10
Guide to Common Construction Materials and Components
Aggregates
There can be no construction of any sort without aggregates. Aggregates are the stone and
sand products found in concrete, asphalt paving, construction entrances, filters, infiltration
trenches, sand filters, enhanced filters, etc. Examples and descriptions of the various aggregate
products used in SWM facilities are reviewed below.
Types of Materials
Stone vs. Gravel - Throughout this manual and others there will be references to both “stone”
and “gravel.” Typically, “stone” refers to a manufactured product produced via crushing of
larger material. A stone particle will have irregular, fractured, angular, rough faces. Gravel
particles are typically naturally occurring material that has a rounded, smooth surface, created
through the action of moving water and natural erosion of the particle’s surface over time. A
“stone” particle will have a much greater surface area than a similar size gravel particle due to
the roughness and angularity of the particle surface. Stone particles will also “knit” together in
a more stable fashion than gravel particles due to the propensity of the angular particles to
interlock with each other. These properties also apply to smaller aggregates commonly
referred to as “sand.”
Sand - Sands may be produced through mechanical crushing like stone, or be naturally
occurring like gravel. When sand has been specified as a filtering media, manufactured sand is
prohibited due to the properties of angular particles noted above. Manufactured sand, due to
the angular configuration, will knit together and significantly restrict flow of water through the
media. Rounded, naturally occurring sand particles will maintain a consistent flow rate over
time if not clogged by external materials. As noted above, “manufactured” sand is prohibited
as a filtering media due to its physical properties.
Size Nomenclature
The size designations of various materials are described below. However, what makes a stone
product that ranges in size from 1½ to 2½ inches in diameter a “#2” stone is determined by the
materials standards as found in the American Society for Testing and Materials (ASTM) C33,
“Standard Specification for Concrete Aggregates,” or in the American Association of State
Highway and Transportation Officials (AASHTO) M43 “Standard Specification for Sizes of
Aggregate for Road and Bridge Construction.” These standards provide the guidance for
aggregate sizes in concrete mix design, and are based on the gradation requirement of the
specification. For example, ASTM C33 defines “#2” stone as consisting of 1½ inch to 2½ inch
particles with the following distribution within those limits: 90% - 100% passing the 2½-inch
sieve, 35%-70% passing the 2-inch sieve, 0% to 15% passing the 1½-inch sieve, and 0% to 5%
passing the ¾-inch sieve. In other cases (e.g., #57, #67), the size refers to a combination of
aggregates. For example, #57 stone is a combination of #5 and #7 stone. Refer to the tables
below for the specific size ranges of each material, as well as the size range for the
combination. Also refer to ASTM C33 or AASHTO M43 for specifics.
