November 2000Revised June, 2001

HVS Test Planfor Goal 7

Dowel Bar RetrofitRehabilitation ofRigid Pavements

Partnered Pavement Research

Prepared for:California Department of Transportation

Prepared by:University of California

Berkeley DynatestWashington State

Department ofTransportation

University of WashingtonSeattle

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TABLE OF CONTENTS

Table of Contents ...............................................................................................................iii

1.0 Introduction ............................................................................................................. 1

1.1 Overview of Caltrans Rigid Pavement Network Condition.................................... 1

1.2 Faulting of Rigid Pavements ................................................................................... 3

1.3 Overview of Existing Caltrans Rigid Pavement Structures .................................... 7

1.4 Current Caltrans Practice for Controlling Step-Faulted Pavements........................ 9

1.5 Overview of Dowel Bar Retrofit Technology....................................................... 11

2.0 Goal 7 Test Plan Overview ................................................................................... 12

2.1 Purpose of the Research and Expected Outcome.................................................. 12

2.2 Program Approach ................................................................................................ 14

2.2.1 Accelerated Pavement Testing with the Heavy Vehicle Simulator .............. 15

2.2.2 Live Traffic Testing ...................................................................................... 17

2.2.3 Laboratory Testing and Material Investigation............................................. 18

2.3 Test Site Selection and Test Section Layouts ....................................................... 19

3.0 In-situ Materials Testing ....................................................................................... 20

3.1 Existing Materials Sampling ................................................................................. 20

3.2 Base/Subbase Materials and Subgrade Soils......................................................... 20

3.3 Dynamic Cone Penetrometer (DCP) ..................................................................... 21

3.4 Ground Penetrating Radar (GPR) ......................................................................... 21

3.5 Falling Weight Deflectometer (FWD) .................................................................. 21

3.6 Grout Sampling Plan ............................................................................................. 22

4.0 Field Test Program................................................................................................ 23

4.1 Instrumentation...................................................................................................... 23

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4.1.1 Multi-Depth Deflectometer (MDD) .............................................................. 23

4.1.2 Joint Deflection Measuring Device (JDMD) ................................................ 24

4.1.3 Thermocouples .............................................................................................. 28

4.1.4 Weather Station ............................................................................................. 29

4.1.5 Failure Mechanisms ...................................................................................... 30

4.2 HVS Testing Program ........................................................................................... 30

4.2.1 Traffic Loading ............................................................................................. 30

4.2.2 Direction of Loading ..................................................................................... 30

4.2.3 Location of Loading on the Slab ................................................................... 30

4.2.4 Environmental Control.................................................................................. 31

4.3 Falling Weight Deflectometer (FWD) Testing Program....................................... 31

4.4 Live Testing Program............................................................................................ 32

5.0 Laboratory Testing Program ................................................................................. 32

5.1 Static Strength Tests of Existing Concrete............................................................ 33

5.2 Static Strength Tests of DBR Grout...................................................................... 33

5.3 Cement Treated Base, Aggregate Subbase and Subgrade Tests ........................... 34

5.3.1 Cement Treated Base .................................................................................... 34

5.3.2 Aggregate Subbase and Subgrade ................................................................. 34

5.4 Dowel Bar Durability Tests................................................................................... 34

5.4.1 Half-cell Potential of Metallic Dowels.......................................................... 34

5.4.2 Corrosion Resistance of Metallic Dowels in Concrete Pavement................. 36

5.4.3 Visual Inspection of Metallic Dowels........................................................... 39

5.4.4 Weight Loss of Metallic Dowels................................................................... 39

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5.4.5 Microscopic Examination of Metallic Dowels.............................................. 41

5.4.6 Destructive Mechanical Performance Tests of FRP Dowels ........................ 41

6.0 Design Evaluations................................................................................................ 45

6.1 Mechanistic Analysis ............................................................................................ 45

6.2 Life Cycle Cost Analysis....................................................................................... 46

7.0 Testing Schedule ................................................................................................... 47

7.1 HVS Field Tests .................................................................................................... 47

7.2 Laboratory Testing ................................................................................................ 47

8.0 Benefits.................................................................................................................. 49

9.0 References ............................................................................................................. 49

Appendix A: Ukiah Test Experiment Plan........................................................................ 50

Location............................................................................................................................. 50

Objectives...................................................................................................................... 50

Test Section Layout....................................................................................................... 52

Pavement Structures...................................................................................................... 52

Time Scales ................................................................................................................... 53

HVS Field Tests ......................................................................................................... 53

Laboratory Testing..................................................................................................... 53

Appendix B: Palmdale DBR Test Experiment.................................................................. 60

Location............................................................................................................................. 60

Objectives...................................................................................................................... 60

Test Section Layouts ..................................................................................................... 62

Pavement Structure ....................................................................................................... 62

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Time Scales ................................................................................................................... 63

HVS Field Tests ......................................................................................................... 63

Laboratory Testing..................................................................................................... 63

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1.0 INTRODUCTION

Caltrans operates a state highway network of more than 24,000 centerline

kilometers, with over 78,000 lane-kilometers of pavements. In 1999, about 25,000 lane-

kilometers (ln-km), nearly 32 percent, required corrective maintenance or rehabilitation.

Between 1997 and 1999, Caltrans had a 27.5 percent increase in the number of lane-

kilometers requiring immediate attention to 11,260 ln-km, and a 16.4 percent increase in

the number of lane-kilometers requiring other corrective maintenance or rehabilitation to

13,807 ln-km.

1.1 Overview of Caltrans Rigid Pavement Network Condition

Rigid pavements make up 18 percent of the centerline-kilometers in the state

network, and 32 percent of the total lane-kilometers. The difference indicates the extent

to which rigid pavements have been used for multi-lane facilities.(1)

Rigid pavements (Portland Cement Concrete pavements [PCCP]) make up 25

percent of the rehabilitation project needs, and they accounted for 24 percent of the total

lane-kilometers in California requiring immediate attention, indicating that a large

number of rigid pavements in California are in need of work to restore their

serviceability. Identification of the distress mechanism causing the loss of serviceability

of these pavements rehabilitation is important.

Most of the highway pavements operated by Caltrans, approximately 75 percent,

were constructed in the 15 years between 1959 and 1974, and were designed for 20-year

lives based on traffic volumes and loads estimated at that time. It has been estimated that

approximately 90 percent of the state’s rigid pavement were constructed in those 15

years.(2)

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Most Caltrans rigid pavements are on heavy truck routes and/or are in urban areas

where heavy traffic volumes exist. Rigid pavements were used extensively for

construction of the state Interstate Highway system—29 percent of the lane-kilometers

requiring immediate attention are located on interstate highways within California.

Faulting is the primary distress mechanism of rigid pavements that affects ride

quality. Ride quality is the primary factor that determines the serviceability of a

pavement for the user. Rough pavements cause discomfort to car and truck drivers and

passengers, increase maintenance and repair costs of vehicles, and in extreme cases, may

increase the potential for accidents.

Caltrans places the highest priority for maintenance and rehabilitation spending

on pavements with poor ride quality and high numbers of vehicles using them. Highest

priority is for pavements with International Roughness Index (IRI) values greater than

316 cm/km (200 inches/mile) and more than 5,000 average vehicles per day (Average

Daily Traffic [ADT]).

Caltrans districts with highest percentages and total lane-kilometers of pavement

with rough ride are:

• District 4 (Bay Area), 25 percent of district ln-km, 1999 total ln-km

• District 6 (San Joaquin Valley), 11 percent of district ln-km, 860 total ln-km

• District 7 (Los Angeles/Ventura counties), 26 percent of district ln-km, 2007

total ln-km

• District 8 (San Bernardino/Riverside counties), 10 percent of district ln-km,

757 total ln-km.

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1.2 Faulting of Rigid Pavements

Faulting is one of the primary factors affecting the ride quality of rigid pavements.

The term “faulting” in rigid pavements refers to a difference in elevation of adjoining

concrete slabs at the transverse joint. Typically, the leading slab (upstream of the joint) is

higher than the trailing slab (downstream of the joint). Faulting can occur at transverse

cracks as well as transverse joints.

Although no mechanical model of faulting exists, it is understood that the

difference in elevation comes from two actions. The first is caused by migration of

material from under the trailing slab to the underside of the leading slab under traffic, as

shown in Figure 1. The second cause of faulting is the movement of the material out

from under the trailing slab and onto the pavement surface, as shown in Figure 2. This

second mechanism is typically associated with wet conditions in the supporting structure

and pumping action of the slabs caused by traffic, particularly heavy truck traffic.

Faulting appears earlier under the following conditions (refer to Figures 1 and 2):

• when the base material beneath the slabs is erodible, meaning that it is not

well bound and will move under the pumping action of traffic and/or water;

• when there is poor load transfer across the joint or crack, which results in

more independent action of the slabs across the joint or crack, and greater

pumping action.

