A Comprehensive Pavement Evaluation System: Application to CRCP : Technical Paper

SCHOOL OF

CIVIL ENGINEERING

JOINT HIGHWAY
RESEARCH PROJECT

JHRP-76-2

A COMPREHENSIVE PAVEMENT
EVALUATION SYSTEM: APPLICATION
TO CRCP

E. J. Yoder

A. Faiz

D. G. Shurig

PURDUE
INDIANA STATE

UNIVERSITY

HIGHWAY COMMISSION

Technical Paper

A COMPREHENSIVE PAVEMENT EVALUATION SYSTEM:
APPLICATION TO CRCP

TO: J. F. McLaughlin, Director

Joint Highway Research Project

FROM: H. L. Michael, Associate Director
Joint Highway Research Project

January 13, 1976

Project: C-36-52J
File: 6-20-6

Attached is a Technical Paper titled "A Comprehensive Pave-
ment Evaluation System: Application to CRCP", which will be
presented at the January, 1976 meeting of the Transportation
Research Board. It has been authored by Messrs. E. J. Yoder,
Asif Faiz and D. G. Shurig. The paper is a summary of some
of the developments resulting from the JHRP research study
titled "Evaluation of CRC Pavements in Indiana" in which the
three authors were investigators. The material has been pre-
viously presented to the Board in Interim and Final Reports
on this study.

The paper may be published by the TRB. It is requested
that approval to offer the paper for such publication be granted,

Respectfully submitted,

Harold L. Michael
Associate Director

HLMsbjp

cc: W. L. Dolch

R. L. Eskew

G. D. Gibson

W. H. Goetz

M. J. Gutzwiller

G. K. Hallock

D. E. Hancher

M. L. Hayes

G. A. Leonards

C. W. Lovell

R. F. Marsh

R. D. Miles

P. L. Owens

G. T. Satterly

C. F. Scholer

M. B. Scott

K. C. Sinha

L. E. Wood

E. J. Yoder

S. R. Yoder

NOT FOR PUBLICATION

Technical Paper

A COMPREHENSIVE PAVEMENT EVALUATION SYSTEM:
APPLICATION TO CRCP

by

Eldon J. Yoder

Professor of Highway Engineering

Asif Faiz
International Bank for Reconstruction and Development

Donald G. Shurig
Associate Professor of Civil Engineering

Joint Highway Research Project
Purdue University
and the
Indiana State Highway Commission

Presented at the
55th Annual Meeting
of the Transportation Research Board

January, 1976

NOT FOR PUBLICATION

ABSTRACT

Since 1972, a continuing study of the performance of CRC
pavements has been in progress at the Joint Highway Research
Project, Purdue University. The objective of the research pro-
gram is to evaluate and recommend design and construction tech-
niques that would help to improve the performance of CRCP.

The evaluation study consisted of the following sequential
steps :

1. Reconnaissance survey

2. Pavement condition survey

3. Detailed field evaluation survey

This approach permitted considerable flexibility in the
conduct of the research. Each sequential step in the research
was designed on the basis of the results of the previous step.
As a result, considerable economy in the research effort was
obtained .

The CRC pavement condition survey was conducted on a state-
wide basis wherein every CRCP construction contract in Indiana
was included in the survey. A total of 89 survey sections, each
5000 ft in length, were used. These were obtained by random
sampling, stratified over the following factors: construction
contract, method of paving, method of steel placement, method of
steel fabrication (type of reinforcement), subbase type and
subgrade parent material.

The results of the CRC pavement condition surveys indicated
that subbase type, methods of steel placement and steel fabrica-

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tion, concrete slump, and age of the pavement since opened to
traffic were significant contributors to pavement performance.

Based on these results, a field investigation of CRC pave-
ments was conducted. The purpose of this phase of the research
was to evaluate the parameters that were found to contribute
significantly to CRCP performance in the condition survey. This
was accomplished by conducting a field testing program on in-
service CRC pavement sections.

For this part of the study, the length of test sections was
taken as 1000 ft. Normally these test sections were required
to lie within the condition survey sections so that a wide in-
ference space, in terms of the independent explanatory variables,
could be maintained.

All the test sections were located on Interstate Highways
in order to obtain a homogeneous set of test sections in terms
of thickness, 9-inches (22.9 cm) and traffic intensity. Where
possible, a good location was compared with a failed location
within each test section.

This paper describes:

1. Concepts underlying the comprehensive evaluation
system.

2. Method of setting up the condition survey.

3. Method of making the evaluation survey.

4. Use of the results of the surveys for establishing
a maintenance research project for CRCP.

Some of the significant findings of the study are included.
The results of the study show that failures in CRCP are a function

of a number of interacting variables. Generally higher pavement
deflection, wider crack widths and nonuniform crack patterns
were associated with failed pavement condition. The support
conditions under CRCP are of particular significance relative
to performance. Granular subbases with high stability and good
internal drainage have shown good performance.

A COMPREHENSIVE PAVEMENT EVALUATION SYSTEM:
APPLICATION TO EVALUATION OF CRCP

by

Eldon J. Yoder
Professor of Highway Engineering

As if Faiz*
International Bank for Reconstruction and Development

Donald G. Shurig
Associate Professor of Civil Engineering

During the past several years a great amount of research
has been concentrated on methods of making condition surveys
and on techniques for pavement rehabilitation. This is particularly
important from the standpoint of the Interstate system in the
United States since, because of its age, there is a need to plan
for its maintenance. Further, the states and counties have large
investments in highways which are in the need of maintenance.
The primary concern of most highway departments at the present
time deals with the need for funding a maintenance management
program to keep the existing highways operative.

