Airfield and Highway Pavements 2023: Testing and Characterization of Pavement Materials

Bituminous mixture design follows volumetric based mix design, and the choice of the optimum binder content is linked to the required volumetric properties such as air voids (Va), and voids in mineral aggregates (VMA). The optimum binder content is selected by an iterative process by varying the binder content, and the one which satisfies the required volumetric criteria is chosen. It should be noted that the choice of a binder content satisfying the required volumetric criteria does not necessarily guarantee a closely packed aggregate skeleton. It will be useful if an analytical formulation is used to design the aggregate gradation and stipulate the required VMA and select an appropriate binder content. Such an approach is presented in this paper. Towards that end, a compressible particle packing model (CPM) is chosen to design and estimate the packing density (PD) for the aggregate blends. The binder content required to meet the required volumetrics is calculated from the estimated PD by linking VMA. It is observed that samples with higher packing density require less bituminous binders for a targeted Va. It is also observed that the binder requirement as determined here was less than what is normally used based on the air void requirement using Superpave mix design method. To quantify the mechanical performance of particle packed bituminous mixtures, the samples are subjected to repeated load haversine compression for a range of temperature and frequency so that their master curves can be constructed. The approach followed here focuses on a reverse mix design strategy by estimating packing density and then by computing the required binder content, and the large number of iterations required to design a bituminous mixture is reduced. From the analysis of master curve of all the samples, it is clearly seen all the mixtures exhibited identical modulus at higher reduced frequencies, and the bituminous mixtures designed with particle packing approach exhibited higher modulus at lower reduced frequencies.

The scope of this study is to understand the feasibility of materials from Mato Grosso do Sul, Brazil, for use in the Superpave method of designing asphalt mixes, as well as to analyze the mechanical and volumetric properties of the resulting mixes. The method of asphalt preparation most used today in Brazil is the Marshall dosage. However, given the current global context of asphalt design and the improvements observed in the industry in recent decades, there is a clear need to adopt and improve better pavement system designs in Brazil. With this study, it is possible to better understand and test new paving techniques that can change the current scenario seen in Brazil. It is clear, when analyzing the major problems that arise in the pavement of Brazilian roads, that cracks, permanent deformation, and a low fatigue life are common occurrences in the region. Through this research, the asphalt mix project carried out in the laboratory was tested both in its volumetric properties and in its mechanical properties. The volumetric properties analyzed fully complied with Superpave’s international standards for asphalt mixtures, and the mechanical properties were congruent with studies that measure similar properties. The main equipment used for the mechanical properties tests was a universal hydraulic testing machine with a capacity of 30 kN of force. The main tests included resilience modulus, fatigue life, permanent deformation (flow number), and dynamic modulus test. With this, the properties of the laboratory molded asphalt mix project can be analyzed and compared with more traditional methods seen in Brazil, as well as can be used as a future reference for comparison with new asphalt mixes made with similar processes in Brazil. In this study, the laboratory-molded asphalt mix was based on the design of 3−30 million ESALs with a design of 100 turns in a Galileo electromechanical rotating machine, reaching 96% of its maximum theoretical density, with 6% of binder, 15.79% of voids in mineral aggregate, 74.64% of volume filled with bitumen, and a density of 2.4932 kg/m³.

The addition of fibers to asphalt mixtures has the potential to improve the resistance of asphalt mixtures. However, the impact of different fiber types and binder grades on the performance (rutting, cracking, and fatigue) of fiber-reinforced asphalt concrete (FRAC) is unknown. This study aims to predict the pavement performance of control and FRAC [carbon, fiberglass, basalt, and polyolefin/Aramid (PFA)] mixtures for warm (New Jersey) and cold (Minnesota) climates using AASHTOWare Pavement ME software (PMED). Laboratory-measured dynamic complex modulus |E*| and data for PG76-22 and PG58-28. Prediction analysis showed that the PFA mix is 8% and 13% more effective in rutting for NJ and MN regions, respectively. Based on the critical distresses (rutting and bottom-up fatigue cracking), the structural layer coefficients are in the range of 0.44 to 0.48 for the MN region; however, for the NJ region, the range is from 0.44 to 0.60. Although FRAC mixtures are expansive, lower thickness, and performance enhancement assure their economic benefits.

