Potholes form when the surface of the road collapses into the subsurface.
This is caused because of Saskatchewan’s cold, harsh climate. When water freezes, it expands and causes the pavement to bend or crack, weakening the road. When ice melts, the pavement contracts leaving holes in the subsurface where water can get in. If water freezes and thaws over and over, the road can become very weak.
Sometimes potholes do not appear until the weight of traffic, especially loaded commercial trucks, have passed over the weak spot in the road.
Some paved highways are more vulnerable to potholes and break ups than others. Typically, aged and cracked roads will allow more water into the sub-grade. Roads that aren’t built as highway (lower grades) have lower grades will stay saturated longer until melt water has dried up and the road has had a chance to dry out.
Thin Membrane Surface (TMS) roads can be very sensitive to spring break-up. These highways do not have a “granular structure” under the surface. It is not a structural asphalt concrete. The TMS is designed as a dust free surface and not designed to handle heavy traffic. If loaded commercial trucks travel over TMS roads with a saturated subgrade, surface breaks are expected. The more trucks that travel the road when the subsurface is weak, the more damage will occur.
Typically, an above average spring runoff and high water tables can make conditions worse. Dry weather helps stabilize the road beds and allows crews to make repairs.
When surface breaks occur in the spring, crews flag the hazard and assess the kind of repair that is needed. The crew may apply gravel material or blade on some asphalt patching material as a temporary repair.
Small potholes will be filled with patching material. Long-term repairs may involve digging out the road and backfilling with a well-drained sand or gravel that will support the pavement and keep water from building up.
A layer of asphalt concrete or a granular seal coat will be placed on top of the backfill to seal off the road.
Selecting the type of repair and whether it will be a permanent or temporary fix depends on a few different factors:
- Highway classification,
- Surface type,
- Overall condition of the road, and
- Age of the road.
Roads scheduled for major rehabilitation work will not receive long term-repairs.
Timing of Repairs
Timing depends on how much repair work is scheduled. Crews may be busy unclogging culverts to ensure proper drainage during the spring. If a long term repair is needed then they may wait until the area dries up before starting the work.
Crews may prioritize their work depending on the type of highway and severity of the break up.
Definitions for Maintenance Treatments
- Spot Seal - Applying liquid asphalt and graded crushed rock on roads to prevent moisture from entering the subgrade and prevent further deterioration. Strip sealing is done in ruts to prevent the moisture from accumulating.
- Deep Patch - Repair by digging into the sub-grade by machine and backfilling with well-drained sand or gravel.
- Machine Patching - The process of spreading base or asphalt mix with a grader or other machine to repair a failed area, wheel ruts, depressions, bumps, etc.
- Crack Sealing - The sealing of cracks on a pavement with liquid asphalt and sand or rubber asphalt.
- Gravel Blading - The reshaping of the road surface and spreading of crushed rock on gravel surfaced highways by blading with a grader.
- Spot Gravel - Defects on unpaved roads can be fixed by spot re-graveling.
- Dust Treatment - Applying of different compounds such as a wood pulp product or asphalt to a gravel surface road to control dust.
- Hand Patching - Hand repair of small potholes or depressions using cold mix, hot mix or base and compacting.
- Sub-grade Stabilization - Clay, silt or gravel materials are used to steady sandy subgrades or cover rough road surfaces on gravel highways.
- Sandvic Blading - Removes or recycles the black coal (bituminous) material from the surface, which is done to improve the ride by smoothing out the ruts on TMS surfaces.
- Micro-surfacing - Mixed crushed gravel, liquid asphalt, mineral filler, water and other additives on the road surface produce what is called a micro-surfacing, which can be used for both preventative and corrective maintenance. It helps restore skid resistance; eliminates minor surface bumps, levels wheel ruts which prevents hydroplaning and prevents further surface deterioration from weather and traffic. Micro-surfacing restores pavement to a uniform black color.
- Seal Coating - Hot liquid asphalt and crushed gravel on the road surface. Seal coating provides a waterproof surface, non-skid surface, reduces deterioration and cracking and prolongs pavement life.