The need for developing maintenance strategies has focused
on development of methods for surveying and analyzing the con-
dition of an existing pavement. These techniques have, by and
large, centered on rapid methods of measuring pavement condition
and have attempted to relate the condition of the pavement to
the Present Serviceability Index (PSI). Along parallel lines,

♦Formerly Graduate Instructor, Purdue University.

but often not coordinated with condition survey methods, has
been the development of techniques for optimizing design and
maintenance of pavement systems.

The purpose of this paper is to present a comprehensive
pavement evaluation system that was developed at the Joint
Highway Research Project, Purdue University. Another purpose
is to demonstrate the use of the method as it was used to evaluate
continuously reinforced concrete pavements (CRCP) in the state
of Indiana.

The application of the method to CRCP is incidental to
the central theme of the paper; the primary purpose is to pre-
sent concepts of evaluation and how these concepts can be inte-
grated to form a comprehensive evaluation system. ■

SURVEY STRATEGIES
At the outset it is necessary to define various surveys
that might be made. Each of the surveys has its use, and like-
wise, each has its limitation depending upon many factors. The
selection of the survey to use is dependent upon the judgement
of the engineer and many times any given step in the evaluation
process can be eliminated depending upon the actual factors under
consideration. For purposes of this discussion use will be
made of terms relating to three basic types of surveys: (1 )
reconnaissance surveys, (2) condition surveys and (3) evaluation
surveys.

Reconnaissance Surveys

These surveys are generally carried out on a routine basis
by most highway departments. They consist of visual inspection
and a qualitative judgement of the condition of pavements made
by a qualified field engineer. Often, this type of survey is
the only one required and conclusions can be derived from it.

Condition Surveys

Condition surveys, at a given time, were made for the pur-
pose of determining the condition of a pavement generally by
use of roughometers , prof i lometers , etc. This type of survey
is not intended to evaluate the structural strength of the
pavement and generally no attempt is made to determine the reason
for the pavement's condition.

Information from this type of survey can lead to the es-
tablishment of priorities and cost estimates for pavement reha-
bi 1 itati on.

Evaluation Surveys

The purpose of evaluation surveys is to determine the
structural adequacy of the pavement and to determine causes for
pavement defects that might be observed. These surveys are more
inclusive and include both laboratory and field tests and accumu-
lation of data which can lead to evaluation of the pavement
structure .

The results of evaluation surveys can also lead to the
establishment of priorities and cost estimates, but in addition,
they permit recommendations relative to new designs and main-

ten ance alternates that might be considered

SEQUENCE OF THE COMPREHENSIVE EVALUATION SYSTEM

The complete system encompasses all of the steps defined
above and permits an evaluation of maintenance priorities con-
currently with the determination of the reasons for pavement
defects. Figure 1 shows the sequence that is followed in the
comprehensive pavement evaluation system. This is a six-step
process as outlined on the flow diagram.

The evaluation process can be stopped during any one of
the phases depending upon the needs of the highway department.
For completeness, however, it is necessary to follow all of
the phases sequentially.

Each of the phases of the survey are self-explanatory
but each, in turn, has one or two important parts that must be
observed if maximum information is to be obtained with minimum
effort.

The condition survey, as envisioned in Figure 1, has at
its heart two principle steps. First, it is necessary to stratify
the data on the basis of known conditions at the site. Second,
each of the strata are statistically sampled and only parts of
the road sections are actually surveyed. Hence, stratification
of the data along with a statistical sampling procedure immediately
dictates that a statistical analysis be made of the data.

In the condition survey analysis, it is necessary to deter-
mine the factors which significantly affect the condition of
the pavement which is observed. Many of the factors which are
listed in the stratification process can be shown to be statis-

tically nonsignificant and hence they may be dropped from the
analysis. It is necessary to make significance tests before
proceeding to the evaluation survey.

As indicated on the flow diagram, however, the significance
tests can be bypassed if it is desired simply to obtain data
which indicate the extent of pavement distress.

After the significant factors influencing performance are
determined, it is possible to make an evaluation survey in which
test sections are statistically laid out and field tests made
and samples of pavement components are obtained on a statistical
basis. Appropriate field and laboratory tests can be made wtth
these samples and an evaluation made of the pavement as shown
in Phase V of the diagram. The primary feature of the evaluation
survey i s .again .stratification and sampling of portions of pave-
ments .

It is possible to complete the process during any one of
the phases listed on the flow diagram. The details of any given
step depend on the results of the preceeding phase. The decision
whether or not to proceed through the comprehensive evaluation
system is dependent upon the needs of the particular situation.

ILLUSTRATION OF THE METHOD
For illustrative purposes, the evaluation system will be
demonstrated by means of a study made of continuously reinforced
concrete pavement in the state of Indiana. The techniques, how-
ever, are applicable to any pavement and the sequential set of
events would be followed in any case.

The use of continuously reinforced concrete pavements in
Indiana dates back to 1938 when an experimental project was
first built on U.S. 40 near Stilesville, Indiana. Since that
time the mileage of continuously reinforced concrete pavement
increased until the end of 1971 when 696 miles (1114 km) of
equivalent two-lane CRC pavements were in service in the state.

In 1972, a continuing study of the performance of CRC pave-
ments was initiated by the Joint Highway Research Project at
Purdue University. The objective of the study was to evaluate
and to recommend design and construction techniques that would
result in better performance of continuously reinforced concrete
pavements .

The evaluation of CRCP in Indiana followed the sequential
steps as outlined in Figure 1.

PHASE I RECONNAISSANCE SURVEY*

Distress was noted on some sections of continuously rein-
forced concrete pavement in Indiana as early as 1970. The
development of distress reached alarming proportions at certain
locations by 1972. It was at this time that the evaluation process
was started.