For many years, coal combustion by-products (CCPs) have been broadly used as a replacement for Portland cement in the production of different types of concrete: in embankments and soil stabilization; however, use of these materials in the pavement industry has been very limited, and few research studies have been conducted in this area. Spray dryer absorber (SDA) materials are a type of CCPs that are derived from flue-gas desulfurization of coal-fired power plants. The current study explores the effect of the incorporation of SDA materials on the high-temperature rheological performance of warm mix asphalt (WMA) mastics. To do this, SDA material and dolomite powder (as a reference filler) were first investigated in terms of different physical and chemical properties, including particle size distribution, specific gravity, Rigden voids, morphological properties, X-ray diffraction (XRD), and X-ray fluorescence (XRF). The fillers were then incorporated in PG 58-28 asphalt binder with 5%, 15%, and 25% replacement of the asphalt binder by volume, making a total of six asphalt mastics. The high-temperature performance of SDA-based mastics was evaluated using a dynamic shear rheometer (DSR) machine and compared with that of dolomite-based mastics. The rheological properties were assessed by performing temperature sweep tests for complex modulus (G^*), phase angle (δ), multiple stress creep (J_nr) at different loading levels, and aging resistance tests. The experimental results indicate that SDA-based mastics have higher resistance to permanent deformation and higher rutting resistance and show better performance in terms of aging compared to the reference dolomite-based mastics with similar filler volume concentrations. Based on the results, it can be concluded that the incorporation of SDA powders in asphalt binders can pave the way to achieving a sustainable, long-lasting, cost-effective, and flexible pavement.

In this work, an empirical study is done to examine the correspondence between the aggregate arrangements within the asphalt mix with the strength of the mix. Indirect tensile strength (IDT) and creep performance are considered as indicators of mechanical strength of asphalt mix. The distribution of shortest inter-aggregate distance and resultant inclination (angle) of the aggregates are considered as indicators of the geometrical arrangement. Three different types of mixes are taken, and three different levels of compaction are applied to one of the mixes. The test results suggest that certain indices representing geometrical arrangement show correspondence to the mechanical strength of the mix.

It is well established that compaction of asphalt mixtures is critical to airport asphalt surface performance. Over-compaction can lead to mixture stability issues, while under-compaction can result in surface porosity or permeability, and accelerated mastic weathering over time. This research reviews the importance, measurement, and specification of airport asphalt compaction and density. Different standard airport pavement density specifications are compared. Furthermore, the differences between paving joints and the paving mat are considered, as well as the relative benefits of specifying a relative density ratio, or a compacted air void content. Finally, methods for improved compaction and better paving joint construction are considered, including joint heaters and pre-construction joint treatments. It was concluded that future specifications should focus on air voids, rather than relative density, as the basis for compaction specification. It was also concluded that new technologies, such as joint heaters and internal joint treatments during construction, should be developed and adopted into practice for better joint performance in the future.

This paper investigated the rutting potential and continuous grade temperature (C-PG) changes of original, aged, and crumb rubber-modified asphalt binders. The original binder was selected based on the research region, and it had a performance grade (PG) of 58-28. Modifications were performed using a single mesh size #20 CR modifier. C-PG of asphalt binders is determined at high, intermediate, and low temperatures. The multiple stress creep recovery test was conducted to evaluate the rutting performance and traffic grade of asphalt binders at regional high temperature as well as at high PG temperatures. MSCR tests were performed using bob and cup (BC), which is also known as the concentric cylinder, geometry since the use of parallel plate geometry was not allowed for binders with discrete particles larger than 250 microns in size. The results show that the crumb rubber modification improved the original binder’s high rutting resistance along with traffic grade bumps and continuous PGs.

