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Soils have a variety of mineral compositions. Although a number of thermal conductivity models have been developed for soils, few quantitatively investigated the effect of mineral composition. In this study, the finite element method was employed to estimate the thermal conductivity of dry porous soils (kdry) considering the impact of mineral composition and porosity. A generalized model is proposed to predict kdry. The proposed model involves two steps. First, a modified form of Johansen’s model to evaluate the thermal conductivity of soil solid (ks) was established. The modified form considers a large number of soil samples where the soil composition varies and an empirical formula is obtained. Second, kdry is observed parabolically decreasing with porosity. Based on the relationship between kdry and porosity, a generalized model to predict the thermal conductivity of dry soil is proposed, and the empirical parameters for various types of soils are also determined for the sake of engineering applications. The performance of the proposed model is validated by comparing the predicted results with experimental data. A working illustration is exemplified for application of the generalized model.

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.

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 experimental 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 (

This study investigates the stiffness development by bender element tests on specimens of artificially cemented clay, considering the effects of cement content, total water content and curing period. Experimental results indicate that the small-strain shear modulus of cemented clay can be well determined by cement content and total water content. A high cement content or a low total water content results in a stiffness increment of cemented clay. The cementation effect of these two factors is taken into account in this study. However, stiffness of cemented clay increases with curing period; this effect can be well characterised by a hyperbolic function. The function is able to capture both short-term and long-term curing effects. Finally, the effects of mix ratio and curing time are combined, and a predictive model for the stiffness development of cemented clay is devised. The model is validated by experimental results on specimens of cemented clay from various sources.

With the increasing popularity of stabilizing soft soils by a cementitious binder, accurate strength prediction of cemented clay with curing period is essential for quality control. In this study, a generalized hyperbolic was proposed to overcome the shortcomings of traditional logarithmic function with regard to both short-term and long-term prediction of strength development. Also, the generalized formula can be used for various cement types, soil types, and curing conditions. It was proved that the model works well for both Ordinary Portland cement (OPC) and Portland blast-furnace cement (PBFC) treated clay. Moreover, the model can also be adopted for stiffness prediction of cemented clay. Based on the proposed model, the predicted strength and stiffness of cemented clay shows high consistency with the measured data from previous literature.

Due to their high permeability and high strength, pervious concrete piles (PCPs) can improve ground bearing capacity. However, clogging of pervious concrete in practice is a potential disadvantage. To investigate the clogging mechanism of PCPs due to sand piping, a series of laboratory simulation tests is conducted on a developed hydraulic conductivity test system. This testing demonstrates the effects of pervious concrete porosity, grading of fine movable particles, mix ratio of skeleton particles to movable particles, relative density of soil, and distance between PCPs on PCP clogging. The experimental test results show that the hydraulic conductivity of PCP decreases for approximately 70 min and then becomes relatively stable. In addition, it is observed that PCP clogging rarely occurs in cases of low pervious concrete porosity, small movable sand particle size, high sand relative density, and large pile distance. The results also show that measurement of electrical conductivity can be an alternative method of hydraulic conductivity measurement. Based on the test results, preliminary clogging models are proposed.

In 2013, the Texas Department of Transportation completed development of its total pavements acceptance device (TPAD), which contains the next generation of rolling deflectometer integrated with ground penetrating radar and video logging. TPAD collects data at 2 mph and provides deflections measurement at 2-in. intervals from three rolling geophones. In this paper, the development of TPAD is described with typical outputs from the data processing software. How TPAD deflections can be used to determine the load transfer efficiencies of joints and cracks is described, along with the correlation with falling weight deflectometer measurements. Four case studies are presented illustrating typical TPAD data on a range of problem concrete pavements in Texas. These case studies include pavements with a debonded concrete overlay, pavements with voids beneath the slab, and a section that has full-depth patching. The TPAD data collected on US-75, which is a jointed concrete pavement in very poor condition, are presented. TPAD provides highly useful data for planning the rehabilitation of concrete pavements in Texas. Since its development, TPAD has been used on 15 major rehabilitation projects. A popular application is to determine if an upcoming project is a good candidate for an engineered thin asphalt overlay or if more major structural improvements are required.

For concrete pavements it is critical to identify weak spots and locations with very poor load transfer efficiency and then to apply localized repairs before placing a structural overlay. Collecting a continuous deflection profile is the most efficient way to identify those locations. The Texas Department of Transportation’s Total Pavement Acceptance Device (TPAD) has been used successfully on two field projects with main goal of identifying these problematic areas. TPAD is an integrated nondestructive testing tool and it collects continuous deflections at approximately 50 mm intervals with three rolling geophone sensors while traveling over the pavement at 2 mph. Empirical threshold values have been established to identify and prioritize the problematic areas. Refinements to the threshold values can be made with additional field performance monitoring data. In addition to continuous deflections, the TPAD unit also collects continuous Ground Penetrating Radar (GPR) data. In a project on IH 20, the GPR data presented clear evidence that there are wet areas beneath the existing concrete slabs due to clogged edge drains. Trapped moisture is one of the main causes for the recurring failures observed on IH20. On the jointed concrete pavement on Loop 12 in Dallas, five different short sections with high deflections were successfully identified. The responsible district has implemented recommendation for pre-overlay treatment on those five short sections through full depth repairs. The TPAD data provides quantifiable and defensible data for selecting the required repair areas before the overlay to minimize premature failures. With its continuing utilization and additional field performance monitoring, it is anticipated that the refinements to the threshold values for TPAD analyses can be made.

