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Potential benefits in applying polypropylene fiber to stabilize expansive soils and cement treated bases is already been reported in previous studies. So a critical need exists to incorporate the use of fiber into the Texas Department of Transportation's (TxDOT's) Guidelines for Modification and Stabilization of Soils and Base for Use in Pavement Structures. The present paper discusses the results collected from the first experiment al test section on FM897 in the TxDOT Paris District. Three 500-ft (152.4m) test sections were constructed with 2 percent cement on FM897 in February 2020 in the north bound lane loaded truck direction which includes a new sandstone base, full depth reclamation (FDR), and control. However, only the new sandstone base and FDR sections were built with fiber. In this project, two types of fibers were used--(a) fibrillated fiber Fibermesh300, and (b) macro-synthetic fiber Enduro 600.The surface and base layers from the new sandstone base section were removed and used for the edge widening area of the FDR and control sections. Based on the laboratory tests, the optimum fiber contents were found to be 0.6 percent and 0.4 percent for a new sandstone base and FDR, respectively. The laboratory Unconfine Compression Strength (UCS) results showed significant improvements (>112.36 percent) when fibers were added to the sandstone base. To have better control, fiber and cement were manually distributed, following the US Army Corps of Engineers' recommendations. Because of unexpected construction equipment failure that caused compaction delays of approximately 5 hours, cement was in contact with moisture for approximately 5 hours before compaction. UCS results showed an approximate 55 percent reduction when there was a 5-hour delay from the time water was introduced (resulting in the start of the hydration process) until the time of compaction. It indicated that there are detrimental effects on UCS i f there is delay on compaction. There were significant reductions on the normalized W1 deflections at 5 months after construction. In particular, the FDR and new sandstone base sections (with fiber) experienced over 52 percent reduction as compared to 1 week after construction FWD data. Furthermore, the averaged W1 deflections were lower than before construction for both FDR and new sandstone base sections (with fiber). This indicates that there were rapid increases in structural capacity and significant strength developed in the fiber sections between 1 week and 5 months. Further research is needed to explain the mechanism and phenomena. [ABSTRACT FROM AUTHOR]

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]

A forensic study was conducted to investigate the premature cracking distress on an ongoing construction project on State Highway (SH) 24. Transverse cracks occurred at approximately every 9-15 m (30-50 ft) along the 9.6 km (5.9 mi) project. The field tests involved both destructive tests, including trenching and coring, and nondestructive tests, including falling weight deflectometer (FWD) and ground-penetrating radar (GPR) tests. The laboratory tests mainly included cement-treated base material and asphalt mixture material series tests. By integrating all the test results, it was concluded that the premature cracking was originating from the cement-treated base (CTB). Although CTB is not a new concept in pavement construction, stabilization of base materials is a complex process, which, if not handled properly, may lead to premature failures. The two primary factors that contributed to the premature failure are (1) an excessive amount of cement in the CTB, and (2) a high moisture content when the CTB was compacted (almost 2% above optimum moisture). It was believed the possibility of premature failure could be reduced significantly, if the lab verification tests were conducted on the CTB before construction started. Pavement life analysis was conducted to evaluate the current structure adequacy to sustain future traffic. In addition, extensive material design was conducted for the final wearing course asphalt mixture, which was intended to mitigate the effect of existing cracks by resisting crack propagation from the underlying structure. [ABSTRACT FROM AUTHOR]

To prevent premature failures of rehabilitated concrete pavements, transportation authorities need tools to characterize the prerehab pavement condition of its load carrying capacity, and to determine the resistance of the overlay material to underlying crack/joint movements. Two quantitative methods, the rolling dynamic deflectometer (RDD) and overlay tester (OT), along with field performance data were employed in rehabilitation studies involving reflective cracks. The RDD is able to continuously assess vertical differential movements at joints/cracks that represent the potential for reflective cracks on existing pavements. The OT has the ability to determine the resistance of the overlay material to underlying crack/joint movements. The RDD W1-W3 deflections were used to determine areas that have a high potential for reflective cracking due to poor load transfer across joints and cracks. This paper documents results from the RDD and OT on the following five rehabilitation projects: (1) SH225; (2) US96; (3) SH12; (4) SH342; and (5) IH35W. Based on the available test results from these five projects, it was observed that the W1-W3 threshold values of 5.5 mils (0.140 mm) for exposed concrete pavement and 6.5 mils (0.165 mm) for composite pavement with existing hot mix asphalt overlay and an OT threshold value of 700 cycles correlated well with the field performance. Ignoring either of these critical factors may lead to premature reflective cracking. [ABSTRACT FROM AUTHOR]