Arid climate conditions of Kuwait, along with the poor asphalt mix design characteristics, have further accelerated the rate of raveling of in-service pavements. Therefore, this study evaluated and modified Kuwait’s current mix design characteristics. To carry out this study, two mix designs, that is, the traditional Marshall mix design used in Kuwait and the new Superpave mix design, were prepared as per specifications. Several key changes were implemented to the mix designs to improve their resistance to moisture damage and raveling. The mechanical properties of the two asphalt mixtures were evaluated through tensile strength ratio (TSR), Hamburg wheel track (HWT), and dynamic modulus (E*) tests. E* test was performed for both unconditioned (UC) and moisture-conditioned samples for one (1C) and three (3C) freeze-thaw cycles to capture the effect of moisture conditioning on the performance of the asphalt mixtures. Results showed that the recommended modifications to the current Kuwaiti mix design procedure were successful and proven to improve the moisture damage resistance of the mixture, which is a leading cause of the raveling of in-service asphalt pavements.

In a practical scenario, it is very common that an open graded friction course (OGFC) layer is subjected to repeated traffic loadings during the rains. Even after the rain, water can be clogged inside the voids. This entrapped water can accelerate OGFC layer’s overall abrasion damage under wheel loads by causing moisture damage to the material. This study employed the Micro-Deval (MD) test to evaluate the durability performance of an OGFC material in wet conditions. It is found that the MD test is effective in measuring the durability performance of an OGFC with satisfactory repeatability. While comparing the effects of binder grade on the OGFC’s performance, it is observed that the OGFC made with a lower PG grade performs poorly than the OGFCs made with higher PG grades. While evaluating the effect of aggregate gradation on the OGFC’s performance, it is found that the OGFC made with a larger aggregate has more damage than the OGFC made with a smaller aggregate. This study found that the MD test is more effective in ranking OGFC materials based on their durability performance than the traditional Cantabro abrasion (CA) test. The correlation between MD and CA test results is also found to be poor because of the differences in loading and test conditions. As the loading and test conditions in the MD test are more field representative, this study recommends the MD test for evaluating the durability performance of OGFC materials in wet conditions.

The AASHTOWare Pavement Mechanistic-Empirical (ME) program is based on a combination of mechanistic and empirical design methods. The lack of comprehensive material input databases for bound and unbound layers remains challenging. This study measured the complex shear modulus (|G*|) and associated phase angle (δ), and viscosity (η) at three aging conditions for five binders used in typical HMA mixtures in North Dakota. The goal was to generate binder inputs for North Dakota’s Pavement ME implementation. Additionally, this study used existing models to predict (|G*|) and δ and compared them to measured values. Results illustrated that |G*| and δ values for the original and short-term aged binders performed satisfactorily at high temperatures according to their performance grades. For unaged binders, the PG58H-34 for HWY 83 and HWY 32 displayed different |G*| and δ values indicating the importance of undertaking local binder characterization. For short-term aged binders, PG 58H-34-HWY 83 showed high stiffness and high elasticity at high temperatures indicating that it is suitable for pavements carrying heavy traffic. PG 58H-34-HWY 32 was the least susceptible to fatigue cracking for long-term aged binders since it had a |G*|·sin(δ) value below 5,000 kPa at 7°C; the rest of the binders are above the threshold at this temperature. Comparing the predicted and measured rolling thin film oven (RTFO)-aged |G*| and δ for the five binders gave R² values above 0.9 for predicted and measured |G*| for all the binders were observed, while for three binders, the R² values were above 0.9 for predicted and measured δ, and for two binders, the R² values were below 0.5. Using measured A and VTS values instead of default values is recommended as a remedy for poor phase angle predictions.

