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Bridge-approach settlement costs hundreds of millions of dollars in repairs annually. Polyurethane-foam injection by two different processes: (1) a patented deep-injection process, and (2) a non-patented process (directly under the slab) were investigated to study the effectiveness of the slab lifting and leveling. A method of evaluating localized roughness by using areas bound by deviation curves was developed. Three field projects were investigated, one of which was repaired over 6 years ago. The deviation curves from these sites are very repeatable, as the plots often overlap. Evaluating the localized roughness, such as the bridge-approach settlement, using the areas bound by deviation curves seems to be a reasonable approach. The slab lifting with polyurethane foam, using either process, was successful at all three sites. The slabs were all raised to the desired elevation, improving safety and ride quality. The roughness was reduced by as much as 70 %. The falling weight deflectometer (FWD) deflections were reduced by as much as 60 % at many monitored locations. It is believed that when there are no other factors to cause the embankment to lose soil, the polyurethane-foam injection can be used to lift the settled approach slabs. Flowable fill should be used tofill any visible voids prior to the polyurethane-foam injection. The advantage of the patented deep injection process over the non-patented process is inconclusive. [ABSTRACT FROM AUTHOR]

Maintenance and rehabilitation (M&R/play a key role in maintaining aging highway infrastructures. Asphalt concrete (AC) overlays have been widely used in M&R across the state. The successful application of an AC overlay requires comprehensive and in-depth knowledge regarding its material characteristics and in situ performance. To better understand the AC overlay's behavior, the Texas SPS-5 sections from the Long-Term Pavement Performance program are investigated in this study. The eight test sections perform satisfactorily even after 17 years of service. The purpose of this study is to extract useful information and propagate this success to similar rehabilitation projects. The study includes two aspects of work complementary to each other: (A) Laboratory material properties testing (binder and aggregate tests, overlay tester test, and the Hamburg wheel track test) and (B) in situ pavement performance evaluation (transverse cracking, reflective cracking, rut depth, and ride quality). By integrating the information from both aspects, the findings are given as follows: (1) AC overlay with 35 % reclaimed asphalt pavement (RAP) can perform well if properly designed and constructed; (2) in terms of resisting reflective cracking 1 unit thick of 35 % RAP is equivalent to 0.26 unit thick virgin mixture; (3) with the 40 % reflective cracking rate criterion, the life for virgin AC with a 125 mm overlay is 65 % longer than that for a 50 mm overlay; (4) in terms of pavement performance, no significant difference exists between 50 mm milling and non-milling if the milling does not remove existing cracks completely; (5) the maximum rut depth of 12.7 mm among the test sections indicates that the mixture is rut-resistant, and the existing pavement with lime-treated base and subbase beneath the overlay provides sound foundation; and (6) the overlay tester can be a viable and simple measure to evaluate the asphalt mixtures' reflective cracking resistance. [ABSTRACT FROM AUTHOR]

This paper presents the results of seven field investigations (US59, IH20, SH342, US75, US90, MLK Blvd., and US96) to identify the underlying causes of settling and irregular cracking in Portland cement concrete (PCC) pavement. Settling and cracking are not intended, and they are detrimental to the long-term performance of PCC pavement. The falling weight deflectometer and dynamic cone penetrometer were utilized to characterize the load transfer efficiency (LTE) and base support conditions. It was found that when there is adequate base support (e.g., a modulus >345 MPa), the irregular cracks remain tight even after decades of truck trafficking, as evident in the IH20 and MLK projects. Irregular cracks on these projects were caused by late or too-shallow saw cutting. In areas that had 50 % lower base moduli, the cracks typically grew to about 57 mm. The subsidence and settling on US59 and US75 were observed in the areas with LTE in the range of 40 %. Tie bars were found to be ruptured in those areas. When LTE exceeds 80 %, the tie bar was intact and no settling was observed. The maximum defections were approximately eight to ten times higher in the area with settling than the area without settling. It is because the low load transfer efficacy would lead to higher deflection under truck trafficking. The high deflection would initiate pumping and then settling. Despite severe spalling observed before the overlay on US96, the stonemastic asphalt overlay is now 5 years old, and no visible cracks can be observed. This is because of the high LTE (exceeding 85 %) and sufficient base support (modulus exceeding 1378 MPa). The results from the seven projects investigated indicate that base support and LTE play a critical role in concrete pavement performance. To minimize the cracking and settling, it is preferable to have a base modulus and LTE exceeding 345 MPa and 80 %, respectively. [ABSTRACT FROM AUTHOR]