As part of a national pool funded study 208 on pavement subgrade performance, 12 full-scale test sections (four soil types and three moisture contents) were constructed and tested under the heavy vehicle simulator (HVS) loading. This paper presents the HVS results on two of the four soils tested: AASHTO Class A-2-4 and A-4 soils, respectively. From the results, it was found that the pavement subgrade performance is a function of soil type, moisture content, and applied stress condition. Additionally, this paper also evaluated the current mechanistic-empirical pavement design guide (MEPDG) subgrade rutting (permanent strain) model through comparing with the actual measurements under the HVS loading. It was found that the MEPDG subgrade permanent strain model needs further improvement, and that a single performance model may not be universally applicable to different subgrade soil types. Consequently, a new permanent strain model for each soil type was developed in this paper, based on the HVS results, and that yielded better predictions. With further validation and field calibration, the proposed models offer promising potential to accurately predict rutting behavior of these two soils. [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]

A premature pavement overlay failure had occurred only 1 day after it was opened to traffic. Crescent-shaped cracks were intermittently spread over a section about 3 mi in length. Dynamic cone penetrometer results demonstrated that the slippage cracks were not linked to weak base or subgrade. Loss of overlays on structurally sound pavements due to poor bonding is an expensive error. A tack coat is considered a simple, relatively inexpensive, yet essential step in the pavement construction process. It is theorized that the ineffective bonding due to poor quality tack coat and/or inappropriate application rate is the primary factor that led to the slippage cracks. Other contributing factors include low asphalt content and high aging ratio that reduced the effectiveness of the bond. The aging ratios exceed the maximum allowable 3.5 specified. Based the investigation results, the contractor did remove and replace the top 50 mm hot-mix asphalt (HMA) overlay at his own expense. Although selection of proper tack coat materials and quantities is essential, there is a lack of proper construction quality control and quality assurance procedure to ensure appropriate surface preparation prior to application of a HMA overlay. [ABSTRACT FROM AUTHOR]

The nondestructive mapping of anomalies and voids under roadway pavements is critical to highway authorities because of the potential loss of support that would lead to safety hazards. 400 MHz ground-coupled penetrating radar (GCPR) was used in this study to characterize the subsurface conditions of three roadway pavements (SH359, IH40, and U.S. 290). The extents of the anomalies in horizontal and vertical directions were visible in GCPR images. Coring, boring, and lab testing were performed to verify the settlement and source of the moisture on SH359. The source of the moisture was from the leaking water pipe, as indicated by the high chloride and chlorite contents. A 1.8-m deep void (3.8 m3 in volume) under IH40 and a 1.8 m×4.6 m×3.7 m (30.6 m3 in volume) void under U.S. 290’s reinforced concrete pavements were successfully identified by GCPR and verified by field boring and coring. Fortunately, the voids near the drainpipes were detected by GCPR in time. Otherwise, the void would have increased in size, and that could have led to a severe hazard. This study has successfully demonstrated that the GCPR is able to identify anomalies and voids. Therefore, engineers can utilize the information from GCPR to undertake remedial actions with confidence. [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]

An introduction is presented in which the editor discusses various reports within the issue on topics including the sustainable development of bridge infrastructures, fast treatment of winter distresses, and required properties of foamed concrete.

A section of jointed concrete pavement on U.S. 75, which was built from 1982 to 1985, in the Paris District of the Texas Department of Transportation (TxDOT) experienced severe pumping and settlement, even though two types of treatment (full depth repair and polyurethane foam injection) were performed. An extensive field investigation was conducted using ground penetrating radar, falling weight deflectometer, dynamic cone penetrometer, and coring to identify the causes of the continued pumping and settlement problems, and develop an optimal repair strategy. The pavement evaluation included tie bar condition, load transfer efficiency (LTE) at transverse and longitudinal construction joints, and base support conditions. Some of the tie bars failed in shear due to corrosion, which resulted in substantially low LTEs (<40%) at longitudinal construction joints. Pumping and settlement problems were more pronounced where the tie bars failed; the resulting large deflections exacerbated the pumping and settlement problems. The results demonstrate the importance of adequate LTEs (>80%) provided by tie bars, base and subgrade support, in providing satisfactory JCP performance. Inadequate design or construction of any of these critical elements could lead to performance problems, potentially including severe settlement, which is quite difficult to repair. To repair this pavement section, the Paris District of TxDOT is planning to retrofit tie bars by the “slot stitching” method, along with filling the voids under the slab using grout, followed by thin overlay using latex modified concrete to correct the differential elevation problems at longitudinal construction joints. It is expected that this repair strategy will address the distress problems and extend the pavement life. [ABSTRACT FROM AUTHOR]