Every year a huge amount of wood and forestry waste is produced, which needs to be landfilled. The bio-oil obtained from pyrolysis of the wood and forestry waste is a low-viscosity material that has a similar chemical structure to petroleum-based asphalt binder. Therefore, it has been used to partially replace the petroleum-based asphalt binder. Bio modification of asphalt binder resulted in a higher aging susceptibility and a decline in the high-temperature grade of asphalt binder. Thus, bio-oil application in asphalt pavement has been limited to low percentages. In a novel approach, and to address the challenges related to bio-asphalt, polyurethane modification (PU) of bio-asphalt was introduced. Polyurethane bonds form when isocyanate groups (-NCO) react with hydroxyl groups (-OH) in bio-oil and asphalt binder. Fourier-transform infrared (FTIR) spectroscopy was used to confirm the presence of hydroxyl groups in wood-based bio-oil, while elemental analysis was conducted to identify its chemical structure. An unmodified asphalt binder commonly used in the state of North Carolina, PG 64-22, was mixed with two different percentages (10% and 20%) of local wood-based bio-oil. Next, the prepared bio-asphalt samples were mixed with two different percentages of methylene diphenyl diisocyanate (MDI) (2% and 4%) to produce the PU-modified bio-asphalt. FTIR was used to examine the chemical reaction of MDI and bio-asphalt, and the formation of urethane and urea bonds. Results confirmed the formation of urethane after the addition of MDI. Dynamic shear rheometer (DSR) was used to evaluate the rheological properties of unmodified and modified samples. An increase was observed in the toughness and complex modulus of bio-asphalt samples when 2% MDI was added to 10% bio-asphalt.

Usage of reclaimed asphalt pavement (RAP) material can have economic and environmental benefits. However, the variability in RAP sources and the uncertainty in long-term performance tend to limit the use of RAP content in asphalt mixtures to 20% of the mixture or less. RAP fractionation is one of numerous methods that have been proposed to increase RAP usage. RAP fractionation into fine and coarse stockpiles aims to improve the consistency of RAP particle sizes as well as binder content and properties to maintain an acceptable mix design and performance. The objective of this study is to characterize the performance of mixtures containing fractionated RAP content for local materials in Manitoba. Cracking and rutting performance of hot-mix asphalt mixes were assessed using Illinois Flexibility Index Test and Hamburg wheel-tracking test, respectively. Results showed that resistance to rutting increased with the increase of RAP content. Cracking resistance decreased with the incorporation of RAP. Additionally, fractionated RAP samples showed better resistance to cracking and rutting than unfractionated RAP samples. The final findings of this research will help transportation agencies in Manitoba to optimize the design of asphalt mixtures containing RAP.

Cracking of asphalt mixtures is a main distress in flexible pavements. The addition of encapsulated rejuvenators during the fabrication of these mixtures is a novel self-healing technique that could extend the service life of the material. This self-healing mechanism consists in the autonomous sealing of cracks due to the release of healing agents contained in biopolymer capsules. However, the reliable use of these mixtures requires the understanding of the impact of the added capsules on the mechanical properties of the material, especially during the initial phase of the service life of the structure. This paper presents the characterization of the linear viscoelastic properties of short-term aged asphalt mortars with and without polynuclear capsules containing sunflower oil using the dynamic mechanical analysis (DMA) technique. The results show that at most temperatures and loading frequencies there are no statistically significant differences in the viscoelastic properties of the mortars with and without capsules, suggesting that the viscoelastic mechanical properties during the initial phase of the service life of these self-healing mixtures are not compromised.

This study assesses the influence of the type of aggregates on the mechanical response of asphalt mastics subjected to water conditioning. This topic is relevant because the durability of asphalt mixtures strongly depends on the asphalt-aggregate interaction and, particularly, on the mineralogical properties of the aggregate. Mastic samples were fabricated with a penetration 60−70 (1/10 mm) asphalt binder and two aggregates with different mineralogical compositions: (1) serpentinite, and (2) quartzite. The linear viscoelastic properties of the mastics were quantified after subjecting them to three conditioning processes (i.e., dry, after 10, and after 20 days submerged in water). The viscoelastic and chemical properties of the asphalt binder (i.e., no filler) were tested under the same moisture conditions and used as part of the analysis. The results show an increase in the dynamic modulus of the mastics with conditioning time and, although this increase is partially due to the hardening effect of water in the binder, it was found that it strongly depends on the type of filler.