Over the years, the design of thin and ultra-thin concrete overlays (TWT and UTW) has improved. The performance of TWT and UTW sections built with various designs in Texas has been evaluated, with the goal of further improving design standards and construction specifications. Distresses observed in TWT and UTW sections built prior to 2005 were associated with (1) panel size and layout, (2) transition areas, (3) sliding of slab panels, and (4) defects in existing HMA. Design improvements were made in 2011 to mitigate those distresses, which included placing joints away from wheel paths and the use of continuously reinforced concrete pavement (CRCP) or thickened slabs at transition areas. Regardless of the slab thicknesses used, the panel layout should be 1.83- × 1.83-m (6- × 6-ft). The goal is to have saw-cut joints away from the wheel paths, and thus reducing wheel load stresses in concrete slabs. The increase in curling stresses due to the use of this slab size compared with smaller size slabs appears to be offset more by reduced wheel load stresses. Comprehensive characterization of the existing HMA condition should be made to identify and address hidden defects before the TWT or UTW overlays. Even with some distresses, TWT and UTW sections in Texas have performed satisfactorily with oldest sections having been in service for more than 14 years with minimal repairs required. No distresses have been observed in two TWT projects built in 2011 and 2012 with the improved design practices.

Lane separations at longitudinal joints not only allow water to infiltrate into layers under the concrete slabs and deteriorate slab support, but degrade load transfer efficiency (LTE) along longitudinal joints, resulting in an increase in load-related stresses in concrete slabs and poor performance of pavement. Slot stitching provides one of the more efficient methods to restore pavement structural capacity due to lane separations. In 2010, three slot stitching design configurations were implemented on US-75 in Sherman, Texas, which experienced lane separations as well as faulting along the longitudinal construction joint. After the dowel bars were installed, the ultra rapid repair method with the use of high early strength, low shrinkage, and low coefficient of thermal expansion (CoTE) backfill materials was utilized to minimize the traffic interruption and to restore the elevation. For measuring the effectiveness of the repair method, LTE at longitudinal joints was evaluated using Falling Weight Deflectometer (FWD). Testing results in this paper demonstrate the effect of slot stitching design, or more specifically the number of slot stitching in a slab and/or bar size, on improving LTE by providing before-and-after LTE measurements and detailed material information. In particular, the design configuration with 5 #8 bars (25.4-mm diameter) was the most cost-effective and efficient, with about 28% improvement in LTE after more than 4 years of service. Moreover, three design configurations with the use of low-shrinkage, low-CoTE backfill materials were demonstrated to improve LTE substantially, with an average increase from 45% to 74%.

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. Keywords: Traffic data, Load spectra, Truck overweight, Weigh-in-motion (WIM), Portable WIM, Texas overweight corridor

TxDOT is expanding its use of Very Thin Overlays (VTO) as they are economically viable in resurfacing operations. Currently, the VTO mixes are placed at thicknesses of 25 mm (or less) rather than 50 mm mats and they are 30% less expensive per square yard than the traditional dense graded materials. The thin mats are also ideal in many urban situations and highly desirable for many maintenance applications. This paper summarized the requirements and rational of the specifications that were developed to ensure successful thin overlay projects. To evaluate the performance of VTO mixtures, three field projects were selected and mixtures were designed for each location using local materials. The VTO performance to date has been very good with excellent skid resistance and crack resistance. Like any overlay, the final IRI is impacted by the pre-existing ride, but the typical range of reduction on roughness is about 35–50%. To mitigate low skid and bleeding of existing seal coat, fine PFC option (19 mm) with a high air void of greater than 20% was constructed. The free asphalt did not migrate to the surface and the thin PFC did increase skid resistance by 400% and substantially reduced tire-pavement noise. District staffs are very pleased with the VTO performance to date, more pavement sections have been scheduled to place the same VTO mixes.