An investigation was conducted to determine the root cause of the premature pavement failure. The premature pavement failure occurred in the form of rutting and alligator cracking. Although the affected portion was repaired by removing and replacing the top 75-mm asphalt concrete (AC), the repaired AC experienced recurring rutting and alligator cracking in a few weeks. Through extensive field and lab testing, it was found that the weak base is the root cause of the premature failure and the brittleness of the AC is secondary. However, both the base and AC were built according to plan and met the current material and field density requirements. It was concluded that density alone for construction quality control is not sufficient, as it was not able to protect against premature failures from occurring. Although there are many different ways to minimize premature failures, an immediate action is to include proof rolling in construction quality control. Proof rolling has been used with success to ensure proper compaction and to locate unstable areas, as the stability is greatly influenced by the degree of densification achieved during compaction. [ABSTRACT FROM AUTHOR]

Spalls and wide cracks represent functional and structural distresses in portland cement concrete pavement. Traditionally, these distresses were repaired by partial depth repair (PDR). The performance of PDR varies substantially. Two types of polymeric patch materials, Material-A and Material-B, were used to repair spalls and cracks. Material-A was used to repair spalls in continuously reinforced concrete pavement. It provided quite satisfactory performance for more than 6 years. Material-B was used to repair cracks in jointed concrete pavement. Its performance was satisfactory when applied to stable slabs. Compared with full-depth repair (FDR), PDRs utilizing polymeric patch materials is much more cost effective, and PDR takes much less time than FDR. It was found that chip-and-patch method would work as well as saw-and-patch method as long as the repair limits include all the delaminated areas. [ABSTRACT FROM AUTHOR]

Asphalt overlay has been widely used in pavement rehabilitation. The most frequently observed distress in an asphalt overlay is transverse cracking. In this study, the Texas long-term pavement performance (LTPP) specific pavement study 5 (SPS-5) test sections are highlighted. Three key factors affecting overlay cracking performance are investigated: (i) surface preparation, (ii) overlay thickness, and (iii) material. A deterioration model is developed to evaluate the effects of these factors. The deterioration process is well captured by incorporating both engineering principles and statistical modeling techniques, and the effects of the three key factors are thoroughly evaluated. The results suggest that (i) milling of existing pavement does not help reduce overlay transverse cracking if existing cracking is not completely removed, (ii) thicker overlay contributes to transverse crack resistance, (iii) Texas type C asphalt mixture is more effective in resisting transverse cracks than type B asphalt mixture (with coarser aggregate and less binder than type C), and (iv) overlays that incorporate reclaimed asphalt pavement (RAP) are more prone to transverse cracking than virgin asphalt. Furthermore, these effects are quantified based on the model estimation results. [ABSTRACT FROM AUTHOR]

Where faulting takes place due to the absence of dowel bars and inadequate subbase support in jointed concrete pavement (JCP), dowel bar retrofit (DBR) is used to improve load transfer efficiency (LTE) and to prevent further faulting of slabs at transverse joints. Even though DBR generally improves LTEs and overall performance of JCPs, not all DBR projects have been successful. Faulting reoccurred within 2 years after DBR treatment on US59 in Texas. An investigation from the cores taken in the project revealed excessive voids under a dowel bar due to poor consolidation of the grouting material. A laboratory investigation was performed to determine the most critical factors for adequate consolidation of grouting materials in DBR. Typical rapid-setting grout materials widely used in DBR were selected and full-scale specimens were made for evaluations. Four testing variables for consolidation performance were investigated: time of placement after mixing, vibration time, slot width, and maximum aggregate size. Maximum aggregate size and slot width were not critical factors for consolidation performance of grout. The most significant factor was vibration time. Twenty s of vibration is recommended. Placement time was also an important factor, with grout materials placed after initial set performing poorly. Delayed placement of grout materials without vibration led to the most voids under the dowel bars. [ABSTRACT FROM AUTHOR]

