks, large boulders, cobbles, and bones.
  • They should also be certain limitations for gradation with the machines. The specifications are usually set by the relevant bodies in different regions and should not be violated.

 

Take Away

Everyone wants to get the best out of their damaged surfaces, and there may be different ways to achieve that.

But judging by the various benefits, full-depth reclamation might just be the best of all. So instead of losing hope in repairing that spoilt pavement in your community, try something different; try FDR.

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