Number Flow Research Articles

Evaluation of asphalt mixtures modified with low-density polyethylene and high-density polyethylene using experimental results and machine learning models

The widespread use of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) plastics has resulted in a large amount of waste plastic that requires appropriate disposal or reuse. One potential solution is to use them in the modification of asphalt concrete (AC) mixtures for more sustainable highways. To study this possibility, permanent deformation and dynamic modulus (DM) of the LDPE and HDPE modified AC mixtures was investigated by conducting flow number (FN), flow time (FT) and DM tests on Superpave gyratory compacted specimens. Machine learning models; multi-layer perceptron (MLP), radial basis function neural network (RBFNN), generalized regression neural network (GRNN) and support vector machine (SVM) were used to predict the DM on the basis of frequency and temperature parameters. The model’s performance was gauged by analyzing the root mean square error, mean relative error, and coefficient of determination. The study findings revealed that the LDPE and HDPE modified AC mixtures provide 2.07 times and 1.27 times better resistance to permanent deformation, respectively, than their counterpart. It was also found that the LDPE and HDPE modified AC mixtures have 2.1 times and 1.4 times higher DM values, respectively, than the Control AC mixtures. Among the machine learning models, MLP (R2 = 0.98) showed best accuracy in predicting DM and thus is recommended to be used in similar studies due to its robustness. Additionally, the feature importance analysis revealed that frequency has the highest impact on DM predictions, followed by temperature and the inclusion of the LDPE.

Rutting and fatigue behavior of neat and nanomodified asphalt mixture with SiO2 and TiO2

Modern asphalt technology has adopted nanomaterials as an alternative option to assert that asphalt pavement can survive harsh climates and repeated heavy axle loading during service life and prolong pavement life. This work aims to elucidate the behavior of the modified asphalt mixture fracture model and assess the fatigue and Rutting performance of Hot Mix Asphalt (HMA) mixes using the outcomes of indirect Tensile Strength (IDT), Semicircular bend (SCB) and rutting resistance; for this, a single PG (64−16) nanomodified asphalt binder with 5 % SiO2 and TiO2 have been investigated through a series of laboratory tests, including: Resilient modulus, Creep compliance, and tensile strength, SCB, and Flow Number (FN) to study their potential role of these nanomaterials to improve the rutting characteristics and fatigue life of wearing asphalt mixture at different temperatures. The outcome of this study revealed the positive role of these materials in enhancing mixture IDT characteristics, fracture energy, and viscoelastic deformation component of crack propagation; on the other hand, at higher temperatures, the modified mixture exhibited a superior performance in reducing the permanent deformation of asphalt mixture with SiO2 followed by TiO2 as compared to neat asphalt mixture.

Influence of field aging on viscoelastoplastic performance of rubberized asphalt mixtures incorporating reclaimed asphalt pavement in arid urban climate

This study investigates the effects of reclaimed asphalt pavement (RAP) and crumb rubber-modified asphalt (CRMA) on the viscoelastoplastic properties of asphalt mixtures under a range of aging conditions. Six asphalt mixtures, with varying RAP contents (0 %, 30 %, and 50 %) and CRMA modifications, were evaluated through dynamic modulus (|E*|) and flow number (FN) analyses. The specimens were subjected to authentic field-aging conditions for periods of 0, 3, 6, and 9 months. The results reveal that increasing RAP content enhances volumetric properties, Marshall stability, and rutting resistance. CRMA significantly improves fatigue performance and further bolsters rutting resistance, although some detrimental effects are observed at lower temperatures. Aging has a pronounced impact on the mixtures’ performance, particularly on |E*|, Prony series coefficients, viscoelastic strain (εve), and viscoplastic strain (εvp). Newly proposed aging indices, the dynamic modulus aging index (DMAI) and viscoplastic aging index (VPAI), effectively capture the changes in viscoelastoplastic behavior under different aging durations. These findings underscore the potential of RAP and CRMA to enhance pavement durability, prolong service life, and contribute to the development of sustainable and resilient infrastructure. The research offers valuable insights into the performance of asphalt mixtures incorporating RAP and CRMA under real-world conditions.

