Pavement Maintenance & Rehabilitation Strategies

The Halifax Regional Municipality (municipality) uses a blend of the pavement maintenance and rehabilitation strategies as outlined below. 

To learn about how the municipality determines which roadways should be paved or resurfaced, or which sidewalks are in need of repair, visit the Paving & Repair webpage.

Skin Patching

As the name implies, a skin patch is a thin asphalt lift, generally less than 40 mm, that is placed directly on pavement without any milling (milling is the partial removal of the surface of a paved area). Skin patching is used to temporarily resolve drainage issues, to minimize poor ride quality on uneven areas of the roadway, and for water infiltration. 

Skin patching is also used to build up low areas and improve the profile of the roadway before applying surface treatments, such as an asphalt overlay or micro surfacing.

In some instances, skin patching may be applied manually, however, for larger areas an asphalt spreader may be incorporated (spreader patching). This temporary solution is used to improve the quality of a roadway until proper rehabilitation can be performed.

Pothole Repair

The municipality has two strategies for repairing potholes:

Firstly, a cold patch – a quick and low-cost strategy, where a pre-mix of asphalt is placed in the potholes and compacted. Cold patches are relatively quick repairs, generally performed during winter months and may not be very effective as the asphalt will continue to deteriorate and continue to form potholes. Cold patches are mainly used as a temporary hold until proper repairs can be scheduled.

Secondly, hot mix repair – where pavement around the pothole is saw-cut and then filled with hot-mix asphalt. This type of repair generally addresses the underlying problems, however, the initial cost is higher and the repair process is more involved.

The municipality considers a pothole of 8 cm or greater in depth to be a P1 (Priority 1), and a pothole of 7.9 cm or less in depth to be a P2 (Priority 2). 

P1 classified potholes have a service standard of seven business days on arterial and major collector roads, 14 business days on minor collector roads and 30 business days on local roads.

P2 classified potholes have a 12-month service standard on all street classifications. Report a pothole here.

Crack Sealing

Crack sealing is a low-cost maintenance treatment that involves sealing slight to moderate severity cracks – between three to 20 mm wide – with a modified asphalt-based sealant. This generally results in a slower rate of growth for the sealed crack and reduces the potential for further deterioration of the pavement structure from water seepage or penetration.

Crack sealing is a preventative maintenance technique and can extend the pavement service life. Some studies have shown that the service life of the pavement is extended by two to five years if the crack sealing is applied within the first three to five years following the previous upgrade. 

Cracks should be sealed once they have reached three mm in width. Crack sealing may be used to seal longitudinal, transverse and random pavement cracks. Crack sealing should not be applied on pavements where the cracking has progressed to the point where there are multiple parallel cracks.

Street Planer Patching

Street planer patching is typically used as a maintenance treatment to repair areas of pavement exhibiting localized accelerated distress. Alligator cracking patching of these distressed areas can extend the pavement service life when localized areas of distress are treated.

Street planer patching is a low-cost maintenance treatment that involves the removal of the existing asphalt, in partial or full depth in a relatively small area, and replacement with new asphalt. It is primarily used in areas where there is localized accelerated distress or where the pavement is in need of rehabilitation (i.e. used as a holding strategy). However, proper materials and procedures are required in order for the patching to be effective.

Chip Sealing

A chip seal is constructed by embedding a small aggregate chip – typically eight mm – into the surface of the asphalt emulsion. A double chip seal is when two layers of emulsion and aggregate chips are placed. Chip seals are typically used on lower volume asphalt or gravel roads as a surfacing material. 

Chip seals may also be used on asphalt pavements to seal the surface, improve skid resistance and extend the service life of the pavement for a few years where surficial distresses are becoming severe. If a chip seal is placed over an asphalt pavement, then it can be classified as a rehabilitation treatment.

Micro-Surfacing

Micro-surfacing is a thin surface treatment that is typically used on pavements that are structurally adequate but have minor surface deficiencies. These deficiencies may include the following:

• Raveling
• Low surface friction
• Minor cracking

Micro-surfacing is not an appropriate treatment for a pavement in poor condition, and it will not address structural deficiencies.

Micro-surfacing is a mixture of polymer-modified asphalt emulsion, aggregate, mineral filler, water and mix set additives. Typical thickness is approximately 12 mm, but is dependent on the maximum size of the coarse aggregate. It is also an emulsion-based system with no heating of the materials. The emulsion must properly dry prior to gaining strength. Therefore, caution must to be exercised if this material is to be placed in cool, wet conditions.

