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Full text of "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NOT FOR PUBLICATION 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NOT FOR PUBLICATION 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- 



Digitized by the Internet Archive 

in 2011 with funding from 

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http://www.archive.org/details/comprehensivepavOOyode 



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 . 

Co ncrete 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 w n pre 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 G r anular 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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25 

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 o f 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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FIG. 2 FACTORIAL DESIGN FOR STUDY OF FACTORS 
INFLUENCING CRCP PERFORMANCE 




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FK55 EFFECT OF 9UBBASE STRENGTH AND PERMEABILITY ON CRCP 
PERFORMANCE 



NOTES 



CURVE NO. 


HWY. 


CONTRACT 


STATIONS 





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TEST SECTION WITHOUT FAILURES 

TEST SE-CTION WITH FAILURES 

NO FAILURES ON ENTIRE CONTRACT 




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DISTANCE FROM START OF TEST SECTION (loVrj 

FIG. 6 DEFLECTION PROFILES OF TEST 

SECTIONS WITH GRAVEL SUBBASE. 



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