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1.
Materials (Basel) ; 17(12)2024 Jun 14.
Artículo en Inglés | MEDLINE | ID: mdl-38930278

RESUMEN

Polyurethane (PU) mixture, which is a new pavement mixture, exhibits different dynamic properties compared to a hot-mixed asphalt mixture (HMA). This paper analyzed whether the Kramers-Kronig (K-K) relation and thermorheologically simple properties applied to the PU mixture. Based on the results, the PU mixture exhibited thermorheologically simple properties within the test conditions. The time-temperature superposition principle (TTSP) was applicable for the PU mixture to construct a dynamic modulus master curve using the standard logistic sigmoidal (SLS) model, the generalized logistic sigmoidal (GLS) model, and the Havriliak-Negami (HN) model. The Hilbert integral transformed SLS and GLS models for the phase angle can accurately fit the measured phase angle data with newly fitted shift factors and predict the phase angle within the viscoelastic range. The core-core and black space diagrams both displayed single continuous smooth curves, which can be utilized to characterize the viscoelastic property of the PU mixture. The K-K relation is applicable for the PU mixture to obtain the phase angle master curve model, storage modulus, and loss modulus from the complex modulus test results with the test temperatures and loading frequencies. The phase angle of the PU mixture at extremely high or low test temperatures cannot be derived from the dynamic modulus data.

2.
Materials (Basel) ; 17(12)2024 Jun 18.
Artículo en Inglés | MEDLINE | ID: mdl-38930353

RESUMEN

In order to provide a basis for the structural analysis, design and maintenance of permeable asphalt pavements, and to promote their engineering promotion and application, this study investigated the dynamic viscoelastic properties of permeable asphalt mixtures (PAC-13) under complex stress states. A Simple Performance Tester (SPT) system was used to measure the dynamic modulus of the mix under complex stress states. The displacement factor and principal dynamic modulus curves were formed by fitting Sigmoidal functions and using 1stOpt (first optimization) software, the phase angle principal curves were further determined, and the dynamic modulus was predicted for the ambient phase (15-25 °C) using the Hirsch model. The results showed that the dynamic modulus of the mixtures decreases with an increasing temperature, and the maximum decrease in the dynamic modulus is 93% when the confining pressure is 100 kPa and the loading frequency is 10 Hz. The dynamic modulus increases with an increasing confining pressure and loading frequency, the maximum increase with an increasing confining pressure is 26.1% when the temperature is 25 °C and the loading frequency is 10 Hz, and the maximum increase with an increasing loading frequency is 411% when the temperature is 25 °C and the confining pressure is 100 Hz. The dynamic modulus has a strong frequency dependence at low temperatures, while it is stress-dependent at high temperatures. Meanwhile, based on the Hirsch model, a new modified prediction model was developed, which can well predict the dynamic modulus of permeable asphalt mixtures at room temperature.

3.
J Exp Biol ; 227(13)2024 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-38842008

RESUMEN

In this report, passive elasticity properties of Octopus rubescens arm tissue are investigated using a multidisciplinary approach encompassing biomechanical experiments, computational modeling, and analyses. Tensile tests are conducted to obtain stress-strain relationships of the arm under axial stretch. Rheological tests are also performed to probe the dynamic shear response of the arm tissue. Based on these tests, comparisons against three different viscoelasticity models are reported.


Asunto(s)
Elasticidad , Octopodiformes , Animales , Octopodiformes/fisiología , Fenómenos Biomecánicos , Viscosidad , Extremidades/fisiología , Resistencia a la Tracción , Reología , Estrés Mecánico
4.
J Orthop Sports Med ; 6(2): 67-72, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38784690

RESUMEN

Hyperlipidemia is linked to atherosclerosis and various diseases. Its strong association with Achilles tendinopathies and xanthomas affects tendon properties through lipid deposition in tendon tissue. We examined the impact of hyperlipidemia on the biomechanical properties of the swine Achilles tendons. Swines were fed a high-cholesterol-high-fat diet to induce hyperlipidemia, and their Achilles tendons were collected and examined for biomechanical properties. The ultimate tensile strength, modulus of elasticity and viscoelastic properties did not exhibit significant differences between hyperlipidemic and control swines. H&E and pentachrome staining revealed extracellular matrix (ECM) disorganization and cellular infiltration in the hyperlipidemic swines, highlighting a marked difference between the control and hyperlipidemic groups. These results suggest hyperlipidemia in young swines alters the tendon composition and may contribute to weak biomechanical properties with time.

