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Nondestructive testing has become an integral part for evaluation and rehabilitation strategies of pavements in recent years. Pavement evaluation employing the Falling Weight Deflectometer (FWD) and the Ground Penetrating Radar (GPR) can provide valuable information about pavement performance characteristics and be a very useful tool for project prioritization purposes and estimation of construction budget at the network level. FWD deflection testing is an accurate tool for determining pavement structural capacity and estimating the required thickness of overlays and hence is an accurate tool for planning for or estimating required current and future construction budgets. GPR is the only tool that a highway agency may use to develop an inventory of pavement layers thicknesses in the most efficient manner possible. By estimating pavement layer thicknesses and stiffness properties more reliable projections of network rehabilitation strategies and needs can be established, thus resulting in cost effective use of available funds. Traditional obstacles for the use of FWD and GPR in pavement evaluation at the network level used to be expenses involved in data collection, limited resources and lack of simplified analysis procedures. This report presents Indiana experience in pavement evaluation with the FWD and GPR at the network level. A network level FWD and GPR testing program is implemented as a part of a study to overcome those traditional obstacles. This testing program included Interstate Highways I – 64, I – 65, I – 69, I – 70 and I – 74 and a number of U.S. Roads and State Routes. It is concluded that network level testing employing the FWD and GPR is a worthwhile, technically sound program that will provide a baseline of structural capacities of in–service pavements in Indiana. Periodical generation of necessary data will be useful for determining how best to quantify structural capacity and estimate annual construction budget. FWD data on 2200 lane miles of the

This study evaluated 18 pavement sections located in high-traffic highways in Virginia to find a premium pavement design with a life span of 40 years or more using current and past field experience. The selected pavement sections were thought to perform well. Eight flexible pavements, six composite pavements, two continuously reinforced concrete pavements, and two jointed plain concrete pavements were investigated. Field testing consisted of (1) falling weight deflectometer (FWD) testing to assess the structural capacity of the different pavements and to backcalculate the pavement layer materials' moduli, (2) ground-penetrating radar (GPR) scanning to determine layer thicknesses and to locate any abnormalities inside the pavements, (3) digital imaging to determine condition indices, (4) longitudinal profile measurements to calculate International Roughness Index, and (5) coring and boring to perform material characterization of pavement layers. Hot mix asphalt tests included resilient modulus and creep compliance. Concrete was tested for compressive strength. The analysis of the collected data suggests that premium pavement designs can be obtained. The field investigations suggest that all the tested sites are performing satisfactorily and show very low structural distress. Limited material-related problems were found at some sites, which induced non-load related distresses. It was also confirmed that FWD, GPR, and digital imaging are very useful tools to assess the condition of existing pavements. Since the three categories of pavements (flexible, composite, and rigid) were found to perform well, the study recommends that evaluation of other pavement sections, which are thought to perform in a less than optimal state, be conducted to define the causes of the less than desired performance. The selection of the most appropriate premium pavement design should be based on a detailed life-cycle cost analysis; hence, such analysis should be performed. Mechanistic empiric

The sealing and resealing of joints and cracks in PCC, HMA, and composite pavements is assumed to be an important component of pavement maintenance. Recently this practice has been challenged by research indicating that sealing may not be cost-effective. The Indiana Department of Transportation currently spends approximately four million dollars annually to perform joint/crack sealing. The primary objective of the research presented in this report is to investigate the costeffectiveness of joint/crack sealing in relation to pavement performance. The results of a mail survey showed that most states, including Indiana, do not have quantitative justification for sealing policies, nor do they know the cost-effectiveness of the operations. Based on the experimental design for this research, nineteen test sites were selected in Indiana, each site having one sealed section and one unsealed section. Collected data including falling weight deflectometer measurements, pavement roughness, visual condition surveys, and core samples were used to evaluate the pavement performance between sealed and unsealed sections. A three-dimensional finite element pavement model was developed to evaluate the test location effect on the load transfer measurements. The temperature effect was evaluated by statistical analyses and a temperature correction factor for deflections on asphalt pavement is provided. A statistical model was developed to compare the pavement performance between sealed and unsealed sections for three pavement types, PCC, HMA and composite. The results indicated that there appears to be no significant differences between the performance of sealed and unsealed sections regardless of pavement type, drainage condition and road classification.

