Distributed Thermal Cracking of AC Pavement with Frictional Constraint

This paper develops a model to simulate the distributed thermal cracking of concrete structures with frictional constraint. This model is developed primarily for the thermal cracking asphalt-concrete (AC) pavement structures; however, with some modifications, it is also applicable to similar problems such as shrinkage cracking of concrete and cracking of reinforced concrete in uniaxial tension. This model reflects the multiscale nature of these problems: microcracking or damage on the mesoscale and localization or redistribution on the macroscale. Randomly distributed fictitious cracks are introduced to represent the inhomogeneities and damage in the material at the mesoscale. Friction is recognized as the mechanism leading to stress redistribution and, therefore, damage localization on the macroscale. When the problem is assumed to be 1D and Coulomb friction is used, a semianalytical numerical scheme is developed. The formation of stress-free open cracks is due to the combination of continuous crack growth and unstable jumps, which involve a nonlinear stability analysis. Equilibrium solutions and stability conditions are given in the paper. Displacement controlled analysis is used to follow the unstable equilibrium path after the structure has lost stability. Numerical simulations clearly show that, with slight mesoscale inhomogeneities and in the presence of a constraining frictional force, microcracking or damage on the mesoscale localizes and finally leads to open cracks distributed at a spacing on the order of the macroscale.     

Effect of Design and Site Factors on the Long-Term Performance of Flexible Pavements

Results are presented from a study to evaluate the relative influence of design and site factors on the performance of in-service flexible pavements. The data are from the SPS-1 experiment of the Long-Term Pavement Performance program. This experiment was designed to investigate the effects of HMA surface layer thickness, base type, base thickness, and drainage on the performance of new flexible pavements constructed in different site conditions (subgrade type and climate). Base type was found to be the most critical design factor affecting fatigue cracking, roughness (IRI), and longitudinal cracking (wheel path). The best performance was shown by pavement sections with asphalt treated bases (ATB). This effect should be interpreted in light of the fact that an ATB effectively means a thicker HMA layer. Drainage and base type, when combined, also play an important role in improving performance, especially in terms of fatigue and longitudinal cracking. Base thickness has only secondary effects on performance, mainly in the case of roughness and rutting. In addition, climatic conditions were found to have a significant effect on flexible pavement performance. Wheel path longitudinal cracking and transverse cracking seem to be associated with a wet-freeze environment, while nonwheel path longitudinal cracking seems to be dominant in a freeze climate. In general, pavements built on fine-grained soils have shown the worst performance, especially in terms of roughness. Although most of the findings from this study support the existing understanding of pavement performance, they also provide an overview of the interactions between design and site factors and new insights for achieving better long-term pavement performance.     

武钢钢渣用作沥青混凝土集料研究

通过对武钢钢渣以及钢渣沥青混凝土的路用性能进行的一系列试验，全面分析钢渣的集料性质以及钢渣沥青混合料的高温变形特性、水稳定性、低温抗裂性、抗疲劳性以及抗滑特性。试验结果表明：钢渣具有良好的物理特性，作为道路用集料，性能优于石灰岩；钢渣沥青混合料同样具有优良的路用性能，也优于石灰岩沥青混合料。     

PCC Airfield Pavement Response during Thaw-Weakening Periods

A field study was performed at two regional airports in Wisconsin during spring thaw to determine its effects on portland cement concrete (PCC) airport pavements. This study was part of a research program to model the performance of airfield pavements for the Federal Aviation Administration. Subsurface temperature and falling weight deflection measurements of the pavement structures were taken at both airports and used to calculate the frost penetration depths, the changes in bearing capacity, and the joint and load transfer efficiencies. This paper summarizes the findings of this study and includes several relationships between various engineering properties of the subsurface layers below the PCC layer, along with a procedure for evaluating pavement performance using falling weight deflection data for PCC pavements during spring thaw.     