A forensic study was conducted to investigate the premature pavement failure of heaving and cracking on the north bound lane of SH6 and to determine (1) the causes of the heaving and cracking; (2) the severity and extent of the problem; and (3) a prevention strategy. Ground penetration radar (GPR), falling weight deflectometer (FWD), dynamic cone penetrometer (DCP), and soil boring and laboratory tests were conducted. Soil maps provided by the Natural Resource Conservation Service (NRCS) and the electrical resistivity tomography (ERT) were utilized to locate areas that may have similar problems for the ongoing project. It was concluded that the heaving was caused by high organic content in soils. The low pH of the lime treated subgrade layer indicated that the lime stabilization was ineffective. This was due to the high concentration of organic matter. FWD and DCP results indicated that the heaved/cracked areas are losing structural load support. Approximately 84% of the bumps/dips detected by the profiler were also detected by the GPR. Based on the GPR results, it was estimated that about 1.2 miles of the roadway may have potential heaving in the future. Although it is not a standard practice to determine the organic content of soil for new construction, it is critical to determine the organic matter through soil boring and laboratory testing in the suspicious areas. It was found that the soil maps provided by the NRCS yielded a reasonable estimate, and can be used as a screening tool. All five locations (O1 to O5) identified by ERT were verified by boring and laboratory tests to have high organic content (1.9–3.3%). Boring results indicated that ERT was able to map the soil strata and could differentiate between sandy and clay soil types. Although ERT was able to identify the anomalies with high organic contents, and the results were confirmed by boring and laboratory testing, additional work is needed to refine the procedure. [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]

As agencies continue looking for cost-effective methods to rehabilitate deteriorated jointed concrete pavement (JCP), rubblization using a resonant breaker has been experimented by the Shanghai Municipal Roadway Authority (SMRA). It was demonstrated that rubblization using a resonant breaker offers a viable option for the SMRA because the rubblized pavement sections have been performing very well with no visible distress. Based on field observation for a typical hot mix asphalt concrete (HMAC) overlay on a nonrubblized JCP, it was found the treatment normally would have reflective cracking for the same overlay thickness in the first three years. Besides the cost advantage over the reconstruction, a resonant breaker also had yielded the minimum disturbance during the rubblization. It was observed that it was very effective to use water during compaction on a rubblized JCP surface to improve compaction efficiency and to control dust. Furthermore, there is no need to apply a prime coat before the HMAC overlay, as there was no detrimental effect that could be identified. The average rubblized JCP moduli were found to be 1,323 to 1,375 MPa, which are within the range reported in the literature. It was believed that there were high possibilities to increase rubblized JCP moduli without sacrificing the performance by increasing the particle size, because a reduction of 200 mm of HMAC was observed when rubblized JCP increased from 345 to 3,445 MPa at a subgrade modulus of 138 MPa and traffic of 30 million ESAL. However, further research is needed to optimize the rubblized JCP moduli in an attempt to reduce overlay thickness without creating reflective cracking. [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]

In Texas, many miles of plain jointed concrete pavement (JCP) were constructed without proper load transfer devices such as dowels. After a number of years of service, some JCP sections without dowels showed distresses in the form of faulting at transverse joints. Some of the sections were designed in accordance with the AASHTO 1986 Guide, which required 50–75 mm thicker slabs in exchange for not using dowels. This pavement design did not work, with faulting at transverse joints that cause poor ride. Dowel bar retrofit (DBR) was performed on four projects to restore the pavement condition. Overall, DBR restored load transfer efficiency and resulted in improvement of ride quality. Even where the subbase stiffness is 5–10 times less than the minimum value required for proper performance of JCPs, properly installed DBR effectively restored pavement condition with minimum faulting after decades of service. Therefore, it indicated that DBR is able to minimize the faulting even where there is poor base/subgrade support. This is significant in that there are no effective and practical methods to improve subbase conditions in existing concrete pavement, whereas DBR can restore pavement conditions at a reasonable cost. However, not all DBR projects were successful. In one DBR project, faulting in the range of 6.4–9.5 mm occurred after less than 2 years of treatment. Forensic investigation revealed voids under the dowel bars, which indicates poor consolidation of the grout material. Efforts are currently underway in TxDOT to improve specifications for grout materials and DBR construction. [ABSTRACT FROM AUTHOR]