A reconnaissance survey was conducted on a section of one
road, 1-65, and encompassed only the northbound lanes of the four-

*The use of the terms PHASE I, PHASE II, etc. refers to the steps
of the evaluation sequence as outlined in Figure 1.

lane divided facility. The road at the location surveyed traverses
glacial drift of Wisconsin Age and the subgrade is highly vari-
able ranging from sands and gravels to plastic clays. Subbase
materials were largely non-stabilized gravels with some crushed
stone and bi tumi nous- stabi 1 i zed gravel. A variety of construction
and design variables were incorporated in the road with the
result that several design and construction features which af-
fect performance became immediately noticeable.

The initial survey consisted of: crack counts, tabulations
of failed areas, observations of pumping, poor drainage condi-
tions and other factors. No attempt was made at this time to
sample the pavement on a statistical basis but rather the entire
length was surveyed visually.

The performance of the pavement then was correlated in
general with the factors listed below:

1. Subgrade type (granular versus clay)

2. Subbase type (gravel, crushed stone, bituminous
stabilized)

3. Steel fabrication (bar mats, wire fabric, loose bars)

4. Steel placement (depressed, preset on chairs)

5. Method of paving (slipformed, sideformed)

6. Slump of the concrete - as obtained from construction
records

The results of this survey indicated, although not con-
clusively, that the following factors were probable contributors
to poor performancei

8

1 . Gravel subbases

2. Use of bar mats

3. Clay type subgrades

4. Slipform paving

Since no definitive conclusions could be reached on the
basis of the first survey, a statewide condition survey was sub-
sequently planned. Note that these were tentative conclusions
and that they were changed after further study.

PHASE II STATEWIDE CONDITION SURVEY
In order to arrive at definitive conclusions and to include
a large range of construction and design variables the scope
of the condition survey was setup to include all the CRC pave-
ments in Indiana. A sampling procedure was used to design the
field survey and statistical methods were used to analyzed the
resulting data.

Study Design

The intent of the study design was to ensure the inclusion
in the study of every CRCP contract that had been completed up
to the tine of the survey. A further purpose was to provide an
inference space for the proposed analysis that would encompass
all the factors under investigation.

Sampling Procedure

A stratified random sample of CRC pavements was used in
the field survey. Stratified random sampling is a plan by which
the population under consideration (in this case, all the CRCP
contracts in Indiana) is divided into strata or classes according

to some principle significant to the projected analysis. This
is followed by sampling within each class as if it were a sepa-
rate universe. The aim in stratification is to break up the
population into classes that are fundamentally different in
respect to the average or level of some quality characteristics
(6).

Only one simple random sample was obtained from each stratum
or class. Such a sample or unit of evaluation was designated
as a field survey section. Each field survey section was a
5,000-ft length of pavement. The location, relative to the
direction of lanes, and beginning of each section were selected
from the total length of CRC pavement in each stratum by the use
of random number tables. Care was taken that a randomly selected
pavement length was located approximately 200 to 300 ft. away
from the exact end or beginning of a construction contract.

The survey sections were stratified on the basis of the fol-
lowing factors: contract, method of paving, method of steel
placement, method of steel fabrication, type of subbase, and
type of subgrade. These factors are described in detail in the
section on statistical design. Data relative to these factors
were obtained from construction survey records.

Statistical Design

A 2x2x3x4x2 factoral design with unequal subclass frequencies
was used to study the factors influencing the performance of CRC
pavements. A number of covariates or concomitant variables were
superimposed on the factorial. The layout of the statistical
design is shown in Figure 2, which also indicates the independent

10

factors and their corresponding levels selected for this inves-
tigation. Though a completely randomized factorial design was
assumed for the analysis, this assumption may be questioned on
the nrounds that a restriction on randomization could have been
caused by the use of five different survey teams.

Data Collection

The survey sections were assigned at random to the five
survey parties. Owing to limitations of time and scheduling,
it was not possible to assign an equal mumber of sections to
each of the survey parties. The primary distress variables in-
cluded close parallel cracks, random bifurcated and intersecting
cracks, spalled cracks, edge pumping, and defects as noted by
breakups, punchouts, and patches.

Regarding parallel cracks, only those having a spacing
closer than 30 in. (76.2 cm) were considered. Parallel cracks
and random bifurcated and intersecting cracks were logged on
the basis of linear feet of longitudinal pavement containing
the particular type of crack under consideration. In addition,
cracks that showed spalling were counted in three categories,
depending upon the degree of spall. Defects were noted as
breakups (obvious structural failures) or those areas that had
been previously patched with asphalt or portland cement concrete.
The defects were logged on the basis of total number observed
per section. An estimate of the area of the defect was also made

Information relating to grade, curvature, pumping and
general data on the physical features of the highway were also
cataloged. The exact location of patches and breakups was noted

11

on the log sheet. In addition, these locations were either
sketched or photographed.

PHASE III CONDITION ANALYSIS

The data obtained from the statewide CRCP condition survey
were statistically analyzed by using a weighted least squares
analysis of covariance procedure. This procedure was necessitated
because of unequal subclass cell frequencies in the data. In
this situation, the different comparisons with which the sums
of squares are associated become nonorthogonal and usual analysis
of covariance leads to biased test procedures.

The covariance analysis results reported in this study were
obtained by using LSMLGP (Least Squares Maximum Likelihood General
Purpose Program), a program at the Purdue University Computer
Center. This program uses a general weighted least squares pro-
cedure (6) which can be applied to missing value problems where
cell frequencies are unequal and also where data are not available
for certain subclasses. The program can only handle main effects
and two-factor interactions, but has provisions for incorporating
covariates (concomitant variables) in the analysis. The method
of analysis is given in reference 7.

Results from Statewide Condition Survey

The analysis of data collected during a statewide survey
of continuously reinforced concrete pavements in Indiana, re-
vealed a number of significant results and correlations. The
survey was statistically designed wherehv each construction con-
tract was required to be in the study. At least one survey sec-

12

tion, 5000 ft in length, was sampled from each contract. In
some cases, more than one 5,000-ft section was evaluated within
a construction contract because of the stratification of factors
used in the statistical study. The results of the statewide
survey provided some definite indications relative to causes
of distress in CRC pavements.