Use of an Infrared Joint Heater to Improve Longitudinal Joint Performance in Hot Mix Asphalt Pavements

Longitudinal joint cracking is one of the most prevalent forms of distress in asphalt concrete pavements. The joint area does not achieve the same density as the mat due to an unconfined edge on the initial pass and a cold joint during the second pass. The lower density allows water to penetrate and the material cracks, usually within one?year of construction. There are many techniques for constructing longitudinal joints, one being to preheat the joint prior to paving the second lane. This paper describes a field study conducted in New Hampshire using an infrared joint heater. Thermocouples were embedded in the pavement to determine the extent of heat penetration from the infrared heaters. Cores were taken along the joint and in the travel lanes for both the control and test sections. Density and strength measurements were taken on the cores. Permeability measurements along the control and test joints were performed. A cracking survey performed one?year after construction showed that the section of pavement where the infrared heater was used had significantly less cracking than the control section.     

Performance of Transverse Cracking in Jointed Concrete Pavements

Environmental effects and repetitive traffic applications can lead to the development of transverse cracks in jointed concrete pavements. Maintaining adequate aggregate interlock load transfer across these cracks is essential to preserving the functional and structural integrity of these pavements. The objectives of this study were to determine the design parameters that significantly affect transverse cracking and to demonstrate methods available for evaluating cracked pavements. Field data collected from in-service jointed concrete pavements located throughout southern Michigan were used to accomplish these objectives. Joint spacing, coarse aggregate type, shoulder type, and pavement temperature were found to have significant effects on transverse crack development and∕or performance. The surface texture of crack faces was assessed using a promising new test method called volumetric surface texture testing. Volumetric surface texture results provided an indication of the aggregate interlock potential of pavements containing various aggregate types. Three performance parameters capable of mechanistically characterizing crack performance were discussed. A relatively simple procedure was described for determining these parameters and evaluating crack conditions. Field data were also used to demonstrate and validate a voids' analysis procedure. This procedure estimates the potential for loss of support near cracks and joints, thus allowing for proper rehabilitation actions to be taken prior to the manifestation of additional distresses.     

Unified DSC Constitutive Model for Pavement Materials with Numerical Implementation

Need for unified and mechanistic constitutive models for pavement materials for evaluation of various distresses has been recognized; however, such models are not yet available. There have been efforts to develop unified models; however, they have been based usually on ad hoc combinations of models for special properties such as elastic, plastic, creep and fracture, often without appropriate connections to various coupled responses of bound and unbound materials, they may result and in a large number of parameters, often without physical meanings. The disturbed state concept (DSC) provides a modeling approach that includes various responses such as elastic, plastic, creep, microcracking and fracture, softening and healing under mechanical and environmental (thermal, moisture, etc.) within a single unified and coupled framework. A brief review is presented to identify the advantages of the DSC compared to other available models. The DSC has been validated and applied to a wide range of materials: geologic, asphalt, concrete, ceramic, metal alloys, and silicon. It allows for evaluation of various distresses such as permanent deformations (rutting), microcracking and fracture, reflection cracking, thermal cracking, and healing. The DSC is implemented in two- and three-dimensional finite-element (FE) procedures, which allow static, repetitive, and dynamic loads including elastic, plastic, creep, microcracking leading to fracture and failure. A number of examples are solved for various distresses considering flexible (asphalt) pavements; however, the DSC model is applicable to rigid (concrete) pavements also. It is felt that the DSC and the FE computer programs provide unique and novel approaches for pavement engineering. It is desirable to perform further research and applications including validation with respect to simulated and field behavior of pavements.     

