Innovative Modification and Testing of Asphalt Crack Sealants

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Description
Asphalt crack sealants are essential for preserving the integrity of asphalt pavements. They act as a barrier against water infiltration, a primary cause of base erosion and structural failure. However, these sealants are susceptible to degradation from traffic wear, weathering,…

Asphalt crack sealants are essential for preserving the integrity of asphalt pavements. They act as a barrier against water infiltration, a primary cause of base erosion and structural failure. However, these sealants are susceptible to degradation from traffic wear, weathering, and thermal stresses. This degradation manifests in multiple failure modes, including loss of cohesion, adhesion, and settlement. Being one of the most cost-effective pavement maintenance techniques, its market size is expected to be worth about $1.1 billion by 2028, with a 56% market share in North America alone. With extreme climatic events, sealants will have a tendency to fail more often. Therefore, this research effort investigated the incorporation of various modifiers into asphalt crack sealants and fillers to enhance their performance and durability, to perform beyond their designed life. Four different modifiers were selected and tested using a specific laboratory testing protocol targeting the failure modes observed in the field and ultimately leading to extended pavement lifespans and reduced maintenance expenditures. Furthermore, a novel test procedure to measure the coefficient of expansion and contraction of control and modified sealants was developed and calibrated as part of this study. These modifiers included an aerogel modified bituminous material, a pre-activated crumb rubber material, a recycled aerogel composite, and synthetic fibers.The testing program included durability and strength testing such as bonding strength, shear thinning, toughness, and tenacity; and thermal behavior testing such as expansion and contraction, thermal conductivity, and specific heat capacity. The coated aerogel modifier provided better toughness, tenacity, and bonding properties with improved thermal properties. The pre-activated crumb rubber reduced the effect of aging, whereas fibers showed promising results across most parameters. As for the recycled aerogel composite, thermal susceptibility was slightly improved, in addition to low temperature behavior for the filling material. Finally, a multiple decision-making criteria method was adopted to rank the best modifier for each material for parking lots and roadways followed by a life cycle cost analysis. A survey was conducted to rate the importance of each factor affecting performance, based on the integration of both quantitative and qualitative criteria, thereby accommodating diverse decision contexts and preferences.
Date Created
2024
Agent

Impact of Three-Dimensional Stress Pulse Configurations and Rest Period on Permanent Deformation Characteristics of Asphalt Concrete Mixtures

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Description
Asphalt concrete (AC) layers in airfield and highway pavements are subjected to complex 3-D stress states due to moving load and maneuvering effects of heavy trucks and aircrafts in highway and airfield pavements. The conditions AC layers are subjected to…

Asphalt concrete (AC) layers in airfield and highway pavements are subjected to complex 3-D stress states due to moving load and maneuvering effects of heavy trucks and aircrafts in highway and airfield pavements. The conditions AC layers are subjected to in pavements evolved significantly with increasing truck loads and repetitions. In addition, truck platooning was recently introduced with the development in automation and connected technologies in the transportation industry. Reliability of pavement designs against permanent deformations can be compromised under such traffic loading conditions.The main goal of this dissertation is to characterize permanent deformation resistance of asphalt mixtures under various stress pulse configuration with varying stress states and rest periods. While the effects of loading duration and stress states were commonly studied in the literature, rest period effect was relatively less understood. Therefore, the focus of this thesis is to assess the effect of rest period using advanced triaxial permanent deformation experiments simulating stress states of truck platoons and maneuvering aircrafts. An experimental program was developed to assess the influence of rest periods under varying stress pulse configurations and paths on the permanent deformation of AC layers. Result showed that increasing rest periods led to increase in permanent deformations consistently about 2-3 times in high temperatures due to the hardening-relaxation or hardening–softening mechanisms. Rest period impact was found to be as important as temperature and stress magnitude for asphalt mixture’s permanent deformation resistance. ii Furthermore, the results showed that the changing stress paths had a significant effect on permanent deformation resistance when compared to conventional repeated-load experiments. A novel repeated load permanent deformation experiment was developed as part of the thesis research. The main idea of the experiment was to induce dynamic and independent stress pulses in the axial as well as the horizontal direction as confinement. With the individual pulsing in axial and horizontal direction, stress states simulating platoon moving loads or aircraft shear loading can be simulated and compared to conventional flow number experiment with dynamic axial pulsing with constant confinement pressure.
Date Created
2024
Agent

Development of Balanced Mix Design for Thin Asphalt Overlays for Collector and Local Roads

Description
Thin overlays are favored by local agencies due to their ability to extend the pavement'slifespan and enhance ride quality. However, the low thickness of thin overlays presents some inherent challenges. The use of conventional mixes for constructing thin overlays has led to…