Several laboratory test protocols exist as standards for evaluation of moisture damage resistance of compacted asphalt concrete mixtures: indirect tensile strength after freeze-thaw conditioning, performance evaluation when submerged under water and subjected to repeated wheel tracking, and measuring the strength or modulus after conditioning of the mixture when subjected to moisture induced stress test (MIST). This study was undertaken to compare the conditioning effect from a freeze-thaw cycle, hot-water bath conditioning (no freeze), and the MIST conditioning. The dynamic modulus and indirect tensile strength of these asphalt mixtures were determined before and after conditioning. It was found that the tensile strength ratio (TSR) for the mixtures exposed to only the hot water bath was significantly lower than those subjected to the freeze-thaw cycle. Drop of mix modulus was observed as a result of moisture-induced damage, albeit to various degrees. Slightly a higher drop of modulus was observed from the freeze-thaw conditioning compared with the MIST conditioning for three of the mixtures.

Thermal properties of hot-mix asphalt (HMA) found in literature are generally limited to laboratory-prepared and un-aged materials. In-service aging of asphalt binder and associated chemical changes may influence bulk thermal properties of HMA. Estimating the urban heat island (UHI) effect for existing pavement infrastructure is an application where accurate thermal properties of aged HMA are needed. Aged HMA pavements approximately 15, 40, and 75 years old were tested for thermal properties of volumetric specific heat, thermal conductivity, and thermal diffusivity. Temperature controlled measurements were conducted over a −20°C to 60°C range. Testing was conducted via a transient line heat source approach using a dual needle sensor device. Thermal properties were observed to vary based on aggregate type and test temperature. Specific heat and thermal conductivity exhibited a substantial effect due to test temperature on measured values. Thermal diffusivity response was largely insensitive to testing temperature.

Non-black pavement surfaces may be more vulnerable to distress associated with high temperatures due to the high surface temperatures of conventional black asphalt. Since asphalt is viscoelastic and temperature sensitive, it is more likely to be damaged by traffic loading at higher temperatures. This contributes to the urban heat island (UHI) effect, thus necessitating the use of coloring or cooling additives to help lower pavement surface temperatures. In response to these issues, iron oxide red, titanium dioxide white-modified bituminous mixtures, and clear asphalt binder were thermally investigated under different heat fluxes and compared with a conventional binder. In addition, the corresponding asphalt mixtures were prepared and compared with conventional asphalt mixtures. Each combination has also been observed for the rate of heating and cooling. Compared to traditional black bitumen, the clear binder and pigment-modified binder absorb up to 15% less heat. In addition, asphalt made with a clear asphalt binder and pigmented asphalt takes more time to heat and less time to cool than conventional asphalt.

The flow behavioral properties of bituminous binders play major roles in the performance of flexible pavements. These rheological properties of bitumen, however, are affected by the oxidative aging, which occurs in the mixing and compaction of asphalt mixtures. Oxidative aging hardens the asphalt binder, making it more brittle and less elastic. This gives way to damages like rutting and fatigue and ultimately lessens the service life of the pavements. Therefore, the correlation of rheological behavior and aging of bitumen can be helpful in understanding and selecting materials, aiding the longer service life of pavements. This study analyzes the flow behavior of base and pyro-oil modified bitumen in the steady shear domain. Viscosity graded bitumen VG30 was selected as the base bitumen. The temperatures for this analysis were chosen as 50°C, 55°C, and 60°C. The testing was performed in linear viscoelastic region of binders. The steady shear rate varied from 0 to 100 s⁻¹. The 25 mm parallel plate geometry was used for the experiments on dynamic shear rheometer. The Superpave rutting factor (G*/sinδ), was also determined by the temperature sweep test at 40°C to 70°C, for each binder. Using cross model, zero shear viscosity was calculated. Further, the correlation between viscosity calculated from the standard test protocol and zero shear viscosity was studied and reported in this study. The effect of aging on modified binders is analyzed by using the rutting factor and ZSV indices. The study also evaluates the rutting behavior, short-term aging, and their correlation in assessing the performance of modified binders containing different percentages of pyro-oil using ZSV. It was found that the addition of 2% pyro-oil decreases the mixing temperature by 6%. The ZSV parameter is found to be more sensitive to aging as compared to rutting factor index.