5.
J Biomech ; 169: 112135, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38744145

RESUMEN

Articular cartilage exhibits site-specific biomechanical properties. However, no study has comprehensively characterized site-specific cartilage properties from the same knee joints at different stages of osteoarthritis (OA). Cylindrical osteochondral explants (n = 381) were harvested from donor-matched lateral and medial tibia, lateral and medial femur, patella, and trochlea of cadaveric knees (N = 17). Indentation test was used to measure the elastic and viscoelastic mechanical properties of the samples, and Osteoarthritis Research Society International (OARSI) grading system was used to categorize the samples into normal (OARSI 0-1), early OA (OARSI 2-3), and advanced OA (OARSI 4-5) groups. OA-related changes in cartilage mechanical properties were site-specific. In the lateral and medial tibia and trochlea sites, equilibrium, instantaneous and dynamic moduli were higher (p < 0.001) in normal tissue than in early and advanced OA tissue. In lateral and medial femur, equilibrium, instantaneous and dynamic moduli were smaller in advanced OA, but not in early OA, than in normal tissue. The phase difference (0.1-0.25 Hz) between stress and strain was significantly smaller (p < 0.05) in advanced OA than in normal tissue across all sites except medial tibia. Our results indicated that in contrast to femoral and patellar cartilage, equilibrium, instantaneous and dynamic moduli of the tibia and trochlear cartilage decreased in early OA. These may suggest that the tibia and trochlear cartilage degrades faster than the femoral and patellar cartilage. The information is relevant for developing site-specific computational models and engineered cartilage constructs.


Asunto(s)
Cartílago Articular , Articulación de la Rodilla , Osteoartritis de la Rodilla , Humanos , Cartílago Articular/fisiopatología , Cartílago Articular/fisiología , Cartílago Articular/patología , Articulación de la Rodilla/fisiopatología , Anciano , Osteoartritis de la Rodilla/fisiopatología , Masculino , Femenino , Persona de Mediana Edad , Fenómenos Biomecánicos , Elasticidad , Viscosidad , Tibia/fisiopatología , Fémur/fisiopatología , Fémur/fisiología , Anciano de 80 o más Años , Adulto , Estrés Mecánico
6.
Polymers (Basel) ; 16(5)2024 Feb 22.
Artículo en Inglés | MEDLINE | ID: mdl-38475283

RESUMEN

This manuscript presents a comprehensive study on the sustainable optimization of asphalt mixtures tailored for regions prone to flooding. The research addresses the challenges associated with water damage to asphalt pavements by incorporating innovative additives. The study centers on incorporating recycled Low-Density Polyethylene (LDPE) and a tailored Carnauba-Soybean Oil Additive, advancing asphalt mixtures with a Control mix, LDPE (5%) + Control, and LDPE (5%) + 3% Oil + Control. A critical aspect of the research involves subjecting these mixtures to 30 wetting and drying cycles, simulating the conditions prevalent in tropical flood-prone areas. The incorporation of innovative additives in asphalt mixtures has demonstrated significant improvements across various performance parameters. Tensile Strength Ratio (TSR) tests revealed enhanced tensile strength, with the LDPE (5%) + 3% Oil-modified mixture exhibiting an impressive TSR of 85.7%. Dynamic Modulus tests highlighted improved rutting resistance, showcasing a remarkable increase to 214 MPa in the LDPE (5%) with a 3% Oil-modified mixture. The Semi-Circular Bending (SCB) test demonstrated increased fracture resistance and energy absorption, particularly in the LDPE (5%) with 3% Oil-modified mixture. Hamburg Wheel-Tracking (HWT) tests indicated enhanced moisture resistance and superior rutting resistance at 20,000 cycles for the same mixture. Cantabro tests underscored improved aggregate shatter resistance, with the LDPE (5%) + 3% Oil-modified mixture exhibiting the lowest weight loss rate at 9.820%. Field tests provided real-world insights, with the LDPE (5%) + 3% Oil mixture displaying superior stability, a 61% reduction in deflection, and a 256% improvement in surface modulus over the control mixture. This research lays the groundwork for advancing the development of sustainable, high-performance road pavement materials, marking a significant stride towards resilient infrastructure in flood-prone areas.

