Computational Modeling and Simulations of Condition Deterioration to Enhance Asphalt Highway Pavement Design and Asset Management

A nation’s economy and prosperity depend on an efficient and safe transportation network for public mobility and freight transportation. A country’s road network is recognized as one of the largest public infrastructure assets. About 93 percent of 2.6 million miles of paved roads and highways in the United States (U.S.) are surfaced with asphalt. Longitudinal roughness, pavement cracking, potholes, and rutting are the major reasons for rehabilitation of asphalt roads. Billions of dollars are required annually for the maintenance and rehabilitation of road networks. If timely maintenance and rehabilitation are not performed, the pavement damages inflicted by heavy traffic repetitions and environmental impacts may lead to life threatening condition for road users. This research is focused on asphalt pavement condition deterioration progression modeling and computational simulations of uncracked and cracked asphalt pavement-subgrade models. The research objectives are to (1) evaluate and enhance asphalt pavement condition deterioration prediction models, (2) evaluate modulus backcalculation approaches for characterizing asphalt pavement layers of selected test sections, (3) develop three dimensional-finite element (3D-FE) asphalt pavement models and study impacts of cracking on pavement structural responses, and (4) implement pavement condition deterioration models for improved structural design and asset management of asphalt highway pavements. The historical asphalt pavement database records of the Long-Term Pavement Performance (LTPP) research program were used to develop asphalt pavement condition deterioration progression models, considering LTPP regions and maintenance and rehabilitation history. The enhanced condition deterioration prediction equations of the International Roughness Index (IRI), rutting, and cracking distresses were developed and evaluated in this research for LTPP datasets of 2,588 for IRI, 214 for rutting, and 2,240 for cracking. The LTPP regions and major maintenance intervention criteria were comfactors considered in all multiple regression equations. The IRI prediction equation also considered the IRI measurement location factor. Additionally, the rutting prediction equation includes additional factors of in situ modulus of pavement layers and base layer type. In comparison, the U.S. national mechanistic empirical pavement design guide (MEPDG) performance prediction models do not include maintenance and rehabilitation and climatic factors which present major limitations of the MEPDG method of pavement thickness design. Both regression analysis and Artificial Neural Network (ANN) analysis methods were used and the results were compared. The IRI multiple regression equation shows R of 0.633, which is slightly lower compared to the ANN IRI model’s R of 0.717. The IRI predictions using the enhanced multiple regression equation are comparable with the ANN results for verification data sets. The prediction equations from multiple regression modeling and ANN modeling of rutting distress show high R values above 0.93 and 0.94, respectively, and reasonably accurate result of model database and verification section. These model equations have got higher R value compared to the MEPDG’s R value. A new cracking model namely Unified Cracking Index (UCI) was developed in this research by combining all crack types which is not available in the MEPDG. The overall UCI combines the densities (% crack area per total area) of the alligator, block, longitudinal, and transverse cracking types. This approach is practical and easy to implement with intervention criteria of maintenance and rehabilitation for life-cycle asset management of asphalt highway pavements. The UCI equations using multiple regression for log transformation and using sigmoidal transformation for the model database shows the correlation, R, of 0.551 and 0.511 respectively, with 19.5 and 4.1 percent errors in predictions compared to the measured LTPP data. In comparison, the ANN model for UCI shosignificant improvements in R value (0.707) with 14.6% error. It also shohigh R value (0.861) and low error for the verification data sets. The MEPDG method includes separate models of alligator crack, longitudinal crack (defined as fatigue induced crack in the MEPDG), and transverse crack. In comparison, this research developed prediction equations not only for alligator, longitudinal, and transverse cracks but for block crack too. Individual ANN model of cracking (alligator, block, longitudinal, transverse) also shoreasonably accurate results. In situ modulus values of existing pavements are other important material inputs for pavement structural response analysis of overlay thickness design. Several modulus backcalculation software, based on the layer elastic static analysis theory, were evaluated in this research for selected LTPP highway sections. The comparisons indicated that the backcalculated modulus values in the LTPP database were generally unreasonable using the EVERCALC 5.0 software. Overall, the backcalculated modulus values using BAKFAA 2.0 and PEDD/UMPED were generally reasonable for all pavement layers. It was also shown that the thickness design of longer lasting pavement performance depends on seasonal layer modulus values considering extreme weather and climate attribute. In order to create a structural response database for pavement-subgrade subjected to design truck axle load, the 3D-FE models of uncracked and cracked asphalt pavement layer were developed using the LS-DYNA finite element software. The structural responses such as surface deflections, stresses and strains at different depths in the pavement-subgrade model were analyzed for critical locations. A full factorial experiment for six independent variables at two levels was designed, and the simulations for 64 treatment combinations were executed for the uncracked model. The results of the 3D-FE models shocomparable results with previous studies using the LS-DYNA software and the outputs of the GAMES linear elastic program. An extended analysis was conducted on the cracked model to study the effect of full depth cracked on effective viasphalt modulus values. Based on the full-depth cracked 3D-FE model results, low-level modulus of weak pavements shoa higher reduction of 81.0 % in the asphalt modulus compared to the compared to the asphalt modulus of the uncracked 3D-FE model, while the high-level modulus and thick pavement shoa low reduction of 13.5 % in the asphalt modulus of the uncracked pavement model. The development of the enhanced pavement condition prediction equations provide significant improvements over the MEPDG method, such as consideration of maintenance and rehabilitation history and climatic regions, using larger number of LTPP datasets, compared to model data sets used in the MEPDG. Therefore, the developed equations are more appropriate for the pavement structural design and asset management of asphalt highways. This implementation will contribute towards longer-lasting asphalt highway pavement assets to serve the public, improve safety, support efficient supply chain and economic growth