Finite Element Analysis of Concrete Pavements Over Culverts

Accelerated distress of Portland cement concrete pavements (PCCP) over structures such as culverts, pipes, and tunnels beneath roadways is a common occurrence. In this article, finite element analysis is employed to analyze the response of concrete pavements over such structures. The factors that influence the overlying pavement slabs include: (1) cover depth, (2) pavement slab thickness and length, (3) cement concrete elastic modulus, (4) foundation modulus, and (5) backfill soil modulus. The tensile stresses at the bottom and top of the slab induced by wheel loads are predicted. In the traditional pavement design only the tensile stress at the bottom of the slab is considered to be significant. However, this study shows that the tensile stress at the top surface of pavement slabs over culverts may also cause the concrete pavements to fail. A laboratory model was employed to study the mechanical characteristics of Portland cement concrete pavement slabs over culverts and to verify the theoretical analysis.     

Utilizing Advanced Characterization Tools to Prevent Reflective Cracking

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.     

Gray System Model for Estimating the Pavement International Roughness Index

The international roughness index (IRI) is a measurement of pavement roughness that is widely accepted for evaluating pavement serviceability, especially its riding quality. Generally, as the age of pavement increases, its condition deteriorates and its IRI value increases. However, the IRI data collected from the Indiana highway system indicate that the IRI values vary considerably for similar pavements and traffic conditions at any given pavement age. This makes it difficult to establish the relationship between IRI and pavement age. In this study, the gray system theory was used to estimate the maximum, mean, and minimum IRI values at different pavement ages. It is believed that the three IRI values are essential for evaluating pavement serviceability. This paper presents the process of the gray system modeling for IRI estimation and discusses the effects of traffic volume on pavement roughness and the estimation accuracy of the gray system models.     

Evaluation of Thermal Cracking at Elmendorf AFB Using SHRP Technology

An evaluation of runway and taxiway pavements was conducted using technology developed or utilized during the Strategic Highway Research Program (SHRP) to determine the effectiveness for identifying thermal cracking propensity of asphalt pavements. SHRP performance grades (PG) of PG52-28 and PG58-28 were measured for the 3 and 6% (weight-to-weight ratio) styrene-butadiene-styrene copolymer-modified asphalt binders employed in taxiway and runway construction. The high temperature SHRP performance grades were above that required by SHRP for the Anchorage, Alaska area according to the SHRP weather database. The low temperature SHRP PG of the binders were found to be insufficient for the area. No rutting has been observed; however, the pavements developed transverse cracks after the first winter following construction of both the runway and taxiway pavements in 1994 and 1996, respectively. The SHRP thermal cracking model failed to predict any cracking within a 10-year period for both pavements. No obvious cause for the model failure could be ascertained. The thermal stress restrained specimen test revealed no significant difference between cracking temperatures for the 3 and 6% styrene-butadiene-styrene-modified binders.     

Evaluation of Full-Depth Asphalt Pavement Construction Using X-Ray Computed Tomography and Ground Penetrating Radar

In the past few years, a number of full-depth or perpetual pavements have been designed and constructed in the State of Texas. A study was conducted to examine the quality of the compaction of the thick asphalt layers within these pavements using advanced forensic tools such as X-ray computed tomography (X-ray CT) and ground penetrating radar (GPR). The GPR is a nondestructive tool for evaluating the uniformity of density in pavements at highway speed. X-ray CT is a laboratory tool that is used to conduct detailed analysis of air void distribution and uniformity in asphalt pavement cores. This paper presents the results of analyzing one of the perpetual pavements constructed in State Highway 114 (SH-114). In this project, two different structural asphalt pavement sections were placed, one included a 1?in. (25.4 mm) stone filled (SF) Superpave mix and the other included a traditional dense graded Type B material. The dense graded Type B material was found to be uniformly compacted. However, major compaction problems were identified with the coarse SF Superpave mix. The poor compaction and associated high percent air vsoids were found to permit moisture infiltration, which could potentially lead to rapid pavement deterioration. The analysis showed very good agreement between the GPR and X-ray CT results and demonstrated the efficiency of using GPR and X-ray CT in the evaluation of asphalt pavement compaction.     