Laboratory performance characterization of polyolefin/ aramid fibers and synthetic aramid fibers reinforced asphalt mixtures

This study was conducted to assess the impact of combined polyolefin/aramid fibers (PFA) and pure synthetic aramid fibers (AF) reinforcement on mix design properties and laboratory performance. The study also investigated the shift in laboratory performance (rutting to cracking and vice versa) with the addition of both type of fibers. One aggregate (diabase stone), one binder type (PG58–28), and two types of aramid fibers (combined polyolefin/ aramid fibers and synthetic aramid fibers), added at 0.05% dosage by mix weight, were used to produce two fiber-reinforced asphalt mixtures (FRAM). Additionally, a control mix was also produced without any reinforcement. Mix design for control and FRAM was performed and Optimum Binder Content (OBC) was determined. The laboratory rutting and cracking performance of the mixtures was assessed using Asphalt Pavement Analyzer (APA), Flow Number (FN) and Indirect Tension Asphalt Cracking Test (IDEAL-CT). Durability and stiffness of these mixtures were also determined by performing Cantabro loss and Dynamic Modulus (DCM) tests. According to the mix design results, PFA reinforced mix showed an offset bulk and theoretical maximum specific gravity. However, both control and FRAM mixtures showed the same OBC (5.7%). Both type of fibers improved the durability of mix. With addition of PFA and AF fibers into the asphalt mix, the performance trend shifted from rut resistant mix to crack resistant mix, respectively. Furthermore, addition of PFA fibers into the asphalt mix increased the toughness and AF fibers make the asphalt mix ductile.

Exploring potential of Marshall-RT as simple performance test to evaluate rutting resistance of asphalt mixtures

ABSTRACT This study explored a new simple monotonic Marshall rutting test (Marshall-RT) to evaluate the rutting resistance of asphalt mixtures. The Marshall-RT test setup combines the Marshall fixture (at the bottom) and the IDT fixture (at the top). The rutting resistance of asphalt mixtures was evaluated using peak load (Pmax) and work done for the deformation damage obtained from the load-displacement curve. Nine plant-produced asphalt mixtures having different types of binders (unmodified, crumb rubber modified binder (CRMB)), and polymer modified binder (PMB)) and gradations having different nominal maximum aggregate sizes (NMAS) were evaluated. The Marshall-RT test parameters (i.e. Pmax and W P m a x ) have shown a strong correlation with fundamental (i.e. Flow Number (FN)), simulative (i.e. Hamburg wheel tracking test (HWTT)), and simple monotonic (i.e. Ideal rutting test (IDEAL-RT)) rutting tests. Moreover, the Marshall-RT test has shown good repeatability, the highest differentiation potential, and consistent ranking with other rutting tests. Furthermore, for high traffic levels (i.e. 100 MSA (Million Standard Axle)), at 50°C preliminary minimum threshold criteria were proposed for Marshall-RT (Pmax and W P m a x ), and IDEAL-RT (RTIndex) as 5 kN, 14 kN-mm, and 90, respectively, to avoid premature rutting failure. Thus, the newly developed monotonic Marshall-RT test can also be used as a surrogate simple performance test to estimate the rutting potential of asphalt mixtures during the mix design and plant production phases as quality control (QC)/quality assurance (QA).