Experimental assessments of methanol-based foaming agent in latex modified foamed binders and warm asphalt mixtures

Latex is one of the natural rubbers that is used to enhance the performance of asphalt pavement for the last few decades. The presence of latex, which is categorized as an elastomer, helps to improve pavement performance and durability. Conversely, higher viscosity of latex modified asphalt binder increases the production-temperatures of asphalt mixture, thus consuming higher energy during asphalt mixture’s production stage. In this study, the effectiveness of methanol as an energy-efficient foaming agent was assessed to reduce the viscosity and enhance the workability of the modified asphalt binder. The basic and rheological properties of the asphalt binders were determined through multiple laboratory tests including expansion ratio and half-life, rotational viscosity, softening point, torsional recovery, and dynamic shear rheometer. The properties of asphalt mixtures were assessed through the service characteristics, mechanical performance, and moisture resistance criteria. It was found that the presence of latex results in an approximately twofold higher expansion ratio and a lower half-life of the asphalt binder at about the same ratio. Through the rotational viscosity test, the application of methanol into asphalt binder decreased the viscosity and led to better workability, despite the addition of latex as an asphalt modifier. The application of methanol into asphalt binder improved the workability of mixture samples and lowered the compaction energy of the compaction process, which are the crucial criteria for a better mixing and compaction process. Methanol foamed asphalt mixtures with latex show much higher resistance to moisture damage and stiffness than control sample even though they were prepared at a lower temperature

Cleaning effect on clogged porous asphalt mixture

Porous asphalt pavements provide developers and planners with a new tool for stormwater management and noise reduction. However, the clogging of pores caused by sediment could significantly affect the permeability of porous asphalt. Thus, the objectives of this study are to determine the effect on the permeability of the clogged porous asphalt mixture, investigate the cleaning effect on the performance of porous asphalt mixture, and study the Image processing of clogged in the porous asphalt mixture. To assess the effect of clogging on permeability, Marshall Stability test and Binder Drawn test were performed. In addition, Image J software analysis was applied to show the sediment's particle size and the void of the mixture. From the Marshall Stability test, the amount of void mixture can be concluded that the void decreases with increasing clay content. From the Binder Drawn test, the retained binder increased as the percentage of bitumen increased. This indicates that the permeability of the mixture is lower in the presence of a blocking agent. The analytical of image study found that the images can be seen more clearly and can distinguish each mixture of materials used. In addition, the total percentage of voids can be identified from the analyzed images

Influence of sawdust ash as filler in asphalt mixture

Using saw dust as a filler in asphalt mixture would go a long way toward alleviating the boycott of certain building enterprises' use of mineral filler in asphalt mixture, as well as decreasing the impact on littering and emissions in the environment. In this study, the performance of Sawdust Ash (SDA) as filler in asphalt mixture was investigated and mainly focused on the addition of sawdust ash in following the order of 0% as control, 3%, 6%, and 9% by bitumen weight. The bitumen used in this study was 60/70 penetration grade. The purpose of this study was to study the effect of sawdust ash on the engineering characteristics of concrete asphalt. Different percentages of sawdust ash were mixed into bitumen using a high shear mixer. The Marshall Stability test was carried out to determine the optimum bitumen content of the mixture. The performance was evaluated through stability and volumetric properties, modulus of resilience and indirect tensile strength. It can be seen that the different percentage of sawdust ash as filler in Hot Mix Asphalt had noticeably different effects on the performance of modified mixture. The added of sawdust ash as a filler in HMA was not enough improvement to the performance of asphalt pavement as the performance of conventional mixture is more stable than modified mixture