This study compares two fatigue failure criteria using uniaxial constant crosshead cyclic fatigue testing results of 14 specimens. To guarantee that the failure occurred in the middle of the specimen, where the strain measurements were carried out, the tests were performed with an asphalt mixture performance tester (AMPT) on thin, right rectangular prismatic specimens trimmed into a dog-bone shape. Furthermore, the tests were conducted at 40°C to address the potential of fatigue cracking in a high temperature environment such as that of Hawaii. The first criterion used was the number of repetitions where the phase angle of the mix becomes a maximum. The second criterion consists of estimating the number of repetitions where the stiffness vs. loading cycles curve reaches a minimum (most negative) curvature. Both criteria provide estimates of the number of cycles where a rapid loss in stiffness due to macrocracking starts. For 3 of the 14 specimens evaluated in this study, the phase angle vs. number of cycles curve was very flat. The flatness of the curve combined with some noise in the data resulted in a substantial underestimation of the location of the failure point using the maximum phase angle criterion. For the other 11 specimens, the values determined with both criteria were extremely consistent. Considering only these specimens, the R² of the linear relationship between the two criteria was 0.997. Hence, the minimum curvature of the stiffness curve appears to provide very consistent results with the accepted existing phase angle criterion when that criterion resulted in reasonable results and provided more realistic failure estimates when the phase angle criterion failed. Hence, the minimum curvature criterion is recommended as a potential alternative for robust estimation of the fatigue failure point.

The Phase 3 expansion of Delhi International Airport involved brownfield construction of major airside infrastructure, imposing constraints on engineering and construction planning. A major challenge was posed for finalization of an appropriate mix design of the bituminous surface course (P-401) and selection of the appropriate binder: polymer modified bitumen (PMB). The mix design had to ensure workability and compactibility through the limited construction time-window, in consideration of the increased transit time, due to the stringent security arrangements for airside delivery of the hot-mix produce from the plant on landside and the weather factors. There was always a competing requirement for stiffness of the mix to be achieved with a stiffer binder versus the lower viscosity requirement for workability. The same was achieved with performance-based selection of the binder and mix design incorporating dynamic shear rheometer (DSR) tests of the binder and compactibility, rutting, and fatigue performance testing of the mix. Aggregate grading design formed an integral part with friction requirements for the surface course being another important parameter to be achieved. The paper presents the process and testing regime for achieving a high-performing asphalt surface course mix for the flexible aircraft rated pavements for the project.

The use of recycled materials, such as reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in asphalt mixes may have detrimental effects relative to long-term performance, in the form of fatigue cracking, reflection cracking, and low-temperature cracking because of the presence of aged binder. One method to restore the properties of the aged binder is to blend recycled materials with rejuvenators. As the recycling efficiency of a rejuvenator depends on the degree of aging of RAP and constituents of virgin and aged binder, it is important to evaluate the rheological properties of the rejuvenated binder before incorporating in asphalt mixes. The focus of this study was to evaluate the effect of the rejuvenator rate on the rheological properties of binders blended with aged binder. For this purpose, a PG 64-22 binder, two different types of rejuvenators, and RAP from two Oklahoma sources were collected. Binder blends were prepared by adding four different rates of rejuvenators, namely 0%, 2%, 4%, and 6% (by weight of virgin binder) and 30% aged binder with the virgin binder. The high- and low-temperature rheological properties of the blended binders were determined. The optimum rejuvenator rates were determined based on the high- and low-temperature continuous grades of virgin binder, ΔTc (virgin binder), ΔTc-6 (ΔTc at −6°C), and ΔTc-5 (ΔTc at −5°C). It was observed that the rejuvenator rate needed to change a binder blend back to the low-temperature grade of the virgin binder was crucial to ensure optimum performance.

