## What is the maximum slope for concrete pavers?

For non-vehicular uses such as embankment stabilization, the maximum slope is determined by the angle of repose of the bedding sand, typically around 35 to 38 degrees. For vehicular traffic, the highest slope in use is 18% (about 10 degrees) in a street in Colman, California. Special consideration is given to the drainage of the bedding sand at the bottom of the slope. Contact ICPI for details and guidance. Intermittent concrete header beams are generally not required.

## How are crosswalks designed?

Concrete headers typically used in paver crosswalks perform like bridge abutments. The pavement on aggregate base located on both sides of the header (in and outside the crosswalk) will deform at the junction of flexible pavement and rigid concrete. Why? Because there’s no interlock between the aggregate base and the adjacent concrete. For that reason, most crosswalks should be placed on a concrete base with concrete headers separating the pavers from the adjacent pavement (typically asphalt). The base on the immediate sides of the concrete base should be stabilized with cement to provide additional stiffness and reduce the likelihood of deformation at its junction with the concrete headers. The concrete base under the pavers should have drain holes, typically 25 to 50 mm diameter. They should be at the lowest elevations and covered with geotextile to prevent loss of bedding sand.

## What is the AASHTO structural number of pavers?

Paver and bedding sand are considered as a single layer whose structural number is 0.44 per inch or 1.82 for 80 mm thick pavers and 25 mm of bedding sand. For more information on structural numbers, see the AASHTO guide for design of pavement structures.

## How is base thickness determined?

ICPI follows the design methods for flexible pavement in AASHTO Guide for Design of Pavement Structures. There is a structural equivalency between asphalt and concrete paver/sand layer. ICPI Tech Spec 4 offers design guidance that follows this design procedure.

## How well do interlocking concrete pavements perform over the long term?

One of the best performance examples for streets and sidewalks is found in North Bay, Ontario – 20 Years Later.  Download an ICPI case study titled “North Bay”

## Are pavers effective for “Traffic Calming”?

Yes,  Pavers are very effective in calming traffic and are a solution for cities and HOA’s to calm traffic on streets or intersections that have a problem with speeding vehicles.  Please review the ICPI article titled “Traffic Calming”.  There is a picture of a “paver speed bump/plateau” under “commercial projects”.  This was install in and HOA community that had problems with speeding vehicles.  This installation greatly reduced the speed of vehicles and also adding a facelift to the intersections in terms of aesthetics and beauty.

## What are the Advantages of Pavers vs. Concrete?

In short there are many advantages.  Here are a few.  First,  Pavers are rated at a minumum of 8000 psi and the Belgard pavers are rated at 9000 psi.  This is about 4 times stronger than concrete.  A typical sidewalk is only 2500 psi.  Second,  Pavers have a very low fade rate.  This means that pavers will maintain their color.  Whereas,  concrete will fade and discolor which results in a “bleached” artificial look.  Third,  Pavers are much less of a maintenance issue.  If you have a stained paver section or a root upheaving from below, one can simply remove the pavers and fix the problem below the surface and replace the pavers.. You cannot do this with concrete.  Lastly,  pavers do not crack.  The reason is because pavers have “joints”and are installed in pieces.  On the other hand,  Concrete will always crack and dis-color.

## Is Geo-Textile Fabric needed on commercial projects?

No,  It all depends on the Soils Report and or the engineer on the project.  In many cases we add Geo-Tex as an extra assurance.  Geo-Textile fabric is designed to stop the sub-grade from mixing with the Base.  This will add extra strength and integrity to your pavement/pavers and insure “flatness” for a longer period up to 25 years.  I recommend the use of Geo-Tex on most commercial projects.  By using Geo-Tex you can also reduce the amount of base needed while still maintaining a high strength of 8000 to 9000 psi.