Load transfer in rigid pavements can come from three sources (refer to Figure 3):

• Aggregate interlock between the slabs across the joint or crack. In the

creation of concrete transverse joints, the concrete is cut only about half way

through the slab from the surface. This cut initiates a controlled crack that

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propagates downward through the concrete. The irregularity of the crack

promotes aggregate interlock and load transfer at the joint.

• Through the base material. This is the weakest means of obtaining load

transfer.

• Load transfer devices. The typical load transfer device used for transverse

joints (or transverse cracks when retrofitted) is a dowel.

Load transfer efficiency (LTE) is a measure of load transfer across a joint or

crack, and can be applied to longitudinal as well as transverse joints and cracks. Loss of

LTE and faulting across longitudinal joints and cracks are safety and maintenance issues,

but do not have an effect on roughness as it is currently measured. Load transfer

efficiency is defined in terms of relative deflections across a joint or crack under loading,

as illustrated in Figure 3.

Extensive evaluation of field pavements across the country indicates that load

transfer efficiency is one of the primary variables controlling the rate of fault

development.(3) Mechanistic-empirical models have been developed to predict fault

development based on LTE, traffic, climate, and base type. These models will be used in

this study to help predict the development of faulting in dowel bar retrofitted pavements.

These models also include a term for “bearing stress” between the dowel and the

concrete that surrounds it in the slab. High bearing stresses in the concrete around the

dowel lead to loosening of the dowel, which reduces its effectiveness in providing load

transfer. High bearing stresses are reduced primarily by increasing the diameter of the

dowel or secondarily by increasing the number of dowels, which distributes the load on

the dowel across a larger area of concrete or across more dowels, respectively.

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Figure 1. Mechanism of base material movement and faulting and in rigidpavements.

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Figure 2. Mechanism of pumping with water and faulting in rigid pavements.

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Figure 3. Load transfer efficiency definition.

In addition to faulting, good load transfer across the transverse joints reduces the

potential for corner cracking. Good load transfer across transverse joints can be provided

by tie bars in the longitudinal joints between lanes and between a lane and a concrete

shoulder.

1.3 Overview of Existing Caltrans Rigid Pavement Structures

Caltrans rigid pavements have no load transfer devices (dowels) at the transverse

joints, except for a few pavement sections built since 1999. The main reason that

Caltrans did not use dowels in the 1950s and 1960s when most of its rigid pavements

were built was because of construction difficulties with dowel placement, which can lead

to early failure of the pavement. Typical dowel practice at that time also included the use

of small diameter dowels (on the order of 19 to 25 mm [3/4 to 1 inch]), with high bearing

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stresses. The result was that dowels were not particularly effective in reducing faulting

even when placed correctly.

Caltrans rigid pavements are also all plain jointed concrete (again, except for a

few experimental sections), meaning they contain no continuous steel reinforcement to

hold transverse cracks in slabs together, with the result that transverse cracks behave as

transverse joints with irregular geometry. Caltrans does not use reinforced concrete

pavement because it is typically more expensive to build and maintain than plain jointed

concrete pavement.

Historically, Caltrans has relied on improving the non-erodability of base

materials and increasing aggregate interlock to mitigate fault development.

Nearly all of the rigid pavements needing rehabilitation were built with cement

treated bases (CTB). In rigid pavements built before August 1964, the CTB layer was

100 mm thick and had a compressive strength requirement of 2067 kPa (300 psi) at 7

days when the PCC slab was 200 mm thick; the CTB was 100 mm thick and had a

compressive strength requirement of 4479 kPa (650 psi) when the PCC slab was 225 mm

thick.

After 1964, the CTB thickness requirements were changed to 105 mm with a

compressive strength of 2756 kPa (400 psi) for 200-mm thick PCC slabs. A 150-mm

thick CTB with a compressive strength of 5168 kPa (750 psi) was required for 225-mm

thick PCC slabs.

Caltrans experience with CTB bases is that in many cases they have deteriorated

through cracking and erosion. Caltrans has also found that their CTB bases have not

prevented fairly rapid development of faulting. As study performed by Mcleod and

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Monismith in 1979 indicated that faulting generally occurred within 1 million to 4

million equivalent single axle loads (ESALs). At today’s traffic rates, this represents less

than five years of traffic for many Caltrans concrete freeways. The rate is somewhat

dependent on the CTB specification used during original construction, with

improvements in CTB compressive strength resulting in a slightly reduced rate of

faulting, as reported in Table 1.

Table 1 Faulting Development in Caltrans Rigid Pavements in the 1970s (4)Millions of ESALs

Faulting Severity CTB before 1967 CTB after 1967Moderate Faulting Begins 1.0 1.0

Severe Faulting Begins 1.5 2.0Severe Faulting is Typical 2.5 4.0

The performance of CTB in Caltrans rigid pavements may be partially related to

construction practice in the 1950s and the early 1960s. During that period, the CTB was

prepared either as road mix (earlier), or placed with a paver (later). In both cases, the

CTB was then planed to a level surface with a motor grader and the resulting loose

material was rolled into the surface of the CTB prior to placement of the concrete. It is

thought that the material rolled into the surface may be highly erodible and may be a

major contributor to the rapid fault development found in Caltrans pavements built during

that period.

1.4 Current Caltrans Practice for Controlling Step-Faulted Pavements

The current Caltrans rigid design guide has a maximum slab thickness of 260 mm

with various types of non-erodible base for which thickness depends on the design traffic

level. Current emphasis is on the use of lean concrete base (LCB), asphalt treated

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permeable base (ATPB), cement treated permeable base (CTPB), and asphalt concrete

base (ACB). CTB can only be used with special permission because of the relatively

poor performance of many CTB sections. Non-erodible bases reduce the faulting

development rate, however, eventually the aggregate interlock degrades in the joints and

faulting will develop. Newer pavements without dowels may eventually become

candidates for dowel bar retrofit.

The most common rehabilitation strategy for failed rigid pavements is the

cracking and seating of the existing PCC slabs followed by an asphalt concrete overlay.

Some of these rigid pavements are failed primarily in terms of roughness from faulting.

In particular, if the truck lanes (outer one or two lanes typically) require an AC overlay

because they are cracked as well as faulted, the inner passenger lanes which are

uncracked but faulted must also be overlaid to maintain a uniform elevation across the

lanes. The AC overlay thickness is typically 120 to 180 mm. AC overlays of rigid

pavement cost about $107,000 per lane-kilometer in 1998-99.

If faulting is the only form of failure on a pavement, it is typically temporarily

eliminated with a diamond grinding process or cracking and seating followed by an

asphalt concrete overlay. Grinding of rigid pavements costs about $35,500 per lane-

kilometer in 1998-99.

In 1998-99 Caltrans contracted out about $29,6500,000 on AC overlays of rigid

pavements, and $5,700,000 on grinding. Maintenance and rehabilitation work performed

by Caltrans forces is not included in these costs.(1)

If load transfer is poor across slabs, pavements that have been diamond ground to

remove faulting may develop faulting again fairly quickly, on the time scale described in

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Table 1. AC overlays do not result in later development of faulting on Caltrans

pavements because Caltrans cracks and seats the slabs prior to overlay. On the other

hand, AC overlays cost about three times more than diamond grinding. The diamond

grinding and AC overlay strategies are the primary options that should be compared to

dowel bar retrofit in terms of Life Cycle Cost to help select the optimal strategy.

1.5 Overview of Dowel Bar Retrofit Technology

Improved techniques for retrofitting existing concrete pavements with dowel bars

have been developed over the past seven years by the Washington State DOT, among

others. Dowel bar retrofitting (DBR) consists of sawing slots for the dowels across

transverse joints, inserting the dowels, and grouting them in place. This is followed by

grinding to remove faulting and smooth the grout surface where the dowels were

installed. The joint load transfer provided by the dowels significantly slows the

development of new faulting under truck traffic.

Dowel bar retrofit is not appropriate if the concrete slabs have multiple cracks or

if there are other significant durability problems with the pavement such as alkali-silica

reaction (ASR), sulfate attack, D-cracking, or other concrete problems. D-cracking is a

concrete materials problem that typically occurs in areas with prolonged freezing

temperatures. It is seldom observed in California.

WSDOT has estimated that based on Washington state traffic volumes, dowel bar

retrofit must last about 13 years in order to be economically viable compared to other

strategies. The cost break point of dowel bar retrofit versus diamond grinding alone and

AC overlay has not yet been established using Caltrans Life Cycle Cost Analysis

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procedures. In addition, both WSDOT and Caltrans are interested in determining the

estimated performance life of DBR projects for inclusion in Life Cycle Cost Analysis.