The smoothness of the pavement surface approaching a Weigh-in-Motion (WIM) scale directly affects the device's ability to accurately estimate static loads from measured dynamic forces. Lack of smoothness creates difficulties in reducing the weighing error to an acceptable level. Efforts were made in this study to determine appropriate values of profile length and roughness of the WIM approach. Roughness data for 19 WIM sites across Texas were collected, and the corresponding calibration records from those WIM sites were employed to verify the smoothness guidelines proposed by AASHTO MP 14 and ASTM E1318. Since there are multiple lanes at each WI site, a total number of 70 profiles were collected. Based on the calibration records from the WIM sites and field roughness measurements, it was found that the upper threshold value of Long Range Index (LRI) of AASHTO method MP 14 should be adjusted in order to screen out the locations that yield unacceptable weighing error. The lower threshold value was found to be unnecessary, because more than 90 % of WIM sites yielded acceptable weighing error even when they exceeded the lower threshold value. The LRI is preferable to the Short Range Index (SRI) as it matched well with the field WIM calibration results. Based on the 70 profiles used to determine appropriate lengths, a profile length of 25.8 m preceding the WIM is found to be sufficient. That is the length required to obtain a valid LRI, according to AASHTO MP 14. The ASTM E1318 requirement of 60 m is too conservative. It is concluded that an LRI of 1.74 m/km for the 25.8 m leading up to the WIM is the only critical factor in AASHTO MP 14 and is the limit recommended. [ABSTRACT FROM AUTHOR]

One of the challenges to the implementation of the mechanistic-empirical pavement design guide (MEPDG) comes from calibrating the transfer functions. This paper focuses on calibration of one of the major distress models in flexible pavement: permanent deformation or rutting. Two key aspects are critical to a successful rutting model calibration: data and method. Regarding the data, existing in-field information only provides total rut depth, which could not meet the requirement of permanent deformation in each structural layer by the M EPDG. Concerning the method, existing work either fails to address calibration factors from a holistic perspective by only focusing on individual sections separately or ignores variability inherent in those factors. In this study, layer-wise permanent deformation from instrumented pavement under accelerated pavement testing serves to accommodate the models calibration. A systematic calibration procedure is established, which globally optimizes all available information across all test sections. Through simulation and numerical optimization, optimal calibration shift factors for three typical flexible pavement materials, asphalt mixture, unbound granular base, and finegrain soil are obtained as 0.60, 0.49, and 0.84, respectively. This implies that the uncalibrated MEPDG is biased toward overprediction of rut depth. It is further suggested that a more rational result for each calibrated factor is to introduce an appropriate distribution to characterize its uncaptured variability. In addition, a case study involving using calibrated MEPDG to predict pavement performance or life indicates that (1) model calibration has a significant impact on the prediction and (2) the "fourth power law" is supported by the MEPDG. [ABSTRACT FROM AUTHOR]

Pavement funding allocation and rehabilitation/maintenance decisions are often based on the degree of rutting. Thus it is critical to have accurate rut measurement. In this study, five different sensor setups and computation algorithms were investigated which include: (1) 5-sensor stringline, (2) 3-sensor average, (3) 5-sensor maximum, (4) 7-sensor stringline, and (5) 7-sensor maximum. The 94 transverse profiles utilized in this study included six profiles from the standard 3.7-m wide pavement (with a well-defined rut basin) and 88 profiles from narrow pavements with a possible edge drop off. It was found that the 5-sensor maximum method yielded the best accuracy for both standard 3.7-m wide and narrow pavements. It is surprising to find that the 3-sensor average yielded better results than the 5-sensor stringline method. Also, regardless of the number of sensors (either 5 or 7) or pavement width (standard or narrow), the stringline method always underestimated the rutting. Based on the available data and analyses performed, it is concluded that, without altering the existing sensor configuration, the accuracy would improve significantly by changing the computation algorithm from 5-sensor stringline to 5-sensor maximum. [ABSTRACT FROM AUTHOR]