FHWA/LA.06/409, A common method used by the Louisiana Department of Transportation and Development (LADOTD) for pavement design of noninterstate highways is to lime treat the subgrade and place a stabilized layer of soil cement over it followed by a layer of hot mix asphalt. One consistent problem with this method of construction is the appearance of reflection cracking in the asphalt layer. This is due to naturally-occurring shrinkage cracking in the soil cement, which propagates upward through the asphalt layer and then forms a combination of transverse and block cracking. As the pavement ages, the cracks accelerate the deterioration of the pavement structure. The results of the first ALF experiment indicated that placing a crushed stone layer either on top of the cement stabilized layer or beneath the asphalt layer would increase the pavement load carrying capacity by five fold when compared to conventional pavement structures with only soil cement base course layer. This concept is generally known as stone interlayer or inverted pavement design. This experiment sought to evaluate alternative materials such as reclaimed asphaltic pavement (RAP) to make the stone interlayer system more economical. Hot mix asphalt pavements built on equivalent thicknesses (3.5 inches) of RAP and crushed limestone base courses built on top of 6 inches of soil layer stabilized with 10 percent cement were evaluated side by side under the accelerated traffic loading test. A third test lane also evaluated the performance of RAP placed on a thicker (10 inch) but weaker cement (5 percent) treated layer. The test results showed that the crushed stone and RAP had very similar pavement performance under accelerated loading. Therefore, the researchers concluded the RAP is a suitable alternative for crushed stone in a stone interlayer system. They also found that in a stone interlayer system, thicker layers of cement treated layers with lower cement content performed better than thinner soil stabilized layers

State Project Numbers: 736-99-0516, 736-99-0170, This report describes the test results of the first project at the Louisiana Transportation Research Center's Accelerated Loading Facility (ALF). In 1995, 9 test lanes were constructed at the Louisiana Pavement Research Facility in Port Allen. These test lanes consisted of 3.5 in. of type 8 wearing and binder course and crushed limestone or soil cement bases made with either 4% or 10% cement and either plant-mixed or mixed in-place courses. These mixed courses had the same structural capacity but with variable shrinkage cracking potentials. The lanes were loaded to failure using the ALF and the results were used to compare the performance of the various base materials., The experiment was organized into three phases. Phase I of the program evaluated a flexible pavement with a typical crushed stone base and compared it to two innovative flexible pavement designs. Phase II compared plant mix stabilized soil bases. Phase III compared other stabilized pavement layer configurations, including the conventional (benchmark) pavement., Pavement condition was monitored by measuring surface deformation, cracking, and falling weight deflectometer surface deflection. A number of lined bores allowed monitoring of moisture content by down-the-hole meters. Ambient climate was recorded and "in pavement" temperatures were measured. Since traffic loading on each section stopped at different distress levels, all test sections were compared at a standard failure level for rutting. Regression models were developed for each test lane in order to be able to predict the number of equivalent single axle loads carried to a standard rutting failure level of 0.75 in. (19 mm). A post-mortem was conducted after loading to investigate the pavement failure modes and base conditions. A pavement performance comparison among various lanes and survival analysis on pavement life was conducted. The relative performance comparisons showed that the stone base performed as well as the soil cement base and that the stone over a cement stabilized base performed best of all. Using an A-4 soil, the 4% cement treated bases performed as well as the 10% cement stabilized bases and the mixed-in-place bases performed similarly to the plant-mixed bases., The Phase I test results suggested a layer coefficient for the stone stabilized soil of 0.10. Estimating the Present Serviceability Index from the roughness, fatigue cracking, and rutting results provides a reasonable relationship for lanes with crushed stone or cement-stabilized soil bases that could be applied in pavement management systems models. Phase II and III test results suggested a layer coefficient for the cement stabilized subbase of 0.16. Performance of the stone over cement stabilized base ("inverted" design) pavement structure was significantly different from that of the other lanes in both failure mode and fatigue life. Cracking was found to initiate at the bottom of the asphalt layer or to reflect into the asphalt layer from the soil cement bases in all pavements except for the "inverted" base pavement where cracking initiated at the surface., A literature survey was conducted to identify analytical pavement models that could be used to predict the performance of the test lanes using pavement material properties, layer thicknesses, and wheel loads applied by the ALF. The VESYS 3A-M and FLEXPASS models were used to predict rutting, cracking, and roughness development with traffic loads and to predict the performance of the test lanes with granular bases. Both of the control section, which consisted of an 8.5 in (216 mm) limestone base over geofabric, while FLEXPASS predictions matched the performance of a test section consisting of 4 in (102 mm) of limestone over (152 mm) stone-stabilized soil. In addition, Jameson and Asphalt Institute models were used to adequately predict the pavement fatigue life for three of the four cement stabilized base layers but not for the “inverted” base. The fatigue prediction model for cement-stabilized base asphalt pavement with a stone interlayer should be further investigated.

