Copyright Goodheart-Willcox Co., Inc. 108 Section 3 Specifications and Materials construction, aggregates are typically used for subbase support under concrete slabs, foundation backfill, under- ground drainage, and fill around pipes, Figure 7-1. Aggregates also serve as one of the three basic ingre- dients of concrete. Aggregates start out as solid rock in the earth’s crust, and over many thousands of years, are broken down by freeze/thaw cycles and other natural action into pieces of various sizes. The larger pieces are called coarse aggregates or gravel the smaller pieces are usually referred to as sand or fine aggregates. There are various kinds of aggregates, such as: Pea gravel, small, rounded pieces ranging in diameter l from ¼″ ¼ to 3/8″. ″ River gravel, larger aggregates dredged from river bottoms, banks, and flood plains. Crushed stone, mined stone that has been mechanically e fractured to a specified size. I t takes many different kinds of materials to construct a building project. Most of these materials are care- fully detailed in the project construction documents. Information about materials may also be included in the drawing notes and the project specifications. The purpose of this unit is to provide you with an overview of the most common materials used in building construction. The materials will be discussed as they relate to numbered divisions in the MasterFormat standard published by the Construction Specifications Institute (CSI). Also discussed are material symbols used on construction drawings and the ways in which materials may be identified on drawings. Division 31—Earthwork Aggregates (also referred to as gravel) are used for many different construction applications. In building X X X X Mesh - W4.0 x W4.0 6x6 – WWF Wire mesh line symbol and note Concrete slab Earth Aggregate subbase (gravel) New topsoil Pea gravel Drain pipe Earth A B Goodheart-Willcox Publisher Figure 7-1. Typical uses for aggregates. A—Gravel used as a subbase support for a concrete slab. Typically, this type of gravel is crushed with some fines in it so it can be compacted. Note the different symbols used for the various materials. Wire mesh, used for reinforcement, is represented by a line symbol consisting of a series of short line segments and a repeating “X” symbol. B—Pea gravel used to fill a curtain or trench drain. This type of gravel has a rounded shape and aids in water drainage. Note that both types of gravel shown in A and B have the same material symbol. Information about the required type is determined by referring to a general note or the project specifications.