CHAPTER 15
MATERIALS TESTING: SOIL AND CONCRETE
In previous chapters of this TRAMAN, you
studied the importance of many and various con-
struction materials. However, one material that
was not discussed was SOIL which, as you will
learn in this chapter, is perhaps the most impor-
tant material of all. Just as a poorly constructed
and weak concrete foundation will not support
a building, neither will a poorly “constructed”
and weak soil, since the ultimate foundation for
any road, airfield, building, or other structure is
the natural earth upon which it is built.
During this chapter you will learn what soil
is. You will learn the different types of soil you
might encounter. You will also learn the basic
properties and characteristics of soil and the
importance those characteristics play in deter-
mining the adequacy of a soil for use as a con-
struction material. In addition, you will learn how
to collect (sample) soil for testing purposes and
how to perform certain tests that you, as an EA3,
will be responsible for performing. Most impor-
tantly, you will learn why those tests are per-
formed and their importance in properly and
correctly identifying and classifying the many
types of soil that exist in nature.
Finally, this chapter begins your studies of
concrete testing. In this chapter you will learn
what the various tests are and the purpose and
importance of those tests. You will learn how to
perform certain tests and how to prepare concrete
samples for other tests that will be performed by
more senior EAs.
SOIL ORIGIN
As defined by Webster’s New World Dic-
tionary, soil is the surface layer of the Earth that
supports plant life. While that is certainly a
correct definition and one that is perfectly satis-
factory to many groups of people, it lacks the
precision required by the civil engineer and soil
technician. A more precise definition is that soil
is a mixture of uncemented or loosely cemented
mineral grains enclosing various sizes of voids that
contain air (or other gases), water, organic mat-
ter, or different combinations of these materials
in varying amounts. The importance of under-
standing this definition will become obvious as
you progress through this chapter; but, first, let
us consider where soil comes from.
SOIL FORMATION
The formation of soil is a continuous process
that is still in action today. Basically, the Earth’s
crust consists of rock, which geologists classify
into three groups: igneous, which is formed by
cooling from a molten state; sedimentary, formed
by the accumulation and cementing of existing
particles and remains of plants and animals; and
metamorphic, formed from existing rocks that
have been subjected to heat and pressure. When
exposed to the atmosphere, this rock under-
goes a physical and chemical process called
WEATHERING, which, over a sufficient length
of time, disintegrates and decomposes the rock
into a loose, incoherent mixture of gravel, sand,
and finer material. It is this process that produces
soils of various designations.
RESIDUAL SOIL
Any soil that results from weathering in place,
and that is not moved during the weathering pro-
cess, is called a RESIDUAL soil. A mantle of
residual soil reflects the characteristics of the
underlying parent rock from which it was derived.
TRANSPORTED SOIL
When the forces of nature cause the mantle
of soil to be moved to a place other than that of
its origin, the soil becomes a TRANSPORTED
soil. One of these soils often bears properties in-
duced by its mode of transportation. The chief
agents of transportation are water, wind, ice, and
the force of gravity.
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