Evaluation of Rutting, Fatigue, and Moisture Resistance of Low-Energy Asphalt Mixtures Modified by Crumb Rubber

Low-energy asphalt (LEA) mixture, as an alternative to hot mix asphalt (HMA) due to its lower mixing temperature, has advantages such as reducing energy consumption and environmental pollutants. LEA has poor performance characteristics due to the presence of water in its manufacturing process and low mixing temperature. All the studies about LEA have been focused only on investigating the performance of this asphalt mixture, and the effect of additives in its modification is one of the research gaps in this field. Therefore, the use of crumb rubber (CR) and determining its optimal percentage in modifying the performance characteristics of LEA is considered an innovation of this research. In this research, the performance characteristics of LEA modified by 10%, 15%, and 20% CR were evaluated. In order to examine the rutting behavior, moisture sensitivity and fatigue resistance, dynamic creep, indirect tensile strength (ITS), and four-point bending beam tests were applied, respectively. The results of creep curves and flow numbers (FNs) indicated that modifying LEA by 15% increased the rutting resistance by 1.92 and 2.3 times, respectively, compared to the HMA specimen at the stress level of 207 and 310 kPa. Moreover, the evaluation of the creep strain slope revealed that modifying LEA significantly reduced stress sensitivity. ITS test showed an increase in tensile strength ratio by 22% in the specimen with 10% CR compared to the unmodified specimen. In the evaluation of fatigue resistance, while LEA containing 10% CR had almost similar results to the HMA specimen, other specimens represented a shorter fatigue life, so that with the increase in CR percentage, the fatigue life decreased. Determination of fatigue life by energy ratio and Rowe and Bouldin criteria showed similar results. Finally, by determining the plateau value (PV) in the ratio of the dissipated energy change method, the lowest PV was assigned to the 10% CR-modified LEA and HMA specimens, respectively.

Assessment of the impact of binder grade on the laboratory performance of fiber reinforced asphalt mixtures

This study aims to evaluate the impact of different fiber types and binder modifications on the volumetric properties and performance (rutting and cracking) of fiber-reinforced asphalt mixtures (FRAM). Four types of fibers (carbon, fiberglass, basalt, and polyolefin/aramid (PFA) mix) and two binder performance grades (PG 58–28 unmodified and PG 76–22 polymer modified) were used to produce a total of ten asphalt mixtures (two control and eight FRAM). All fibers were introduced at the manufacturer-recommended dosages (i.e., carbon, fiberglass, basalt: at 0.16%, and PFA: at 0.05%) by mix weight. The mix design and volumetrics properties were examined to assess the impact of FRAM on volumetric properties of modified and unmodified binders. Mix characteristics, durability, rutting, and cracking performances were also evaluated by performing several tests, including dynamic modulus test |E*|, Cantabro loss, Asphalt pavement Analyzer (APA), Flow Number (FN), and Indirect Tensile Asphalt Cracking Test (IDEAL-CT). Mix design results showed that FRAM at 0.16% dosage increased the air voids of the unmodified binder (PG58-28). PFA fibers did not have an impact on air voids or volumetric properties of the asphalt mix regardless of modification. Performance results showed that FRAM were highly durable than control mix, but durability is significant for polymer modified binder (PG76-22). Furthermore, only PFA reinforced mixtures showed better rutting resistance for both modified and unmodified binders. The addition of fibers did not show any impact on cracking performance of modified and unmodified binder prepared asphalt mix. Finally, PFA reinforced mix also indicated higher fracture toughness (Gf) and carbon fibers improved the ductility of asphalt mix.

Rutting Resistance Evaluation of Highly Polymer-Modified Asphalt Binder and Mixes Using Different Performance Parameters