DBR in Washington and other states has typically used epoxy coated dowel bars.

The epoxy coating is intended to slow dowel bar corrosion. The use of fiber reinforced

polymer (FRP) dowels has been suggested as a means of eliminating the potential for

corrosion failure. The effects of the lower stiffness of FRP dowels on faulting

development, and their fatigue characteristics under repeated loading in rigid pavements

is not known at this time.

WSDOT began using four dowels per wheelpath (8 dowels per joint) as standard

design. Caltrans used uniform spacing of dowels across the entire transverse joint (9

dowels per joint) on the DBR experiment project on I-10 in Los Angeles County in 1999.

WSDOT has recently moved to the use of three dowels per wheelpath (6 dowels per

joint), but has not been able to assess the impact of the new design on performance.

WSDOT has generally found no problem with DBR on slabs with longitudinal

cracks, and on transverse cracks, but has not yet determined from field projects whether

the long-term performance of those slabs are the same as for uncracked slabs.

2.0 GOAL 7 TEST PLAN OVERVIEW

2.1 Purpose of the Research and Expected Outcome

The goal of this research is to establish whether the dowel bar retrofit (DBR)

rehabilitation technique provides adequate performance relative to its cost for the

rehabilitation of rigid pavements. If the additional pavement life obtained with DBR and

construction cost result in a Life Cycle Cost that is comparable to or less than traditional

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rehabilitation or reconstruction strategies, then DBR will likely be considered by Caltrans

as an option for pavement rehabilitation. Life cycle cost advantages alone do not

determine which option will be selected, but it is used in combination with other factors

such as traffic delay constraints, available funds, and long-term plans for a facility.

This test plan is designed to provide Caltrans and the other research partners with

important information regarding the DBR rehabilitation treatment. The research program

is expected to provide the following:

• Data on the feasibility of the dowel bar retrofit rehabilitation treatment based

on the existing condition of the concrete slabs. The existing condition would

be evaluated in terms of level of faulting, fatigue cracking, corner cracking,

and age of the slabs.

• Magnitude of load transfer restoration provided by DBR.

• Determination of the expected life of a DBR pavement based on the condition

of the slabs at the time of rehabilitation and the measured load transfer

efficiency.

• Mechanism of failure of the dowel bars at the end of their useful life.

• Best practice of dowel bar retrofit treatment in terms of design, materials, and

construction.

• An indication of the best rehabilitation treatment based on life-cycle-cost-

analyses.

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2.2 Program Approach

In order to obtain the expected outcome of the research, the program will address

the following four areas of research:

1. Field Accelerated Pavement Testing with the Heavy Vehicle Simulator

HVS): to collect full-scale data quickly, although with heavier loads than

normally occur under real traffic. This testing also includes measurement of

load transfer efficiency (LTE) and other pavement properties with the Falling

Weight Deflectometer (FWD). Several generic types of dowels will be

included in the field test sections. Note that an HWD (Heavy Weight

Deflectometer) will be used for FWD measurements—the only distinction is

that the HWD is capable of applying greater loads than an FWD.

2. Field Live Traffic Testing: to collect field data on a long-term basis

(approximately two years) under real loads. This testing permits calibration of

HVS and analysis results.

3. Laboratory testing of materials: permits evaluation of additional variables

that cannot be included in the HVS testing, such as corrosion of the dowels

and dowel types not included in the field test sections. Laboratory testing is

also used to characterize materials used in the HVS test sections.

4. Modeling:

· Finite element analysis of doweled concrete pavement joint: allows for

performance prediction of other options without testing; permits

extrapolation of HVS results.

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· Compilation of performance data from existing DBR projects

throughout the USA: allows for calibration of HVS and analysis results

to field project results.

· Life-Cycle-Cost-Analyses.

The objectives for each research area follow.

2.2.1 Accelerated Pavement Testing with the Heavy Vehicle Simulator

The general objective of the accelerated pavement testing with the HVS is to

evaluate the performance of full-scale pavement with and without dowel bar retrofit

under wheel loading with respect to faulting and joint distress. The results will be used to

determine whether the DBR treatment will provide the performance desired by Caltrans

and other research partners. The HVS trafficking is intended to accelerate pavement

damage while closely approximating the distress mechanisms that would occur under

normal traffic loading.

Accelerated pavement testing will be conducted at several locations to test various

slab conditions under various environmental conditions, particularly differences in

support from the underlying layers and differences in curling due to different climates.

The variables considered in the test program will be:

• pavement age, represented in the number of years since the pavement was

constructed;

• existing condition, represented as the amount of physical distress determined

from visual inspections, deflection testing, laboratory testing, and traffic; and

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• climate condition, represented by precipitation regime at the project location

(wet or dry). Climate condition will be controlled if necessary at a given site

to maintain relatively constant temperature and subsurface water conditions

by means of the temperature cabinet and introduction of water into the

pavement.

The matrix of accelerated pavement testing proposed for this research goal is

summarized in Table 2.

Table 2 Matrix of Variables for Accelerated Pavement Testing

Pavement Conditions Climate Condition

Age ExistingCondition Wet Dry

Old Bad

Old Good

New Bad

More detailed descriptions of each experiment are presented in Appendix A.

At each location, accelerated pavement will be conducted on three or four slabs,

including the joints at each end of the slab. The slabs to be tested will include all or some

of the following conditions:

• Two undoweled joints, which will serve as the control section,

• Doweled joints,

• Doweled transverse cracks,

• Slabs with and without a longitudinal crack.

The control and dowel bar retrofitted sections will be tested using bi-directional

loading of 40, 80, and 100 kN on dual wheels with highway tires, and possibly the 150

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kN aircraft single-tire wheel to accelerate damage. The legal limit for a highway wheel

load is 44.4 kN. The performance of the various test sections will be evaluated by

measuring the load transfer efficiency across the joints and/or transverse cracks. The

HVS loading will be applied at a speed of seven kilometers per hour along the slab in

both directions. Trafficking loads will be channelized over the dowels in the wheelpath

in order to accelerate damage.

The estimated time for completing each HVS location is four to six months,

depending on the number sections to be tested and the individual performance of the

pavements.

2.2.2 Live Traffic Testing

Live traffic testing will be performed at locations where safety, maintenance, and

other considerations allow the district to permit it. At the current time it is assumed that

this will only be implemented at Ukiah.

The objective of these tests is to evaluate the longer-term performance of the

dowel bar retrofit treatment under normal loading conditions. This is a long-term test

program that will permit the calibration of HVS results to normal traffic loads and speeds

and seasonal variation over several years.

Live traffic testing will be conducted on test sections that will replicate the HVS

test sections described in Section 2.3. A weather station will be used to record weather

conditions at the test site. Load transfer efficiency and slab corner movement will be

recorded using deflection gauges placed beneath the shoulder surface at the edge of the

slabs and an automatic data acquisition system placed off the roadway. The estimated

time for completing the live traffic testing is about two years from the time that they are

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instrumented. Because the sections will be subjected to live traffic, all of the sections

will be trafficked at the same time. Testing may continue somewhat longer, depending

upon district considerations and the durability of the instrumentation.

2.2.3 Laboratory Testing and Material Investigation

Laboratory testing will provide information regarding the structural integrity and

condition of the existing slabs, properties and durability of the various construction

materials, and the effects of construction and design variables on the performance of the

DBR rehabilitation treatment. The laboratory testing will be divided into two primary

areas of interest: laboratory testing of existing in-situ materials and durability testing of

materials used in the DBR treatment.

2.2.3.1 Laboratory Testing of In-situ Materials

Laboratory testing of in-situ materials is necessary to establish the condition of

the existing concrete slabs. Cores will be obtained in order to determine the compressive

strength characteristics of the slabs and cement treated bases (if applicable and possible).

In-situ dynamic cone penetrometer (DCP) testing will be conducted to estimate the

strength of bases, subbases, and the subgrade. Raw materials used for the DBR grout will

be sampled and beams and cylinders will be prepared from the grout to measure its

strength gain.

2.2.3.2 Laboratory Durability Testing of Dowels

For DBR to be effective in reducing the potential for faulting, the properties of the

dowels must remain relatively constant throughout the design life, and preferably long

19

afterward. Metallic bars have the risk of corrosion while fiber reinforced polymer (FRP)

dowels have the risk of damage due to fatigue loading. The potential for damage to FRP

dowels of environmental degradation is minimal unless they exposed to sunlight prior to

their installation in the slab.

Samples from representative manufacturers of several types of dowels will be

collected. Metallic dowel types (plain steel, epoxy coated, stainless clad, hollow

stainless) will be subjected to accelerated corrosion testing in the laboratory. Relative

corrosion rates will be measured. The translation of the accelerated laboratory results to

field conditions in different climate regions in California will require careful

consideration. As a minimum, the different dowel types will be ranked from the

accelerated laboratory testing, after consideration of any potentially biases of the test

conditions for the different dowel types.