After only 2 months in service, the frontage road of US 290 developed a series of depressions that caused a very poor ride. The main cause of the premature failure was attributed to disintegration of the cement treated base (CTB) layer. This was attributed to two primary factors: (1) a very coarse gradation of the aggregate used in the CTB layer which produced a mix that was prone to segregation during placement; and (2) the CTB layer was placed in two lifts, which were not well bonded together. Another contributing factor was the lack of bond between the CTB and the hot mix asphalt (HMA) surface layer. Secondary factors include high air voids in the HMA layer and low HMA layer thickness. The material, when prepared carefully in the lab at the design cement content, passed the strength requirement of 2.07 MPa. But this coarse mix appears to have been difficult to place correctly in the field. The coarsely graded aggregate used on this project appears to be prone to segregation, either during placement or compaction. The ground penetration radar results (with confirmation by core samples) indicated that most of the problems were at the bottom of the upper CTB lift. The CTB was placed in two lifts and very poor condition was found between the two CTB layers. This problem was coupled with a thin, porous, and poorly bonded HMA layer that permitted moisture to enter the CTB layer. Similar failures have also been reported recently on other CTB projects in Houston. [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]

This paper presents three field projects to illustrate the integrated approach to forensic investigations of roadway pavement failures used widely in Texas. In each case, the combined ground-penetrating radar (GPR) and falling weight deflectometer (FWD) data were extremely useful for identifying contributing factors, such as stripping in the hot mix or localized areas of wet or weak base. Dynamic cone penetration (DCP) is used for validating problems with base and subbase layers. Laboratory tests are often required to complete the investigation, especially if the repair strategy calls for in-place recycling of the existing structure. The extent of stripping and high porosity that caused delamination for Projects 1 and 2 was detected by GPR and verified by core samples. GPR, FWD, DCP, and field soil samples all showed indications that the existing base on Project 1 was wet and the stiffness was only about one-third that of a typical flexible base in Texas. FWD data demonstrate that the pavement structures for Projects 1 and 2 were inadequate, so a rehabilitation strategy was selected that included structural strengthening. In Project 3, GPR, lab density, and permeability tests indicate that the dramatic pavement failures were attributable to moisture entering the base through a poorly compacted asphalt concrete layer and poor longitudinal joints. The base material was found to be highly susceptible to moisture and did not meet the Texas Department of Transportation’s compressive strength requirements when subjected to capillary soaking. The repetitive triaxial test results revealed that the stiffness and load-carrying capability became inadequate when the base materials were exposed to moisture. The pavement structure had been totally replaced in 2004. [ABSTRACT FROM AUTHOR]

Since reflective cracking is related to both the existing pavement condition and the overlay material, appropriate tools are needed to characterize both properties. The rolling dynamic deflectometer (RDD) was employed to measure the continuous deflection profiles that relate to vertical movements of the underlying joints and cracks. An overlay tester (OT) was utilized to characterize the asphalt mix’s ability to resist reflective cracking. The reported threshold values were employed in the study that include: (1) W1–W3=6.5 milsfor composite pavement with old asphalt concrete (AC) overlay; (2) W1–W3=5.5 mils for exposed concrete pavement; and (3) 700 cycles of the OT were employed to evaluate six field rehabilitation projects (SH12, IH20, US96, SH73, SH225, and IH44). It was found that although there were severe transverse cracks and spalling on US96, all W1–W3 deflections were less than 5.5 mils, indicating low risk for reflective cracking. A stone-mastic asphalt (SMA) layer was placed 3 years ago and the performance is excellent. There are no visible cracks or distresses. The SMA was tested with the OT and exceeded 700 cycles (excellent property on resisting reflective cracking). For comparison, there were severe reflective cracks within 4 years on SH225 even with good underlying support and low vertical movements (all W1–W3 deflections less than 6.5 mils) on the jointed concrete pavement (JCP). The reflective cracks were due to a stiff/brittle mix (with OT life of 2 cycles) used on top of the JCP. Dowel bar retrofit (DBR) and full depth repair did improve load transfer and lowered W1–W3 deflections on the SH73 project. After 10 years of service, those locations had minor cracks, as opposed to severe reflective cracks in sections without DBR or full depth repair. Based on the results obtained, the RDD, OT, and the three threshold values provide an objective evaluation that correlates to field performance data. It is strongly recommended that both tools be used for the rehabilitation of concrete pavement with an AC overlay to evaluate the potential for reflective cracking. [ABSTRACT FROM AUTHOR]