Reflective cracking potential in hot mix asphalt (HMA) overlays on Portland cement concrete (PCC) pavement depends on the condition of PCC pavement in terms of slab stability at discontinuities (cracks and joints) and asphalt material characteristics in terms of their ability to resist reflective cracking. To develop a more comprehensive HMA overlay on PCC pavement program that minimizes reflective cracking potential and thus improves HMA overlay performance, TxDOT employed evaluation tools for both continuous deflection measurement of PCC slabs and overlay mix material characteristics. Rolling Dynamic Deflectometers (RDD) evaluate deflections on pavement surface continuously, providing valuable information on the stability of concrete slabs and load transfer efficiencies at discontinuities such as cracks and joints. Overlay testers (OT) evaluate the capacity of asphalt mixtures to resist reflective cracking. Since the performance of HMA overlay on PCC pavement depends on the extent of reflective cracking, design criteria should be developed for both slab stability and asphalt material properties. To that end, RDD and OT were utilized for the evaluations of HMA overlay on PCC pavements in four projects in Texas: (1) IH20, (2) SH225, (3) SH12, and (4) US96, with the objective of developing design criteria. This paper documents the efforts made to evaluate the PCC pavement condition before overlay, overlay material properties, and long-term performance of the four sections. CAM and SMA mixtures have been used successfully to retard reflective cracking, as they have exceeded eight years of life expectancy. Threshold values were validated for slab stability and asphalt materials, and applied for the designs of three rehabilitation projects.

Significant efforts have been made to identify the correlations between pavement design, materials and construction variables and pavement performance for new pavement construction; in response to these efforts, specifications and design standards have been developed to optimize pavement performance. On the other hand, less positive correlations have been found between pavement repair materials/methods and the performance of repairs. This issue is primarily due to the incompatibility between existing pavement and repair materials including bonding at the repair interface, as well as the complex nature of pavement behavior near distressed areas. As a result, the variability in the performance of pavement repairs has been rather large. As more pavement sections have reached or even exceeded their design lives, with more frequent distresses, it is important to identify optimum repair methods and/or materials. This paper presents the field performance of several repair strategies with Fiber Reinforced Polymer Patching Binder (FRPPB) patching material for the repairs of spalling, partial-depth punchout and longitudinal joint separations in rigid pavement, for retarding reflection cracking in asphalt overlay on jointed concrete pavement, and for repairs at the transition area between rigid and flexible pavements by the Texas Department of Transportation (TxDOT). The repairs for these distress types have been a challenge to TxDOT districts; repair specifications with acceptable properties of repair materials and methods have not been as well-developed as the specifications for new construction have, resulting in a large variability in the performance of repairs of these distresses. The performance of repairs for the distresses mentioned above with FRPPB has been excellent, with no need for repeated repairs up to this point. The results from this study indicate that if the right materials are used for repairs, along with the correct repair method, the performance of pavement repairs and rehabilitations could be substantially enhanced, minimizing traffic delays and financial resources associated with further repairs and rehabilitations.

Rehabilitating the roadways in the energy sector is one of Texas Department of Transportation’s (TxDOT) top priority activities and is also a high profile activity attracting a lot of legislative oversight. Adding to this problem is that many of these roadways are often in remote areas where there is no access to quality paving materials. In addition, there is no detour and the roadway must be opened at end of work day. The FDR offers great potential to stabilize roadways in-place making use of existing materials and determining the optimal stabilizing agent to make these roadways structurally adequate. Although TxDOT has utilized the FDR for several decades, the performance results vary. Some FDR projects last over 10 years without any distress. However, there were several premature failure occurred within one month of trafficking. This paper presented a successful FDR project using foamed asphalt. The main reason of using foamed asphalt is its one-pass operations that can open to traffic immediately after compaction. Lab mix design was conducted to determine the optimum asphalt and cement contents. FWD tests were conducted to evaluate the change of foamed asphalt base. The determined modulus from foamed asphalt base can be used for future design purpose. The backcalculated moduli for foamed asphalt base increased from 493 ksi (2 weeks after construction) to 800 ksi (6 months after construction). District personal is very pleased with the performance of FDR using foamed asphalt.

Three field projects are presented to demonstrate the application of electromagnetic spectrums for subsurface void detections. It was found that when the void is air-filled, a large negative peak will appear in the waveform, since the dielectric constant of air is much lower than for any surrounding material. Coring and drilling were used for verification purpose. Void sizes from 50 mm to 2 m were successfully detected in this study by using 400 MHz ground-coupled penetrating radar. There is a strong correlation for the arrival times and the size of the void. When the size of the voids increased, the arrival times for the top of voids become longer (e.g., approximately 8 to 10 %, depending on the size of voids). There are inversions and significant negative reflections in the ground-penetrating radar (GPR) image where the defect (air-filled void) is. In contrast, water-filled voids were detected and confirmed in case study 3 with positive peaks. The electromagnetic spectrum was able to locate voids in time. Otherwise, the voids would have grown in size and probably caused the pavement to collapse, which may have caused human casualties and property loss.

Traditionally, in-place air voids are obtained based on field cores. Coring is a destructive and time-consuming process. This study presents a high speed Non-Destructive Testing (NDT) technique with Ground Penetrating Radar (GPR) to characterize the in-place air voids. A total of 92 cores were retrieved from three field projects to establish relationship between the air voids and the measured dielectric by GPR. A statistical model was developed to express the air void value as a function of dielectric and other variables. Contour air void maps could also be produced for the entire pavement sections. The results from the underlying studies have been used as the basis for the repair strategy selections.

