12 December 2001
INTRODUCTION. The majority of materials utilized in coastal
construction are quite similar to those used in dry-land construction. However, their
introduction into the marine environment results in a need for the designer to expand
his view of material degradation methods. In addition to the increased corrosive
environment and possible freeze-thaw cycles, they must withstand relentless wave
pounding and marine organisms that can attack most materials in a variety of ways.
Primary material selection criteria are physical properties and strength, durability,
adaptability, cost, availability, handling requirements, maintenance requirements, and
environmental impact. Much of the information related to this topic is contained in
Section VI-4 of the CEM.
CONSTRUCTION MATERIALS CONSIDERED, ANALYZED, OR
COMMONLY USED. The primary materials used in construction of coastal projects are
stone, concrete, beach sand, steel, timber, composites, and geotextiles. These
materials are critically important to the success and longevity of the project. Knowledge
of past material performance on similar coastal projects is an important consideration
for the design engineer. Detailed information on the materials discussed below and
their selection criteria can be found in Section VI-4 of the CEM.
Availability. In addition to the technical considerations for material
selection, local availability of materials plays a big role in cost, both for initial
construction and for future maintenance and repair planning. A summary of this and
other material availability issues is contained in Section VI-3-7 and VI-4-1 of the CEM.
EARTH AND SAND. Coastal projects tend to be fairly large and require a
significant volume of construction materials. When feasible, structures are designed to
use earth or sand as an economic filler material, and in many cases the mechanical
strength properties of the soil are an integral part of the design. Some varieties,
properties, and common uses of earth and sand in coastal construction are described in
Section VI-4-2 and VI-4-3 of the CEM.
STONE. Used extensively to construct coastal structures, stone is by far
the most common material used in the United States for breakwaters, jetties, groins,
revetments, and seawalls. A description of types of stone and their uses for coastal
projects is contained in Section VI-4-1 and VI-4-3 of the CEM.
CONCRETE. Concrete is the predominant construction material for
waterfront facilities due to its durability, strength, and economy as a bulk construction
material, and the basic components to make concrete are readily available at most
locations. To optimally design a breakwater, for example, it is important to budget for
minimum capital cost without excessive maintenance costs over the lifetime of the
structure. Common breakwater designs based on an inner mound of small rocks or
rubble provide stability, while an outer armor of large boulders protects the structure