Adhesive Materials

Adhesive pavement materials are those that are pliable when they are first installed. That is, these materials have no predetermined shape and are poured as a “plastic” ma­terial into a temporary form of any shape or size. Adhesive materials are highly adapt­able and relatively inexpensive in comparison to other pavement materials, especially for irregularly shaped paved areas.

Concrete Concrete is the most commonly used adhesive material that is relatively inexpensive and adaptable to numerous landscape uses. Concrete is poured in place to a depth of about 4 inches for most residential landscape pavements and is char­acterized by its gray color and relatively smooth surface. However, expansion and control joints that appear as surface lines extending across the pavement typically divide concrete’s surface (Figure 12—39). Expansion joints are vertical cuts that ex­tend through the entire concrete slab and are then filled with a rubberized or as­phalt-like material. Expansion joints are needed to allow the concrete to expand and contract without cracking. Control joints are vertical cuts that extend to about 1/4" below the surface and are located in order to “control” the location of cracks if they occur. The location of expansion and control joints should be considered from both a technical and visual standpoint so that they are intentionally placed (Figure 12-40).

One of the potential disadvantages of concrete is its drab gray color. This can be altered in a number of ways. First, color pigments can be added to the concrete while it is being mixed, thus changing the color to various shades of gray, black, buff, or red. Additionally, the surface of concrete can treated with chemicals to give it a “wet” appearance, or it can be buffed to highlight its color and texture. And gravel aggregates can be added to the concrete while it is being mixed and then revealed by washing or treating the surface when it is curing. This technique is called exposed aggregate concrete and gives the concrete surface a gravel-like appearance.

Concrete is an apt pavement material to:

• fit irregularly shaped, curved, or complex paved areas (Figure 12-41).

• define fluid, flowing ground forms that wind through the landscape.

• cover a large ground area with minimum cost.

• provide a utilitarian surface that can be used for almost any landscape use.

• create patterns of lines generated by expansion and control joints.

• imprint patterns of other materials and elements on its surface to produce custom designs and textures (Figure 12-42).