Samples from FRP dowels will be subjected to shear fatigue testing. A new

device will need to be developed to run this test.

2.3 Test Site Selection and Test Section Layouts

The test site locations will be selected and evaluated based on the matrix of

variables presented in Table 2. Selection will depend in large part on which locations

districts can make available for lane closure and HVS testing. A description of each of

the test sites is presented in Appendix A.

Three to four sections will be tested under the HVS and three to four under

normal traffic, if possible, for each DBR experiment location. The sections will be

numbered chronologically as testing proceeds. Live traffic sections will be numbered

based on the HVS sections the live traffic sections replicate plus the two letters LT. For

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example, the live traffic section that replicates HVS Section 553 will be designated

Section 553LT.

Typical Caltrans plain jointed rigid pavements were described in the introduction

of this test plan. Sections representative of those eligible for DBR will be selected for the

HVS test sections.

3.0 IN-SITU MATERIALS TESTING

Existing materials including the PCC slabs, base materials, and subgrade soil will

be tested to determine their thickness and strength. In addition, the grout used for the

DBR installation will be sampled and tested.

3.1 Existing Materials Sampling

Three cores per test slab (102-mm diameter) will be taken from the existing

concrete slabs and transported to the UCB laboratory. Tests will be performed on these

cores to determine the in-situ compressive strength of the concrete and to verify the

concrete slab thickness.

3.2 Base/Subbase Materials and Subgrade Soils

Where possible, materials samples of the base, subbase and subgrade materials

will be obtained and taken to the UCB laboratory for testing. Estimated quantity of the

materials is shown in Table 3.

Table 3 Field Material Sampling PlanMaterial Quantity Responsible for Sampling

CTB appropriate amount UCBAB 25 kg UCB

Subgrade Soil 25kg UCB

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3.3 Dynamic Cone Penetrometer (DCP)

Dynamic Cone Penetrometer tests will be conducted through the aggregate base,

subbase, and subgrade soil in locations where slab cores have been obtained. The DCP

provides information regarding the in-situ shear strength of the unbound pavement layers.

The DCP results for a material can be correlated to the CBR and elastic modulus. Work

is underway at UCB to relate DCP measurements to R-value.

3.4 Ground Penetrating Radar (GPR)

GPR testing will be conducted on the test sections to evaluate its effectiveness in

measuring:

• Dowel bar vertical location in the slabs;

• Horizontal and vertical alignment of the dowels bars in the slabs; and

• Presence of any voids between the grout and the dowel bars.

At this time, coring is the only option to determine dowel location, dowel

alignment (or even the presence of dowels) once the construction process has been

completed. Dowel misalignment and lockup can cause failure of the dowel bar retrofit.

3.5 Falling Weight Deflectometer (FWD)

The FWD will be used to measure deflections on the existing pavement at the slab

center, edges, corners, and across joints. This data will be used for backcalculation of

pavement layer moduli and load transfer efficiency across the transverse joints and

transverse cracks. Load transfer efficiency (LTE) will be measured with the FWD:

• Before the dowel bar retrofit;

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• After the dowel bar retrofit; and

• After HVS testing.

LTE in each of the cases listed above will be measured twice in a 24-hour period,

once in the early hours of the morning when the slab temperature is lowest and there is

maximum upward curl of the slabs at the joints, and once in the late afternoon when the

slab temperature is highest and there is maximum downward curl of the slabs at the joint.

The critical case for LTE is the night-time condition, when the joints are at maximum

opening due to thermal contraction, and the upward curl at the joints can create a

cantilever condition.

3.6 Grout Sampling Plan

Cylindrical samples of size 100 × 200 mm and prismatic beam samples of size

152 × 152 × 533 mm will be made from the concrete material (grout) placed in the field.

Eight cylinders and eight beams per test section will be collected and transported to the

Pavement Research Center laboratory at UCB to perform strength tests. Table 4 shows

the sampling schedule for grout. The grout sampling and respective tests are intended to

provide information about the strength gain and ultimate strength of the DBR grout.

Table 4 Field Grout cylinder sampling, 100 mm x 200 mmGrout SampleCuring Time

Number ofSamples perTest Section

Number of TestSections

Total Number ofCylinders

100 × 200 mm

Total Number ofBeams

152 × 152 × 533 mm3 Hours 2 3 or 4 6 or 8 6 or 824 Hours 2 3 or 4 6 or 8 6 or 87 Days 2 3 or 4 6 or 8 6 or 828 Days 2 3 or 4 6 or 8 6 or 8

Total Cylinders: 24 or 32 24 or 32

23

4.0 FIELD TEST PROGRAM

The purpose of the field test program is to develop joint distress relations for full-

scale slabs under realistic loading conditions and to evaluate the performance of the

dowel bar retrofit rehabilitation technique. The HVS field test program is conducted to

quickly develop the joint distress relations and evaluate the performance of the DBR

treatment. The purpose of the live traffic field test program is to calibrate the results of

the HVS field test program under normal loading and seasonal climate conditions.

4.1 Instrumentation

Instrumentation will be placed in/on test sections to measure curling, joint

deflections, and load transfer efficiency (LTE). Joint deflection measuring devices

(JDMD) and, if possible and practical, Multi-Depth Deflectometers (MDD) will be

placed in three test sections to capture displacements caused by HVS trafficking.

Thermocouples will be placed in the slabs to relate curling and joint opening to

temperature change.

The following sections describe the instruments that will be used.

4.1.1 Multi-Depth Deflectometer (MDD)

If possible and practical, Multi-Depth Deflectometers (MDD) will be placed in

three test sections to capture displacements caused by HVS trafficking. MDDs use

Linear Variable Differential Transformers (LVDTs) to measure vertical deflections under

dynamic loading at several depths in the pavement structure. Figure 5 shows a typical

MDD installation on a rigid pavement.

24

PCC

Aggregate Base

Subgrade

Joint

Chucks attached to rod anchored 3.3 m down

MDDs

Figure 5. MDD setup for measurement of pavement structure deflection at joint orcrack.

4.1.2 Joint Deflection Measuring Device (JDMD)

JDMDs will be used to measure vertical and horizontal displacement caused by

HVS loading and environmental changes. JDMD are dc-operated Linear Variable

Differential Transformers (LVDTs) that are mounted on plates attached to a rod driven 1

m into the shoulder for absolute vertical displacement measurement. For relative

displacement, the LVDTs are mounted on blocks glued to one side of a selected

transverse joint to measure horizontal displacement across a joint. The particular LVDT

model used, an HSD 750-500 manufactured by Macro Sensors, was chosen because it is

25

hermetically sealed and has the ability to withstand moisture. The HSD 750-500 has a

total range of 25.4 mm.

An HVS test section on PCC includes trafficking across two joints such that one

full slab and two partial slabs are trafficked. Five JDMDs measuring absolute joint

displacement will be placed near the shoulder edge: one at the corner of each slab at each

joint (4 total) and one at the center of the full slab, as shown in Figure 6. A sixth JDMD

will measure the relative displacement of the joint nearest the tow end of the HVS to

obtain measurement of horizontal joint movement.

TT

TT

JDMD TMDD TCFigure 6. Location of instrumentation on typical test section.

JDMDs will also be placed at slabs that won’t be tested by the HVS in order to

capture displacements due to environmental changes. These JDMDs will be installed

below the road surface safe from traffic so that measurements can continue when the test

section is opened to traffic. A smaller model HSD 750-250 (12.7 mm range) or smaller

will be used for this purpose. Typical JDMD setups are presented in Figures 7–10.

26

PCCAC Shoulder

Base

Anchor to base

LVDT

To data

Figure 7. JDMD setup for absolute vertical deflection measurement of PCC.

Base

To data acquisition

Anchor to base

PCC

LVDT

Figure 8. JDMD setup for absolute vertical deflection measurement, front view.

27

Base

Anchor to base

To data acquisition

PCC

LVDT

Figure 9. JDMD setup for absolute vertical deflection measurement at middle slab.

To data acquisition

LVDT for Vertical Displacement Measurement Relative to Slab B

LVDT for Horizontal DisplacementMeasurement Relative to Slab B

A B

Target and LVDT Blocks Epoxied to PCC Surface

PCC

AggregateBase

Joint

Figure 10. JDMD setup for relative horizontal and vertical displacementmeasurements over a crack or joint.

28

4.1.3 Thermocouples

Type K thermocouples will be installed in the PCC in various locations to

measure temperature at the surface, 50, 100, 150, and 200 mm below the surface.

