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Improving the durability and long-term performance of asphalt concrete (AC) has become a major concern, especially with the increase in the use of recycled materials, warm mix asphalt additives and modified binders. This paper presents an evaluation of different mix design approaches to balance the mechanical properties of AC mixtures. The current volumetric-based design method was enhanced with a performance-based analysis methodology that specifies the parameters from the overlay tester, Hamburg wheel tracking device and indirect tension tests. Two typical Superpave mixes from different plants that exhibited a poor performance, especially in cracking, were selected for this evaluation. The mixtures were first designed following the current volumetric-based design process and characterized under the proposed performance-based analysis. Two alternative approaches that consider the influence of the asphalt content and the aggregate gradation were explored to improve the engineering behavior of the mixtures. From this evaluation, two mixtures that could potentially yield optimal volumetric and balanced mechanical properties were developed. The optimization of the aggregate gradation is a promising approach to formulate a mixture with a balanced stability and durability, as judged by its rutting and cracking potentials.

Proof rolling after completion of compaction of earthwork using intelligent compaction (IC) technology can be used to assess the uniformity of the compacted geomaterials and to identify less stiff compacted areas. To better understand the process of quality management using IC technology, a three-dimensional finite element model was developed to document the theoretical limitations and the sensitivity of IC technology. The model can also be used for setting the target values, and can be part of a methodology to extract the moduli of geomaterials in more rigorous and defensible specifications. Different levels of complexity in relation to linear versus nonlinear behavior of geomaterial and different levels of roller operating conditions (static versus dynamic, moving versus stationary) can be assigned to the model. Such model can only be used with confidence if it is calibrated and validated with experimental field data. Five test sites including single-layer (subgrade only) and two-layer (subgrade and base) geosystems were instrumented using in-ground sensors for calibrating the model. Different vibratory IC rollers from different manufacturers were used to implement IC tests at vibratory stationary as well as moving conditions at the test sites. In all scenarios, a locally calibrated transfer function was necessary to accommodate the differences in the numerical models and vibration data obtained from the IC measurements on test sections with distinct geomaterial conditions. The study also concluded that the predictive power of the numerical models improves if the field measurements and laboratory data are integrated, and more importantly the variability of the materials is incoprorated.

This paper aims to evaluate the effectiveness of a mechanical test that can assess the quality of mineral aggregates commonly used to produce asphalt concrete, in relation to crushing potential, in a more consistent and repeatable manner. Several aggregate types including limestone, dolomite, sandstone, granite, and gravel were sampled from different locations around Texas. The aggregate samples were subjected to various mechanical aggregate tests, primarily the aggregate crushing value (ACV) (BS 812-110:1990) test. A new index, the aggregate crushing potential (ACP), is proposed for the ACV test to improve its characterization potential. The main output parameters from aggregate tests such as the Los Angeles abrasion, magnesium sulfate soundness, acid-insoluble residue, and micro-deval abrasion, which are routinely performed to discriminate the properties of coarse aggregates, were collected. In addition, the dynamic friction test was conducted to measure the friction properties of several of the aggregate sources. Analyses were carried out between the ACV test results and the measured aggregate parameters. The proposed ACP index was identified as a suitable indicator of the durability of coarse aggregates. From this study, the ACV test partnered with the ACP index showed potential to delineate the quality of aggregates, in relation to crushing resistance, more practically and consistently, and eventually may supplant more tedious aggregate test methods.

An evaluation of deep soil mixing (DSM) technology in stabilizing expansive soils was conducted by designing and constructing two full-scale test sections. The test sections were instrument...

Due to the impact of modern information technology, the construction of transportation infrastructure has entered the “Intelligent Era.” The conventional construction technology is also undergoing a paradigm shift. In this paper, the term “intelligent construction” is defined, and the status quo of global transportation infrastructure construction with emerging intelligent construction technologies is summarized. The framework of intelligent construction is presented on all aspects of the integration of modern information technology and the conventional highway technologies. The essential elements of intelligent construction include sensing, analysis, decision-making, and execution. Big data, machine learning, and expert system are applied to provide practical technical solutions for intelligent construction. This paper also elaborates on the process of intelligent decision-making and auto-feedback machine controls. Finally, the future development of intelligent construction is laid out. The globally coordinated efforts by the International Society for Intelligent Construction (ISIC) will help the leading development and implementation of intelligent construction into the future.