Many miles of CRCP and JCP in Texas suffer distresses due to longitudinal joint separation and slab faulting. The absence or ineffectiveness of tie bars causes larger deflections of concrete slabs and pumping, ultimately resulting in lane separation, cracking and faulting of slabs. In addition to full depth repair, slot stitching, stapling, and cross stitching have been used by districts to repair longitudinal cracks and longitudinal joint separations. Field results indicated that districts have successful experiences with slot stitching and stapling to restore load transfer along longitudinal joint and provide horizontal anchorage to prevent further lane separations. Longitudinal joints that had been repaired with slot stitching did not appear to have suffered any further separation or major faulting. Houston district has utilized stapling in many projects. Some of the stapling projects last for more than 8 years. Condition survey results indicated that the performances vary significantly when different slot filler (or elastomeric) materials were used in stapling projects. Few areas showed poor performance as the filler materials had cracked, spalled, and de-bonded from the wall of the slot. In some areas, chunks of the filler material had come out of the stapling joints. The cross stitching may be used to repair cracks/separations that are fairly tight. For wider cracks/joint separations and/or faulted slabs, cross stitching is not suitable. Slot stitching with Class P concrete filler material is the most cost effective approach to repair wide longitudinal joint separations. The cost would be double if full depth repair was used instead of slot stitching to repair the wide longitudinal joint separations.

Some of the conventional Full-Depth Repairs (FDR) in Jointed Concrete Pavement (JCP) suffered recurring failures in less than one year. Under very heavy truck trafficking, tie bars were ruptured, and the slabs were settled for as much as 100 mm. This indicates the conventional method of slab replacement does not address the underlying problem. Falling Weight Deflectometer (FWD) and Dynamic Cone Penetrometer (DCP) were utilized to determine Load Transfer Efficiency (LTE) and base/subgrade support conditions, respectively. After one month of the heavy truck trafficking since opening to traffic, some transverse joints had LTE less than 10%. DCP results confirmed extremely weak base/subgrade support. It was concluded that the weak base/subgrade support was one of the main culprits for the recurring failures. For more effective repair of failures in JCP with heavy truck traffic, an innovative FDR technique with two layers of steel reinforcements and tie/dowel bars to adjacent JCPs was developed. The weak and poor base/subgrade layers were completely removed and replaced with concrete and steel reinforcements. Both longitudinal and transverse repair joints were designed considering the compatibility of concrete volume changes between the existing JCP slabs and repair slabs. Condition survey results indicated that the performance to date has been excellent with no visible distress under almost two years of the heavy truck traffic. For the repair of JCP sections with recurring failures, the implementation of the proposed technique with steel reinforcements and joint designs is expected to result in improved performance.

Three premature failures (related to weak, moisture-susceptible aggregate base) were investigated and the results are presented in the paper. Falling Weight Deflectometer (FWD) tests were conducted to determine the structural load bearing capacity. Laboratory tests were performed to evaluate the aggregate base’s susceptibility to moisture. One successful project that used crushed aggregate base as an interlayer to mitigate reflective cracking was studied. The crushed aggregate base interlayer performed well while other treatments failed. The weak and moisture-susceptible aggregate base, in conjunction with a thin, porous and brittle surface AC, caused premature failures for the three studied projects. It was theorized that the weak base deformed under the traffic load, and this cracked the brittle/thin surface mix. FWD test results for all three projects yielded much higher deflections than the target design deflections, indicating insufficient load bearing capacity. Two key factors for minimizing premature failures are: (1) prevention of water infiltration into the base through good surface mix, and (2) building a base that is moisture resistant. The strategy of using a crushed aggregate base as an interlayer has been utilized on other projects with success, provided it meets two key requirements: (1) Class 1 Texas Triaxial class, after 10 days capillarity and (2) the 10-day final dielectric should not exceed 13.

Several strategies with Fiber Reinforced Polymer Patching Binder (FRPPB) have been used for the repair of jointed concrete pavements. The primary goal of such repairs is to minimize and delay the reflective cracks through a subsequent overlay. The same material has been used successfully in various districts to repair spalls in continuously reinforced concrete pavement, to fill voids at longitudinal joints, and to repair bridge approach slabs that have significant movement. Field results from US59 indicate that FRPPB can be used effectively to retard reflected cracks in AC overlays over JCP. The responsible engineers are very pleased with the FRPPB performance, as the section has provided excellent ride quality over the last 9 years and has required zero maintenance. Since most movements that cause reflected cracks are near the transverse joint, removing a slot at the transverse joint and filling it with FRPPB has proven to be a viable option for mitigation of reflected cracks. To date, the oldest spall repair has been in service for over 8 years, and is still performing well. FRPPB is able to adhere and adapt to volume changes in the surrounding concrete pavement, and conforms to settled or moving concrete slabs without any crack development.