This study focused on evaluating the rutting performance of three different highly polymer-modified asphalt (HiMA) binders (i.e., O, T and B) using binder-based [i.e., multiple stress creep recovery (MSCR) and force ductility (FD)] and mix-based [flow number (FN) and Hamburg wheel tracking test (HWTT)] rutting performance tests. The binder-based rutting indicators were compared with mix rutting performance to determine a parameter that can help in the correct prediction of HiMA rutting resistance. In addition, the study looked into application of a simple performance test, the indirect rutting tolerance index (IDEAL-RT), for HiMA mix rutting prediction. The MSCR test revealed different rankings of recovery at 0.1- and 3.2-kPa stress levels. Moreover, the T and B binders did not satisfy the stress sensitivity criteria (Jnr_difference) of Max 75%. The force ductility tests revealed that the peak force observed for polymer network phase in HiMA was significantly higher than base binder stiffness, which is in contrast with force distribution in polymer-modified binders (PMBs). The mix rutting resistance ranking (O>T>B) was similar in all the tests (i.e., FN, HWTT, and IDEAL-RT). Although IDEAL-RT can be used to compare the rutting resistances of HiMA mixes, detailed future work is required to establish its acceptability in comparing various types of mixes and the minimum requirements of RTIndex. The comparison between binder and mix rutting indicators demonstrated that MSCR testing on binder at stress levels of 6.4 kPa and higher can be used to predict the rutting resistance of HiMA binders. Parameters like slope and cohesion energy and a newly introduced parameter—work done for polymer activation (WPA)—from FD tests can be used to determine the polymeric phase dominance in HiMA binders. Overall, this study provides pavement stakeholders with a framework for rightly predicting the rutting resistance and polymeric phase dominance of HiMA binders and mixes using MSCR, FD, and IDEAL-RT tests.

Effect of Crumb Rubber on the Moisture and Rutting Behavior of Low-Energy Asphalt and Determining the Best Flow Number Model

The advancement of technology and the increasing growth of environmental threats have led experts in the field of transportation to find alternatives for hot mix asphalts (HMAs). One of these alternatives is low-energy asphalt (LEA) mixtures. LEA mixture consists of hot asphalt binder and coarse aggregates and wet sand, which, having a lower mixing temperature, has caused a significant reduction in energy consumption and pollutants emitted from asphalt binder. According to previous studies, the influence of crumb rubber (CR) on the rutting and moisture performances of LEAs has not been investigated so far. In this regard, due to the softness of this type of asphalt mixture and its weakness against rutting and moisture, in this study, as an innovation, CR was used to modify LEA mixtures in three weight percentages of 10, 15, and 20. Considering the high moisture sensitivity of LEA mixtures due to the presence of water, the ability of CR to overcome this weakness and its potential to be replaced with antistriping additives were also investigated using the indirect tensile strength (ITS) test. In addition, in order to evaluate the rutting resistance, LEA mixtures were subjected to the dynamic creep test at a temperature of 54.4°C and at two stress levels of 270 and 310 kPa. According to ITS test results, it was found that although the modified LEA mixtures with 10 and 15% CR met the minimum requirement, the tensile strength ratio (TSR) value recorded for mentioned mixtures was still lower than that for HMA. Therefore, it is recommended to use antistripping additives in the use of LEA-containing CR, especially in areas with a high probability of moisture damage. The results of creep curves and flow numbers (FNs) extracted from four different models of three-stage, Fnest, Francken, and stepwise showed that although the LEA sample without additive had lower rutting resistance than HMA, the modification of this mixture to 15% CR significantly increased the rutting resistance. Moreover, considering the variety of variables in the process of making LEA compared to HMA, the comparison of FN determination models and the introduction of the most stable model were conducted in this research. According to the laboratory and statistical analysis results, it was found that the Francken model had less sensitivity to the variables, so it is suggested to determine FN for LEA mixtures.

Effect of flow number of pilot-stage centrifugal atomizer on idle performance of internally staged combustor

Idle performance is critical to the combustion stability of internally staged combustors. Five pilot-stage atomizers are compared in an internally staged combustor, and the effects of the flow number (FN) on the combustion characteristics and emissions are investigated under idle conditions. Experimental results show that the maximum outlet temperature is 1.02–1.04 times the average outlet temperature, and the maximum temperature is located at the dimensionless radial location of 0.66. The key influencing mechanism of the temperature distribution lies in the matching between the spray angle of the pilot-stage atomizer and the angle of the recirculation zone. When the flow number (FN) of the pilot-stage atomizers was increased from 1.6 to 10, the combustion efficiency (η) showed a “decrease-increase-decrease” trend, whereas the emission of unburned hydrocarbon (UHC) showed a opposite trend. At the meantime, the emission of CO remained unchanged, and NOx remained at the undetectable level. In addition, the low sensitivity of pressure loss (3.3%-4%) and combustion stability (0.66%-0.85%) to idle conditions is attributed to the influence of combustion efficiency and outlet temperature. After a comprehensive evaluation, it is determined that an intermediate FN of 5.0 possesses the most balanced combustion characteristics and emissions under idle conditions in the pilot-stage atomizer.