NJTxtr—A Computer Program Based on LASER to Monitor Asphalt Segregation

Abstract: This paper describes the research funded by the New Jersey Department of Transportation to develop an automated technology to monitor segregation during construction of hot-mix asphalt concrete pavements. A Laser-based system was used to measure surface texture and to detect segregation. Two segregated test sections and a control test section were tested to evaluate the applicability of Laser texture method to detect and quantify segregation. Laser texture data were gathered from all three sections. Ratios of texture in segregated areas to that in nonsegregated areas were set as the basis for detection of different levels of segregation. By combining the level of segregation and extent of segregation, an AREA index was developed to determine the acceptability of a pavement section. Based on AREA index, pay adjustment factors were proposed to reduce the payment to account for loss of pavement life due to segregation. Further remedial actions were proposed to correct segregated pavement sections with acceptable AREA index. Based on the above concepts, Windows-based computer program NJTxtr was developed to detect and quantify segregation. This computer program uses the Laser-equipment-collected pavement texture data and determines whether the pavement section is acceptable or unacceptable based on the level of segregation within a pavement section, and provides bonus or penalties to the contractor. The paper describes a novel technology using laser and associated software for construction quality control of asphalt concrete pavements. The proposed methodology was applied to detect segregation in an interstate highway section in New Jersey, and this section was repaved based on visual observation and recommendation from this study.     

Stochastic Spatial Excitation Induced by a Distributed Contact on Homogenous Gaussian Random Fields

The contact between vehicle tire and pavement surface random field is typically modeled as a point contact in the literature of vehicle-pavement interaction. In reality, tire-pavement interface can be considerably larger than a point contact, particularly when a tire is not very stiff and pavements are relatively soft. This paper developed a methodological framework that approximately aggregates one- and two-dimensional random fields within the contact area by taking local, weighted spatial average to account for the distributed contact. Statistical properties such as power spectral density, autocorrelation function and variance of the induced spatial excitation are related to the counterparts of the original random field. It was found that the distributed contact acts like a low-pass filter whose bandwidth is governed by the contact interface and the weight function.     

Field Trial for Asphalt Pavements Reinforced with Geosynthetics and Behavior of Glass-Fiber Grids

This paper presents details of a large field trial and some observations conducted to evaluate the practical efficiencies of geosynthetically reinforced asphalt pavements in Shanxi Province, China. Three glass-fiber grids (LB2000 II, TGG-8080, GGA 2021), one plastic grid (Tensar AR1), two geotextiles (nonwoven needle-punched and nonwoven heat-bonded), and one geocomposite (Tensar AR-G) application were selected for evaluation. These geosynthetics were installed in the interface between new asphalt pavement layers (APL) and new cement-stabilized gravel–sand base courses coated by emulsified asphalt or within new APL in the reconstruction of asphalt pavement sections (Program I), or in the interface between old APL and new overlay layers in the asphalt overlay pavement sections (Program II). In each program, reinforced sections with different geosynthetics were compared with each other and with nonreinforced sections to determine relative performance. Inspections after construction showed that the integrated damage ratio and deflection in the pavement sections reinforced with glass–fiber grids were less than other pavement sections. Furthermore, after about 4?years of service, glass-fiber grids were dug out and no breaking and node movement were discovered. Nevertheless, observations indicated that geosynthetics may not be effective, if bearing capacity of the base course/subgrade is inadequate, or if the overlay thickness is too thin, or if preconstruction repair of distressed old pavement is incomplete.     

Factors Affecting Initial Roughness of Concrete Pavement

Past studies have shown that initial pavement roughness greatly affects future pavement roughness and roughness progression rate. Initial pavement roughness is also an important input to the roughness prediction model in mechanistic-empirical design guide. This study analyzed the design and construction factors affecting initial pavement roughness. Initial international roughness index of 90 concrete pavements constructed in Wisconsin from 2000 to 2004 were analyzed using multiple regression method. The factors considered in this study included concrete pavement slab thickness, project location, dowel bar placement, joint spacing, base type, and pavement length. The factors affecting initial pavement roughness were identified.     