Thin overlays are favored by local agencies due to their ability to extend the pavement'slifespan and enhance ride quality. However, the low thickness of thin overlays presents some inherent challenges. The use of conventional mixes for constructing thin overlays has led to numerous premature failures, primarily due to the relationship between compaction, the Nominal Maximum Aggregate Size (NMAS), and lift thickness. The current study's objective was to utilize a balanced mix design to enhance the quality of mixes used by local agencies by developing two new dense-graded mixes and one Stone Matrix Asphalt (SMA) mix. Local mixes were collected and studied, working closely with industry experts. This research work aimed to identify the performance characteristics of commonly used mixes, optimize these mixes, and design new mixes that better suit their intended application, thereby prolonging the life of overlays. The findings indicated that while the current mix designs are fundamentally wellstructured, they are not appropriate for the given application due to the unsuitability of a 12.5 mm NMAS for mix designs below 38 mm, especially considering that most overlays are less than that. The results also showed that the current mixes are already optimized in terms of cracking and rutting resistance. Three new mixes with 9.5 mm NMAS aggregates and SBS modified binder were designed. These include two dense-graded mixes using PG 76-22 SBS and PG 70-28 SBS modified binders, and one SMA mix utilizing the PG 76-22 SBS modified binder. All theseii mixes demonstrated better cracking properties compared to commonly used mixtures. While their rutting properties were either comparable or occasionally inferior but meeting the rutting criteria. Based on these findings, it can be proposed that the use of a 9.5 mm NMAS mix improves compaction and compatibility with lift thickness. Additionally, these mixes reduce susceptibility to cracking and extend service life of the overlay. To get a superior overlay mix, SMA can be employed as it had 2.5 times better CT Index compared to the conventional 12.5 mm mix.
Date Created
2023
Agent

Development of a Novel Aerogel-Based Modified Bituminous Materials

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Description
Thermal susceptibility is one of the biggest challenges that asphalt pavements must overcome. Asphalt mixture’s thermal susceptibility can increase problems related to permanent deformation, and the expansion-contraction phenomenon triggers thermal cracking. Furthermore, there is a common worldwide interest in environmental…

Thermal susceptibility is one of the biggest challenges that asphalt pavements must overcome. Asphalt mixture’s thermal susceptibility can increase problems related to permanent deformation, and the expansion-contraction phenomenon triggers thermal cracking. Furthermore, there is a common worldwide interest in environmental impacts and pavements. Saving energy and mitigating the urban heat island (UHI) effect have been drawing the attention of researchers, governments, and industrial organizations. Pavements have been shown to play an important role in the UHI effect. Globally, about 90% of roadways are made of asphalt mixtures. The main objective of this research study involves the development and testing of an innovative aerogel-based product in the modification of asphalt mixtures to function as a material with unique thermal resistance properties, and potentially providing an urban cooling mechanism for the UHI. Other accomplishments included the development of test procedures to estimate the thermal conductivity of asphalt binders, the expansion-contraction of asphalt mixtures, and a computational tool to better understand the pavement’s thermal profile and stresses. Barriers related to the manufacturing and field implementation of the aerogel-based product were overcome. Unmodified and modified asphalt mixtures were manufactured at an asphalt plant to build pavement slabs. Thermocouples installed at top and bottom collected data daily. This data was valuable in understanding the temperature fluctuation of the pavement. Also, the mechanical properties of asphalt binders and mixtures with and without the novel product were evaluated in the laboratory. Fourier transform infrared (FTIR) and scanning electron microscope (SEM) analyses were also used to understand the interaction of the developed product with bituminous materials. The modified pavements showed desirable results in reducing overall pavement temperatures and suppressing the temperature gradient, a key to minimize thermal cracking. The comprehensive laboratory tests showed favorable outcomes for pavement performance. The use of a pavement design software, and life cycle/cost assessment studies supported the use of this newly developed technology. Modified pavements would perform better than control in distresses related to permanent deformation and thermal cracking; they reduce tire/pavement noise, require less raw material usage during their life cycle, and have lower life cycle cost compared to conventional pavements.
Date Created
2022
Agent

Evaluating the Effectiveness of a Pavement Preservation Program: A Case Study

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Description
A successful implementation of a Pavement Management System (PMS) allows agencies to make objective and informed decisions in maintaining their pavement assets effectively. Since 2008, the City of Phoenix, Arizona, has implemented PMS to maintain approximately 7,725 km (4,800 mi)…