Study on performance deterioration regularity of hot regenerated asphalt mixture under multiple aging factors

Several elements, including ultraviolet light, humidity, temperature, vehicle load, etc., have an impact on the asphalt pavement concurrently during the road service process, gradually diminishing the road’s service level. The self-created Life Cycle Analysis System (LCAS) was employed to simulate the cumulative effects of multiple aging components during the service process. The freeze–thaw splitting test, dynamic creep test, and notched semi-circular bending test were conducted after the hot recycled and the fresh asphalt mixtures were subjected to varying durations of simulated aging. The results indicate that initially, the road performance of the hot recycled asphalt mixture is comparable to the fresh asphalt mixture. However, the fresh asphalt mixture outperforms the hot recycled mixture in all but water stability over time. The attenuation degree of the flow number (FN) differs by 22.5% between the two kinds of mixtures, while the fracture energy differs by 53.3%. The performance of the hot recycled asphalt mixture degrades much more rapidly than that of the fresh asphalt mixture. The LCAS method can well simulate the actual service environment of asphalt pavement constructed with RAP materials and provide help for the performance evaluation of RAP pavement in road engineering and subsequent related research.

Investigation of Using Crushed Glass Waste as Filler Replacement in Hot Asphalt Mixtures

Due to the depletion of natural aggregates and high maintenance cost of highway systems, developing sustainable asphalt concrete (AC) mixes that use waste materials instead of virgin raw materials is necessary. A large amount of waste glass material is globally generated per year that could be beneficial to sustain the asphalt industry. In this context, the present paper evaluates the properties and performance of AC mixtures that utilize crushed waste glass as a replacement material of filler aggregates. Three AC mixes with percentages of filler replacement in the range from 0%, 25%, to 50% were fabricated. Complex modulus testing was performed to evaluate the dynamic modulus |E*| and phase angle δ over a range of temperatures and loading frequencies. In addition, the flow number (FN) test was conducted to assess the rutting potential of the mixtures. The results showed that the mix containing 25% of crushed glass is likely to better resist fatigue cracking; however, the inclusion of glass in the AC reduced the rutting resistance compared to conventional hot mix asphalt (HMA). Finally, the results of the flow number test and the simple performance indicators were compared and used to rank the mechanical performance of the various mixtures.

Investigation of the rutting performance of modified stone matrix asphalt (SMA) using the dynamic creep and Hamburg Wheel-Tracking Device tests

ABSTRACT In this study, Forta Fibers (FFs) with a constant length of 19 mm and 0.5 kg/ton were added to the stone matrix asphalt (SMA) to investigate flexible pavement's permanent deformation. Hence, the Hamburg Wheel Tracking Device (HWTD) and Dynamic Creep test were performed to investigate the rutting performance of the SMA. The results of the HWTD showed that using FFs reduces the rutting depth of the SMA by about 42% compared to the control specimens by continuing the loading cycles up to 5000. Also, the amount of Stripping Inflection Point (SIP) for the SMA and SMA modified with FFs occurred in more than 10000 passes, which increased the resistance to moisture susceptibility. Besides, the dynamic creep test results showed that the number of loading cycles of SMA modified with FFs was 61% higher than the control specimen. Also, the Flow Number (FN) of specimens containing fibers was about 44% higher, which indicates an increase in the rutting resistance of the modified specimens compared to the control specimens. Also, an increase in creep modulus of modified specimens resulted in less plastic deformation. Finally, the resilient modulus result showed that the SMA modified with FFs is more resistant to permanent deformation.

