Used in urban renewal projects, in pedestrian plazas and malls, courtyards, sidewalks, crosswalks and even streets, colored concrete paving blocks add contour, color and charm. The blocks are available in a spectrum of earth tones reds, browns, golds, and beiges. The geometric shapes are varied hexagonal, I-shape, Z-shape, rectangular and wavy rectangular. Set without mortar on a prepared, compacted sand base, the irregularly shaped pavers interlock like puzzle pieces to form an eye-catching mosaic of blending and contrasting colors.

Concrete pavers are about 8 1/2x4x3 inches in size and weigh 9 to 10 pounds each. The deep durable hues of the pavers are produced by synthetic iron-oxide coloring pigments. The color will not wear away in service. The paving blocks are cast by compacting a zero-slump concrete of crushed aggregate, cement and sand. Due to low water-cement ratio, the minimum compressive strength for the blocks is 8000 psi. As to freeze-thaw durability, they pass the ASTM C 67-73 freeze-thaw test, even when a 3 percent saline solution is substituted for plain water. Water absorption, by ASTM C 140, is only 5 percent, and, because the pavers are small units, cracking should not be a problem.

To install the paving blocks, soil is removed and the subbase is compacted to provide a 5- to 10-inch cut below the finished grade. Depending on what type of traffic the pavement is to bear pedestrian, automobile, or bus a 4- to 7-inch layer of course aggregate and at least a 1-inch course of sand are then added and leveled. Pavers are laid and fitted together, without mortar, in a pattern diagonal to the direction of traffic. Because no mortar is used, there is no curing time. Having sand and not mortar around each paving brick provides good drainage, too.