This paper presents the results of several investigations to identify the underlying causes of longitudinal cracking problems in Portland cement concrete (PCC) pavement. Longitudinal cracking is not intended and detrimental to the long-term performance of PCC pavement. Longitudinal cracking problems in five projects were thoroughly investigated and the findings indicate that longitudinal cracking was caused by: (1) late or shallow saw cutting of longitudinal joints; (2) inadequate base support under the concrete slab; and (3) the use of high coefficient of thermal expansion (CTE) aggregates. When the longitudinal cracks were caused by late or shallow saw cutting of longitudinal joints, cracks developed at a very early stage. However, when there was adequate base support, the longitudinal cracks remained relatively tight even after decades of truck trafficking. Another cause of longitudinal cracking was inadequate base support, and cracking due to this mechanism normally progressed to rather wide cracks. Some cracks were as wide as 57 mm. Evaluations of base support by dynamic cone penetrometer in areas where longitudinal cracks were observed indicate quite weak subbase in both full-depth repaired areas and surrounding areas. This implies that the current requirements for the subbase preparation for the full-depth repair are not adequate. Another cause of longitudinal cracking was due to the use of high CTE aggregate in concrete. Large volume changes in concrete when coarse aggregate with high CTE is used could cause excessive stresses in concrete and result in longitudinal cracking. To prevent longitudinal cracking, attention should be exercised to the selection of concrete materials (concrete with low CTE) and the quality of the construction (timely and sufficient saw cutting and proper selection and compaction of subbase material). [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]

This paper describes a successful failure analysis to determine the causes of loss of backfill sand from a mechanically stabilized earth (MSE) wall, and cracks on the concrete approach slabs on top of it. The Texas Department of Transportation was concerned that the cracks on the approach slabs may be related to the excessive loss of backfill from behind the MSE walls, and that the embankment structure may be unsafe due to potential voids under the concrete slab. Several cubic meters of sugar sand had washed out of the wall and deposited adjacent to the paneled walls. A series of destructive and nondestructive tests were carried out to determine the causes of the problems. It was found that the cracking of the approach slab and the loss of backfill were unrelated. Suggestions for resolving both problems were made based on this study. [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 forensic study was conducted to identify the cause of the premature cracking on three recently completed projects that were built with the same design. Nondestructive [ground penetration radar, falling weight deflectometer (FWD), GeoGauge, and Portable FWD], nuclear density gauge, dynamic cone penetration, and extensive laboratory tests were performed. It was found that the initial stiffness of the treated base was found to be excessively high by FWD backcalculation. Some sections of the backcalculated base moduli were over 20.7 GPa. This indicates that the layer is excessively brittle for a base material, similar to lean concrete. Six specimens (that were made without a mellowing period) exhibited cracks. There was no cracking for six specimens that had two days of mellowing. It was concluded that the culprit of the transverse cracking in the main lanes was the shrinkage of lime treated base layers. The longitudinal cracks are related to the edge drying and the transverse cracks are related to the insufficient mellowing period. Based on the findings of this study, the District implemented a 2-day mellowing period for Quicklime treated caliche base. Three newly constructed pavements (age 8, 5, and 2 months) were surveyed. No cracking can be observed so far, and the District thinks the cracking problem has been mitigated by the 2-day mellowing period. Without the mellowing period, cracking had normally occurred 1 to 2 months after construction.. [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]

The main objective of the forensic study was to identify the cause(s) of the pavement failure on a temporary detour of an interstate highway in Austin, Texas. Ground penetrating radar (GPR), falling weight deflectometer (FWD), coring, trenching, and comprehensive laboratory tests were performed. It was found that the main cause of the premature failure was attributed to material and construction practices. The base material used on this project did not meet the Triaxial class 1 requirement; it tested as a class 2.3 material. The base material was found to be highly moisture susceptible; it did not meet the Texas Department of Transportation's (TxDOT's) compressive strength requirements when subjected to capillary soaking. In addition, the repetitive triaxial test results revealed that the stiffness and load-carrying capability and resistance to permanent deformation became inadequate when the base material was exposed to moisture. It is believed that moisture entered this pavement primarily through poorly compacted AC layers and longitudinal joints. Cores taken in March 2004 from the original type B and C layers confirmed that the majority of cores have air voids exceeding 9%. The lower type B layer was also badly segregated and debonded from the upper type C layer at some locations. GPR results also indicated that the joints in the pavement were excessively porous. Further tests on the recovered binder for the type B layer indicated that the binder was prematurely aged, most probably from overheating during production. [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]

