When it comes to rehabilitating worn-out stretches of road, recycling methods hold a lot of appeal. Not only can these processes leave behind pavement that will last longer and hold up better under constant use, but it can be a very cost-effective solution, as well. Without the need for laying down completely fresh asphalt, in-place recycling means less needs to be spent on materials. It’s also more sustainable, as it doesn’t involve trucking in loads of new aggregate or producing new materials.
But even though in-place recycling in general is a better way to rehab roadways compared to traditional methods, contractors still need to pay attention to the type of in-place recycling they use. The two main variants of this process are hot in-place recycling and cold in-place recycling. Each technique uses a different approach, and what works well in one scenario may not be as successful in another. Understanding the differences between them is critical for making the right call.
At Rock Solid Stabilization and Reclamation, Inc., we’re dedicated to helping road and highway contractors get the best results from their projects. That’s why we’ve put together this guide to the differences between hot and cold in-place recycling to serve as a helpful resource.
What is Hot In-Place Recycling?
The hot in-place recycling process begins with the existing road surface being heated with specialized heating units that soften the asphalt. Once it is soft enough, the machine uses a series of teeth to either scarify the surface or grind it up. A chemical agent is added to the surface asphalt to improve its viscosity, after which it is either leveled or replaced depending on whether it was removed or not. In some cases, additional aggregate may be mixed into the recycled material to give it more strength.
What is Cold In-Place Recycling?
Cold in-place asphalt recycling shares many of the same processes used in hot in-place recycling. However, the key difference is that cold in-place recycling does not involve heating the existing surface before removal. With the use of milling machines, the existing surface is pulverized and crushed before it is mixed with recycling agents and chemical additives that create better results. The cold recycled asphalt mixture is placed back onto the roadway with conventional paving machines and compacted to create a level surface. The final step usually is the addition of a thin surface layer to keep the recycled aggregate in place and protect it from moisture.
Key Differences Between the Approaches
Beyond the use of heat to soften the surface level, these two asphalt recycling techniques differ in some important ways. These include:
- Treatment Depth — Cold in-place recycling removes and pulverizes up to the first four inches of the pavement. On the other hand, hot in-place recycling only treats the first one to two inches.
- Curing — With hot in-place recycling, curing time is limited to a few hours as the materials cool back down to ambient temperature. But in cold in-place recycling, the curing period can last weeks as moisture slowly evaporates.
- Added Strength — The cold recycling method adds more strength to the finished road, whereas the hot method only treats surface cracks and defects because its treatment is shallower.
- Traffic Impact — Traffic can be allowed onto a road treated with hot in-place recycling within hours, due to the rapid curing time. However, cold in-place recycling requires traffic to be rerouted for a longer period.
- Environmental Impact — The use of propane-powered heating units means the hot in-place recycling method produces more emissions than the cold in-place technique.
When Should You Use Each Method?
Choosing the right technique for a specific project will depend on numerous factors. For example, cold recycling is not recommended for projects taking place during cold weather or in areas with high humidity because of the impact environmental conditions can have on the curing process. Generally speaking, however, contractors tend to use hot in-place recycling to correct surface-level issues such as cracking. On the other hand, cold in-place recycling is the better choice when it comes to resolving deeper structural problems with the road.
Work With Rock Solid for Complete Expertise
No matter which in-place recycling method works best for your project, you can count on Rock Solid Stabilization & Reclamation, Inc., to support your work. Our expertise with both methods of sustainable road construction means we can help you keep your project on-track and ensure it provides the right level of performance and cost-efficiency. To learn more about what we can do for you with our eco-friendly services, reach out and speak with a member of our team today.