A successful implementation of a Pavement Management System (PMS) allows agencies to make objective and informed decisions in maintaining their pavement assets effectively. Since 2008, the City of Phoenix, Arizona, has implemented PMS to maintain approximately 7,725 km (4,800 mi) of pavements. PMS is not a static system but a dynamic system requiring regular updates to reflect pavement performance and meet the agency's goals and budget. After upgrading to the Automated Road Analyzer (ARAN) 9000 in 2017, there is a need for Phoenix to evaluate its PMS. A low pavement condition index (PCI) for newly paved roads and the requirements for more than 35% of scheduled fog seal projects to be upgraded to heavier treatments observed, also motivated this research effort. The scope of this research was limited to the flexible pavement preservation program and the objectives are: (1) to evaluate the effectiveness of the existing City of Phoenix PMS and (2) to recommend improvements to the existing PMS. This study evaluated technical and non-technical aspects of Phoenix’s preservation program. Since pavements in a structurally sound condition are good candidates for preservation treatment, a single pavement performance indicator, which allows agencies to be more flexible with their preservation treatments and minimize the pavement performance data collection and modeling efforts, was explored. A simple yet measurable and trackable pavement performance indicator, Surface Cracking Index (SCI), representing the overall pavement condition to perform PMS analysis for a preservation program, was proposed. In addition, using a performance indicator, the International Roughness Index (IRI) to represent the ride quality or roughness, is a challenge for many local governments due to the nature of urban roadway related conditions such as stop and go driving conditions, abrupt lane change maneuvering, and lower prevailing speed. Therefore, a surface roughness indicator, Mean Profile Depth (MPD) measuring pavement surface macrotexture, was explored, and is proposed to be integrated in the PMS to optimize preservation treatments and recommendation strategies. While Phoenix will directly benefit from this research study outcomes, any agency who uses PMS, or plans to use PMS for their preservation program, will also benefit from this research effort.
Date Created
2022
Agent

Investigating the Role of Climate on Airfield Pavement Deterioration and Distress Occurrence Using Data from PAVEAIR Online Database

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Description
Differences in climatic conditions, aircraft traffic, and maintenance practices drive airfield pavements to perform differently. Through the Federal Aviation Administration’s (FAA’s) PAVEAIR online database and the National Oceanic and Atmospheric Administration’s (NOAA’s) online public platform, historical pavement condition and climate…

Differences in climatic conditions, aircraft traffic, and maintenance practices drive airfield pavements to perform differently. Through the Federal Aviation Administration’s (FAA’s) PAVEAIR online database and the National Oceanic and Atmospheric Administration’s (NOAA’s) online public platform, historical pavement condition and climate data from nearly 200 airfields in the dry freeze (DF), dry no-freeze (DNF), wet freeze (WF), and wet no-freeze (WNF) climatic regions were collected to evaluate pavement performance and distress trends. This research details the methodologies employed in the PAVEAIR pavement inspection data retrieval and dataset organization, and further presents the results of a two-part analysis. First, rate of deterioration (ROD) of various pavement families were evaluated by fitting a linear regression to the pavement condition index (PCI). Then, historical distresses data were analyzed for various pavement families in the different climatic regions. Families were assigned with respect to climate, pavement structure (conventional asphalt or asphalt overlays), and branch type (apron, taxiway, and runway). The regression results showed that pavements in the WF region have the highest ROD, followed by the pavements in the DNF region. In terms of branch type, in three of four climatic regions, aprons have the fastest rate of deterioration, followed by taxiways and runways, respectively. The distress analytics revealed that cracking type of distresses were the most common in all the regions regardless of the pavement family. The results showed that climatic data alone were not adequate to characterize airfield pavement behavior due to the multivariate factors affecting pavement deterioration. An accurate pavement and distress prediction modeling effort should at least include additional information on the structure and traffic level.
Date Created
2021
Agent

Numerical Analysis of the C* Fracture Test Specimen using the Generalized Finite Element Method

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Description

The experimental assessment of cracking distresses in asphalt concrete pavements is crucial to the longevity of pavements. As such, fracture parameters obtained from experiments play a key role in facilitating the use of fracture mechanics theories and prediction of …

The experimental assessment of cracking distresses in asphalt concrete pavements is crucial to the longevity of pavements. As such, fracture parameters obtained from experiments play a key role in facilitating the use of fracture mechanics theories and prediction of cracking distresses in asphalt concrete (AC) pavements. The stress intensity factor (SIF) is among the fracture parameters derived from fracture mechanics theory. Many fracture mechanics based laboratory tests have been developed with the goal of calculating such key fracture parameters. The C* Fracture test is unique among them because it incorporates rate dependent loading into the calculation of fracture parameters via the theory of the C* Line integral. However, unlike other laboratory fracture tests, the C* Fracture test does not have any analytical solution or previous sources from literature which describe geometric shape factors used in the calculation of SIFs. Numerical modeling of the C* Fracture test specimen is also limited in literature. Therefore, there is a need for a high-fidelity numerical model of this fracture test in order to develop SIF functions. In this thesis, the numerical models of the C* Fracture test were developed using the Generalized Finite Element Method (GFEM). GFEM is particularly effective at modeling problems with discontinuities in complex 3-D structures. The use of the GFEM to solve this problem allows a high-fidelity numerical model to be created without a large computational cost and labor intensive mesh crafting. After verifying the model accuracy using convergence analysis, the specimen geometry was modeled by changing the crack size. A SIF function was developed that includes a specific geometry dependent shape factor for the C* Fracture test based on Linear Elastic Fracture Mechanics (LEFM).