Reflective cracking through jointed concrete pavement overlays has been a persistent problem. Several different rehabilitation strategies have been used in Texas. This paper is a summary of the performance of strategies used in the past 10 years. The performance of the crack-retarding grid has been disappointing as it has been related to several premature failures. Only one project has realized a benefit of the crack-retarding grid, where the reflective cracking was delayed by about 1 year. The writers believe the small openings in the crack-retarding grid and the lack of an effective bond may be the causes of the layer separation. A proprietary crack-retarding asphalt material has been performing well over two years of monitoring. In one experimental project, 100% of the cracks reflected through conventional overlay material in the first year. Both Petromat fabric underseal and crack-retarding asphalt material have been performing satisfactorily to retard reflective cracking. However, there is a large cost difference between these two treatments. Seven experimental treatments on a major section of US 59 were evaluated. The worst-performing section on the US 59 project was the break-and-seat method, which failed due to weak subgrade support. The weak subgrade is unable to support cracked concrete, which leads to a rocking action under traffic loads. It is concluded that for future projects, the break-and-seat method should not be applied on subgrade with a dynamic cone penetrometer penetration rate exceeding 25 mm per blow. A flexible base overlay with thin asphalt surfacing and the Arkansas (large stone) mix have performed well. Flexible base overlays were able to absorb the joint movement and eliminate the reflective cracking. The flexible base should be of top quality with very low moisture susceptibility. In Texas, this involves specifying a Texas triaxial Class 1 material with classification of “good” in suction/dielectric tests. It is also critical to provide an effective seal for the flexible base. A chip seal followed by a thin 75-mm hot mix layer is recommended. [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]

This paper documents an investigation into the cause of structural distress (alligator cracking and deep rutting) found in a foamed-asphalt warranty project in Texas. This is a unique forensic study involving a warranty specification, where the contractor may or may not be liable for the cost of repairs, depending on the outcome of the study. Extensive field tests, including FWD, seismic, GPR, and DCP, were conducted. Laboratory tests were also done to determine gradation, moisture content, capillary action, and indirect tensile strength. Four trenches were opened to test each layer directly and to obtain samples for laboratory testing. Two of the trenches were located in distressed/failed areas, while two others were in intact areas. Based on this study, the forensic team concluded that the rutting and alligator cracking are associated with failure of the foamed asphalt base. Since the subgrade strength in the failed areas was similar to the intact areas, the subgrade strength could not have been the sole cause of the failure. The foamed asphalt base was found to be susceptible to moisture and exhibited a severe loss of strength when subjected to moisture. Thus, it is imperative to verify the moisture susceptibility during the design phase. Based on the findings of this study, the contractor did repair the failed section at his own expense. [ABSTRACT FROM AUTHOR]

This paper focuses on the cause, possible solutions, and future prevention of pavement heave at a new construction project. We speculated that heaving on the east side of the project was caused by a reaction between the lime stabilizer and minerals in the soil. Because of a difference in soil chemistry, the west side of the project (which was still under construction) did not show evidence of heaving. A forensic investigation was initiated to test our hypothesis. The findings of the investigation concluded that the cause of the heaving on the east side of the road was related to the formation of the expansive mineral, ettringite. Ettringite formed due to the reaction of the lime stabilizer with seams of high sulfate soil on the east side. Laboratory testing did not find any effective stabilizer for the high-sulfate soils on the east side. Therefore, reconstruction would involve removing and replacing the treated layer with a select material that has less than 2,000 ppm sulfates. Test results indicate that there was no threat of sulfate heave on the west side. District personnel had performed the field conductivity tests to evaluate and monitor the concentration of the sulfate content on the remaining project. The treatment of 3%/72-h mellowing period/3% lime treatment was employed on the west side. The whole project has been completed for 1 year and no heave has been observed. [ABSTRACT FROM AUTHOR]

The main objective of this study is to identify the cause of the punchouts observed on Interstate Highway 30 (IH-30), and to identify possible rehabilitation alternatives. Several nondestructive tests, as well as coring and trenching, were conducted in both distressed and nondistressed areas. Middepth horizontal cracks were found during routine repair and by the trenching performed in this study. It is believed that due to temperature variation at an early stage, horizontal cracks developed at the middepth interface between the steel and concrete. The truck traffic caused the horizontal cracks to deteriorate further. Repetitive truck traffic and thermal loading forced the concrete to crack vertically from the middepth where there were horizontal cracks. The closely spaced transverse and longitudinal cracks, along with the delamination, caused punchouts. Although the problem is not imminent, an immediate seal plus a 75 mm heavy-duty stone matrix asphalt (SMA) overlay will probably provide the most cost-effective remedy for this section of IH-30. Existing distressed areas should be repaired before the rehabilitation. To slow the deterioration, the district should use a latex modified chip seal or asphalt rubber seal (AC15-5TR) followed by a 75 mm heavy duty SMA. This is to provide bonding between the concrete and SMA overlay. If the district chooses to do nothing at this time, it will become costly in 2–3 years if current environmental and traffic conditions hold. The cost to repair a severely deteriorated continuously reinforced concrete pavement (CRCP) would be several times more than the 75 mm heavy duty SMA overlay. [ABSTRACT FROM AUTHOR]

