TM
5-822-14/AFJMAN
32-1019
CHAPTER 5
QUALITY CONTROL
5-1. General Purpose. Quality control is essen-
mix will exhibit a uniform color throughout;
tial to ensure that the final product will be
whereas, a streaked appearance indicates a nonu-
adequate for its intended use. It must also ensure
niform mix. Special attention should be given to
that the contractor has performed in accordance
the edges of the pavement.
with the plans and specification, as this is a basis
e. Compaction. Equipment used for compaction
for payment. This section identifies those control
is the same that would be used if no cement were
factors which are most important in soil stabiliza-
present in the soil, and is therefore dependent
tion construction with cement, lime, lime-fly ash,
upon soil type. Several methods can be used to
and asphalt.
determine compacted density: sand-cone, balloon,
oil, and nuclear method. It is important to deter-
5-2. Cement Stabilization. Those factors which
mine the depth of compaction and special attention
are most important for a quality control stand-
should be given to compaction at the edges.
point in cement stabilization are: pulverization,
f. Curing. To assure proper curing a bituminous
cement content, moisture content, uniformity of
membrane is frequently applied over large areas.
mixing, time sequence of operations, compaction,
The surface of the soil cement should be free of dry
and curing. These are described in detail below.
loose material and in a moist condition. It is
a. Pulverization. Pulverization is generally not a
important that the soil-cement mixture be kept
problem in cement construction unless clayey or
continuously moist until the membrane is applied.
silty soils are being stabilized. A sieve analysis is
The recommended application rate is 0.15 to 0.30
performed on the soil during the pulverization
gallons per square yard.
process with the No. 4 sieve used as a control. The
5-3. lime Stabilization. The most important fac-
percent pulverization can then be determined by
calculation. Proper moisture control is also essen-
tors to control during soil-lime construction are
tial in achieving the required pulverization.
pulverization and scarification, lime content, uni-
b. Cement content. Cement content is normally
formity of mixing, time sequence of operations,
expressed on a volume or dry weight basis. Field
compaction and curing.
a. Pulverization and scarification. Before appli-
personnel should be aware of quantities of cement
required per linear foot or per square yard of
cation of lime, the soil is scarified and pulverized.
pavement. Spot check can be used to assure that
To assure the adequacy of this phase of construc-
the proper quantity of cement is being applied, by
tion, a sieve analysis is performed. Most specifica-
using a canvas of known area or, as an overall
tions are based upon a designated amount of
check, the area over which a known tonnage has
material passing the 1 inch and No. 4 sieves. The
been spread.
depth of scarification or pulverization is also of
c. Moisture content. The optimum moisture con-
importance as it relates to the specified depth of
tent determined in the laboratory is used as an
lime treatment. For heavy clays, adequate pulveri-
initial guide when construction begins. Allowance
zation can best be achieved by pretreatment with
must be made for the in situ moisture content of
lime, but if this method is used, agglomerated
the soil when construction starts. The optimum
soil-lime fractions may appear. These fractions can
moisture content and maximum density can then
be easily broken down with a simple kneading
be established for field control purposes. Mixing
action and are not necessarily indicative of im-
water requirements can be determined on the raw
proper pulverization.
b. Lime content. When lime is applied to the
soil or on the soil-cement mix before addition of
the mixing water. Nuclear methods can be used to
pulverized soil, the rate at which it is being spread
determine moisture content at the time construc-
can be determined by placing a canvas of known
tion starts and during processing.
area on the ground and, after the lime has been
d. Uniformity of mixing. A visual inspection is
spread, weighing the lime on the canvas. Charts
can be made available to field personnel to deter-
made to assure the uniformity of the mixture
throughout the treated depth. Uniformity must be
mine if this rate of application is satisfactory for
checked across the width of the pavement and to
the lime content specified. To accurately determine
the desired depth of treatment. Trenches can be
the quantity of lime slurry required to provide the
dug and then visually inspected. A satisfactory
desired amount of lime solids, it is necessary to
5-1
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