Temperatures will be recorded during data collection of JDMDs and MDDs and

automatically at sections not subjected to HVS testing. For automatic data collection,

Campbell Scientific CR10X data acquisition systems will be used.

Given that the HVS will be testing on existing PCC, holes will need to be drilled

into the PCC to provide an installation point for thermocouples. Sets of thermocouples

will be placed in the middle of a slab, center edge, corner, and at the transverse center

near a joint.

A typical thermocouple setup is presented in Figure 11.

Thermocouple Wiresto Data Acquisition Wooden Dowel

Hole Drilled forInsertion of Thermocouples

Tape to Hold Thermocouple Wires in Desired Levels

Thermocouple Ends at 0, 50, 100, 150, and 200 mm Below Surface

Figure 11. Typical thermocouple installation with wires on wooden dowels fortemperature readings at various depths.

29

4.1.4 Weather Station

Weather data, including air temperature, relative humidity, wind speed, and

rainfall, will be collected using a Davis Weather Station. A picture of the Davis Weather

Station is shown in Figure 12.

Figure 12. Davis Weather Station used to obtain weather data at test sites.

30

4.1.5 Failure Mechanisms

The failure mechanism for the test sections is the reduction in load transfer

efficiency (LTE) across joints and cracks. If any faulting occurs, it will be measured.

However, faulting is not expected because of the bi-directional trafficking to be applied

by the HVS.

Other causes of failure may include:

• Distresses caused by the retrofit process itself (dowel misalignment and

lockup),

• Deterioration of the dowel due to corrosion, cracking, or loosening.

4.2 HVS Testing Program

4.2.1 Traffic Loading

The HVS trafficking will be initiated using a 40-kN load on dual tires and

gradually increased to 80 kN and then to 100 kN. The traffic load will finally be

increased to 150 kN using a single aircraft tire to accelerate the process, if required.

4.2.2 Direction of Loading

Bi-directional loading will be used on all sections.

4.2.3 Location of Loading on the Slab

Loading with the dual wheel tires will be centered on the natural wheelpath of the

pavement and over the centerline of the retrofitted dowel sets in each wheelpath for all

tests. No transverse wander will be used for HVS loading.

31

4.2.4 Environmental Control

No environmental control will be provided, but environmental conditions during

testing will be monitored. The testing will be sequenced at each location to reduce or

balance the impact of weather on comparisons between different experiment variables.

4.3 Falling Weight Deflectometer (FWD) Testing Program

FWD Deflection data will be obtained along three rows: 1) the centerline of the

lane on which the HVS test sections are located, 2) along the edge adjoining the AC

shoulder, and 3) along the edge adjoining the adjacent lane. Note that in some cases, it

may not be possible to conduct tests on all three rows. In particular, tests along the edge

adjoining the adjacent lane are sometimes not possible due to the location of a k-rail

barrier.

Data will be taken within the limits of the project. The FWD will be properly

setup to achieve plate loads of 10 and 20 kips (44.5 and 89 kN). The spacing of the

geophones starting from the loading plate will be as follows: 0, 200, 300, 800, 1200,

1600, and 2000 mm. To measure deflections across a joint, the FWD will be positioned

such that the joint/crack of interest is between geophone 2 (200-mm setting) and

geophone 3 (300-mm setting).

The first test (centerline or edge) will always start at the center of a slab, which is

required for structural and load transfer efficiency analyses using the pavement analysis

program ELMOD. The coordinates of each test with respect to the coordinates of the

first test are critical as it tells the program where the tests were conducted. Each test will

have an ID number X.Y, with X denoting the distance from the first test and Y denoting

the position on the slab as follows: center slab (.1), centerline joint (.2), slab center at the

32

shoulder edge (.21), slab corner at the shoulder edge (.3), slab center at the adjacent lane

edge (.23), and slab corner at the adjacent lane edge (.33), as shown in Figure 13.

Station 0 Station 5 Station 10

Centerline

Shoulder Edge

5.1 10.2

5.21 10.3

10.335.23Adjacent Lane Edge

Direction of Traffic

Figure 13. FWD load plate locations and their respective Y-coordinates.

4.4 Live Testing Program

The live test sections will be instrumented exactly the same as the HVS test

sections. Data will be collected using an automatic data acquisition with a data logger

collecting temperature, rainfall, wind speed and other climate data, and deflections from

the JDMDs, on a regular basis. The data will be downloaded from the data acquisition

system via cell phone.

5.0 LABORATORY TESTING PROGRAM

The laboratory testing program included in this test plan includes the following

objectives:

1. Measure strength of existing concrete in the retrofitted slabs.

2. Measure strength and strength gain of grout used for dowel bar retrofit.

33

3. Characterize underlying pavement materials, including the cement treated

base, aggregate subbase, and subgrade.

4. Measure dowel bar durability: relative corrosion resistance of different

metallic dowel types using representative products of each type. Also,

develop and perform an appropriate durability test for fiber reinforced

polymer dowels.

5.1 Static Strength Tests of Existing Concrete

Static compressive strength tests will be performed on 100-mm diameter cores

following ASTM C39.

5.2 Static Strength Tests of DBR Grout

Static compressive strength tests will be performed on 100 mm diameter × 200

mm tall cylinders following ASTM C39. Static flexural strength tests will be performed

on 152 × 152 × 533 mm beams following ASTM C78.

These specimens will be made in the field using grout materials sampled as it is

being placed in the dowel bar slots. The specimens will be cured in the field for the first

24 hours and tested following the schedule shown in Table 4. The field curing conditions

will include spraying a curing compound over the surface and leaving the specimens in

the shade at ambient temperatures. Specimens will be transported to the UCB laboratory

in Richmond within approximately 24 hours, and further curing will occur under

conditions of 23°C temperature and 95 percent relative humidity.

34

5.3 Cement Treated Base, Aggregate Subbase and Subgrade Tests

5.3.1 Cement Treated Base

If the CTB has sufficient strength to permit sampling, cores will be taken for

observation of their condition. Permeability tests may also be performed on the CTB

cores.

5.3.2 Aggregate Subbase and Subgrade

If they can be collected, the aggregate subbase and subgrade will be tested for

gradation and Atterberg limits.

5.4 Dowel Bar Durability Tests

Testing of dowel bars will include both destructive and non-destructive tests.

Non-destructive tests will be performed at regular intervals. Destructive tests will be

performed on one of the replicates every four months, which will destroy that specimen

for further monitoring. The measurement methods and the time basis on which they will

be performed is shown in Table 5. Further description of each of the tests is presented in

the following sections.

5.4.1 Half-cell Potential of Metallic Dowels

The half-cell potential measurement has been widely used in the field due to its

simplicity and general agreement among researchers that this technique provides a good

indication of the existence of active corrosion along the steel reinforcement in concrete.

35

Table 5 Metallic (plain steel, epoxy coated, stainless clad, hollow stainless)Dowel Bar Test and Measurement Methods

DowelType Test Frequency Purpose

metallic1 Half-cell potential Weekly To monitor corrosion state insitu

metallic Corrosion resistivity Weekly To measure the potential forcorrosion

metallic Visual inspection WeeklyTo inspect physical change:stains, cracks, and change ofspecimen dimension.

metallic Weight loss Every othermonth

To inspect mass loss and cross-section loss.

metallic Microscopic inspection Afterweight loss

To study the corrosion damageon micro-structure of the steel.

fiberreinforcedpolymer(FRP)

Destructive mechanicalperformance tests: flexuralmodulus (stiffness), shearstrength, tensile strength

To bedetermined

To study shear and fatigueproperties of FRP dowels

1 metallic dowel types include plain steel, epoxy coated, stainless clad, and hollowstainless

All metals display a different interface potential with respect to a reference

electrode. During corrosion, the metal is polarized and the interface potential changes.

The half-cell potential method (ASTM C876-91) is based on the principle that the

potential decreases as the corrosion process progresses.

Half-cell measurements may be made relatively easily using only a potential

meter and a standard reference electrode, such as a copper-copper sulfate electrode

(CCS). As shown in Figure 14, the voltmeter connects the steel with the CCS such that

the steel is at the positive terminal of the voltmeter. The potential recorded in the half-

cell measurement can be used to indicate the probability of corrosion of the steel

reinforcement, as shown in Table 7. A potential map that plots the potentials obtained on

the locations of the reference electrode is usually used to indicate the possible sites of

active corrosion.

36

Figure 14. Copper-copper sulfate half cell circuitry.

Table 7 ASTM Criterion for Corrosion of Steel in Concrete (ASTM C876-91)Measured Potential (mV vs. CSE) Corrosion probability>-200 Low, 10% risk of corrosion-200 ~ -350 Intermediate<-350 High, 90% risk of corrosion

It is more accurate to correlate the measured potential and the corrosion condition

of embedded steel. By correlating measured potential with the concrete resistivity, the

corrosion sites along the dowels can be located more accurately.