7.
J Orthop Sports Med ; 5(4): 391-397, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37982013

RESUMEN

Infraspinatus tendon is the most affected tendon of the rotator cuff, being an important posterior component of the shoulder joint. Hyperlipidemia is a predisposing factor in the progression of rotator cuff tears and retear. We studied the effect of hyperlipidemia on the biomechanical properties of rotator cuff tendons. The infraspinatus tendon of the rotator cuff from hyperlipidemic swine were collected and tested for ultimate tensile strength (UTS) and modulus of elasticity. Dynamic mechanical analysis was performed to examine viscoelastic properties. The findings revealed no significant difference in UTS but had significantly lower modulus of elasticity in the infraspinatus tendon of the hyperlipidemic group compared to the control group. Moreover, differences in the dynamic modulus, storage modulus, and loss modulus were not statistically significant between the hyperlipidemic and control swine. There was no difference in water content between the groups but the hyperlipidemic group had fatty infiltration aiding the initial decrease in mechanical properties. These findings suggest an association between fat deposition and early changes in the biomechanical properties of the tendons in the shoulder rotator cuff in hyperlipidemic state.

8.
Materials (Basel) ; 16(21)2023 Oct 25.
Artículo en Inglés | MEDLINE | ID: mdl-37959449

RESUMEN

The ultrasonic test is a promising non-destructive testing technique for evaluating the properties of asphalt mixtures. To investigate the applicability and reliability of ultrasonic testing technology (UTT) in evaluating the performance of asphalt mixtures, ultrasonic tests, indirect tensile tests, compression tests, and dynamic modulus tests were carried out at various temperatures. Subsequently, the distribution characteristics of ultrasonic traveling parameters for asphalt mixtures were analyzed. The variation of ultrasonic pulse velocity and amplitude in dry and wet states with temperature was studied. Then, the correlation between the ultrasonic parameters and both the volume parameters and the mechanical performance parameters of asphalt mixtures was revealed, and the functional relationship between ultrasonic pulse velocity and compressive strength was established. Finally, the reliability of predicting high-frequency dynamic modulus by ultrasonic velocity was verified. The laboratory tests and analysis results indicate that both ultrasonic pulse velocity and amplitude in dry and wet conditions show a decreasing trend with an increase in temperature. Ultrasonic parameters are greatly influenced by asphalt content and mineral aggregate content of 9.5~13.2 mm and 13.2~16 mm. The dynamic modulus at a high-frequency load can be predicted by using ultrasonic velocity, and predicting the results for OGFC and SMA mixtures deduced by using the UPV at a high-frequency load have higher reliability.

9.
Materials (Basel) ; 16(19)2023 Sep 26.
Artículo en Inglés | MEDLINE | ID: mdl-37834546

RESUMEN

Of major concern is the lack of correlation between the material design and structural function of asphalt pavement in China. The objective of this paper is to identify the layer in asphalt pavement where permanent deformation occurs most seriously and to propose a control index for that layer's asphalt mixture. The permanent deformation of each layer was determined through the utilization of thickness measurements obtained from field cores. The results indicate that the reduction in thickness is more significant in the driving lane than in the ridge band and shoulder. This phenomenon can be attributed to the intensified densification and shearing deformation that arise from the combined impacts of recurrent axle loads and high temperatures. Compared to surface and base layers, the bearing layer is the primary area of concern for permanent deformation in asphalt pavement. Therefore, it is imperative to incorporate the ability of bearing-layer asphalt mixture to withstand permanent deformation as a crucial design parameter. The dynamic modulus of the bearing-layer asphalt mixture is significantly influenced by the type of asphalt, gradation, and asphalt content, compared to other design parameters. Based on the relationship established between dynamic modulus and dynamic stability, with creep rate as the intermediate term, a control standard was proposed to evaluate the permanent deformation of the bearing-layer asphalt mixture. This study can provide reasonable and effective guidance for prolonging pavement life and improving pavement performance.

10.
Int J Biol Macromol ; 253(Pt 7): 127452, 2023 Dec 31.
Artículo en Inglés | MEDLINE | ID: mdl-37844817

RESUMEN

In this study, interpenetrating polymer network hydrogels were developed based on sage seed gum (SSG) and globulin protein (Glo) extracted from the mucilage-free seeds. By combining Glo hydrogel with the SSG network the inherent weak gelation of the single SSG system was compensated. As the fraction of Glo increased, various properties of the interpenetrating polymer network (IPN) hydrogels improved substantially. Electrophoretic analysis under reducing conditions showed that Glo dissociated into subunits of approximately 30 kDa and 20 kDa, suggesting it comprises 11S globulin. FTIR spectrum revealed new peaks at 1645 cm-1 and 1537 cm-1 in the amide I and II regions, respectively, for the IPN hydrogels, indicating interactions between two hydrogel networks. Based on the weight loss measurements, the IPN hydrogels exhibited lower mass loss, particularly at higher Glo fractions up to 6 %. The IPN hydrogels also displayed enhanced elasticity, pseudoelasticity, thixotropy, and creep resistance compared to SSG hydrogel, indicating suitability for food, pharmaceutical, and biomedical applications. More broadly, this research provides a sustainable strategy toward innovative material development while advancing bio-based hydrogels.