IT Issues for the Management of High-Quantity, Low-Cost Assets

Transportation infrastructure asset management efforts have historically focused on collecting data on assets with high capital costs, such as bridges and pavements. Road signs and pavement markings, on the other hand, are high quantity, low capital cost assets but are also critical elements of the transportation infrastructure. These high quantity assets serve a critical function, safety, and thus they are receiving attention. Mandated by law, the Federal Highway Administration has been working to establish minimum retroreflectivity standards for signs and pavement markings. This paper seeks to address the information technology (IT) problems that emerge when developing an overall asset management system for high-quantity, low-cost assets. These IT problems include asset identification, asset location, data availability, data fragmentation, and automated data collection. A discussion of the issues related to these problems is presented to promote awareness of the myriad problems that do exist and to facilitate the development of more comprehensive systems to manage the automation of infrastructure asset management systems.     

Experimental and Modeling Studies of Permanent Strains of Subgrade Soils

Mechanistic-empirical pavement design guide for flexible pavements as per the AASHTO design guide requires characterization of subgrade soils using the resilient modulus (MR) property. This property, however, does not fully account for the plastic or permanent strain or rutting of subgrade soils, which often distress the overlying pavements. Soils such as silts exhibit moderate to high resilient moduli properties but they still undergo large permanent deformations under repeated loading. This explains the fallacy in the current pavement material characterization practice. A comprehensive research study was performed to measure permanent deformation properties of subgrade soils by subjecting various soils under repeated cycles of deviatoric loads. This paper describes test procedure followed and results obtained on three soils including clay, silt, and sandy soils. The influence of compaction moisture content, confining pressure, and deviatoric stresses applied on the measured permanent deformations of all three soils are addressed. A four-parameter permanent strain model formulation as a function of stress states in soils and the number of loading cycles was used to model and analyze the present test results. The model constants of all three soils were first determined and these results were used to explain the effects of various soil properties on permanent deformations of soils. Validation studies were performed to address the adequacy of the formulated model to predict rutting or permanent strains in soils.     

3D Finite Element Study on Load Transfer at Doweled Joints in Flat and Curled Rigid Pavements

This study examines load transfer across doweled joints in rigid pavements using 3D finite element analysis. A recently developed dowel modeling strategy is employed that allows the efficient and rigorous consideration of dowel/slab interaction. Parametric studies on the response of a typical, dowel‐retrofitted pavement system subjected to axle loads and varying degrees of slab curling are conducted. To examine the effect of slab support on pavement response, the studies consider two different foundation types: layered elastic with an asphalt‐treated base and a dense liquid foundation. The results of the studies are discussed with emphasis on the effect of slab curling and foundation type on joint load transfer and the potential for joint distress. While there are significant differences in response for the ATB‐supported slabs and the slabs founded on a dense liquid, slab curling does generally increase dowel shears and dowel/slab bearing stresses. However, further examination of the parametric study results that accounts for compressive fatigue of the concrete at the dowel/slab interface indicates that slab curling may not significantly increase the potential for damage to the slab concrete surrounding the dowels.     

Probabilistic Approaches for Pavement Fatigue Cracking Prediction based on Cumulative Damage Using Miner’s Law

In mechanistic-empirical (M-E) pavement design, pavement damage is modeled as a random variable with a pre-specified distribution (normal or lognormal). The extent of fatigue cracking in terms of percentage cracking is computed as the probability of cumulative damage exceeding unity. This paper provides a methodological framework for characterizing damage distribution under mixed traffic loading (multiple strain levels) with an improved forecast of traffic spectrum based on renewal theory. Using the linear Miner’s law for damage accumulation, analytical representation of damage distribution is obtainable owing to the proportional relationship between maximum tensile strain of pavement and traffic load under linear elasticity condition. Numerical computation shows that percent of cracking from derived damage distribution is greater than that from hypothetical normal or lognormal distributions traditionally used in the M-E pavement design. The method developed here and the derived model can be used in pavement design and pavement management systems.