This special issue of the International Journal of Geomechanics contains 10 papers that cover numerical and experimental investigations on various aspects of sustainable civil infrastructures. The topics include the self-healing capability of asphalt, cracking and fracture of asphalt pavement and portland cement concrete, soilimprovement techniques (including compaction and vertical drains), and various foundation systems. There are two papers on asphalt. The self-healing of asphalt mixtures can extend the fatigue life of asphalt pavement. Huang et al. developed a method based on fuzzy evaluation and the analytic hierarchy process for evaluating the self-healing capability of asphalt mixtures. The feasibility and effectiveness of the method were validated by a case study. To understand the mechanisms of material failure is essential for the design and construction of sustainable civil infrastructures. Chen et al. proposed a multiscale numerical modeling approach to analyze the distress of asphalt pavement on steel bridge decks and applied the approach to a case study. Their results highlighted the importance of bridge structure and pavement evenness in the distribution of pavement cracks. One paper focuses on concrete fracture and damage. Xu et al. investigated the spallation failure of fiber-reinforced concrete slabs under impact loading. Their numerical simulations showed that fibers can remarkably improve the tensile strength of concrete slabs and effectively limit the initiation and propagation of cracks. Soil improvement is an important element of sustainable civil infrastructures. Three papers are related to soil-improvement techniques, including compaction and vertical drains. Nie et al. presented an integrated theoretical and case study on anomalous data detection for roller-integrated compactionmeasurement. Their results showed that the proposed bidimensional anomalous data-identification method rendered a more accurate correlation, whereas the proposed neighbor-weighted estimation method improved the precision of compaction evaluation. Two papers are related to vertical drains. Azari et al. applied an elastic–viscoplastic model to model soft soil improved with vertical drains and compared their simulation results with field measurements. Their results showed that the distribution of the overconsolidation ratios in the disturbed zone greatly influenced the viscoplastic strain rates, creep strain limits, and consolidation. Parsa-Pajouh et al. evaluated the efficiency of several proposed formulations for plane-strain modeling of vertical drain-assisted consolidation through an integrated numerical and experimental investigation. By comparing the predicted and measured pore pressures in well-controlled laboratory tests, the advantages and disadvantages of these formulations were discussed. The remaining four papers deal with foundation systems. A better understanding of soil–structure interaction can lead to optimized foundation design and construction, which increase the sustainability of many civil infrastructures. Zhou and Dai presented a new strut-and-tie model for the analysis of force distribution among piles, pile caps, and superstructure components, including struts and ties. Through two case studies, they demonstrated the effectiveness and accuracy of their model. Farouk and Farouk examined the effect of a superstructure’s rigidity on the contact stress and differential settlement for plane two-bay frames. They found that the rigidities of walls and slabs have significant effects on the resultant average contact stresses and the maximum settlements under the footings, which affect the differential settlements. They provided new charts and equations for calculating the average contact stress and maximum settlements under the inner and outer footings for plane two-bay frames. Zhang et al. developed a numerical model to investigate the working mechanism of pervious concrete piles. Their model was validated by a case study. Their results showed that pervious concrete piles can reduce foundation settlement caused by their high stiffness and permeability and, hence, are particularly suitable for reinforcing foundations with low bearing capacity and soils with poor permeability. Yang et al. conducted a numerical investigation on the load-displacement behavior of a reinforced strip footing using a double-yield model. The effects of various parameters, such as burial depth, reinforcement length, and arrangement of two reinforcement layers, were studied. Their results showed that the load-displacement behavior of strip footings simulated with the double-yield model is more realistic than that with the Mohr-Coulomb model, and the optimal burial depth and length of reinforcement obtained from their study agreed well with values reported by previous investigators.