Regarding first the extent of distress in the state, the
following data were indicated:

1. 69.7 percent of CRCP sections surveyed did not
show any defects.

2. 26.9 percent of CRCP sections had from one to five
defects per section.

3. 3.4 percent of CRCP sections had more than five
defects per section.

This information was based on 89 sections, each 5,000 ft
long, of equivalent two-lane or three-lane CRC pavement.

The following summary of results pertains to the effect of
various factor influencing the performance of CRC pavements in
Indiana.

1. Subbase type was found to be a significant contributor
to the performance of CRC pavements; gravel subbases
showed the poorest performance. Crushed stone and slag
subbases, in general, showed good performance, and at
the time of the survey the bituminous-stabilized subbases
showed little or no distress (since the condition survey,
breakup has been encountered on some of the bituminous-
stabilized subbase sections).

13

2. For most combinations of methods of paving and steel
fabrication, depressed steel performed better than pre-
set steel on chairs.

3. All other factors being constant, loose bars showed good
performance compared to the use of bar mats and wire

f abri c.

4. Concrete slump had a significant effect on pavement
performance; the optimum slump range was between 2.0
and 2.5 in. Slump values of 1.5 in. and greater showed
generally good results.

5. Pavements that were sideformed, performed the same as
those that were slipformed.

6. Distress of CRC pavements is associated with traffic.

7. The primary mode of pumping of CRC pavements is edge
pumping. The results of the condition survey indicated
that pavements with gravel subbases were more susceptible
to pumping. Pavements with crushed-stone and bituminous-
stabilized subbases showed some indication of pumping,
while pavements with slag subbases did not pump.

8. Subgrade parent material type (granular or fine-grained)
was not a significant contributor to performance of

CRC pavements. This refers to type of subgrade and not
to other factors such as degree of compaction.

Summary Statement - Condition Survey

The conclusions reached from the results of the condition

14

survey wore valid from the standpoint of identifying significant
factors which influenced performance of CRCP. The conclusions
differed in some respects to those reached in the first survey.
The data also showed the extent of distress of the pavements
on a statewide basis. It was nossible to infer reasons for
performance (for examnle gravel suhbases vs stone subbases or
use of chairs vs deoressed steel), but these reasons could not
be determined with certainty. Hence, an evaluation survey was
set tin to delineate possible causes and effects for the relative
performance .

PHASE IV DETAILED EVALUATION SURVEY
Kith resnect to the broad framework of the study, the
detailed field. investigation constituted the primary element
of the fourth phase of the research. A laboratory testing
program was included in the fourth phase. These two steps
(field and laboratory tests) of the research are presented
toqether because the results obtained from the two parts must
be analyzed together. A primary purpose of Phase IV was to
determine the effect of pavement materials in performance.

Design Study

The field investigation was designed to include only the
CRC pavements that are part of the Interstate Highway System in
Indiana. As a result only 9-in. thick pavements were evaluated.
This measure was taken for the purpose of obtaining a homogeneous
set of pavement sections with respect to pavement thicknesses
and percentage of steel reinforcement.

15

The design of the detailed evaluation study was based on
the results of the statewide condition survey. The factors that were
found to be statistically significant in the condition survey
were used as the stratification criterion for sampling the test
sections for the field study. The stratification scheme con-
sisted of the following factors:

1. method of paving (slipformed; sideformed)

2. method of steel placement (depressed steel, steel preset
on cha i rs )

3. type of steel reinforcement (wi re f abri c , bar mats, loose
bars )

4. type of subbase (gravel, slag, crushed stone, bituminous
stabi 1 i zed )

A total of 31 test sections were included in the field in-
vesti gation .

Delineation of Test Sections

The test sections used in the field investigation were
delineated according to the following criteria:

1. The test section, 1000 ft in length, was a tangent
section with flat gradients (less than + i Dercent) under
uniform grade conditions, i.e., completely under fill,
cut or at grade conditions.

2. It was required that the test section lie within the
internal portion of the continuous slab, substantially
removed from construction or expansion joints.

3. The test section was located wholly within one physio-
graphic unit, e.g., ground moraine, glacial terrace,

16

f 1 ood plain, etc .

4. Wherever possible, a test section was located to in-
clude at least one location where significant distress
as indicated by a breakup or a patch was observed.

5. The structural components of the pavement section were
required to conform to a combination of levels of fac-
tors comprising the stratification scheme.

6. The 1000-ft test section was located wtihin one of the
randomly selected 5000-ft survey sections used in the
statewide condition survey.

Collection of Field Data

The typical layout and the data collected at each test section
are outlined in Figure 3. The first step in the data collection
procedure was to divide the test section into ten segments of
1 00- f t length each. Where possible two test locations, corres-
ponding to failed and good pavement conditions respectively,
were selected within each test section. A failed-test location
was defined as one showing distress, indicated by a patch or
a breakup. Conversely, a good- test location was defined as one
showing no apparent distress. Two test locations were also
used in test sections, which did not show any indication of
a failure. One location corresponded to an area with a uniform
and evenly spaced crack pattern while the other was representative
of an area with a relatively more dispersed and nonuniform trans-
verse cracking. These crack patterns were evaluated subjectively
by visual examination. In certain sections without failures,

17

tests were conducted only at one location because of limitations
of t i me .

At a test location, tests on the subbase and the subgrade
were made at two points. One test point, located at the pave-
ment-shoulder interface, was designated as the shoulder position.
The other test point was the hole through the pavement from which
a concrete core had been extracted. This was designated as the
core-hol e position.