Numerical Investigation of Particle Focusing Patterns in Laminar Pipe Flow With High Reynolds Numbers

The inertial focusing characteristics of particles in laminar flow pipes with high <i>Re</i> numbers were studied based on the “relative motion model”. In order to solve the problem of long pipes with high <i>Re</i> number flow, periodic boundary conditions were imposed on the inlet and outlet of the pipe. The research results show that the use of periodic boundary conditions can effectively reduce the computational, and the mechanical properties of particles in high <i>Re</i> flow can be calculated by using <i>L</i>=4<i>D</i> pipe. The difference from the low <i>Re</i> number is that as the <i>Re</i> number continues to increase,the lift force of the particles in the radial direction is no longer distributed as a parabola. The lift curve has a concave area between <i>r</i>⁺ =0.5 ~ 0.7, and there is a tendency for a new inertial focus point to appear in this section. By means of particles of <i>a</i>⁺ =1/17 for <i>Re</i> &gt; 1 000, this new focus point position is solvable. In addition, in the analysis of the flow field, a secondary flow occurs around the particle, and its intensity gradually increases with the <i>Re</i> number and the closeness of the particle to the wall. The generation of the secondary flow affects the spatial distribution of the particle lift.

Heat conduction in general relativity

We study the problem of heat conduction in general relativity by using Carter’s variational formulation. We write the creation rates of the entropy and the particle as combinations of the vorticities of temperature and chemical potential. We pay attention to the fact that there are two additional degrees of freedom in choosing the relativistic analog of Cattaneo equation for the parts binormal to the caloric and the number flows. Including the contributions from the binormal parts, we find a new heat-flow equations and discover their dynamical role in thermodynamic systems. The benefit of introducing the binormal parts is that it allows room for a physical ansatz for describing the whole evolution of the thermodynamic system. Taking advantage of this platform, we propose a proper ansatz that deals with the binormal contributions starting from the physical properties of thermal equilibrium systems. We also consider the stability of a thermodynamic system in a flat background. We find that new ‘Klein’ modes exist in addition to the known ones. We also find that the stability requirement is less stringent than those in the literature.

Toward an asymptotic description of Prandtl–Batchelor flows with corners

The Prandtl–Batchelor theorem states that the vorticity in a steady laminar high Reynolds (Re) number flow containing closed streamlines should be constant; however, apart from the simple case of circular streamlines, very little is known about how to determine this constant (ω0). This paper revisits earlier work for flow driven by a surrounding smooth moving boundary, with a view to extending it to the case where the enclosing boundary has corners; for this purpose, a benchmark example from the literature for flow inside a semi-circle is considered. However, the subsequent asymptotic analysis for Re≫1 and numerical experimentation lead to an inconsistency: the asymptotic approach predicts boundary-layer separation, whereas a linearized asymptotic theory and computations of the full Navier–Stokes equations for Re≫1 do not. Nevertheless, by considering a slightly modified problem instead, which does not suffer from this inconsistency, it is found that, when extrapolating the results of such high-Re computations to infinite Re, the agreement for ω0 is around 5%, which is roughly in line with previous comparisons of this type. Possible future improvements of the asymptotic method are also discussed.

CaTSM: A Pseudo‐Spectral Thermodynamically Consistent Model of Compressible Flows

AbstractWe introduce a pseudo‐spectral algorithm that includes full compressible dynamics with the intent of simulating near‐incompressible fluids, CaTSM (Compressible and Thermodynamically consistent Spectral Model). A semi‐implicit scheme is used to model acoustic waves in order to evolve the system efficiently for such fluids. We demonstrate the convergence properties of this numerical code for the case of a shock tube and for Rayleigh‐Taylor instability. A linear equation of state is also presented, which relates the specific volume of the fluid linearly to the potential temperature, salinity, and pressure. This permits the results to be easily compared to a Boussinesq framework in order to assess whether the Boussinesq approximation adequately represents the relevant exchange of energy to the problem of interest. One such application is included, that of the development of a single salt finger, and it is shown that the energetic behavior of the system is comparable to the typical canonical development of the problem for oceanographic parameters. However, for more compressible systems, the results change substantially even for low‐Mach number flows.