A forensic study was performed to determine: (1) the extent of voids in the retaining wall backfill in the first 1 m behind the wall panels; (2) the extent of moisture in the suspected wet areas where the District is planning to add turnarounds under the bridges; (3) severity of bridge approach settlement and its ride quality; and (4) whether or not there is global stability concern for FM (Farm to Market) 310, FM 1304, and Chart Rd. mechanically stabilized earth (MSE) walls. Ground penetration radar (GPR), dynamic cone penetration (DCP), drilling, elevation surveys, and instrumentation was performed in this study. Although voids and soft layers were found under the concrete slab, they are all near the MSE wall. Periodic survey results from April 2006 to March 2007 indicate that there is no significant settlement (<10 mm). The piezometer measurements in the MSE walls indicate that the water table was low. The safety factor was found to be 1.4, which is above the minimum requirement of 1.3. Therefore, it was concluded that there is no global stability issue. Longitudinal profiles collected in June 2006 and July 2007 indicated that the maximum settlement in one year was found to be 6 mm for the Chatt Rd. overpass. Although there are some settlements on other overpasses, they are all less than 5 mm. There are no criteria on annual allowable settlement for bridge approaches. Thus, it was decided to continue to monitor the approach slabs without any immediate rehabilitation. [ABSTRACT FROM AUTHOR]

This paper presents the performance of three rehabilitation methods on six highways to restore the condition of concrete pavement: (1) polyurethane foam injection (PFI), (2) dowel bar retrofit (DBR), and (3) full depth repair (FDR). PFI was able to raise the slabs to the target levels; however, it was not able to maintain the slabs at the target levels and thus prevent slabs from further settlement. In addition, new cracks have been observed in some slabs and it was believed that PFI might have created uneven supports that allowed the truck traffic to shatter the slabs. Long-term benefits of DBR were demonstrated on a project with 10 years of traffic, where asphalt overlay was placed. Only minimum reflective cracks were observed on the DBR sections as compared to severe reflective cracks on sections without DBR. In another project, DBR effectively restored the ride quality that reduced the International Roughness Index (IRl) from 2.83 m/km to 1.26 m/km. The poor ride of this pavement section before DBR was due mainly to severe faulting. This illustrates that dowel bars, provided excellent load transfer at transverse contraction joints, which minimized the potential for faulting. FDR has been used to repair localized pavement distresses. However, subsidence of slabs and cracks reappeared on the slabs that received FDR, due partly to the inadequate base support Currently, there are no objective test methods and criteria for base preparation in the FDR specifications. To improve the effectiveness of FDR, current FDR specifications need to be revised. [ABSTRACT FROM AUTHOR]

A forensic study was performed using a rolling dynamic deflectometer (RDD) and overlay tester (OT) to investigate the reflective cracks on SH87. Comparative tests were performed on the BU90 that has no cracks. The test results show that BU90 has lower density and lower asphalt content than SH87. This means the hot-mix asphalt (HMA) on BU90 has less resistance to reflective cracking than SH87. The OT confirmed that the cycles to failure are less for BU90 than for SH87. Thus, in terms of individual layer properties, the wearing surface and crack-retarding layer on SH87 has a greater crack resistance than that on BU90 and the asphalt mixes were not the principal reason for the cracking. The three main contributing factors for the reflective cracking on SH87 are: (1) thinner HMA, (2) higher joint movements, and (3) poor bonding between layers. Based on the reliability concept, at 90 % confidence level, the threshold W1-W3 deflection values were found to be 4.4 mils and it is much less than 6.5 mils developed from the IH20 project that has 100 mm of HMA as opposed to 64 mm for the SH87 project. It reaffirms that thicker HMA takes longer to have reflective cracking and it also needs a higher threshold W1-W3 deflection value. Thus, the thicker HMA overlay on BU90 (183 ram) would delay the reflective cracks. The methodology presented demonstrates RDD and OT's abilities to characterize the reflective cracking potential and the proposed threshold value provides a good foundation for further refinement when additional data are available. [ABSTRACT FROM AUTHOR]

Cost effective design methodology demands accurate performance modeling. Fatigue cracking is one of the major performance indicators in flexible pavement systems. Through literature review, a decision was made to modify the fatigue cracking model in the original VESYS5 program. The revised model in VESYS5W has the same basic form as suggested by the Asphalt Institute (AI) and the 2002 Mechanistic-Empirical Pavement Design Guide (MEPDG). The main challenge in modeling fatigue cracking is to determine appropriate input parameters. Efforts were made to compare the experimental results of full-scale accelerated pavement testing (APT) to the VESY5W predictions using the material parameters suggested by AI and the 2002 MEPDG. The test data employed in this paper are obtained from the full-scale APT conducted by the Federal Highway Administration (FHWA) under a national pooled fund study TPF-5(019). Test results from five lanes at testing temperatures of 19°C were utilized in the comparisons. It was found that the VESYS5W prediction using the material parameters from 2002 MEPDG yielded a much better fit to the experimental results than those using AI material parameters. The VESYS5W predictions using the AI material parameters always underestimated the fatigue cracking life. To match experimental results, shift factors were applied. The shift factors ranged from 0.48 to 3.1 for the predictions using the material parameters from the 2002 MEPDG. However, the shift factors for the AI material parameters ranged from 3.6 to 14.4. In summary, VESYS5W predictions using 2002 MEPDG material parameters provided satisfactory fits to the experimental results with relatively small (≤3.1) shift factors. Based on the FHWA's APT test results and the VESYS5W analyses, two equations are recommended for prediction of fatigue cracking in pavements with conventional mix and with asphalt modifier. [ABSTRACT FROM AUTHOR]