Recent developments of innovative technologies and materials have offered many exciting opportunities for engineers to design and build more sustainable civil infrastructures. Innovation may come in the form of, e.g., better material performance, lower production costs, improved construction and monitoring techniques, reduced health, and environmental impacts. The use of new materials or technologies in an infrastructure project requires a rethink of the existing design philosophy and construction processes. Collaboration between all parties involved (owner, design consultant, contractor, and local authority) is also necessary. Pilot field, laboratory, or numerical studies are often, though not always, undertaken to evaluate the performance of the new technique prior to full-scale applications. This special issue covers a wide range of contemporary issues in the field of geotechnical, pavement, and bridge engineering. The aim of the special issue is to share ideas, knowledge, and experience on the recent developments of innovative materials and technologies for sustainable civil infrastructures. This special issue includes 12 papers that have been subject to the same rigorous peer review process as regular articles in this Journal. There is one paper in this special issue on the sustainable development of bridge infrastructures. Mehrabi discusses advances in evaluation, health monitoring, and rehabilitation of cable-stayed bridges. In addition, the author presents a unified approach for inservice evaluation and cable replacement design of cable-stayed bridges. The author introduces its first application to the Luling Bridge in Louisiana. The cable replacement design accommodates an extraordinary construction sequence to address constraints on space and traffic flow. Temporary cables minimize stress variation and allow for the live load without restriction. The new cable system allows individual strand installation and tensioning, and is expected to facilitate future inspections and replacement. The bridge evaluation process and cable replacement design is unique and successful, which is useful for sustainable development of all cable-stayed bridges. There are three papers in this special issue that discuss the use of innovative techniques to reduce the risk of damage to key infrastructure. The first paper by Huang et al. discusses the use of a global positioning system (GPS) to monitor the Shuping landslide in the Three Gorges Reservoir in China. More than 10 years of ground surface movement data are presented. The triggering factors for surface movement are correlated with fluctuations of reservoir water levels and rainfall records. This important case history shows that long-term and near-real-time monitoring is invaluable for the understanding of landslide movements and their hydrological triggers. On a similar note, in the second paper, Yang discusses the use of remote sensing techniques (satellite images and aerial photos) to determine the probability of road interruption due to landslides for different rainfall return periods. Rainfall-induced landslides are common in Taiwan and often result in road closures. Yang develops a validated landslide prediction model using logistic regression for a rural township in Taiwan. The study area is mainly hilly and mountainous and covers five main roads and 13 villages. The model provides the local authority a useful means to prioritize road maintenance works and to select emergency evacuation routes with lower probabilities of landslide occurrence. High-speed railway (HSR) bridges are important infrastructure in many countries. To ensure their safe operations during the construction of new underpass bridges, in the third paper He et al. describe a risk assessment method and an automated early warning system and their application for a project in Tianjin City, China, where a new bridge was constructed to cross the Beijing-Tianjin Intercity Railway. During construction of the underpass structure, settlement and deformation of the HSR bridges were closely monitored and compared with the predetermined threshold values. This successful case history demonstrates the importance of risk control for the protection of existing key infrastructure. There are three papers in this special issue that discuss different aspects of innovative pavementmaterials andmanagement. The first paper, by Wang et al., develops a fast treatment of winter distresses by using a 1-cm-thick prefabricated rollable pavement based on a textile-reinforced concrete. They find that this innovative prefabricated rollable pavement has high mechanical resistance and positive texture characteristics. With this technique, winter distresses can be repaired and the roadway can be opened for traffic within only a few hours. This technique has the potential to prolong roadway life and enhance sustainability. In the second paper, Steyn et al. investigate the required properties of foamed concrete for possible implementation as an alternative to engineered material arresting system on airports. As part of the investigation, plate load tests, unconfined compressive strength tests, stiffness tests, and density evaluations are carried out on the foamed concrete, using a range of plate sizes that represent different contact areas of tires for vehicles entering an arrestor bed. They find that foamed concrete can be used as an arresting material because the compressive strength and energy absorption of foamed concretemet the requirements. Foamed concretewith densities of 600 and 800 kg=m allow formore settlement, while the stress-deformation relationship is very similar to that ofmaterial currently used in arrestor beds. The third paper, by Chang and Lin, explores the building information modeling to be used in Taiwan as a basis for developing the concept of road information modeling (RIM) for underground pipeline management. Residents in urban areas rely on a complex and dense network of underground pipelines. Underground infrastructure presents unique challenges for

The placement of an asphalt overlay is the most common method to rehabilitate existing concrete pavements. Reflective cracking, however, has been a serious problem with asphalt overlays for a long time. To prevent reflective cracking, it is critical to evaluate existing concrete pavements and identify the joints/cracks with poor load-transfer efficiency (LTE) before placing an asphalt overlay. The most common equipment for this evaluation is a falling weight deflectometer (FWD). However, FWD testing is conducted only at discrete points and is time consuming. It is desirable to use the rolling dynamic deflectometer (RDD) that can continuously characterize each slab and all joints and cracks (e.g., LTE). The RDD was developed in the 1990s at the Center for Transportation Research in Austin, Texas. The RDD is one of the few operational rolling deflection systems that provide continuous data to make project level decisions on rehabilitating concrete pavements. In contrast to the FWD, no RDD data analysis software is available. This paper discusses RDD data interpretation and its application on evaluating existing concrete pavement for asphalt overlays. First of all, some basics of RDD deflection data interpretation are discussed. Several common patterns within the RDD data are identified, and associated interpretation and limited verification are presented in this paper. The RDD deflection data measured before an asphalt overlay on Interstate Highway-20, Texas, and the observed asphalt overlay performance (in terms of reflective cracking) are then presented, and the relationship between RDD deflection and reflective cracking rate is further investigated. Finally, guidelines for evaluating existing concrete pavements using RDD are proposed.

Effects of varying dosages of a water-bearing warm mix asphalt (WMA) additive, Advera®, on a performance grade (PG) binder, PG 64-22, were evaluated. The effectiveness of an amine-based liquid anti-stripping (AS) agent, AD-here® HP Plus, on the Advera®-modified binder was also studied. Furthermore, the effect of reduced oxidative ageing on Advera®-modified binder was investigated. The optimum dosage of Advera® was found to be 6% (by the mass of the binder), which did not alter the base binder's PG. A fairly small amount (0.5%) of the AS agent was found to be effective in increasing the fatigue and low temperature resistances of the Advera®-modified binder. A notable reduction in the high PG temperature was observed when the Advera®-modified binder was aged (short term) at 135°C, and this observation is in agreement with the test results of the Advera® mix, which showed excessive rutting and moisture susceptibility. Test data from a rotational viscometer showed no reduction in the viscosity and the product...

