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.

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.

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.

The presence of expansive soils underneath pavement structures is considered one of the most common sources of pavement distresses, due to differential settlements caused by differential moisture distribution attributed to soil heterogeneity and seasonal climatic fluctuations. The cost of the repairs to the infrastructure caused by expansive soils is estimated to exceed 10 billion dollars annually in the US, as reported by Puppala and Cerato (2009). Although many studies have been developed to better understand the volume change of unsaturated soils and incorporate the effect of swelling/shrinkage behavior into pavement design procedures, current methodologies are still based on simple correlations with index properties or other empirical methods. Such solutions lead to poor or uneconomical design practices. The objective of this study was to calibrate and implement a new mechanistic, stochastic model that predicts pavement distresses caused by the presence of expansive soils. Three major tasks were completed to fulfill the objective of this study: 1) a laboratory research program performed to estimate the volume change of compacted specimens, with different expansion potential, due to the simultaneous application of suction and net normal stresses, 2) the calibration of a new mechanistic free-swell model for expansive soils tailored to pavement structures, based on elevation information collected from the Long Term Pavement Performance (LTPP) program, and 3) the incorporation and calibration of the free-swell stochastic model results into the current Pavement Mechanistic-Empirical (ME) Design procedure using the International Roughness Index (IRI) models. The results presented includes: 1) an empirical model to estimate volume change due to the coupled effect of suction, and net normal stresses, for soils with different soil index properties, 2) a calibrated model to adjust the free-swell results of the mechanistic-stochastic model developed by Olaiz et al. (2021), and 3) an updated IRI equation for asphalt concrete pavements to account for volume change fluctuations due to changes in suction stress conditions. The models presented can be easily implemented into currently available pavement design procedures and greatly improves over the existing empirical models that have been used for more than four decades.

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.