The National Concrete Pavement Technology Center found Portland cement pervious concrete overlays have great potential to reduce roadway noise, improve splash and spray, and improve friction as a surface wearing course.
The group's study, An Integrated Study of Pervious Concrete Mixture Design for Wearing Course Applications, was sponsored by the Federal Highway Administration (FHWA) and the Ready Mixed Concrete Research & Education Foundation and consisted of two parts. First, researchers conducted fundamental material property investigations and a constructability study. They then designed and constructed a pervious concrete overlay on the MnROAD Low Volume Road, a cold region pavement test track near Albertville, Minn. This second part of the project involved full-scale construction and long-term testing to discover successes, failures, and lessons learned.
The MnROAD overlay represented the first wet-on-dry pervious concrete overlay. It has been in place for more than three years. The overlay has been a success and is performing remarkably well with regard to its surface durability, hydraulic performance, and low noise.
Long-term testing of the MnROAD overlay found that, to ensure good performance during the construction and service periods, a pervious concrete mixture for a pavement overlay must possess the following properties:
- High workability for ease of placement
- Uniform porosity or void structure throughout the pavement for noise reduction
- Adequate bond with underlying pavement and proper strength for traffic load
- Sufficient resistance to wearing, aggregate polishing, and freeze-thaw damage
A systematic study using a large number of mix designs was conducted to investigate effects of a wide variety of concrete materials and mixture proportions on pervious concrete performance, including concrete workability, compaction density, strength, freeze-thaw durability, and overlay bond strength. The results indicate that pervious concrete mixtures can be designed to be highly workable, sufficiently strong, permeable, and durable under freeze-thaw conditions, making them suitable for pavement overlays. Such overlays will not only function well structurally for carrying designed traffic loads but also perform well environmentally for noise reduction, skid resistance, and splash and spray reduction.
The results of the studies conducted for this project show that a pervious concrete overlay can be designed, constructed, operated, and maintained. A pervious concrete overlay has several inherent advantages, including reduced splash and spray and reduced hydroplaning potential, as well as being a very quiet pavement.
The good performance of this overlay in a particularly harsh freeze-thaw climate in Minnesota shows pervious concrete is durable and can be successfully used in freeze-thaw climates with truck traffic and heavy snow plowing.
The study may be accessed from the RMC Research & Education Foundation website and from the Iowa State University Institute for Transportation website. It is also available as a hard copy.