Simulation of drift-diffusion process at high Péclet numbers by the random walk on spheres method

Abstract In this paper, we address the problem of flow simulation at high Péclet numbers by the random walk on spheres (RWS) method. Conventional deterministic methods here face difficulties related to high solution gradients near the boundary in the region known as the boundary layer. In the finite-difference methods, this leads to introduction of very fine meshes which in turn causes problems of stability and high dimensions. The RWS algorithm is mesh free, but the high Péclet number flows should probably also affect the efficiency of simulations. However, it turns out that the RWS algorithm can be well adapted to this case. We present an analysis of the RWS algorithm for different examples of flows with high Péclet number. Simulations are carried out for different boundary conditions and for two-layered material with different diffusion coefficients of exciton’s mobility.

Investigating the effect of using unclassified fractionated reclaimed asphalt pavement materials on the properties of hot mix asphalt

Reclaimed Asphalt Pavement (RAP) incorporation is bounded by many specifications that limit its increased utilization. One of them, which many road agencies adopt, is the allowance of RAP from known single origin “classified RAP” only to be utilized in new mixtures. A lot of asphalt plants cannot afford space for multiple small RAP stockpiles in their yards and are forced to accumulate “unclassified” RAP materials collected from several projects into a single zone, hence, the “classified RAP” specification restricts the benefits of their utilization. In this context, this study aimed to investigate the pros and cons of using unclassified fractionated RAP with 15%, 25% and 45% percentages in Superpave asphalt mixtures. Complex modulus testing was performed on three replicates of each asphalt concrete (AC) mixture to evaluate the dynamic modulus |E*| and phase angle Φ properties over a range of temperatures and loading frequencies. As well, Flow number (FN) test was conducted to assess the rutting potential of the mixtures. The results showed that no significant difference existed between |E*| and Φ values of conventional hot asphalt mixture (HMA) and other RAP mixtures over the full analyzed range of frequency which indicates that the utilization of low, medium or high percentages of unclassified RAP materials may be indeed appropriate. Finally, the results of the flow number test and the simple performance indicator were compared and used to rank the rutting resistance of the assessed mixtures.

Toward Next‐Generation Lava Flow Forecasting: Development of a Fast, Physics‐Based Lava Propagation Model

AbstractDuring effusive volcanic crises, the eruption and propagation of lava flows pose a significant hazard to nearby populations, homes, and infrastructure. Consequently, timely lava flow forecasts are a critical need for volcano observatory and emergency management operations. Previous lava flow modeling tools are typically either too slow to produce timely forecasts, or are fast, but lack critical aspects of lava physics or important forecasting outputs. In particular, the strong thermal stratification present in laminar, high‐Prandtl number flows has generally been neglected. Bulk rheological changes have previously been computed from cell‐averaged temperatures, assuming that the flow is thermally mixed. Here, we detail the development and initial testing of Lava2d, a new two‐dimensional depth‐averaged finite volume model of lava flow propagation over natural terrain which accounts for bulk rheological changes due to thermorheological stratification. We use a novel approach to energy conservation based on tracking cooling and solidifying at the flow base and at the moving flow surface, allowing for the estimation of more realistic vertical thermorheological profiles, while maintaining computational efficiency, producing very timely model runs. We validate our approach with three examples: comparison with theoretical propagation of crust‐dominated lava flows, comparison with a large‐scale molten basalt experiment from the Syracuse University Lava Project, and efficiency testing and comparison with the initial phase of the 1984 Mauna Loa lava flows. Our model is shown to produce rapid, realistic forecasts, making it a good candidate for operationalization in active volcanic regions such as in Hawai'i.