Storage of cementitious materials onsite is essential for rapid repair operations. However, materials may have limited shelf lives and are prone to degradation in the presence of moisture. Typical industry practice involves storing these materials inside specialized silos before distribution, which is likely impractical for most work environments. This paper investigates methods of storage to reduce moisture damage and to monitor moisture present in cementitious materials. Various techniques were evaluated to reduce moisture in storage containers, and large bulk sacks of rapid-setting materials were installed with sensors to monitor moisture. Two different sensors were tested for monitoring moisture: a standard soil moisture probe and an engineered radio frequency identification reader (RFID) moisture detector. Desiccant poles were found to be the most beneficial of the techniques tested in reducing humidity and removing water from the storage container. The RFID moisture detector was found to be able to detect moisture events better than the soil moisture sensor, which was unable to detect moisture events even when stored outside in rainy conditions. Recommendations for future storage conditions and monitoring are provided. This paper demonstrates the capability of moisture monitoring in cementitious material bulk containers and provides groundwork for further optimization of storage protocols.

Rigid pavements form a significant portion of the aircraft pavement network, both in Australia and in the USA. The strength of the concrete used in rigid aircraft pavements is usually expressed as the 28 day flexural strength, and this has a substantial influence on the required thickness of the concrete slabs. The selection, specification, and verification testing of concrete strength are all interlinked, and this creates challenges for the airport pavement design and construction industry. Challenges include different definitions of characteristic strength used in different jurisdictions, the selection of an efficient but workable and low-risk concrete strength for pavement thickness design, the statistically based specification of concrete strength acceptance requirements, and the search for more efficient test methods for concrete acceptance testing during construction. This paper explores these challenges and outlines potential improvements for the benefit of the aircraft pavement industry.

Using deicing chemicals, such as sodium chloride (NaCl), on roadways lowers the freezing point of water, resulting in less skidding, less hydroplaning, and more friction. NaCl corrodes reinforcement structures and is prone to environmental factors that result in runoff and dilution. NaCl also has limitations regarding its deicing capabilities; therefore, a supplement should be used to decrease corrosion and aid in lowering the freezing point of water, such as AMP, which is a liquid inhibitor specifically used to augment NaCl brine. Incorporating AMP as a solute in NaCl brine aids with bonding to the road’s surface and lowers water’s freezing point even further than NaCl alone. This study was conducted to explore the optimum solution of AMP and NaCl with respect to hardened concrete properties and freeze-thaw resistance for concrete containing a 20% fly ash replacement for cement. Fresh and hardened properties of concrete were determined following AASHTO or ASTM standards. Compressive strength, tensile strength, and flexural strength were used to compare the impact of AMP on hardened properties. Durability was determined using relative dynamic modulus (RDME) and scaling following BNQ 2621. Incorporating AMP into a NaCl brine solution had a neutral reaction when increasing AMP, thus, resulting in minimal losses in hardened properties or scaling resistance with up to 15% AMP. The freeze-and-thaw results indicated a decrease in resistance in the durability factor when the cement was replaced with fly ash.

The accumulation of snow on roadway surfaces has the potential to result in deadly accidents and financial damage. Heated pavement systems (HPS) have gained popularity in recent years as a way of mitigating the snow accumulation on rigid pavements. While these approaches seem promising, they are also costly due to the raw resources used, which accelerates the depletion of these raw materials. This research aims to present a sustainable approach for de-icing the accumulated snow on rigid pavements. The method depends on using waste rubber tires as the source of heating to be applied to the rigid pavements. Depending on the mesh of steel wires embedded inside the rubber tires. It has been noticed that passing current through these steel wires embedded inside the rubber can produce heat. The outcomes of the investigation validate the effectiveness of the suggested method of heating the pavement and melting the snow.

The mathematical complexity of reliability analysis can be challenging for pavement engineers. Most engineers, however, are quite experienced in applying the concept of the safety factor, SF, in design. Monte Carlo simulation is used in this paper to show that reliability is related to SF for any given level of assumed variability in material properties and traffic. A range of SF between 1 and 5 is found to be adequate in describing R from 50% to 99.9% for typical concrete pavement sections. The methodology developed is simple to follow and leads to practical values of the overall standard deviation, S_o, required in AASHTO 86/93 designs. Findings corroborate the stipulation that for rigid pavements, S_o typically lies between 0.3 and 0.4. The approach described eliminates the shortcomings of the reliability methodology of AASHTO 86/93, which emerges as mathematically and philosophically well-grounded, consistent with broader engineering practice and deserves to be reconsidered.