Appendix B: Host Countries and Contacts

While the team was unable to arrange a meeting with Belgian highway authorities, a local contractor did get permission and arranged to take several team members on a spontaneous tour on the first weekend of the study. The trip was of interest since very few quiet concrete surfaces were available for review on the quiet pavement scan. This miniscan was facilitated through Romaine Buys, founder of Belgium-based Robuco, a contracting firm that specializes in PCC surface dressings.

Belgium has a long-standing noise policy (more than 20 years) on pavements.

According to Buys, Belgium began its noise-reduction program using porous pavements, but it has since eliminated the use of all porous asphalt pavements because of problems with clogging, reduced skid resistance, poor durability with raveling in the wheel tracks, and increased winter maintenance activities. The cost for cleaning the porous surfaces is reported to be $0.60 per square meter.

At one site visited, a section of concrete pavement had been diamond ground, resulting in a very smooth ride. Because of time constraints, the team members were not able to get out of the vehicle to determine the effective noise reduction. Concrete was used on a major truck route that carries a 45 percent mix of heavy trucks called “super singles” (which have only one pair of tires per axle, compared to U.S. heavy trucks with two pairs of tires per axle in the back) for an ADT of 30,000 vehicles. The volume of truck traffic caused major rutting. The first quiet pavement was used in the late 1980s. Belgium receives 120 to 150 days of rain per year.

Belgium now uses EAC pavements and SMAs, both optimized for noise. The porous surfaces provided a slightly better noise benefit than the SMA and EAC, but the government believes the latter provides a better blend of durability and noise reduction.

Wirtgen has developed a single paver that can do a two-lift operation, allowing for lower- quality aggregates in the base while using higher quality aggregates in the surface. Highway E40 (Brussels to Oostende) is a CRCP overlay of an asphalt pavement with fine EAC surface. The SMA and EAC had perceptible acoustical differences in favor of the EAC. High frequencies were evident on the SMA, and lower frequencies on the EAC. There were no maintenance concerns with the EAC, and winter maintenance requires about the same salt quantities as SMA.

All asphalt surfaces for noise reduction in Belgium use an SMA-type surface. Most newly constructed high-traffic routes in Belgium are concrete. N285 at Gooik, Belgium, included larger size stone EAC pavement (32-mm maximum size) and was louder than the E40 site. The large stones most likely produce the increased noise. There were no maintenance concerns with this 17-year-old pavement.

A noise test section is in place on N255 in Herne, Belgium. A report published in October 1999 by the Ministry of the Flemish Community and written by Chris Caestecker of the Flemish Brabant Roads and Traffic Division said, “Fine concrete pavement offers positive acoustical results not only in relation to other pavements but also in relation to bituminous pavements. After 3 years, fine concrete pavement still preserves its acoustical characteristics. This durable cement concrete pavement can certainly be qualified as noiseless pavement and can be compared with noiseless bituminous pavements. . . The rolling noise produced on fine concrete pavements remains almost constant. As a result, this kind of pavement continues to score well.”

A section of 35-year-old pavement on A12 at Miese, considered the first EAC section in Belgium, is now very rough and loud. The section was mechanically removed concrete surface with a broom behind the paver. Durability and low maintenance are the major features of this section.

Test sections of E40 from Brussels to Liege experimented with diamond grinding to optimize for noise. The contractor used a wider-than-normal blade spacing to reduce noise. The diamond-ground pavement was perceptively smoother and quieter than the adjacent section of EAC.