5.4.2 Corrosion Resistance of Metallic Dowels in Concrete Pavement

In the field, dowel bars are exposed to moisture and de-icing salts in the vicinity

of the joints, and it is recognized that it is not possible to construct and maintain a

watertight joint. Consequently, metallic dowels bars are subject to corrosion. The loss of

cross-sectional area of the dowels bars can result in the loss of load transfer efficiency

across the joint.

37

The American Concrete Paving Association estimates that steel dowel bars can

fail in as little as seven to fifteen years while the concrete highway slab itself can perform

for 35-40 years. Both stainless steel and epoxy-coated steel are often used for structural

applications because of their high corrosion resistance.(5, 6) Due to the special situation

of pavement joints, the corrosion resistance of these materials when used as dowel bars in

pavements is not clear and no comprehensive, well balanced study has been performed

yet.

This project includes an evaluation of the corrosion resistance of various

commercially available steel dowel bars, including plain steel, stainless steel, and epoxy-

coated steel. The goal of this research is to develop a database of accelerated laboratory

results for the selection of a steel dowel type. The corrosion state of dowels cast in

concrete and conditioned in the laboratory will be monitored by non-destructive tests in-

situ, close physical inspection, and eventually destructive weight-loss measurement.

Mechanical performance and microscopic study of the dowel bars will help further the

study.

5.4.2.1 Specimen Preparation and Conditioning

Beam specimens, 152 × 152 × 533 mm will be cast with the dowels inside in the

longitudinal direction, at mid-slab height and width. A joint will be formed in the middle

of the beams using backer board or plastic. The joint will be cast through the entire

beam.

The concrete grout material for the beams will be prepared using a typical dowel

bar grout mix design, a typical Fast Setting Hydraulic Cement (FSHC) meeting Caltrans

current DBR specifications, and locally available aggregate used by a DBR contractor.

38

To the extent possible, the grout material will match that typically used in practice in

California under current specifications.

Four dowel types will be included in the experiment:

• plain steel dowels

• epoxy coated dowels,

• stainless-clad dowels, and

• concrete filled, hollow stainless dowels.

All dowels will be 38 mm in diameter unless that size is not available. A set of

each of the four types of dowel will be obtained from representative manufacturers.

Prior to casting, all dowels will be weighed. Coated thin metal wires will be

attached to the dowels prior to casting to permit half-cell potential and resistivity

measurements.

Once cast, three replicates of each of the four doweled beams will be conditioned

for up to one year under the following conditions:

• 38°C, 100 percent relative humidity

• 4°C, 100 percent relative humidity

• 38°C, 50 percent relative humidity

• 4°C, 50 percent relative humidity

The specimen conditioning and dowel types are summarized in Table 6.

39

Table 6 Dowel Bar Specimens and Test ConditionsTest Conditions

Dowel Bar Type 38°C, 100%Relative

Humidity

4°C, 100%Relative

Humidity

38°C, 50%Relative

Humidity

4°C, 50%Relative

Humidity

Plain steel 3 replicates 3 replicates, 3 replicates 3 replicates

Epoxy-coated steel 3 replicates 3 replicates 3 replicates 3 replicates

Stainless-clad 3 replicates 3 replicates 3 replicates 3 replicates

Concrete filled,hollow stainless steel 3 replicates 3 replicates 3 replicates 3 replicates

5.4.3 Visual Inspection of Metallic Dowels

As the laboratory testing continues, the dowels will be visually inpsected for

corrosion on the portion of the dowel bar visible in the joint. The concrete may also

eventually crack if there is significant corrosion on the parts of dowel embedded in the

concrete, and the corrosion product is expansive.

5.4.4 Weight Loss of Metallic Dowels

Weight loss analysis is the simplest, and longest-established, method of

estimating corrosion losses of metals and alloys. A weighed sample of the metal or alloy

under consideration is introduced into the process, and later removed after a reasonable

time interval. The sample is then cleaned of all corrosion products and is re-weighed.

The proportionality between the weight loss m and the current rate Icorr, or

corrosion reaction rate is given by Faraday's Law:

m = IcorrtanF

where:

40

F = Faraday’s constant (96,500 coulombs/equivalent)

n = number of equivalents exchanged in the corrosion reaction

a = atomic weight

t = time

A corrosion rate (CR) in terms of mass loss per unit time per unit area is given by

the following equation:

CR = mAt

where A is the corrosion area.

From the first equation, the mass loss per unit time per unit area can be converted

to a total thickness loss, or average corrosion penetration rate (CR) (mm y-1) by the

following equation:

CR = mAtD

where D is the density of the metal.

Weight loss analysis has a number of attractive features that account for its

sustained popularity. First, it is simple—no sophisticated instrumentation is required to

obtain a result. Second, it is direct—direct measurement is obtained without theoretical

assumptions or approximations. Finally, it is versatile—it is applicable to all corrosive

environments and provides data on all forms of corrosion.

Initial preparation of the sample surface, and for cleaning the sample after use, is

critical in obtaining useful data. ASTM G1 gives useful guidelines for preparation,

cleaning, weighing of corrosion samples.

41

In the third equation above, it can be seen that the metal averages the amount of

weight loss over the period of exposure. It also assumes that the corrosion of the metal is

uniform. So it is important to evaluate the corrosion area visually. ASTM G46 gives

procedures for analysis of localized corrosion.

5.4.5 Microscopic Examination of Metallic Dowels

Scanning Electron Microscopy (SEM) may be used to study the microstructure of

the dowel bars in the corrosion area. The microscopic examination of the damage

mechanism will facilitate the understanding of the corrosion mechanism and the

prediction of corrosion resistance in the various dowel bars used.

5.4.6 Destructive Mechanical Performance Tests of FRP Dowels

The primary chemical durability issue for fiber reinforced polymer (FRP) dowels

is exposure to ultraviolet light, which breaks the bonds in the polymer. Given that FRP

dowels will be embedded in slabs in the field, with minimal exposure to direct sunlight

during their life, this is not expected to be a major issue. However, tt is important that the

FRP dowels be kept away from direct sunlight during storage prior to construction.

The primary durability issue for FRP dowels is fatigue damage from repeated

bending and repeated shear loading. Damage to the dowels during construction, such as

notching and nicks due to rough handling which can lead to the nick or notch propagating

through the dowel, will also be an issue. Notching or nicks can also occur under loading

due to penetration of sharp aggregates in the concrete into the dowel.

42

5.4.6.1 Shear Fatigue Test of FRP Dowels

To address the potential for fatigue damage of FRP dowels, a test will be

developed to subject the dowels to direct repeated shear. The test will consist of casting

short dowels in a concrete prism with a cast joint in the middle, as illustrated in Figure

15. The prism will be tested in the SHRP Shear Tester (SST). An opening in the range

of 2 to 5 mm will be set between the two concrete prisms, and the dowel will be

subjected to direct shear over that opening. The specimen will be subjected to a repeated

sinusoidal shear stress wave, the magnitude of which will be selected based on finite

element analysis of doweled joints in full-scale pavements under highway loads.

Movement between the two prism halves will be measured with an LVDT.

43

Figure 15. Diagram of FRP dowel shear fatigue test setup using the SST.

The shear displacement should increase with repeated loads due to loosening of

the dowel in the concrete and/or stiffness reduction in the dowel. The frequency of the

shear wave will be selected based on slow moving highway traffic loading speeds.

This test will be performed at two temperatures, two stress levels, two

temperatures, and two replicates. It will be performed on two types of FRP dowels, and

will be replicated (except for temperature) on two steel dowels, for reference. The

factorial is summarized in Table 8. A total of 20 tests will be performed. If the test is

44

successful, it will be repeated with notched dowels in the joint opening. The actual notch

dimensions and geometry will need to be determined.

Table 8 Experiment Design for FRP Dowel Shear Fatigue Tests.*

Dowel Type 50°Chigh stress

5°Chigh stress

50°Clow stress

5°Clow stress

Steel dowel 2 replicates 2 replicatesFRP dowel type 1 2 replicates 2 replicates 2 replicates 2 replicatesFRP dowel type 2 2 replicates 2 replicates 2 replicates 2 replicates*Entire matrix will be repeated with notched FRP dowels if successful.

5.4.6.2 Flexural Frequency Sweep Test of FRP dowels

Flexural frequency sweep tests will be performed on the FRP dowels to evaluate

their bending stiffness as a function of time of loading and temperature. This test will

measure the bending stiffness in the axial direction. The shear fatigue test, described in

Section 5.4.2.1, will provide an indication of the stiffness in the cross-direction.

