Road Buckling in Heat: Understanding and Preventing Pavement Failure During Extreme Temperatures

The heat wave had been building for days, with temperatures soaring past 100 degrees Fahrenheit across the Pacific Northwest. On a four-lane highway outside Portland, drivers suddenly encountered a hazard that appeared without warning: a section of concrete pavement had buckled, heaving upward nearly twelve inches in the space of a few feet. A motorcyclist who hit the hump at highway speed was thrown from his bike. Multiple cars suffered tire and suspension damage. The road was closed for hours while crews worked to grind down the buckle and restore traffic. As climate change makes extreme heat events more frequent and intense, heat-related road buckling is becoming an increasingly serious infrastructure challenge.

Road buckling, also known as pavement blowup, occurs when the pavement expands from heat and has no room to expand further, causing it to buckle upward. The phenomenon affects both concrete and asphalt pavements, though the mechanisms differ. Understanding why roads buckle and how to prevent it is essential for transportation engineers facing a warming climate.

The Physics of Pavement Buckling

Thermal Expansion

All materials expand when heated and contract when cooled. Concrete and asphalt have coefficients of thermal expansion that cause them to lengthen approximately 0.00001 to 0.00002 feet per foot for each degree Fahrenheit of temperature increase. A thousand-foot section of pavement that heats up by 50 degrees Fahrenheit will try to expand by six to twelve inches — more than the expansion joints can accommodate.

The bridge earthquake response design principles for accommodating movement share similarities with pavement expansion management — both require careful consideration of the forces generated by constrained thermal movement.

Compression and Buckling

When pavement cannot expand because it is constrained by adjacent sections, friction with the subgrade, or fixed structures, the thermal expansion forces are converted into compressive stress. When the compressive stress exceeds the pavement’s buckling strength, the pavement suddenly buckles upward, creating the characteristic hump or blowup.

Types of Heat-Related Pavement Failure

Concrete Blowups

Concrete pavement blowups occur when concrete slabs expand against each other, typically at joints that have become filled with incompressible material such as debris, sand, or vegetation. The expansion forces cause the slabs to lift at the joint, creating a sudden step or hump.

Asphalt Shoving

Asphalt pavement does not buckle in the same dramatic manner as concrete, but it can shove, rut, and deform under extreme heat. Asphalt softens at high temperatures, and traffic loads can push the softened pavement into waves and ruts. The pipeline leakage prevention techniques for monitoring material degradation under thermal stress are conceptually related to pavement performance monitoring.

Reflective Cracking

Reflective cracking occurs when cracks in the underlying pavement structure propagate through an asphalt overlay. Thermal expansion and contraction of the underlying layer causes the overlay to crack at the same locations, allowing water infiltration that accelerates deterioration.

Factors That Increase Buckling Risk

Joint Maintenance

The most common cause of concrete pavement blowups is joints that have become filled with incompressible material. When joint sealant fails or is not maintained, debris fills the joint space. When the pavement expands, it cannot move into the joint because the debris blocks the expansion space.

Age and Deterioration

Older pavements are more susceptible to buckling because materials have degraded over time. ASR in concrete, oxidation in asphalt, and cumulative fatigue damage all reduce the pavement’s ability to withstand thermal and traffic loads.

Poor Construction

Pavements constructed during cool weather without proper joint spacing or with joints that are not cut to the correct depth are at increased risk of buckling. Improper curing of concrete and inadequate compaction of asphalt also contribute to heat-related failures.

Prevention and Mitigation

Proper Joint Design

Adequate joint spacing, joint width, and joint sealant are essential for preventing concrete pavement blowups. Joints must be cut to sufficient depth to create a plane of weakness that controls cracking, and they must be wide enough to accommodate thermal expansion.

Joint Maintenance

Regular joint cleaning and resealing prevents debris accumulation that blocks expansion. Many transportation agencies have joint maintenance programs that clean and seal joints on a regular cycle.

Stress Relief Joints

In areas with extreme temperature ranges, stress relief joints — wider joints that provide additional expansion space — can be installed at regular intervals. These joints accommodate the cumulative expansion of long pavement sections.

Reflective Pavements

Light-colored pavements and reflective surface treatments reduce pavement temperature by reflecting solar radiation. Cool pavement technologies can reduce surface temperatures by 10 to 20 degrees Fahrenheit, significantly reducing thermal expansion forces.

FAQ

How hot does pavement need to get to buckle?

Pavement buckling typically occurs when air temperatures exceed 100 degrees Fahrenheit, but the actual pavement temperature is significantly higher — often 140 to 160 degrees Fahrenheit. The specific triggering temperature depends on the pavement design, materials, and condition.

Is road buckling becoming more common?

Yes. As climate change increases the frequency and intensity of extreme heat events, heat-related pavement failures are occurring more frequently in regions that historically did not experience such high temperatures.

Can road buckling be predicted?

Transportation agencies can predict buckling risk based on pavement age, condition, joint maintenance history, and forecast temperatures. When high-risk conditions are identified, agencies may implement preventive measures such as watering the pavement to reduce temperature.

How are buckled roads repaired?

Emergency repairs involve grinding down the buckled section to restore a level surface. Permanent repair requires removing and replacing the damaged pavement, restoring joints, and ensuring that adequate expansion space is provided.