UFC 3-260-03
15 Apr 01
CHAPTER 6
EVALUATION OF RIGID PAVEMENTS USING DIRECT SAMPLING
1. GENERAL. This chapter presents criteria for evaluating all types of rigid pavements and overlays
using data from direct sampling. The data required for the evaluations were presented in chapter 3.
Computer programs are available to assist in a pavement evaluation and are discussed in chapter 9.
2. FACTORS LIMITING LOAD-CARRYING CAPACITY. The load-carrying capacity of rigid pave-
ments is limited by the strength of its weakest component--the portland cement concrete, base course,
or subgrade. The ability of a subsurface layer to withstand the loads imposed on it depends on the thick-
ness and strength of material above it and its strength in its weakest condition. An evaluation must also
take into account possible future changes in moisture content and density as well as the effects of freez-
ing and thawing where pertinent.
3. SELECTION OF THICKNESS VALUES. The in-place thicknesses of the portland cement concrete,
base courses, and any overlays are determined from actual measurements, existing data, or from labor-
atory samples. Thicknesses should be measured to the nearest 6.5 millimeters (1/4 inch).
4.
SELECTION OF STRENGTH VALUES.
a. Concrete Flexural Strength, R.
(1) The R value to be used for each feature in the evaluation should be the arithmetical
mean of all R values, except in special instances where, in the opinion of the evaluating engineer, a
slightly lower or higher value is more representative of existing conditions.
(2) When the evaluation is being based on design and construction data, the representative
R value should be the arithmetical mean of the R values obtained in the construction-control beam
tests. Small changes in mix design that might have been necessary during construction to obtain the
design strength should be disregarded when selecting representative R values. However, if there was
a change in design strength that necessitated a change in mix design, this change should be considered
and a representative R value obtained for each facility for which the design strength was changed.
(3) When the evaluation is being based on the results of tests conducted at the time of evalu-
ation or when tests are being performed to check existing data, the amount of data available for arriving
at a representative R value will generally be limited to a relatively few test results. The representative
R value may be determined by using the results of tensile splitting tests and calculating the R value as
presented in appendix B, or by conducting flexural strength tests. The results of all tests from a feature
should be used to compute an arithmetical mean. High or low results should not be discarded unless it
is definitely established that erroneous results were obtained because the sample was defective or
because incorrect test procedures were used.
b. Strength Values for Nonrigid Overlays.
(1) Rigid Pavement Procedure. For the evaluation of nonrigid overlay on rigid pavement
using rigid pavement evaluation procedures, it is necessary to establish whether the nonrigid overlay
portion meets the design requirements given in TI 825-01/AFM 32-1124 (I)/NAVFAC DM 21.10, for Army
and Air Force and MIL-HDBK-1021/4 for Navy and Marine Corps. Should it not meet design require-
ments, early failure can be anticipated.
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