A series of tests performed at a test section consisted of
the f ol 1 owi ng :

Deflection Measurements: Pavement deflections were evaluated
with the Dynaflect (11,12). At the center of each 100-ft seg-
ment two deflection measurements were taken, one at a crack
position, and the other at the mid-span position between two
transverse cracks. These measurements were taken along the
center line of the traffic lane, by using only the sensor between
the steel wheels.

A second set of deflection measurements were obtained by
using all the sensors and were taken: across the traffic lane,
at 1.0 ft, 3.5 ft, and 6.0 ft from the outside pavement edge,
approximately corresponding to the outside edge, the right wheel
path and the lane centerline positions, respectively. The
transverse deflections were determined at both a crack position
and an adjacent mid-span position between two transverse cracks.

Crack Width Measurements: Crack widths were measured by means
of a 50X, direct measuring pocket microscope. The points, where

18

crack width measurements were made, corresponded to the positions
along a crack where deflections were evaluated.

Crack Interval I Measurements : Pavement segments 50 ft in length
were first measured on either side of a test location. This
was followed by crack interval measurements along the pavement
edge over the 100-ft section centered on a test location. In
addition, the number of crack intersections were counted over
the 100-ft section at each test location.

Sub grade and Subbase Evaluation: In-place penetration tests
were made on subbase and subgrade by means of the High Load
Penetrometer (2) and the Dynamic Cone Penetrometer ( 1 3 ) , respectively,
These tests were performed at both core-hole and shoulder posi-
tions at each of the two test locations. In all, eight pene-
trometer tests, four each on subbase and subgrade were per-
formed at each test location. The penetration test values
were converted to in-place California Bearing Ratio (CBR) by the
use of calibration charts. Before conducting the penetration
tests, in-place nuclear density and water content determinations
were made on the subbase and the subgrade. As a check on nu-
clear moisture content and density measurements, moisture content
of the subbase and subgrade materials was determined by the stand-
ard procedure and subgrade density was measured by means of a
thin-walled tube sampler. These tests were made at the shoulder
position after the penetration tests. At the completion of a
series of tests on the subbase or subgrade, material was sampled
from under the pavement at the pavement-shoulder interface for

19

laboratory testing. In case of failed locations, care was
taken to sample the material some distance away (about 5 ft.)
from the failed area. In most cases the subbase material directly
under the failed area had densified to a degree that it could
not be extracted by a pick.

The two methods of penetration tests are shown in Figure
4. These penetration tests permit rapid determination of the
relative stability of insitu materials. The penetrometer shown
in Figure 4a was used on fine-grained soils, whereas the instru-
ment shown in Figure 4b was used on granular materials (bases
and subbases). The test values were converted to CDR values
(see references 2 and 13 for correlations) although this would
not have been necessary from the standpoint of the evaluation
process .

Concrete Cores : Concrete cores were obtained from the two
test locations within each test section. These cores were taken
from the traffic lane, close to the point from where the sub-
grade and subbase materials were sampled.

Laboratory Testing Program: Concrete cores obtained from the
field were subjected to the following tests:

a. Specific gravity and absorption tests

b. Pulse' veloci ty measurements

c. Bulk density measurements

'iext the cores were cut and segments without any steel
from above and below the level of reinforcement were tested

20

for: specific gravity, water absorption, pulse velocity, bulk
density, and spl i tti ng -tensi le strength.

The series of tests on subgrade soils and granular sub base
materials included standard classification and compaction tests.
Permeability tests, utilizing a constant head permeameter, were
made on selected samples of slag, crushed stone, and gravel
subbases.

For bitumi nous -stabi 1 i zed subbase materials, the grain-size
distribution and asphalt content were determined.

All laboratory tests were conducted in a random order, in
order to distribute any random variation in test procedures
or among testing personnel over all the measurements.

PHASE V EVALUATION
Approach to Data Analysis

The characteristics of the design of the field study of-
fered two dichotomies that could be profitably used in data
analysis. These were:

1. Comparison of failed-test locations with good-test
locations, within test sections showing significant
di stress .

2. Comparison of test sections showing distress (as indi-
cated by a breakup or a patch) with test sections in
good condition and showing no apparent distress.

The following paragraphs present a portion of the analysis
of just the second item given above. These data are presented
to illustrate techniques for designing a maintenance research
program on the basis of the results.

21

The primary aim of this comparative analysis was to identify
material properties and performance characteristics that are in-
dicators of potential distress in CRCP. Only data from struc-
turally sound locations were included in the study. The objective
of using such data was to isolate inherent deficiencies in the
pavement structure even wnpre no superficial evidence of dis-
tress was present.

For failed-test sections, the data were obtained from
structurally sound (good -test)locations within test sections
showing significant distress. Where two test locations were
sampled wtihin a test section without distress, data from only
one randomly selected test location were used.

This comparison also includes test properties representa-
tive of the whole test section such as: concrete slump, temp-
erature variables, load repetitions, and deflection measurements
taken at 100-ft intervals along the length of the test section.

Analysis of Data

The number of test sections in each of the "without" and
"with" failure categories were 15 and 16 respectively. Dif-
ferences between the two categories with respect to material
properties and performance characteristics were tested by the
t-test. Sample variances were pooled where homogeneity of
variance was indicated by the F-test; otherwise, the t-test
was based on estimates of separate variances for the two cate-
gories. The hypotheses for the statistical tests were developed
on basis of comparisons between good and failed-test locations.

In other cases, where a factorial arrangement was used,

22

data were analyzed within the framework of a nested factorial
design (1). An equal number of randomly selected test sections
were nested within each of the pavement condition categories.

All data were analyzed by appropriate computer programs.