The Resilient Modulus (Mr) of pavement materials and subgrades is an important input, parameter for the design of pavement structures. The Repeated Loading Triaxial (RLT) test, typically determines Mr. However, the RLT test requires well trained personnel and expensive, laboratory equipment in addition to being relatively time consuming. Therefore, highway, agencies tried to seek different alternatives. Various empirical correlations have been used to, predict Mr in the last three decades. Such correlations include parameters such as the soil, support value (SSV), the R-value, and the California bearing ratio (CBR). In addition, different, in-situ tests were used to develop models for the estimation of Mr of different pavement, materials. These tests are characterized by the ease of operation and their ability to assess the, structural integrity and estimate the elastic moduli of in-situ pavement layers. They have an, additional advantage of being able to assess the pavement structure without destroying it.

SPR 000¿1(147) 396¿9B, As part of the Long Term Pavement Performance (LTPP) Program, the Arizona Department of Transportation (ADOT) constructed five Specific Pavement Studies 9 (SPS‐9) test sections on U.S. Route 93 near Kingman. This project, SPS‐9B, studied the effect of asphalt specifications and mix designs on flexible pavements, specifically comparing Superpave mix designs with commonly used agency designs. Opened to traffic in 1992, the project was monitored at regular intervals until the pavement was rehabilitated in 2006. Surface distress, profile, and deflection data collected throughout the life of the pavement were used to evaluate the performance of various flexible pavement design features, layer configurations, and thickness. In terms of structural cracking and smoothness, the agency standard mix design performed better than the Superpave mix designs in this study. This report documents the analyses conducted as well as practical findings and lessons learned that will be of interest to ADOT.

A common method used by the Louisiana Department of Transportation and Development (LADOTD) for pavement design of noninterstate, highways is to lime treat the subgrade and place a stabilized layer of soil cement over it followed by a layer of hot mix, asphalt. One consistent problem with this method of construction is the appearance of reflection cracking in the asphalt layer. This is, due to naturally-occurring shrinkage cracking in the soil cement, which propagates upward through the asphalt layer and then forms a, combination of transverse and block cracking. As the pavement ages, the cracks accelerate the deterioration of the pavement structure., The results of the first ALF experiment indicated that placing a crushed stone layer either on top of the cement stabilized layer or, beneath the asphalt layer would increase the pavement load carrying capacity by five fold when compared to conventional pavement, structures with only soil cement base course layer. This concept is generally known as stone interlayer or inverted pavement design., This experiment sought to evaluate alternative materials such as reclaimed asphaltic pavement (RAP) to make the stone interlayer, system more economical. Hot mix asphalt pavements built on equivalent thicknesses (3.5 inches) of RAP and crushed limestone base, courses built on top of 6 inches of soil layer stabilized with 10 percent cement were evaluated side by side under the accelerated traffic, loading test. A third test lane also evaluated the performance of RAP placed on a thicker (10 inch) but weaker cement (5 percent), treated layer. The test results showed that the crushed stone and RAP had very similar pavement performance under accelerated, loading. Therefore, the researchers concluded the RAP is a suitable alternative for crushed stone in a stone interlayer system. They, also found that in a stone interlayer system, thicker layers of cement treated layers with lower cement content performed better than, thinner soil stabilized layers.

