PAVING OPERATIONS AND EQUIPMENT
The modern use of asphalt for road and street
construction began in the late 1800s and grew rapidly
with the emerging automobile industry. Today, asphalt
technology is complex, and the equipment and
techniques, used to build asphalt pavement structures,
are highly sophisticated. This chapter presents only the
basic components, procedures, and principles of paving
The extensive knowledge and skills,
required to perform the operations, must be gained
through formal training and on-the-job-training
NOTE: One rule that has remained constant
throughout the long history of the use of asphalt in
construction is this: a pavement is only as good as the
materials and workmanship that go into it. No amount
of sophisticated equipment can make up for the use of
poor materials or poor construction practices.
Modern paving is broadly divided into rigid paving
and flexible paving. Both types consist of an aggregate
blend (sand, gravel, crushed stone, etc.), bound together
by a hardening or setting agent, called a binder. The
primary difference between the two types of paving,
from the standpoint of ingredients used, lies in the
character of the binder.
The binder for most rigid paving is portland
cement, and for this reason, rigid paving is often
referred to as concrete paving. In flexible paving, the
binder consists of bituminous material. Paving mixes,
containing bituminous material, are referred to as
Asphalt-paving mixes may be produced from a
wide range of aggregate combinations, with each
combination having its own characteristics and being
suited to specific design and construction uses. Aside
from the asphalt content, the principal characteristics of
the mix are determined by the relative amounts of
aggregates. The aggregate composition may vary from
a coarse-textured mix to a fine-textured mix, depending
on aggregate size and design specifications.
The selection of bituminous material depends upon
the type of pavement, temperature extreme, rainfall,
type and volume of traffic, and type and availability of
equipment. In general, hard penetration grades of
asphalt paving are used in warm climates and softer
penetration grades in cold climates. Heavier grades of
asphalt cutbacks and tars are generally used in warm
Asphalt materials are produced by the refining of
petroleum (fig. 16-1). Asphalt is produced in a variety
of types and grades, ranging from hard, brittle solids to
almost water-thin liquids. The semisolid form, known
as asphalt cement, is the basic material.
Liquid asphaltic products are generally prepared by
cutting back (blending) asphalt cements with petroleum
distillates or by blending with an emulsified agent and
water known as asphalt emulsion. Types of liquid
asphaltic products are shown in figure 16-2.
Table 16-1 indicates various uses of asphalt for
different types of construction.
The basic idea in building roads, airfields, or
parking areas for all-weather use by vehicles is to
prepare a suitable foundation, to provide necessary
drainage, and to construct a pavement that has the
1. Has sufficient total thickness and internal
strength to carry expected traffic loads.
2. Is capable of preventing both the penetration and
accumulation of moisture.
3. Has a top surface that is smooth and skid
4. Is resistant to wear and distortion.
5. Is resistant to deterioration caused by weather
conditions or by deicing chemicals.
The foundation ultimately carries all traffic loads.
Therefore, the structural function of pavement is to
support a wheel load on the pavement surface and to
transfer and spread that load to the foundation without