Space limitations will not permit a detailed discussion of
the ANOV models used in the analysis. However, it is pertinent
to note that of the factors studied in the evaluation survey,
the subbase was found to be prime suspect for cause of much
of the distress. The ANOV results showed no significant effect
of subgrade CBR. The results of t-test indicated no difference
between percent compaction of the subgrade and subbase in
failed vs no-failed sections. In every case, however, percent
compaction was low.

Properties of Granular Subbases

In view of the earlier analyses that brought to light sig-
nificant differences among the properties and behavior of crushed
stone, slag, and gravel subbases, the subbase data was first
segregated by subbase type. The properties of the gravel sub-
bases were comparatively analyzed relative to poor and adequate
pavement condition. Such an analysis could not be done on the
other subbase types owing to paucity of data. Finally the
variation of important subbase characteristics with subbase type
was tabulated.

The CBR data for gravel subbases was analyzed using ANOV.
Only ten test sections were used for each condition type. Results
derived from this analysis indicated little difference in subbase

23

C BR relative to pavement condition. On the other hand, the
CBR values obtained at the core-hole (an average CBR of 44 per-
cent) were significantly larger than those measured at the
shoulder (an average CBR of 35 percent). In any case, the CBR
values were invariably low.

The grain-size distribution, percent compaction, and
permeability of gravel subbases were essentially the same at
both the sections with and without failures - as was shown by
the results of t-tests on these properties. Even so, the degree
of compaction achieved for the gravel subbases was uniformly
low (about 93 perdent of standard AASHTO on the average).

Comparison of Subbase Types. Table 1 describes the variation
of subbase CBR, permeability, and degree of compaction with
subbase type. Though no clear differences in the properties of
the gravel subbases were evident between sections with failures
and sections showing no apparent distress, the gravel subbases
were not sufficiently compacted and had relatively low permea-
bility and strength.

The results bring to light important differences among the
properties of the different subbase types. Crushed stone sub-
bases were the most permeable while slag subbases had the lowest
permeability. The relatively poor water transmission charac-
teristics of the slag subbase was more than balanced by its
high strength, as indicated by CBR.

Interaction Between Permeability and Strength: It is worthwhile

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to note that concrete pavement performance is also a function of
the interaction between subbase permeability and strength (CBR).
In Figure 5, the estimated field permeability values are plotted
against field subbase CBR values measured at the shoulder-slab
interface. These values pertain to 46 test locations of the
detailed field study. Test data for crushed stone and slag
subhases are shown with separate indicators. In addition, values
obtained at failed-test locations are differentiated from the
values at good-test locations. The data were grouped in nine
categories corresponding to three levels each of subbase CBR
and permeability. For low subbase strength (CBR < 40 percent),
mainly gravel subbases, the percentage of failed test locations
decreased from 53 percent in the low permeability group (k <
100 ft/day) to 25 percent in the high permeability group ( k >
1000 ft/day). For medium subbase strength (40 percent < CBR <
80 percent), no failures were observed where permeability was
greater than 1000 ft/day. Where subbase strength (CBR > 80 per-
cent) was high (applies only to slag and crushed stone subbases)
no failures were indicated irrespective of permeability.

Jeflection as a Predictor of Performance

As would be evident, the experimental design associated
with section-wide deflection measurements was somewhat inadequate,
as most effects cannot be tested due to restriction errors.

The major interest in the analysis of deflection measure-
ments, taken over the total extent of each test section at 100-
ft intervals, was to determine if pavement condition, as indicated

26

by the presence or absence of failures, could be differentiated
by such section-wide measurements.

Figure 6 shows the deflection profiles developed from
deflection measurements made at 100-ft intervals on three
test sections with gravel subbases. The values shown are the
average of crack and midspan deflections, measured 6.0 ft from
the pavement edge. Profiles Mo. 1 and No. 2 apply to two test
sections, separated by the median strip, on Construction Concract
K-7677, Interstate Highway 1-65. At the time of the field
study, the test section with deflection profile No. 2, had four
concrete patches and four breakups and substantial edge pumping
was indicated over the section. The test section on the opposite
lanes, illustrated by deflection Profile No. l,had no breakups,
patches or any other indication of significant distress, although
extensive edge pumping was observed. Yet the deflection Profile
No. 1 exhibits higher overall deflections than the Profile Mo. 2.
This is explained with reference to the Profile Mo. 3, obtained
at a test section on Contract R-7913 (1-65). This latter contract
has been completely free of distress in spite of having been
under traffic since 1970. Deflection Profile Mo. 3 represents
excellent pavement condition as indicated by deflections of a
relatively small magnitude (less than 0.50 milli-in.). This
should be the deflection pattern of a pavement giving good per-
formance. The deflection pattern given by Profile No. 1 sig-
nified potential trouble, although no physical distress was in-
dicated at the time of the field study. The high deflections

27

reflect loss of support caused by the erosive action of pavement
pumping and/or consolidation. Under the action of repeated
loads, it becomes a matter of time before distress will be
manifested in the form of breakups. After extensive pavement
distress, the discrete segments of the broken continuous slab
attempt to conform to the shape of the pumped subbase that had
developed voids earlier. This settlement of the pavement slab
can be observed by visual inspection of a failed location.
The deflections observed at this stage are smaller than those
before the breakup because now the slab is again in contact
with the subbase and has regained some of the lost support.
This is the condition shown in Profile No. 2.

As a rule, sections of oavmment showing signs of poten-
tial distress had higher deflections than those that had al-
ready failed (Profile Mo. 1 vs Profile No. 2 in Figure 6).
Hence, it was concluded that pavement deflection is a good
indicator of potential distress. The pavement represented
by Profile No. 1 has recently shown extensive distress.

Summary of Resul ts

The comparison of test sections with failures as opposed
to sections without failures, relative to material properties
and performance characteristics evaluated at structurally sound

28

test locations, resulted in a number of significant results.
Simiarly the evaluation of section-wide pavement characteristics
also established some significant trends. These findings bring
to light inherent deficiencies in the pavmment structure
that eventually lead to distress.