A common method used by the Louisiana Department of Transportation and Development (LADOTD) for pavement design of noninterstate, highways is to lime treat the subgrade and place a stabilized layer of soil cement over it followed by a layer of hot mix, asphalt. One consistent problem with this method of construction is the appearance of reflection cracking in the asphalt layer. This is, due to naturally-occurring shrinkage cracking in the soil cement, which propagates upward through the asphalt layer and then forms a, combination of transverse and block cracking. As the pavement ages, the cracks accelerate the deterioration of the pavement structure., The results of the first ALF experiment indicated that placing a crushed stone layer either on top of the cement stabilized layer or, beneath the asphalt layer would increase the pavement load carrying capacity by five fold when compared to conventional pavement, structures with only soil cement base course layer. This concept is generally known as stone interlayer or inverted pavement design., This experiment sought to evaluate alternative materials such as reclaimed asphaltic pavement (RAP) to make the stone interlayer, system more economical. Hot mix asphalt pavements built on equivalent thicknesses (3.5 inches) of RAP and crushed limestone base, courses built on top of 6 inches of soil layer stabilized with 10 percent cement were evaluated side by side under the accelerated traffic, loading test. A third test lane also evaluated the performance of RAP placed on a thicker (10 inch) but weaker cement (5 percent), treated layer. The test results showed that the crushed stone and RAP had very similar pavement performance under accelerated, loading. Therefore, the researchers concluded the RAP is a suitable alternative for crushed stone in a stone interlayer system. They, also found that in a stone interlayer system, thicker layers of cement treated layers with lower cement content performed better than, thinner soil stabilized layers.

The first Louisiana accelerated loading experiment, Evaluation of Louisiana’s Conventional and Alternative Base Courses, showed that pavement performance could be enhanced signifi cantly if a layer of stone was placed over the cement stabilized subgrade and below the fl exible hot mix asphalt concrete (HMAC) layer. The concept is referred to as “stone interlayer design.” The increase in performance level could be attributed to strengthening the area between the soil cement and the fl exible layer and providing a medium for moisture discharge. Although the stone interlayer could not be eff ectively evaluated in an accelerated test, the stone interlayer should reduce the refl ective soil cement shrinkage cracking.

03-3P, Field and laboratory testing programs were conducted to develop models that predict the resilient modulus of subgrade soils from, the test results of DCP, CIMCPT, FWD, Dynaflect, and soil properties. The field testing program included DCP, CIMCPT, FWD, and Dynaflect testing, whereas the laboratory program included repeated load triaxial resilient modulus tests and physical, properties and compaction tests. Nine overlay rehabilitation pavement projects in Louisiana were selected. A total of four soil, types (A-4, A-6, A-7-5, and A-7-6) were considered at different moisture-dry unit weight levels. The results of the laboratory and, field testing programs were analyzed and critically evaluated. A comprehensive statistical analysis was conducted on the collected, data. The results showed a good agreement between the predicted and measured resilient modulus from the various field test, methods considered. The DCP and CIMCPT models were enhanced when the soil moisture content and dry unit weight were, incorporated. The results also showed that, among all backcalculated FWD moduli, those backcalculated using ELMOD 5.1.69, software had the best correlation with the measured Mr. Finally, the Mr values estimated using the approach currently adopted by, the LADOTD were found to correlate poorly with the measured Mr values.

