What are the best practices for preparing the existing pavement surface for overlay placement?

1 Assess the condition

The first step is to assess the condition of the existing pavement and identify the type and extent of distresses, such as cracking, spalling, faulting, or joint deterioration. You also need to evaluate the structural capacity and load transfer efficiency of the pavement, using methods such as falling weight deflectometer (FWD) or ground penetrating radar (GPR). Based on the condition assessment, you can determine the appropriate type and thickness of the overlay, as well as the repair and treatment needs of the existing pavement.

2 Repair the distresses

The next step is to repair the distresses that may affect the performance of the overlay or cause reflective cracking. For example, you may need to seal or fill the cracks, patch or replace the spalled or broken slabs, or stabilize the subgrade or base if they are weak or unstable. You should also restore the joint functionality and load transfer by resealing the joints, dowel bar retrofitting, or diamond grinding. The repair methods should be compatible with the overlay material and design.

4 Apply a bond breaker or a bond coat

The fourth step is to apply a bond breaker or a bond coat, depending on whether you want to achieve a bonded or unbonded overlay. A bond breaker is a material that prevents the bond between the overlay and the existing pavement, such as asphalt emulsion, geotextile, or polyethylene sheet. A bond breaker is used when you want to reduce the stress transfer and reflective cracking from the existing pavement to the overlay. A bond coat is a material that enhances the bond between the overlay and the existing pavement, such as cement grout, epoxy, or polymer. A bond coat is used when you want to increase the structural capacity and load transfer efficiency of the overlay.

5 Check the surface profile and levelness

The fifth step is to check the surface profile and levelness of the existing pavement and make any adjustments if needed. You should ensure that the surface is smooth and uniform, without any bumps, dips, or irregularities that may affect the overlay thickness or drainage. You can use methods such as diamond grinding, milling, or leveling course to correct the surface profile and levelness. You should also verify that the surface meets the specified tolerance and smoothness requirements for the overlay.

6 Place the overlay

The final step is to place the overlay according to the design specifications and quality control procedures. You should follow the recommended practices for mixing, transporting, placing, finishing, curing, and jointing of the overlay material, whether it is asphalt, concrete, or other types of materials. You should also monitor the temperature, humidity, and wind conditions during and after the placement, and protect the overlay from any damage or moisture loss.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?