The following is a summary of the significant results:

1. Subgrade Properties: The only significant result in

the analysis of subgrade properties showed that subgrade
soils at sections without failures were relatively more
coarse grained and sandy than sections where failures
had occurred.

2. Subbase Properties: This analysis clarified the reasons
for the better performance of certain subbase types.
Crushed stone subbase, at the section without failures
was found to possess a high strength (CBR of 90 percent)
and excellent internal drainage (over 2000 ft/day).

The failure on another section with a crushed stone
subbase was a function of poor stability {very low CBR),
resulting from inadequate compaction. The good con-
dition of pavements on slag subbases was due to the
very high stability (CBR of over 100 percent) of this
subbase. At structurally sound locations, gravel sub-
bases were found to have a moderately high permeability
but showed poor stability characteristics, probably
a function of insufficient compaction.

3. Concrete Properties: It was shown that sections showing
no failures were paved with a higher slump concrete.

29

The results of data analysis further indicated that
the modulus of elasticity of concrete had a significant
bearing on pavement condition. Concrete cores obtained
from sections without any distress were tested to have
an average dynamic modulus of elasticity of 6.15 million
psi whereas cores, obtained from good locations on
sections that had failures, had an average dynamic
modulus of 4.97 million psi.

Dynamic Pavement Deflection: Dynamic pavement deflections
were shown to be a good indicator of pavement condition
if used judiciously. Once the continuous slab breaks
up into discrete segments, the usefulness of deflections
measurements is impaired. As expected at good test
locations, no difference in dynamic deflections was
observed between sections with failures and sections
without failures.

An evaluation of section-wide deflection measurements
taken at 6.0 ft from the pavement edge showed that for
9-in. CRCP, dynamic deflections less than 0.5 milli-in.,
as measured by Dynaflect, are indicators of good pavement
condition. Deflections in the range of 0.6-0.9 milli-in
spell a potential distress condition while values above
1.0 milli-in. are indicators of severe distress with a
high probability of pavement breakups.
Crack Width: It was noted that crack widths observed
at test sections with failures were significantly wider
than those measured at good test sections, even though

30

crack widths at only structurally intact locations
were measured. The average crack width at good sections
was 0.0087 in.

Crack Spacing: No difference in either the mean crack
spacing or the variance of crack intervals was observed
between sections falling in the two categories. The
variance of crack spacing at failed test locations was
significantly higher than the variance at good locations
Frequent incidence of bifurcated cracks, as well as
closely spaced cracks which may intersect at a later
date, was observed to be associated with failures.
Also, high incidence of very closely spaced cracks is
indicative of incipient failure.

PHASE VI DESIGN OF MAINTENANCE TYPES
The evaluation of significant factors relating to performance
of CRCP led to recommendations for altering the designs of the future
These recommendations are not included herein. As a part of
these recommendations, however, it became obvious that there
was a need to recommend maintenance strategies that might be
adopted .

Data relative to the most economical maintenance were meager,
and as a result, a field experiment was established to evaluate
this factor. This field experiment was evolved on the basis
of known factors which have significantly influenced performance
of CRCP in Indiana, and was established for a specific section
of Interstate highway to combat known contributors to performance,

31

i.e., poor drainage condition, high deflections, etc.

The endpoint of the research could only be accomplished by
dividing a section of highway into smaller units with similar
characteristics. A section of Interstate pavement 4.6 mi (7.4 km)
in each direction, or a total of 9.2 mi (14.8 km) was selected
as the test pavement.

This particular section was selected for study since it
contains all of the significant features identified as major
contributors to performance of CRCP. It has a gravel subbase
and bar mats on chairs. These are three important factors
identified earlier as contributors to potential failure. This
pavement has shown, as predicted, very poor performance.

Objective of Research

The maintenance types considered were determined on the
basis of results of the evaluation. Hence, the types of
maintenance considered were directed to three principle factors:

1. Improvement of drainage of subbase.

2. Methods of reducing pavement deflection.

3. Methods of patching failed areas.

Initial Tests

Deflection readings were taken in the Fall of 1974 with
the Dynaflect at 25-ft (7.6 m) intervals over the study area.
At the same time, a condition survey of the pavement was made
noting the locations of breakups, patches, intersecting cracks
and combination cracks.

32

Method of Selecting Study Sections

Using the data derived from the above tests, three factors
were chosen as indicative of the overall condition of the pave-
ment. These were: (l) lineal feet of cracks spaced less than
30 in. (76.2 cm) plus lineal feet of intersecting cracks per
100-ft (30.5 m) station, (2) total area of patching or breakups
per station and (3) maximum deflection per 100-ft (30 m) section.

Using this technique, the sections of navement were then
stratified and assigned rating numbers of 1 to 12 as shown in
Fi gure 7 .

Selection of Maintenance Methods

An attempt was made to apply as many types of appropriate
maintenance as possible to the various ratings. Table 2 shows
the types of maintenance that were considered to be appropriate
for the given rating numbers. Input into this selection was
given by FHWA, ISHC and Purdue personnel.