Asphalt Overlay

An asphalt overlay produces a new road surface with improved ride quality and skid resistance. An asphalt overlay may be an appropriate treatment to address the following pavement surface distresses:

• Raveling
• Low surface friction
• Minor cracking
• Minor rutting

For an asphalt overlay, the road surface is cleaned and tacked prior to placing the asphalt lift. In areas where curb and gutter are present, a gutter reveal may also be considered. The gutter reveal includes milling to a width of less than one metre adjacent to the curb to maintain the gutter following overlay placement.

An asphalt overlay can be placed directly over the existing road surface. Crack sealing and planer patching are applied to isolated areas of distress prior to the asphalt overlay application. An asphalt overlay will result in a grade raise, as no milling or asphalt removal is completed prior to placing the overlay except where curb and gutter are present.

Mill and Overlay

Mill and overlay consists of the partial removal of existing asphalt concrete and overlaying it with hot mix asphalt. A mill and overlay rehabilitation will extend the service life of pavement, by removing some deteriorated or distressed asphalt from the pavement surface and providing a new surface.

Mill and overlay has the potential for reflective cracking to occur, where cracking extends below the milling depth. Additionally, it will not address thermal cracking or asphalt deterioration below milling level.

Mill and overlay has the same benefits as the asphalt overlay rehabilitation. In addition to treating the same distresses as thin asphalt overlay, mill and overlay may also be an appropriate treatment for the following:

• Minor to moderate cracking
• Minor to moderate rutting and distortion
• Minor to moderate rippling and shoving
• Roads with existing curbs and gutters
• Roads where grade raises cannot be accommodated

Partial Depth Cold in Place (CIP) Recycling

Partial depth cold in place (CIP) recycling is the process of removing the existing asphalt partial depth, typically by milling, and screening the milled materials on site to limit oversize particles. The screened material is then stabilized with either an emulsion or expanded asphalt and placed back on the road using a paver, then compacted. 

Once the stabilized material dries out and attains the optimum moisture content for long-term stability, it is surfaced with one or two lifts of asphalt that prevents water infiltration in the cold in place material.

Full Depth Recycling (FDR)

Full depth recycling (FDR) is the process of pulverizing the existing asphalt concrete full depth and blending with the existing granular material. This is generally followed by two lifts of asphalt concrete. As with CIP, it is considered a “green” paving solution and has the same benefits as CIP recycling.

FDR is more likely to result in a grade raise than CIP, possibly rendering it unsuitable for roadways with existing curb and gutter or where grade raises cannot be accommodated. As such, CIP or mill and overlay may be a more appropriate rehabilitation for roads where existing curb and gutters are present, or where there are grade raise restrictions. In addition, FDR typically requires a 50:50 blend ratio of asphalt and granular materials, although the ratio may vary depending on the quality amount of asphalt to granular materials to be stabilized. Partial depth removal of the asphalt concrete may be required by milling of pavement where a wide range of asphalt depth exists.

Full Depth Recycling (FDR) with Expanded Asphalt (EA)

Full depth recycling (FDR) with expanded asphalt (EA) – FDR w/ EA – is similar to regular FDR (pulverization,) but adds an additional step of stabilizing the blended mix of pulverized asphalt concrete and granular material with an expanded asphalt, followed by a one lift overlay. This provides a higher strength and quality mix than regular FDR.  

As with CIP, FDR with stabilization is considered a “green” paving solution with the same advantages and disadvantages as regular FDR, although the extra step of stabilizing the blended mix of pulverized asphalt concrete and granular material has an added cost. This option is usually used in rural areas or areas without curb and gutter.

FDR w/ EA may be considered where the existing asphalt concrete and granular materials cannot produce a blended mix with sufficient quality and strength. Cement may also be used as an alternative to expanded or foamed asphalt.

Partial Depth Reconstruction

Partial depth reconstruction is the removal of existing asphalt concrete, followed by the placement of a gravel leveling course and resurfacing with two or more lifts of asphalt concrete. A partial depth reconstruction is an appropriate treatment for most distresses. 

Full Reconstruction

Full reconstruction is the removal of asphalt concrete and granular material to a specified depth, and the replacement with new material. The reconstruction will follow a specified design based on the roadway classification, traffic volume and structural composition.