A comprehensive evaluation of pavement condition and an understanding of the underlying causes of pavement distress is vital in selecting the optimal rehabilitation strategy. Three projects were investigated in this study to demonstrate the application of nondestructive testing technologies in this selection process. Ground Penetrating Radar (GPR), Falling Weight Deflectometer (FWD), and Dynamic Cone Penetrometers (DCP) were successfully used on these TxDOT projects. GPR was employed successfully to locate defects in the hot mix surface layer that were responsible for the chronic distress on US 69. This roadway was rehabilitated previously but the strategy used had not addressed the root cause of the pavement problem. FWD and DCP data were also used to determine the structural capacity or layer moduli of the pavement system that allows the designer to derive the overlay thickness. Coring and trenching were utilized to verify the defects detected in the GPR data. The advantage of nondestructive testing is that it provides a comprehensive evaluation of subsurface conditions throughout the entire project, not only at locations where coring and trenching are performed. Furthermore, GPR was employed to verify a rehab design of an old JCP pavement on SH 73. Originally, the plan called for pressure grouting to fill the subsurface voids. However, GPR found no voids under the JCP slab; this was validated in subsequent coring. Therefore the GPR results helped district personnel to eliminate the cost of the pressure grouting. For comparison purposes, GPR results from IH 45 and US 82 (where there were voids under JCP slabs) were utilized. [ABSTRACT FROM AUTHOR]

This paper describes the effects of increased wheel loads on the performance of thin asphalt pavements. Twelve instrumented full-scale test pavements were built inside a temperature/moisture controlled environment, and subjected to accelerated trafficking by means of a Heavy Vehicle Simulator (HVS). The test sections had constant geometry and materials, but the subgrade soil type and moisture content varied. Since tests are in progress, only eight test pavements were used to determine load damage exponents (LDEs). Each test pavement had six test sections for different load levels (22 to 103.5 kN). An LDE model was developed to predict rutting as a function of structural number (SN , load repetitions and load intensity. Good correlations between the model prediction and measurements were found as at least four test pavements have an R- value higher than 90%. Four test pavements had LDEs higher than 7.8, indicating significant impact of loading on rutting performance. It is believed that the high LDEs obtained in this study were attributed to low structural capacity (or structural number, SN) of the test pavements. Thus, it demonstrates that the well known 4th-power law (LDE=4) is too conservative for low SN pavements. With 10% overloading, 4th-power law will underestimate the damage of these light pavements by approximately 68% as compared to those from 8th-power law. A general trend was observed, based on available data, for A-2-4 and A-4 soils that LDE increases with increasing moisture content. [ABSTRACT FROM AUTHOR]

This study evaluates the use of 3D laser scanning technology to measure pavement roughness. Three 100 m test sections, ranging from smooth to very rough (with apparent cracks, areas of distress, and manholes) were selected to investigate the capability of the 3D laser scanning technology. Rod and level surveys were conducted to establish the reference profile for each test section. In addition, Multiple Laser Profiler (MLP) was employed to measure the multiple paths of each test section. Results from multiple paths of 3D laser scanning were compared with those from MLP and rod and level surveys. The 100 m reference profiles indicate similar results between the 3D laser scanning and rod and level survey. With 95% confidence, the statistical paired-samples T-test indicates that there is no significant variation between the results from rod and level surveys and 3D laser scanning. The data include IRI from 2.83 to 13.15 m/km such that they represent a wide spectrum of pavement conditions. The coefficient of correlation (R) between the MLP and 3D laser scanning from 20 longitudinal profiles is 0.99. The 3D laser scanning is a static method and thus the data do not have to be filtered and therefore there is no associated cut-off wavelength problem. Based on the results gathered, the 3 D laser scanner is able to collect reliable profile data and has high potential to be used as a QC/QA tool for construction acceptance. Through 3D laser scanning technology, pavement engineers are able to visualize the pavement roughness covering the entire pavement width in unprecedented detail that consists of extremely rich and accurate point-cloud data. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including the sustainable civil infrastructure, the use of reservoir siltation for backfill applications and the use of recycled materials in pavements.