Layout of Study Sections

The layout of study sections of a given maintenance type
was governed by four criteria:

1. It was desirable to make a section of one tyoe of
maintenance as long as possible;

2. Retain at least one "no-maintenance control section"
for each rating number 1-12;

3. Use as many different types of maintenance methods
as possible for each rating number;

33

Table 2 Possible Maintenance*

Rating Mo. Type of Maintenance

1 (7) No Maintenance (7)

2 (10) No Maintenance (5); Patch (5)

3 (2) No Maintenance (1); Patch (1)

4 (5) No Maintenance (1); Underseal & Overlay (2);

Underseal (0); Overlay (1); Concrete
Shoulders (1 ) ; Drain (0)

5 (11) No Maintenance (1); Patch, Underseal & Overlay (4);

Patch & Underseal (1); Patch & Overlay (1);

Patch & Concrete Shoulders (0); Patch &

Drain (3); Patch, Drain & Concrete Shoulders (1)

6 (3) No Maintenance (1/2); Patch, Underseal &

Overlay (1/2); Patch & Underseal (1);

Patch & Overlay (0); Patch & Concrete Shoulders

(0) ; Patch & Drain (1 )

7 (3) No Maintenance (1); Drain (1); Overlay (1)

8 (5) No Maintenance (1); Patch & Overlay (1);

Patch & Concrete Shoulders (1); Patch &
Drain (2); Patch (0)

9 (7) No Maintenance (2); Patch & Overlay (2); Patch

& Concrete Shoulders (2); Patch & Drain (1);
Patch (0)

10 (2) No Maintenance (1/2); Underseal & Overlay (1/2);

Concrete Shoulders (1); Drain (0)

11 (0) No Maintenance (0); Patch, Underseal & Overlay (0);

Patch & Drain (0); Patch & Concrete
Shoulders (0); Full Depth Bituminous (0)

12 (5) No Maintenance (1); Patch, Underseal & Overlay (0);

Patch & Drain (1); Patch & Concrete
Shoulders (1/2); Full Depth Bituminous (1);
Patch, Underseal, Overlay, Drain & Concrete
Shoulders (1); Patch, Drain & Concrete
Shoulders (1/2)

( ) indicates the number of sections of each type.

*This list of possible maintenance is considered to be a "shopping
list" of various procedures. These were greatly reduced in number
based on length of section, etc.

34

Allocate the maintenance to be used to the rating
numbers with the fewest actual sections of that
rating first. (Note that this criterion is a
means for attaining the first three criteria.)

SUMMARY

In this paper the authors have outlined a comprehensive
system for pavement condition evaluation. It has been the
primary purpose to outline principles that can be used for a
variety of pavements. The method has been illustrated using an
evaluation of continuously reinforced concrete pavements.
The techniques, however, are not unique to this type of pave-
ment but have application to all types of pavements under a
variety of traffic and environmental conditions.

The heart of the method lies in stratification of the
known factors surrounding the pavement, and along with this a
statistical analysis of the data. It is necessary to follow
a sequential series of events, although the process can be
concluded at several locations depending on the needs of the
engi neer .

35

REFERENCES

10,

11

12

Anderson, V. L., McLean, R
Realistic Approach, Marcel
418 pp.

A. , Design of Experiments
Dekker Inc., New York, 1974

The Boeing Company, "High Load Penetrometer Soil Strength
Tester", Document No. D6-24555, The Boeing Company .Commerci al
Airplane Division, Renton, Washington, 1971, pp. 1-16.

Burr, I. W. and Foster, L. A., "A Test for Equality of
Variances", Department of Statistics, Purdue University,
Mimeo Series 282, April 1972.

Cashell, H. D. and Teske, W. E., "Continuous Reinforcement
in Concrete Pavements", Proceedi ngs .Highway Research Board,
Vol . 34, 1955, pp. 34-56.

Cedergren, H. R. , et. al . , "Guidelines for the Design of
Subsurface Drainage Systems for Highway Structural Sections",
Offices of Research and Development, Federal Highway Admini-
stration (FHWA), Washington, D. C, 1972, 25 pp.

Deming, W. E., Some Theory of Sampling, Dover Publications,
Inc., New York, 1950, pp. 213-214.

Faiz, A. and Yoder, E. J., "Factors Influencing the Per-
formance of Continuously Reinforced Concrete Pavements",
Record 485, Transportation Research Board, Washington, D.C.,
1974, pp. 1-13.

Faiz, A. and Yoder, E. J., "Evaluation of Parameters Sig-
nificantly Influencing the Performance of CRC Pavements",
presented at the 1974 Annual Convention of American Concrete
Institute, San Francisco, April 1974 (to be published).

Harvey, W. R., "Least Squares Analysis of Data with Unequal
Subclass Frequencies", Agriculture Research Service, U.S.
Department of Agriculture, ARS 20-8, 1960.

Highway Research Board, "Continuously Reinforced Concrete
Pavement", NCHRP Synthesis of Highway Practice, No. 16,
1973, pp. 1-18.

Scrivner, F. H., et. al . , "Detecting Seasonal Changes in
Load-Carrying Capabilities of Flexible Pavements", NCHRP,
Report 76, Highway Research Board, 1969, 37 pp.

Scri vner , F. H. , et .
Pavement Deflection"
1966, pp. 1-11 .

al., "A New Research Tool for Measuring
, Record 129, Highway Research Board,

36

13. Van Vuuren, D. J., "Rapid Determination of CBR with the
Portable Dynamic Cone Penetrometer, The Rhodesian Engineer,
Paper No. 105, Salisbury, 1969.

14. Williamson, T. G., and Yoder, E. J., "An Investigation of
Compaction Variability for Selected Highway Projects in
Indiana," Record 235, Highway Research Board, 1968, pp. 1-12

15. Yoder, E. J., "Pumping of Highway and Airfield Pavements",
Proceedi ngs , Highway Research Board, Vol. 36, 1957, p. 388.

16. Yoder, E. J., and Gadallah, A. A., "Design of Low Volume
Roads," paper presented at the Kuwait Conference on Low
Cost Roads, November, 1974.

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CONTRACT

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TEST SE-CTION WITH FAILURES

NO FAILURES ON ENTIRE CONTRACT

01 234 56789

DISTANCE FROM START OF TEST SECTION (loVrj

FIG. 6 DEFLECTION PROFILES OF TEST

SECTIONS WITH GRAVEL SUBBASE.

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