The conventional method of estimating the contact area of compaction rollers is based on simplifying assumptions such as the homogeneous and linear elastic behavior of the underlying compacted geomaterials. This study evaluates a stress-dependent approach for estimating the contact area of roller compaction considering the nonlinear behavior of compacted geomaterials. For this purpose, a finite element model was developed to simulate the roller compaction of unbound materials considering both the nonlinear behavior of geomaterials and the soil–drum interaction by means of using advanced contact algorithms. The contact area of the drum was estimated based on the stress distribution at the soil–drum interface for more representative pavement responses than those obtained from Hertzian models. The contact areas from this approach showed good agreement with those measured in the field.

Mechanistic-Empirical (ME) pavement design approaches consider seasonal moisture variations in the subgrade and unbound aggregates base (UAB) layers as an important design parameter. Unders...

Understanding the effect of reclaimed asphalt pavement (RAP) on the mechanical performance of asphalt concrete (AC) mixtures may lead to improved mix design aiming to maximize the use of recycled materials while yielding optimal volumetric properties and balanced performance. This paper presents an experimental evaluation of the RAP content and source on the mechanical performance of AC mixes as measured by overlay tester, Hamburg wheel tracking device, and indirect tension tests. Several Superpave mixes with 12.5 mm nominal maximum aggregate size and recycled binder replacement ratios ranging from 0 to over 50 were designed and evaluated in this study. A performance interaction diagram was used to interpret collectively the cracking susceptibility, rutting potential, and tensile strength of the AC mixes. Asphalt concrete mixes with high RAP content can be balanced with proper individual mix design and their performance assessed through mechanical characterization. Furthermore, AC mixes with RAP from different sources yielded different cracking and rutting potentials. The performance tests and analysis methodology from this study could potentially be incorporated into the balanced mix design process to provide well-performing mixes containing optimal amounts for recycled materials.

The infiltration of water from precipitation through the hot mix asphalt layers in flexible pavements can lead to significant decrease in the moduli of the underlying layers, especially the base layer. As a result, the weakened pavement structure can suffer more damage and deteriorate faster compared with the same pavement under its normal condition. The objective of this study is to develop a framework that can lead to public-domain software that highway agencies can use on a regular basis to conduct a rigorous analysis of the moisture-related structural damage in flexible pavements. A framework of a numerical analysis that integrates the unsaturated hydraulic analysis with finite element structural performance has been developed using two open-source software packages. The framework has been applied to different pavement structures with different drainage systems. Analyses show a significantly longer period of time when the base layer experiences high degrees of saturation in a pavement with poor drainage compared with that for a pavement with proper drainage. Consequently, it is demonstrated that the pavements weakened because of moisture infiltration suffer a significantly higher amount of damage for a longer period of time under traffic, and thus experience shorter service lives. The proposed framework can be potentially used to evaluate and improve the resilience of pavement networks against extreme events that cause heavy precipitation, as well as to evaluate the impact of drainage structures and conditions on life during structural analysis and design of pavements.

The current design methods of concrete pavements assume that the pavement layers will experience stresses/strains that are within their elastic limits. The increase in industrial traffic has led pavement engineers to increase the thickness of the concrete layer to withstand the heavy loads without considering the impact on the foundation layers resulting, in some cases, in premature failure. This highlights the importance of relying on an analysis tool capable of accurately predicting the responses of each pavement layer to ensure that the design limits are not exceeded. Current rigid pavement analysis tools model the supporting layers as a single bed of spring elements (Winkler foundation), which leads to a design process that primarily focuses on the concrete layer and overlooks the advantages or disadvantages of considering specific material properties for each supporting layer. To overcome this limitation, researchers from The University of Texas at El Paso have incorporated a three-dimensional solid foundation model into a finite element analysis tool called rigid pavement analysis system (RPAS). In this study, a comparison between the Winkler and three-dimensional solid foundation models in RPAS has been carried out to evaluate the effects that heavy vehicle loads may have on the responses of roller-compacted concrete (RCC) pavements. The results show that the supporting layer responses are greatly affected by the heavy vehicle loads and ultimately have a significant impact on the overall RCC pavement performance. Additionally, the results show the benefits of using stabilizing materials to optimize the pavement structure by reducing the thickness of the concrete pavement layer and increasing the stabilized foundation layer thickness.