Focuses on a study that presented the field and analytical results of a comparative research on an in-service pavement of the United States 281 lanes in Jacksboro, Texas. Information on the Texas Mobile Load Simulator; History of pavement and its condition; Details on the test strategy; Pavement related temperature variation and subsurface moisture movement.

The article discusses the developments of the technologies implemented by the Texas Department of Transportation (TxDOT) to address the challenges on the pavement structural conditions in the state. It provides brief overview of the implementation projects and the testing devices the agency used to determine the condition of its pavement structure. The agency also utilizes the Rolling Dynamic Deflectometer (RDD) to check for reflective cracking potential.

An introduction is presented in which the editor discusses various reports within the issue on topics including the innovative transportation technology, pavement research and surface properties.

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.

Transverse cracking is a major distress in asphalt pavements in north-western Oklahoma. Assessment of probable causes of such distresses is helpful to the design of new pavements and maintenance and rehabilitation of existing pavements. In this study, probable causes of transverse cracking were identified using field investigation and a parametric study using AASHTOWare Pavement ME Design. Specifically, non-destructive and destructive tests were performed on two flexible pavement sections, namely US 270 and US 287 in Oklahoma. Also, soil samples and asphalt cores were collected for laboratory testing. The Ground Penetrating Radar results revealed that the disturbance zone was confined within the pavement structure and cracks were generated at the surface and propagated downward at both sites. The Dynamic Cone Penetration and Falling Weight Deflectometer test results indicated that both pavement sections were structurally adequate to support the current level of traffic for 10 years or more, with proper maintenance. The cracking resistance of the asphalt cores collected from both pavement sections was ranked as poor based on the Illinois Flexibility Index Test. The field and laboratory investigations indicated that stiffer and brittle asphalt mixes at both sites resulting from aging during the long service life were primarily responsible for the transverse cracking observed in the field. Also, a large number of thermal cycles with significant difference between low and high temperature, observed from the weather data, was a likely contributing factor. In addition to field and laboratory investigations, a parametric study was conducted using the AASHTOWare Pavement ME Design. The influence of the changes in pavement structural components, material properties and the average hourly temperature on transverse cracking was examined. Binder grade and pavement thickness were found to be the most influential factors. A hybrid approach involving field and laboratory testing and a parametric study using the AASHTOWare Pavement ME Design was found to be a useful tool for assessment of probable causes of transverse cracking in asphalt pavements. [ABSTRACT FROM AUTHOR]

Traditionally, traffic loading characteristics are collected for pavement design and performance prediction purposes using permanent roadside weigh-in-motion (WIM) stations. However, high installation and maintenance costs associated with these permanent WIM stations dictate that their deployment be mostly limited to major highways, such as the interstate network. Quite often however, pavement damage on high volume rural highways with heavy truck proportions is more severe than anticipated, and there is no effective way of quantifying the traffic loading on these highways. Therefore, this study was conducted to evaluate the potential application of portable WIM systems as a means for bringing the WIM technology to these high volume rural highways. A portable WIM unit was deployed in the Texas overweight corridor in Hidalgo County (Pharr District) near the USA-Mexico border on highway FM 1016 for collecting traffic data for a minimum of three weeks in each direction. The collected traffic data were analyzed to generate traffic parameters such as volume, load spectra, and overloading information both in terms of the gross vehicle weight (GVW) and axle weight. The computed traffic parameters were successful in partially explaining some of the existing pavement conditions on this highway. Overall, the study findings indicated that the portable WIM unit can be used as a convenient and cost-effective means for collecting reliable traffic information for design, analysis, and monitoring purposes. However, proper in-situ calibration of the portable WIM unit at each site is imperative prior to any real-time traffic data collection. [ABSTRACT FROM AUTHOR]