Research results

Protecting airport pavements
Study of and countermeasures against airport pavement blistering in snowy cold regions

Blistering at an airport in Hokkaido
Blistering at an airport in Hokkaido
Numerous areas of blistering on a runway
Numerous locations of blistering on a runway
Measurement of pavement temperature using infrared thermography.Areas where blistering has occurred have different temperatures than the surrounding pavement.
Measurement of pavement temperature using infrared thermography.
Areas where blistering has occurred have different temperatures than the surrounding pavement.


Cause of the blistering phenomenon
Cause of the blistering phenomenon

A phenomenon known as “blistering” has become a problem at airports in snowy cold regions. This phenomenon, which is thought to be caused by recent climate change, is caused when the sun’s rays raise the temperature of pavement, causing water inside to vaporize. The resulting vapor pressure then lifts the pavement. If blistering is allowed to advance, it can lead to separation. And if such separation happens in many places, the surface of the pavement becomes bumpy and evenness is lost. Moreover, because blistering causes cracks to appear in the pavement, it can interfere with aircraft operation and cause runways to become unusable.

To study countermeasures against blistering that occurs on runways, CERI took core samples from locations where blistering has occurred to examine its causes. This activity produced the following results:
1) Moisture penetrates into cracks that appear in the pavement’s surface.
2) Impermeable layers that do not allow moisture to pass are formed due to the use of asphalts that are comprised of many composites to increase durability.
3) Separation occurs between the asphalt’s composite layers, thereby weakening the pavement.
4) Gaps in the pavement (spaces in the asphalt’s composite layers) collapse under the weight of aircraft.

CERI proposed the following countermeasures as means of controlling blistering. These countermeasures are currently being implemented by the Hokkaido Regional Development Bureau.
1) Review methods for designing asphalt composites and change the types of asphalts used.
2) Propose materials that are less susceptible to interlayer separation to prevent separation between asphalt composite layers.
3) Propose construction methods that reduce the constructed joint grid and pavement compositions that retard blistering.


Although these countermeasures are currently producing positive effects, CERI is conducting follow-up studies and verifications to confirm their long-term serviceability.

(Contact: Road Maintenance Research Team, CERI)

Research on application of soil pavement on actual roads
Pavement that is both people- and environment-friendly


Figure 1: Structural diagram of soil pavement
Photo 1: Conceptual view of soil pavement
Photo 1: Conceptual view of soil pavement

Photo 2: Application of soil pavement on an actual road
Photo 2: Application of soil pavement on an actual road

In recent years, people have had greater need to feel closer to “plants” and “soil” in their daily activities in Japan, and have shown desire to incorporate nature into various parts of their lives. However, conventional pavements have a very artificial image and do not give people a sense of “nature.” Given this, there are expectations that soil pavement with natural texture will be developed as a people- and environment-friendly pavement technology.

Soil pavement materials is made by mixing various binders, such as cement, lime, resin, or asphalt, to natural soil (primarily decomposed granite soil). The pavement is then spread, leveled, and compacted (Figure 1, Photo 1).

The main characteristics of soil pavement are as follows:

It is people-friendly:
- Its moderate softness should make walking on it more comfortable and reduce injuries from falling
- Because of its water-retention ability, it should provide a feeling of coolness by reducing surface temperature during summer.

It is environment-friendly:
- Its soil-like properties and texture harmonize with the surrounding environment.
- Locally produced materials can be utilized.

Because this kind of soil pavement has lower durability than asphalt pavement, it has been used primarily in park paths and pedestrian walks. However, because it offers so many benefits, PWRI is conducting research toward making soil pavement useable on national highway sidewalks. We are also promoting test constructions in various areas in real roads (Photo 2), and are monitoring customer satisfactions as well as long-term durability.



(Contact: Pavement Research Team)