The flexural frequency sweeps will be performed in the asphalt concrete flexural

beam machine using special clamps for the round dowels, as shown in Figure 16. The

test will be performed at two strain levels and two temperatures. Frequencies will be 20,

10, 5, 2, 1, 0.5, 0.2, 0.1, 0.05 and 0.01 Hz. The factorial is shown in Table 9.

Table 9 Experiment Design for FRP Dowel Flexural Frequency Sweep TestsDowel Type 50°C

high strain5°C

high strain50°C

low strain5°C

low strainFRP dowel type 1 2 replicates 2 replicates 2 replicates 2 replicatesFRP dowel type 2 2 replicates 2 replicates 2 replicates 2 replicates

45

Figure 16. Diagram of flexural frequency sweep test setup using the asphaltconcrete flexural beam machine.

5.4.6.3 Tensile Strength of FRP dowels

At present, a specific tensile strength test has not been developed. Such a test

may be developed and performed if deemed appropriate.

6.0 DESIGN EVALUATIONS

6.1 Mechanistic Analysis

Finite element analyses, material characterization, and results from the HVS

testing will be used to model the failure mechanisms in dowel bar retrofitted concrete

pavement so that predictions can be made for real traffic and pavement conditions in

California. This modeling will permit extrapolation of the limited HVS test section

results to develop predictions for other pavement and traffic scenarios.

The main output variables for the finite element analyses will be the bearing stress

on the concrete due to the dowel and the predicted load transfer efficiency. If possible,

these will be related to faulting.

46

The finite element analysis will consider the following variables:

• Dowel spacing

• Dowel size

• Number of dowels in the wheel path

• Dowel looseness

• Base/subgrade type and condition

• Slab dimensions

• Temperature regime in the slabs

The EverFE 3-dimensional finite element analysis program will be the primary

tool used for this analysis. EverFE is expected to be upgraded in the next year to meet

the requirements of this goal. The upgrade is being performed by the University of

Maine and the University of Washington and is being made possible by funding from

Caltrans.

The first step in the analysis will be the verification of the model used to predict

performance on the HVS test sections. After verification and any necessary

modifications, the model will be used to predict performance in different conditions.

6.2 Life Cycle Cost Analysis

After the best estimates of dowel bar retrofit performance life have been

established for different climate regions in the state, traffic levels, and pavement designs,

a life cycle cost analysis will be performed to estimate the required design life for DBR to

be economically justified. These results will provide an indication of the economics of

47

DBR, but must be used by Caltrans in conjunction with other criteria, per the Caltrans

Highway Design Manual, to determine when and where to use or not use DBR.

7.0 TESTING SCHEDULE

The following sections present the estimated time schedule for HVS field tests

and laboratory testing involved in this test plan. A Gantt chart containing the schedule

for the major tasks in the project based on current assumptions is shown in Figure 17.

7.1 HVS Field Tests

HVS testing takes one to two months per test section. The HVS is expected to

operate 24 hours per day, 7 days per week at each location. The two sites that have been

identified for HVS testing are on US101 in Mendocino county (District 1), and on SR14

in Los Angeles County (District 7). The US101 site will likely be tested in the spring of

2001. The SR14 site will be tested between the fall of 2001 and the summer of 2002.

7.2 Laboratory Testing

The testing of in-situ materials and concrete grout should be completed within

two months after construction of the DBR test sections.

The corrosion and FRP dowel testing will take one year to complete, beginning in

June 2001. Analysis of the data is expected to take approximately 4 months.

Finite element modeling and analysis will likely take 18 months. Life cycle cost

analysis should be completed at approximately the same time.

ID Task Name Duration Start Finish1 Goal 7 Dowel Bar Retrofit 545d Fri 01-12-00 Thu 02-01-03

2 Ukiah HVS tests 545d Fri 01-12-00 Thu 02-01-03

3 construct Ukiah sections 43d Fri 01-12-00 Tue 30-01-01

4 HVS tests Ukiah sections 66d Fri 02-02-01 Fri 04-05-01

5 set up Ukiah instrumentation 40d Mon 07-05-01 Fri 29-06-01

6 monitor Ukiah instrumentation 394d Mon 02-07-01 Thu 02-01-03

7 write Ukiah report 44d Fri 01-06-01 Wed 01-08-01

8 lab test Ukiah grout 23d Tue 30-01-01 Thu 01-03-01

9 Palmdale HVS tests 242d Thu 28-06-01 Fri 31-05-02

10 construct Palmdale sections 2d Thu 28-06-01 Sun 01-07-01

11 HVS tests Palmdale sections 137d Thu 20-09-01 Fri 29-03-02

12 lab test Palmdale grout 22d Thu 28-06-01 Fri 27-07-01

13 write Palmdale report 45d Mon 01-04-02 Fri 31-05-02

14 corrosion testing 305d Fri 01-06-01 Thu 01-08-02

15 cast corrosion specimens 17d Fri 01-06-01 Mon 25-06-01

16 monitor corrosion 261d Fri 15-06-01 Fri 14-06-02

17 write corrosion report 110d Fri 01-03-02 Thu 01-08-02

18 FRP lab testing 152d Mon 03-09-01 Tue 02-04-02

19 set up FRP tests 21d Mon 03-09-01 Mon 01-10-01

20 perform FRP tests 90d Mon 01-10-01 Fri 01-02-02

21 write FRP lab report 42d Mon 04-02-02 Tue 02-04-02

22 finite element analyses 217d Thu 01-11-01 Fri 30-08-02

23 life cycle cost analyses 45d Mon 01-07-02 Fri 30-08-02

24 write final report 45d Mon 02-09-02 Fri 01-11-02

25 finish goal 0d Fri 01-11-02 Fri 01-11-02

Qtr 2 Qtr 3 Qtr 4 Qtr 1 Qtr 2 Qtr 3 Qtr 4 Qtr 1 Qtr 2 Qtr 3 Qt2000 2001 2002

Figure 17. Gantt chart (schedule and tasks) for Goal 7.

48

49

8.0 BENEFITS

The primary benefits of this project to Caltrans and the other research partners is

to provide information and tools to design and construct dowel bar retrofit projects for

maximum performance and to determine whether and under what conditions dowel bar

retrofit is the most cost-effective strategy for rigid pavement rehabilitation. Caltrans is

currently considering widespread use of dowel bar retrofit.

In addition, this project will provide information regarding the most effective

dowel materials, and the number of dowels to place in each wheelpath.

9.0 REFERENCES

1. Maintenance Program, California Department of Transportation. California, State ofthe Pavement Report, 1999. Sacramento, March, 2001.(http://www.dot.ca.gov/hq/maint/99sop.pdf)

2. Presentations by James Roberts, Robert Marsh and Kevin Herritt, ConcretePavement Rehabilitation Workshop/Seminar, Ontario, California, 16-18 July, 1997.

3. Darter, M., and E. Barenberg. Design of Zero Maintenance Plain Jointed ConcretePavements, Vol. 1, Development of Design Procedures." Federal HighwayAdministration Report No. FHWA-RD-77-111, 1977.

4. Macleod, D. R., and Monismith, C. L. Performance of Portland Cement ConcretePavement. Department of Civil Engineering, Institute of Transportation Studies,University of California, Berkeley. February 1979.

5. Sagues A., H. Perez-Duran, and R. Powers, “Corrosion Performance Of Epoxy-Coated Reinforcing Steel In Marine Substructure Service,” Corrosion, 1991 Nov,Vol 47 Number 11:884-893.

6. Gu, P., S. Elliott, J. Beaudoin, and B. Arsenault, “Corrosion Resistance Of StainlessSteel In Chloride Contamination Concrete,” Cement And Concrete Research, Vol.26, Number 8, pp.1151-1156, 1996.

50

APPENDIX A: UKIAH TEST EXPERIMENT PLAN

LOCATION

Three sections will be tested on State Highway 101 near Ukiah in Mendocino

County, California (see Figure A1). The site is located in the coastal mountain range.

The selected test site is located in a road cut section. The existing pavement is

approximately 30 years old with concrete slabs 200 mm thick resting on a cement treated

base. The pavement has skewed transverse joint spaced 3.6 m up to 12 m apart. The 5-

to 6-m long slabs all have a transverse crack located mid-slab. The 12-m long slab has

two transverse cracks located at approximately one-third slab length from the joints. Few

of the slabs exhibit longitudinal cracking. Figure A2 shows the layout of the project site.

Objectives

The objective of the accelerated pavement testing to be performed with Caltrans

HVS No. 2 (HVS2) on the Ukiah test sections sections is to evaluate the performance of

full-scale pavement with different type of dowel bar retrofit under wheel loading. The

testing will examine faulting and joint distress to determine whether dowel bar retrofit

will provide the performance desired by Caltrans and the other research partners. The

HVS trafficking is intended to accelerate pavement damage without significantly

changing the distress mechanisms that occur in the field.