Date Created
2021-05
Agent

Enterprise Distress Cost: United States Air Force Airfield Pavement Inventory

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Description

United States Air Force airfield PAVER pavement management system enterprise data was reviewed for 67 networks. The distress survey extents and severity fields were joined with treatment costs estimated using RSMeans to determine the costliest distress. In asphalt surfaced pavements…

United States Air Force airfield PAVER pavement management system enterprise data was reviewed for 67 networks. The distress survey extents and severity fields were joined with treatment costs estimated using RSMeans to determine the costliest distress. In asphalt surfaced pavements Longitudinal/transverse cracking, weathering, and block cracking resulted in the most pavement condition index (PCI) deducts while the costliest distresses are weathering, block cracking and longitudinal cracking. In portland cement concrete surfaced pavements linear cracking, joint seal damage, and joint spalling resulted in the most PCI deducts while the costliest distresses are joint seal damage, linear cracking, and corner spalling. The results of this data were then compared to airfield attributes: Pavement Temperature Group, Dominant American Association of State Highway and Transportation Officials (AASHTO) Soil Classification, Pavement- Transportation Computer Assisted Structural Engineering (PCASE) Climate Zone, and years since last maintenance. Maps showing the Pavement Temperature Group, Dominant AASHTO Soil Classification, and PCASE Climate Zone are included in Appendix A. Alligator cracking is most prevalent at the airfields with PTG 64-34 (Ellsworth, Fairchild, Hill, and Offutt) and 58-22 (Niagara and Vandenberg). Rutting is most prevalent at PTG 64-34 (Ellsworth, Fairchild, Hill, and Offutt). An increasing trend of joint spalling, corner spalling, and corner break with decreasing soil quality (AASHOTO A-1 to A-8 soils). The PCASE Climate Zone Cost Indices the cost index for weathering is approximately double in the moist region over the dry region. The cost index for block cracking is approximately double in the cold region over the hot region. It is recommended that the agency review its pavement performance modeling in the pavement management system to increase the recommendation of pavement preservation treatments and review the use of higher quality materials for pavement maintenance treatments.

Date Created
2020
Agent

Using Mixture Design Data and Existing Prediction Models to Evaluate the Potential Performance of Asphalt Pavements

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Description
Several ways exist to improve pavement performance over time. One suggestion is to tailor the asphalt pavement mix design according to certain specified specifications, set up by each state agency. Another option suggests the addition of modifiers that are known…

Several ways exist to improve pavement performance over time. One suggestion is to tailor the asphalt pavement mix design according to certain specified specifications, set up by each state agency. Another option suggests the addition of modifiers that are known to improve pavement performance, such as crumb rubber and fibers. Nowadays, improving asphalt pavement structures to meet specific climate conditions is a must. In addition, time and cost are two crucial settings and are very important to consider; these factors sometimes play a huge role in modifying the asphalt mix design needed to be set into place, and therefore alter the desired pavement performance over the expected life span of the structure. In recent studies, some methods refer to predicting pavement performance based on the asphalt mixtures volumetric properties.

In this research, an effort was undertaken to gather and collect most recent asphalt mixtures’ design data and compare it to historical data such as those available in the Long-Term Pavement Performance (LTPP), maintained by the Federal Highway Administration (FHWA). The new asphalt mixture design data was collected from 25 states within the United States and separated according to the four suggested climatic regions. The previously designed asphalt mixture designs in the 1960’s present in the LTPP Database implemented for the test sections were compared with the recently designed pavement mixtures gathered, and pavement performance was assessed using predictive models.

Three predictive models were studied in this research. The models were related to three major asphalt pavement distresses: Rutting, Fatigue Cracking and Thermal Cracking. Once the performance of the asphalt mixtures was assessed, four ranking criteria were developed to support the assessment of the mix designs quality at hand; namely, Low, Satisfactory, Good or Excellent. The evaluation results were reasonable and deemed acceptable. Out of the 48 asphalt mixtures design evaluated, the majority were between Satisfactory and Good.

The evaluation methodology and criteria developed are helpful tools in determining the quality of asphalt mixtures produced by the different agencies. They provide a quick insight on the needed improvement/modification against the potential development of distress during the lifespan of the pavement structure.
Date Created
2020
Agent
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