A stretch of State Highway (SH) 6 in Texas has been experiencing poor ride quality problems caused by continuous pavement swelling and heaving. Because of this, the Texas Department of Transportation (TxDOT) Waco District annually spent hundreds of thousands of dollars to overlay the pavement to keep it smooth. This study is motivated to identify the root causes and solutions to the critical problem. During the forensic study, a systematic approach is employed, which includes nondestructive and destructive tests. On the basis of the overall test results, it is revealed that the problem was initiated within the lower portion of the pavement structure (i.e., subgrade) rather than in the upper pavement structure (i.e., asphalt concrete and flexible base). It was further found that the major factors contributing to the subgrade problem include (1) swelling soils, (2) water penetrating into the expansive clay soils, (3) high organics content in the soil, (4) loss of strength of the lime stabilized laye...

Many Full-Depth Repairs (FDRs) have suffered recurring failures and thus there is a critical need to enhance the understanding of the failure mechanisms. Three premature failure projects were investigated. Recurring pumping, settlement and cracks are strongly related to poor Load Transfer Efficiency (LTE), which was obtained with a falling weight deflectometer. Cores were taken to examine the condition of the tie bars. The results from highway IH20 reveal that recurring failures occurred on the same slabs that had poor anchoring to the adjacent slabs. There was zero resistance on the pull-out test before the concrete was poured in 2009. Low LTEs of less than 40% were measured in 2010. Cores taken in 2010 revealed significant surrounding voids at the tie bar, indicating that the epoxy did not ever develop sufficient anchoring strength. The deflections at the joints were 3-5 times higher than those at the center slab. Similar failure mechanisms were observed on the IH35 and US75 projects that had poor LTE. ...

Density criterion for base materials is the most common practice in quality control and quality assurance for pavement construction. However, cases in which the base material has met the density requirement but turned out to be the cause of a premature failure exist. It means meeting the density requirements would not prevent the premature failures from occurring. Field studies indicated that these base materials are found to be either too weak to provide sufficient base support or too brittle, which causes cracks in base layers which in turn leads to secondary damage in other pavement layers. This paper documents the pavement layer moduli obtained from eight forensic investigations spanning 10 years. Falling-weight deflectometer and dynamic cone penetration tests were conducted to determine the layer moduli on sections that were either too weak or too brittle. In some cases, laboratory tests were performed to evaluate the base materials’ reactions to the stabilizers (lime or cement) and base susceptibili...

Over the past few years, the number of Super Heavy Load (SHL) moves on the Texas highways has drastically increased, resulting in severe damage, particularly on low volume roads. One of the major failure modes on these low volume roads is peeling the fresh seal coats that have been employed as a primary maintenance option by the Texas Department of Transportation (TxDOT). In this paper, a mechanistic-empirical (M-E) guideline that incorporates a Microsoft Excel spreadsheet program was developed to aid in the evaluation and characterization of the damage (peel-off) potential of seal coats when subjected to SHL vehicle loading. Field validations were conducted to validate and calibrate the guideline. It was observed that the pavement surface temperature is the most critical factor along with pavement slope in travel direction, combination of aggregate and binder types, and curing period. Additionally, the texture depth that was measured using the sand patch test method was found to play a significant role in characterizing and controlling seal coat damage. Overall, the developed M-E guideline exhibits great promising potential to serve as an aid for evaluating and mitigating seal coat damage due to SHL vehicle loading on low volume roads in Texas.