The dowel bar retrofit experiment will consider the following variables:

• Two undoweled joints. This will be the control section.

• Two doweled joints and inclusion of a longitudinal crack.

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• One doweled joint and one doweled crack

If the damage is not excessive following HVS loading, some of the retrofitted

joints/cracks will be left in place and opened to regular traffic. Data will continue to be

collected from the test sections as they are subjected to live traffic and environmental

conditions.

The dowel bar retrofitted and control sections will be evaluated using bi-

directional loading using 40-, 80-, and 100-kN dual and possibly an aircraft wheel under

a 150-kN load to accelerate damage. The performance of the various test sections will be

evaluated by measuring the load transfer efficiency across joints/cracks. The applied

loads will be moving at a speed of seven kilometers per hour along the slab in both

directions. The loading will be channelized (no traffic wander) in line with the dowels.

The data collected through accelerated pavement testing and measurement of

environmental conditions will be used in the evaluation of the adequacy of the dowel bar

retrofit rehabilitation treatment.

The results of the dowel bar retrofit of rigid pavements will provide Caltrans and

the other research partners involved in this study with the information needed to design

and construct dowel bar retrofit projects to obtain maximum performance. The results

will also help to determine where dowel bar retrofit is the most cost-effective strategy for

rigid pavement rehabilitation.

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Test Section Layout

Three sections have been selected for HVS testing:

• Section 553: 11.4-m long slab located between Stations 86 and 124. This slab

has two transverse cracks located at Stations 96 and 107, respectively (see

Figure A3).

• Section 554: 3.3-m long slab located between Stations 186 and 197. This slab

has a longitudinal crack starting at Station 189 and ending to the joint at

Station 197. This longitudinal crack is located at about two-thirds the width

of the slab measured from the shoulder (see Figure A4).

• Section 555: 3.5-m slab located between Stations 383 and 396. This slab has

a longitudinal crack that crosses the length of the slab and is located at about

two-thirds the width of the slab measured from the shoulder (see Figure A5).

These three sections will also be opened to live traffic upon completion of HVS

trafficking. The test section numbers will be amended with a “-LT” as follows to identify

them as live traffic sections, (i.e., Sections 533-LT, 544-LT, and 555-LT).

Pavement Structures

The slabs are 200 mm thick and 3.7 m wide. The slabs are on a cement treated

base about 100 mm thick resting on the natural subgrade. All of the slabs have asphalt

concrete shoulders and have skewed, plain transverse joints with spacing varying from

3.3 m. to 12 m.

Figures A3 to A5 show the instrumentation layout for Sections 553, 554, and 555

and Sections 553-LT, 554-LT, and 555-LT.

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Time Scales

HVS Field Tests

Caltrans has indicated that the test sections will be available for HVS testing for a

period of 4 months. The detour construction, pavement testing, and detour removal is

expected to begin in December 2000 and be completed by May 2001. The schedule for

HVS testing is summarized in Figure 17 in the main body of this document.

Laboratory Testing

The schedule for laboratory testing is shown in Figure 17 in the main body of this

document.

Figure A1. Ukiah project lo

s

Project Limit

cation

PM 29.62

54

.

Figure A2. Slab layout and test sections.

55

TT

TT

8.0 m

5.131 m 3.302 m 2.946 m

AC Shoulder

PCC

2.43

8 m

3.65

8 m

JDMDMDDTCT

Joint 10 Joint 7Joint 8Joint 9

Figure A3. Section 553 (HVS).

56

TT

TT

AC Shoulder

PCC

2.43

8 m

3.65

8 m

JDMDMDDTCT

3.926 m 4.953 m3.353 m

8.0 m

Joint 17 Joint 16 Joint 15 Joint 14

Figure A4. Section 554 (HVS).

57

TT

TT

AC Shoulder

PCC

2.43

8 m

3.65

8 m

JDMDMDDTCT

8.0 m

4.953 m 3.505 m 5.029 m

Joint 32 Joint 31 Joint 30 Joint 29

Figure A5. Section 555 (HVS).

58

59

60

APPENDIX B: PALMDALE DBR TEST EXPERIMENT

LOCATION

Four sections will be tested on State Route 14 approximately 6 kilometers south

of Palmdale in Los Angeles County (see Figure B1). The test site is located in a road cut

with steep side slopes. The existing pavement is approximately 3 years old with 200-mm

thick concrete slabs resting on 100 mm of cement treated base and 150 mm of aggregate

sub base. The pavement has transverse joints spaced 3.7, 4.0, 5.5, and 5.8 m apart.

Figure B2 shows the layout of the project site.

Objectives

The objective of the accelerated pavement testing to be performed with Caltrans

HVS No. 2 (HVS2) at the Palmdale test sections is to evaluate the performance of full-

scale pavement with different type of dowel bar retrofit under wheel loading. The testing

will examine faulting and joint distress to determine whether dowel bar retrofit will

provide the performance desired by Caltrans and the other research partners. The HVS

trafficking is intended to accelerate pavement damage without significantly changing the

distress mechanisms that occur in the field.

The dowel bar retrofit experiment will consider the following variables:

• First test section has four epoxy coated steel dowels per wheel path.

• Second test section has three epoxy coated steel dowels per wheel path.

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• Third test section has four dowels per joint, with one epoxy coated doweled

joint and one stainless steel hollow doweled joint plus one combination of

epoxy and hollow doweled crack.

• Fourth test section has four dowels per joint, with one joint and one crack for

Fiber Reinforced Polymer dowels and one joint for epoxy coated dowels.

The dowel bar retrofitted sections will be evaluated using bi-directional loading

with a dual-tire wheel under 40 kN, 80 kN and 100 kN loads, and possibly an aircraft

wheel under a 150-kN load to accelerate damage. The loading will be along the inside

wheelpath closest to the adjoining traffic lane. This load location was selected because of

extensive cracking along the asphalt concrete shoulder sides of the slabs from previous

testing. The longitudinal joint between the slab to be tested and the adjoining traffic lane

slab is an untied cold joint with minimal load transfer efficiency.

The performance of the various test sections will be evaluated by measuring the

load transfer efficiency across joints/cracks. The applied loads will be moving at a speed

of seven kilometers per hour along the slab in both directions. The loading will be

channelized over the centerline of the wheelpath and dowels. The estimated time for

completing the HVS testing is four to six months from September of 2001. The data

collected through accelerated pavement testing and measurement of environmental

conditions will be used in the evaluation of the adequacy of the dowel bar retrofit

rehabilitation treatment.

The results of the tests on dowel bar retrofit of rigid pavements will provide

Caltrans and other research partners with the information needed to design and construct

62

dowel bar retrofit projects to obtain maximum performance and to determine where

dowel bar retrofit is the most cost-effective strategy for rigid pavement rehabilitation.

Test Section Layouts

Four sections have been selected for HVS testing:

• Section 556 (Slab 39): 4.0-m long slab located between stations 893+20 and

893+30. The approach slab (Slab 38) has a transverse crack and the following

slab (Slab 40) has a longitudinal crack. Figure B3 shows this test section.

• Section 557 (Slab 36): 3.8-m long slab located between stations 893+00 and

893+10. This slab has a transverse crack. Figure B4 shows this test section.

• Section 558 (Slab 42): 5.8-m slab located between stations 893+30 and

893+40. Figure B5 shows this test section.

• Section 559(Slab 33): 5.3-m long slab located between stations 892+90 and

893+00. This slab has a transverse cracks located in the middle of the slab.

Figure B6 shows this test section.

Pavement Structure

All of the slabs are 200 mm thick by 3.7 m wide. The lengths vary to match the

joint spacing of the adjacent lane. The slabs are on a cement treated base constructed in

1998 following 1964 Caltrans specifications: approximately 100 mm of CTB resting on a

150-mm aggregate subbase on natural subgrade. All the slabs have asphalt concrete

shoulders. The slabs are made with a blend of 80 percent Fast Setting Hydraulic Cement

and 20 percent portland cement.

63

Figures B3 to B6 show the instrumentation layout on Sections 556, 557,558 and

559.

Time Scales

HVS Field Tests

Caltrans District 7 has indicated that the test sections will be available for HVS

testing for a period of 12 months. The schedule for HVS testing is summarized in Figure

17 in the main body of this document.

Laboratory Testing

The schedule for laboratory testing is shown in Figure 17 in the main body of this

document.

64

Project Location

Figure B1. Palmdale Project Location

Figure B2. Slab Layout and Test Sections

65

K-rail

Section 556

Figure B3. Section 556 (HVS)

66

Figure B4. Section 557 (HVS).

67

Figure B5. Section 558 (HVS).

68

Figure B6. Section 559 (HVS).

69