Performance of dense graded asphalt incorporating cellulose fiber

In past years, cellulose fiber has been increasingly used on pavement asphalt and has become one of the causes that increases pavement strength and reduces environmental challenges, as it provides a key, sustainable alternative to other technical materials. Cellulose fiber is utilized to increase asphalt binding qualities and on-the-ground paving performance. One of the main challenges affecting dense grade asphalted surface and quality performance is the high cargo weights, which increase road usage, owing to different difficulties such as fatigue cracking and other deformations due to overload on roads. The primary objective and goal of this study is to explore the efficacy of adding cellulose fiber to asphalt utilizing a dry approach. In this study, five different percentages of cellulose fiber content were employed, which are as follows: (0%, 0.2%, 0.3%, 0.4%, and 0.5% from the total weight of aggregate). In addition to this investigation, an asphalt grade of 60/70 penetration is chosen. In order to discover the optimal modifier, the predicted performance of the modified binder is compared to that of the unmodified binder. The study is carried out utilizing Marshall stability, resilient modular tests, dynamic creep, and abrasion tests to compare the findings obtained from changed and unmodified asphalt samples. The results achieved in this research have proclaimed cellulose fiber to be an effective material to be employed as an addition to the asphalt binder because it enhances performance by enhancing paving strength and rigidity for future development

Engineering properties of porous asphalt mixture incorporating kenaf fiber

Porous asphalt (PA) is one type of flexible pavement known as pavement that has a permeability capability designed to control rainwater and reduce surface runoff. However, the structure is subject to damage from cracking, grooves, stripping and rapid aging under the effects of repeated vehicle loads on the road, hot weather and heavy rain. The use of kenaf fiber benefits in an effort to increase the strength, lifespan and durability of road pavements because kenaf fiber tends to be used for crack control and strengthens the path by resisting cracking stress. Therefore, the purpose of this study was to evaluate the performance of porous asphalt incorporating kenaf fiber and to determine the optimum fiber content of kenaf fiber modified porous asphalt. The mixtures containing varying percentages of kenaf fiber were evaluated to check which samples provided the best performance. The laboratory test as per requirement was carried out which are LA Abrasion, Resilient Modulus, Marshall Stability and Flow and Dynamic Creep. The results showed that the addition of 0.3% kenaf fiber gave the lowest value of abrasion and kenaf fiber content contributed the highest value of Resilient Modulus. While the kenaf fiber content for Marshall Stability is 0.5% and the Dynamic Creep is 0.4%. Using ranking method, the optimum fiber content can be identified which is 0.3%. The modified PA mixture with kenaf fiber resulted in improved performance of PA as a road surface material. In conclusion, asphalt mixtures containing kenaf fiber improved the stability and strength of the mix

Mechanical performance of dense-graded asphalt mixture incorporating steel fiber

Dense graded asphalt is usually used for highways, main roads, industrial and distributor roads due to their densely packed constitution. In order to improve more on its durability, stability and service life various additives are introduced and among them are steel fibers. Steel fiber has been reported that it increases the mechanical performance of asphalt mix. This paper reports on a comprehensive study on the mechanical properties of dense-graded asphalt AC10 incorporating steel fibers. Mechanical properties studied include abrasion resistance, stability, density, stiffness, resilient modulus and dynamic creep of asphalt mixtures. The tests carried out are Abrasion test, Marshall Stability, resilient modulus and dynamic creep. Steel fiber content used was 0%, 0.2%, 0.4% and 0.6% of the asphalt mixtures. The laboratory results showed that steel fiber addition into DGA AC10, improve all the mechanical properties covered in this investigation except the stiffness. Although the addition of steel fiber reduces stiffness properties that makes it revealing to the deflection, the modified samples still shows improvement in abrasion, stability, density, resilient modulus and dynamic creep

Performance of asphaltic concrete modified with recycled crushed bricks

The pavement industry relies greatly on this conventional material in constructing the road. However, the shortage of the mined material has led to the need of finding alternative with local materials to partially substitute the asphalt components. The conventional pavement industry also contributed to thermal and greenhouse emission resulting from the mining activities. In addition, throughout the year, the amount of construction and demolition (C&D) waste generated from civil construction activities particularly in Malaysia is increasing in alarming rate. Recycling the C&D waste specifically in bricks is viewed as reasonable potential as aggregate modifier in the impulse for greener and sustainable asphalt pavement production. In this paper, recycled crushed bricks (RCB) is introduced to bituminous wearing course as partial replacement for coarse aggregates. The coarse aggregate is partially replaced with RCB in proportions of 0%, 10%, 20%, 30% and 40% by weight. This study summarizes the results of laboratory evaluation of Los Angeles Abrasion Value, Aggregate Crushing Value and Marshall Test. Results show that asphaltic concrete modified with 10% RCB has the lowest abrasion and crushing values which were 20.2% and 30% respectively. Similarly, the mix has the highest Marshall Stability and lowest flow which 15.61 kN and 3.37 mm respectively. Thus, partial replacement of coarse aggregates with 10% RCB in bituminous mix is suitable to be used in wearing course and can be used as alternative material in bituminous mix to reduce the dependency on natural aggregates and utilize the C&D waste efficiently