Field observations have indicated significant damage to pavement structures due to sustained saturation of foundation layers after heavy rainfalls. Highway agencies need to have insight int...

This paper evaluated alternative test methods to determine the crushing potential of aggregates and documented the influence of aggregate characteristics on the engineering properties of as...

This paper investigates the process of selecting the aggregate gradation according to the Superpave mix design specifications and evaluates the volumetric properties and mechanical performa...

The resistivity of aggregates used as fill within mechanically stabilized earth (MSE) walls has been found to be a good indicator of its potential to corrode metal reinforcements. As such it is important to accurately measure the fill resistivity. Previous studies have found that resistivity is affected by the gradation of the material, as finer particles normally have much lower resistivity than coarse particles. The resistivity is also greatly dependent on moisture content. To estimate how the variation in moisture content can affect the resistivity, and the in-service performance of MSE walls, laboratory resistivity measurements were performed on 23 materials at varying moisture contents. The results were used to develop a model to estimate the resistivity of a given material knowing its minimum resistivity, porosity, and degree of saturation greater than 50%. Model predictions can potentially be used to estimate the resistivity of in-service wall fill and to harmonize field and laboratory resistivity measurements. The model could be used in future corrosion modeling that considers the seasonal or long-term moisture contents of the fill, similar to the recently developed Mechanistic Empirical Pavement Design (MEPDG) procedure.

Preventive pavement maintenance methods such as slurry seals are cost-effective treatments that increase the longevity of pavements. The incorporation of recycled materials such as reclaimed asphalt pavement (RAP) into asphalt pavement helps to further reduce costs and energy consumption. The present research studied the feasibility of incorporating RAP into slurry seal mixtures or RAP slurry seals. Two slurry seal mixtures containing cement and hydrated lime as fillers were tested. The first mixture comprised slurry seal made with virgin aggregate and the second used RAP as the aggregate. The wet track abrasion test (WTAT) and loaded wheel test (LWT) were conducted to evaluate the performance of the mixtures. Wet cohesion and friction tests (sand patch and British pendulum) were performed on the selected slurry seal mixtures with the best performance under WTAT and LWT. The results show that it is possible to prepare slurry seal containing RAP. Although the curing time relative to the virgin aggregates increased by 1 h for RAP aggregate, the wear value in the WTAT decreased by half. Lateral displacement and the British pendulum test results improved considerably for slurry seals made with RAP aggregates. The results of the sand patch test on WTAT samples showed that slurry seals made with RAP should be lightly rolled after lay-down to improve their friction life. Cost analysis indicates that the use of RAP as an aggregate in slurry seal decreased costs by up to 14%. RAP slurry seal showed better overall performance with lower cost than the virgin slurry seal.

The incorporation of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in asphalt mixes is encouraged as long as the modified mix exhibits equal or improved performance. Through the integration and data mining from several statewide databases, and extensive laboratory and field testing, this paper investigates the performance of asphalt mixes containing RAP, RAS, or both relative to similar mixes with virgin components. The integration of several databases permitted a network-level investigation of performance patterns. The reasonableness of the observed performance patterns was assessed using the results from the Hamburg wheel tracking tests (HWTT) and indirect tensile strength tests performed on specimens from several sites included in a network-level database. Furthermore, the retrieved network-level data were cross-referenced to the results from a historical performance database. At project level, HWTT and the overlay tester tests were performed on samples from several dozen sites to characterize laboratory performance. Field performance of these sites was also documented through periodic cracking and rutting surveys. From the network-level assessment, the impact of RAP, RAS, or both on the performance of the mixes was found to be mix-dependent. The combination of RAP and RAS seems to negatively affect cracking resistance. Further, dense-graded and Superpave mixes with RAP, RAS, or both exhibit higher cracking potential with minimal impact on rutting resistance. The project-level field performance evaluation shows that fatigue cracking propagates at a higher rate for sections with RAP and RAS than for sections with only RAP.

