Interlocking concrete pavers are increasingly being used to highlight sidewalks, intersections and crosswalks, as well as nature trails and park promenades. The extensive replacement of ceramic tiles, asphaltic pavements and other surface materials began about a decade ago and continues today.

"The availability of different shapes and colors for concrete paving stones make them a flexible design tool, so they can be used to enhance neighborhood identities and distinctiveness," explains Ellen Baldo, RLA, of Designs Etc. Baldo has designed a number of recent Wilmington projects using interlocking concrete pavers for their beauty and durability, including nine blocks of 13th Street, several blocks of North market Street, and pedestrian trails in the Brandywine section of town.

"Also, several of the locations crossed national historic districts," Baldo remarks. "We were able to work with the paver manufacturer to create a custom blend of reds-- now called Wilmington Blend-- that matches the previously used bricks that are still visible on many of the old houses.

"When you stand back from them, you can't see the difference. Concrete pavers also drain better, move less, are easier to install than brick or other pavers, and are consistent in size," Baldo explains.

A design review commission was established by Wilmington municipal authorities and concerned citizens to monitor building demolition, alterations and new construction within the designated districts.

Guidelines were created for sidewalk re-paving, visually pleasing signage, one-way traffic patterns, the coordinated redesign of store fronts, streetlighting and other elements. Use of interlocking concrete pavements was accepted as a unifying force in many of the designs.

Engineering studies in the United States and worldwide show that pavers and bedding sand are at least as equivalent structurally to the same thickness of asphalt. However, in hot weather, the strength of asphalt diminishes as it softens, making it more prone to rutting.

Interlocking concrete pavers, on the other hand, are not subject to softening and rutting in hot weather, even when under constant loading from trucks and buses.

Beginning in 1986, sections of Market Street Mall, in downtown Wilmington, were paved with colored, richly textured concrete paving stones. The intricate and beautifully designed paving patterns used on the 700 and 800 blocks of the Mall won a national industry award for excellence in creating variation and harmony within a small, confined area. These interlocking pavers featured a multi-colored blend, custom created by randomly mixing batches of terra-cotta and charcoal-colored concrete during the production process.

According to the Sterling, VA-based Interlocking Concrete Pavement Institute, concrete pavers should meet standard ASTM C 936 established by the American Society for Testing and Materials. This rigorous standard requires a minimum compressive strength of 8,000 psi (pounds per square inch), compared to the usual compressive strength of 3,000 psi to 4,000 psi for pavement-quality poured concrete.

The interlocking pavers have a water absorption rate of less than 5 percent compared with 9 percent for poured concrete. They resist heaving from freeze-thaw, don't deform in heat, are slip- and skid-resistant and can withstand heavy loads. Made from all-natural materials, paver systems can provide increased water infiltration to decrease ponding and surface water run-off.

Selecting the most appropriate alternative for a particular pavement requires consideration of a number of factors, including both initial costs and life-cycle costs. Although the use of premium materials such as concrete pavers may increase the initial capital cost of construction, the performance benefits over the life span of the pavement can result insignificant savings over conventional pavement alternatives. lasn