Spring Road Failures

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, has passed over the weak spot in the road.

Vulnerable Highways

Some paved highways are more vulnerable to potholes and surface breaks than others. Typically, aged and cracked roads will allow more water into the subgrade. Roads with lower structural capacity and grades stay saturated longer until 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.

Highway Repairs

When surface breaks occur in the spring, crews place red diamonds signs at 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 until permanent repairs can be completed.

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.
• 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 unblocking culverts from debris and ice 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 failures.

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-gravelling.
• Dust Treatment – Applying different dust suppressant products on a gravel surfaced road to control dust.
• Hand Patching – Repair of small potholes or depressions by shovelling cold mix, hot mix or base material and compacting with hand packer or roller.
• Sub-grade Stabilization – Clay, silt or gravel materials are used to steady sandy subgrades or cover rough road surfaces on gravel highways.
• Sandvik Blading – Removes or recycles the black coal 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.