The fi rst Louisiana accelerated loading experiment, Evaluation of Louisiana’s Conventional and Alternative Base Courses, showed that pavement performance could be enhanced signifi cantly if a layer of stone was placed over the cement, stabilized subgrade and below the fl exible hot mix asphalt concrete (HMAC) layer. The concept is referred to as “stone, interlayer design.” The increase in performance level could be attributed to strengthening the area between the soil, cement and the fl exible layer and providing a medium for moisture discharge. Although the stone interlayer could not, be eff ectively evaluated in an accelerated test, the stone interlayer should reduce the refl ective soil cement shrinkage, cracking.

LA 736-17-0103, Use of the 1986 AASHTO Design Guide requires accurate estimates of the resilient modulus of flexible pavement materials. Traditionally, these properties have been determined from either laboratory testing or by backcalculation from deflection data. Since Louisiana has chosen the backcalculation approach, there was a need to review the available computer programs and determine which were most suitable for use in Louisiana., A literature review was conducted to determine which of the programs worked best for other investigators and to select a small group for trial use in Louisiana. Deflection data was secured on a series of experimental sections constructed from pavement materials which had been previously tested. The programs chosen for study included: BOUSDEF, EVERCALC, MODULUS and WESDEF. Two other programs, MODCOMP2 and ELSDEF, were initially included but technical difficulties necessitated their elimination from the study. some of the programs had different control options, such as MODULUS and EVERCALC; therefore, a total of seven program options were included., Statistical analyses were conducted using ANOVA techniques and the Student-Newman-Keuls, Duncan's Multiple Range and Least Significant Difference tests to determine whether the backcalculated and laboratory determined moduli were significantly different. Overall, these tests showed that MODULUS Step 3 and WESDEF provided the best match between estimated and laboratory measured moduli when all pavement layers were considered. The ability to run multiple deflection basins, automatic temperature corrections for hot mix asphalt moduli and internally developed estimates of layer moduli made MODULUS the choice of project investigators. Additionally, the selection of MODULUS by SHRP for use in the LTPP project ensures that any program improvements will be fully documented and made widely available to the technical community.

02-1GT, With the coming move from an empirical to mechanistic-empirical pavement design, it is essential to improve the quality control/quality assurance (QC/QA) procedures of compacted materials from a density-based criterion to a stiffness/strength-based criterion. The nondestructive in-situ tests such as the Geogauge, Dynamic Cone Penetrometer (DCP), and Light Falling Weight Deflectometer (LFWD) can be effective tools for assessing of subsurface conditions and evaluating the stiffness of pavement materials and embankments. This report evaluates the potential of these three devices to reliably measure the stiffness characteristics of highway materials for possible application in the QC/QA procedures during and after the construction of pavement layers and embankments. To achieve this, field and laboratory testing programs were conducted. The laboratory program included construction of different sections inside two boxes (5 x 3 x 2.5 ft) located at the Geosynthetic Engineering Research Laboratory (GERL) at the Louisiana Transportation Research Center (LTRC). The field tests were conducted on highway sections selected from various projects in Louisiana. In addition, six test sections and three trench sections were constructed and tested at the LTRC Pavement Research Facility (PRF) site. The field and laboratory tests included Geogauge, LFWD, and DCP tests in conjunction with two standard tests such as the Plate Load Test (PLT) and Falling Weight Deflectometer (FWD) test. The California Bearing Ratio (CBR) laboratory tests were also conducted on similar samples collected during the field and laboratory tests. A statistical analysis revealed good correlations between the measurements obtained from the three investigated devices and those obtained from the standard tests, thus demonstrating that the investigated devices can reliably measure the in-situ stiffness of highway materials, subgrades and embankments.