In the last 10 years, TxDOT has utilized Dowel Bar Retrofit (DBR) in five projects. International Roughness Index (IRI), Falling Weight Deflectometer (FWD), Rolling Dynamic Deflectometer (RDD), and coring were employed to evaluate DBR effectiveness in those five projects. Different versions of special specifications were utilized for each DBR project. The main variables in different versions of the specifications are grout material and slot width requirements. Out of the five projects, four projects (SH73, SH73/SH87, US69, and US287) have performed to the designers’ satisfaction. Those four projects demonstrated that DBR was able to improve Load Transfer Efficiency (LTE) and minimize reflective cracking on an AC overlay. The US69 project reveals that after DBR, Diamond Grinding (DG) should be applied to restore the ride quality. Faulting of greater than 25 mm has been successfully corrected by DBR and DG on the US287 project, which still provides good ride quality after 6 years of service. The experiences from these four projects suggest that DBR with either DG or an AC overlay can be used effectively to extend pavement life and restore the ride if it is done properly. However, on the US59 project, the DBR performance is unsatisfactory. Visible faulting of 6.4 mm–9.4 mm developed in less than 2 years. It was found that the primary cause for the unsatisfactory performance was excessive voids under the dowel bar, which prevented proper load transfer at the joint. X-ray tomography results indicate that approximately 50% of the area under the dowel was void. The following four main variables were investigated in the laboratory for potential causes for voids around dowels: (1) time of placement after grout mixing, (2) vibration time of grout, (3) slot width, and (4) maximum aggregate size. It was found that maximum aggregate size, in the range of 9.5 mm–12.7 mm was not a critical factor for the consolidation of the grout. Although slot width above 63.5 mm may be beneficial, it was not a critical factor for grout consolidation either. The factors that had significant effects on consolidation of the grout were time of placement after mixing and vibration time. Delayed placement of the grout without vibration led to substantial voids. These two factors might be the causes for the voids under dowels that led to poor performance of DBR on US59. The most significant factor for the consolidation of grout materials is vibration. Although vibration has been included in the current Texas Department of Transportation (TxDOT) special specifications for DBR, it should be properly enforced to ensure optimum consolidation. Based on the test results, 20 s of vibration is recommended for each slot. In addition, it is preferable to place grout into the slots before the initial set takes place, or within the manufacturers’ recommended working time.

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 wa...

Before partial-depth repair using proper materials was implemented, Houston District of Texas Department of Transportation had to repair spalls and punchout constantly in the Continuously Reinforced Concrete Pavement (CRCP) pavements on US290 and SH6. The full-depth repair to address the cracking on US75 did not work well. Spalls, wide, cracks and punchouts due to mid-depth horizontal 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 were used to repair the distresses. Material A is polyurethane-based and Material B is epoxy-based. Material A was used to repair spalls in CRCP. It provided quite satisfactory performance for more than 9 years. Material B was used to repair cracks in jointed concrete pavement and CRCP. Its performance was satisfactory when applied to stable slabs and the loose concrete was completely removed. Compared to full-depth repair (FDR), PDRs utilizing polymeric patch materials are much more cost-effective, and PDR takes much less time than FDR. It is believed that both chip-and-patch and saw-and-patch methods would work as long as the delaminated areas are completely removed and the concrete slabs are stable (e.g. no settlement or movement under moving trucks).

In order to understand the reoccurring failures on the slabs or adjacent slabs that received Full-Depth Repair (FDR) treatments, efforts were made to investigate the causes of the failures on IH35W and US75. In addition, one successful FDR project on SH78 was studied to verify and validate the hypothesis of the failure mechanisms. Load Transfer Efficiencies (LTEs) were evaluated with a falling weight deflectometer, and the base and subgrade moduli were determined by Dynamic Cone Penetration (DCP). Cores were taken to examine the condition of the tie bars. Furthermore, design and construction practices were reviewed and evaluated. The common symptom for both IH35W and US75 projects was the poor LTE (less than 40%). When the LTE was lower, there were higher deflections, visible pumping, and settlement. Settlement is strongly related to the poor LTE. Tie bars were found to be ruptured in the US75 pavement, and they were not properly anchored in the IH35W pavement. Because of these ineffective tie bars, poor LTE and settlement was prevalent. On SH78, all LTEs remain above 90% even after 14 years of trafficking. The superior performance of the SH78 pavement suggests that proper procedures are critical when removing concrete and drilling holes for new tie bars, to avoid damage to, and subsequent failure of the adjacent slabs. The anchoring of the tie bar is critical to the performance of the FDR. Pull out tests should be performed to determine the type of epoxy, time before concrete pouring, embedment depth, and other construction parameters will provide adequate strength. Based on the DCP and field performance results, it is concluded that the most accurate indicator of joint performance is LTE, while the base and subgrade support are secondary.

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; ...

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.

Recycled asphalt pavement (RAP) has been increasingly used in flexible pavement construction and rehabilitation. Laboratory and in-place evaluation of the performance of RAP and hot-mix asphalt (HMA) produced with RAP is necessary to the successful use of RAP. Extensive research work has been reported with a focus on laboratory tests of RAP materials. But comprehensive evaluation of the long-term in-service pavement performance with RAP is still at its early stage. In this study, the Texas Specific Pavement Studies Category 5 experimental sections from the Long-Term Pavement Performance program provide an opportunity to investigate the in situ performance of HMA with RAP based on about 16 years of data. In the underlying flexible pavement rehabilitation project, the factorial design includes surface preparation, material, and thickness factors. In particular, a relatively high percentage of RAP, with a content of 35% by weight, was adopted in the asphalt overlay. An in-depth investigation of the pavement performance involving two typical distresses, ride quality and transverse cracking and rutting, is conducted. Compared with sections without RAP (HMA with virgin materials), sections with RAP demonstrated higher cracking amount, less rut depth, and similar roughness change over time. The overall evaluation revealed that a well-designed mix with 35% RAP could perform as satisfactorily as that produced with virgin materials to meet the in-service performance requirement.

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 ...

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 (

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.

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.

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.

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.

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.

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...

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.

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.