The service life of mechanically stabilized earth walls depends on the corrosion rate of the metallic reinforcement used in their construction. The resistivity of the backfill aggregates needs to be measured accurately to estimate realistically the corrosion rate of the reinforcement. Resistivity testing is usually performed using the traditional soil box on the portion of the aggregates that passes a No. 10 or No. 8 sieve to either select or reject the backfill. For a more reasonable characterization of the corrosivity of coarse backfills, it is desirable to use their actual gradations. To that end, several resistivity boxes that were double and quadruple the dimensions of the original box were constructed. In addition to the three standard gradations specified by the Texas Department of Transportation, over 20 backfill materials sampled from sources throughout Texas were fractionated to fines, fine sand, coarse sand, and gravel. Resistivity tests were performed separately on each of these four constituents for each backfill. The results were used to evaluate a relationship that would allow the estimation of the resistivity of any desired backfill gradations from the resistivity values of these four constituents. The proposed model looks promising since the resistivity of the backfill composed of the actual gradation can be estimated with reasonable certainty. The results of this study can potentially help highway agencies and contractors use a number of local quarries that are currently disqualified based on the resistivity values obtained from only testing materials that pass a No. 8 or No. 10 sieve.

Earthwork and unbound aggregates, are among the most critical components of the construction of transportation infrastructures. Their structural performance can only be assured with appropriate quality management to ensure the materials used are similar to the ones selected in design stage, proper processing of the material to ensure that the materials are uniformly mixed and contain appropriate amount of moisture before compaction, and proper compaction equipment to ensure adequate density and stiffness. The primary tool for quality management is currently a density gauge to ensure that proper density, and in some instances moisture content, are achieved during construction. However, in-situ nondestructive testing (NDT) devices that estimate the stiffness parameters of constructed pavement layers have been emerging over the past decades. Such stiffness parameters are more representative of the structural performance, predicted during the mechanistic-empirical based design process. This paper summarizes a series of laboratory and small-scale evaluations to establish a mechanistic approach for quality management of compacted geomaterials. A synthesis of current state of practice is followed by the evaluation of two nondestructive testing devices during controlled laboratory conditions. The small-scale results were interpreted to represent the moisture and stiffness variations in the field. Based on the results of a range of geomaterials, a mechanistic-based quality management framework was developed.

This paper presents a rational approach to answer the questions of how many field tests need to be performed at a test site to determine its subgrade strength properties, and what inference...

Several highway agencies have either implemented or considered implementing performance tests to predict the cracking potential of asphalt concrete (AC) mixes in the laboratory setting. One such te...

Monitoring and identifying the changes in mechanical properties of the railway track due to climatic fluctuation and operation are crucial. Few systematic methods exist for measuring the mechanical properties of the ballast and foundation layers of a railway track. The Spectral Analysis of Surface Wave (SASW) approach, a nondestructive seismic testing method to measure mechanical properties, has been implemented to evaluate the subsurface conditions of pavements. Due to its straightforward method of data analyses, the possibility of automation and the similarities in layering mechanism and stress distributions in the railway tracks and the pavements, the SASW approach can be employed for rapid assessment of the subsurface conditions of the railway tracks. However, the application of the SASW approach to railway tracks is challenging due to the presence of ties and rails over the tracks and the large variations in characteristics of the ballast and subgrade. This study paper presents the means of studying the complication related to the implementation of the SASW for railway tracks and a suggested alternative in implementing the approach in an optimal manner.

Intelligent compaction (IC) allows real-time monitoring of earthwork from vibration-based measurements of the drum in contact with the ground. IC technology can be employed for the quality management of compacted geomaterials with the purpose of constructing better quality and longer-lasting pavements, when used in conjunction with in situ modulus-based nondestructive spot test devices. Different studies have attempted with limited success to relate roller measurement values with in situ moduli or stiffness values. This study presents a geostatistical approach using a fixed interval analysis to establish a spatial correlation between IC measurement values within defined sublots and spot test measurements using a plate load test or a lightweight deflectometer. Closely spaced spot test measurements show the variability of the material properties of compacted geomaterials. The spot test measurements do correlate better to the roller measurement values when the inevitable variability in the compacted geomaterial is considered.