Asunto(s)
Globulinas , Hidrogeles , Polímeros
11.
Front Bioeng Biotechnol ; 11: 1205512, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37324417

RESUMEN

Introduction: The knee meniscus distributes and dampens mechanical loads. It is composed of water (∼70%) and a porous fibrous matrix (∼30%) with a central core that is reinforced by circumferential collagen fibers enclosed by mesh-like superficial tibial and femoral layers. Daily loading activities produce mechanical tensile loads which are transferred through and dissipated by the meniscus. Therefore, the objective of this study was to measure how tensile mechanical properties and extent of energy dissipation vary by tension direction, meniscal layer, and water content. Methods: The central regions of porcine meniscal pairs (n = 8) were cut into tensile samples (4.7 mm length, 2.1 mm width, and 0.356 mm thickness) from core, femoral and tibial components. Core samples were prepared parallel (circumferential) and perpendicular (radial) to the fibers. Tensile testing consisted of frequency sweeps (0.01-1Hz) followed by quasi-static loading to failure. Dynamic testing yielded energy dissipation (ED), complex modulus (E*), and phase shift (δ) while quasi-static tests yielded Young's Modulus (E), ultimate tensile strength (UTS), and strain at UTS (εUTS). To investigate how ED is influenced by the specific mechanical parameters, linear regressions were performed. Correlations between sample water content (φw) and mechanical properties were investigated. A total of 64 samples were evaluated. Results: Dynamic tests showed that increasing loading frequency significantly reduced ED (p < 0.05). Circumferential samples had higher ED, E*, E, and UTS than radial ones (p < 0.001). Stiffness was highly correlated with ED (R2 > 0.75, p < 0.01). No differences were found between superficial and circumferential core layers. ED, E*, E, and UTS trended negatively with φw (p < 0.05). Discussion: Energy dissipation, stiffness, and strength are highly dependent on loading direction. A significant amount of energy dissipation may be associated with time-dependent reorganization of matrix fibers. This is the first study to analyze the tensile dynamic properties and energy dissipation of the meniscus surface layers. Results provide new insights on the mechanics and function of meniscal tissue.

12.
Materials (Basel) ; 16(12)2023 Jun 10.
Artículo en Inglés | MEDLINE | ID: mdl-37374483

RESUMEN

The dynamic modulus of elasticity (Ed), specified by ultrasonic pulse velocity measurements, is often used, especially for concrete built into construction, to estimate the static modulus of elasticity (Ec,s). However, the most commonly used Equations for such estimations do not take into account the influence of concrete moisture. The aim of this paper was to establish this influence for two series of structural lightweight aggregate concrete (LWAC) varying in their strength (40.2 and 54.3 MPa) and density (1690 and 1780 kg/m3). The effect of LWAC moisture content turned out to be much more pronounced in the case of dynamic modulus measurements than for static ones. The achieved results indicate that the moisture content of the concrete should be taken into consideration in modulus measurements as well as in Equations estimating Ec,s on the basis of Ed specified by the ultrasonic pulse velocity method. The static modulus of LWACs was lower on average by 11 and 24% in relation to dynamic modulus, respectively when measured in air-dried and water-saturated conditions. The influence of LWAC moisture content on the relationship between specified static and dynamic moduli was not affected by the type of tested lightweight concrete.

13.
Materials (Basel) ; 16(5)2023 Feb 24.
Artículo en Inglés | MEDLINE | ID: mdl-36902990

RESUMEN

Dry-processed rubberized asphalt mixture has recently attracted a lot of attention as an alternative to conventional asphalt mixtures. Dry-processed rubberized asphalt pavement has improved the overall performance characteristics compared to the conventional asphalt road. The objective of this research is to demonstrate the reconstruction of rubberized asphalt pavement and evaluate the pavement performance of dry-processed rubberized asphalt mixture based on laboratory and field tests. The noise mitigation effect of dry-processed rubberized asphalt pavement was evaluated at the field construction sites. A prediction of pavement distresses and long-term performance was also conducted using mechanistic-empirical pavement design. In terms of experimental evaluation, the dynamic modulus was estimated using materials test system (MTS) equipment, the low-temperature crack resistance was characterized by the fracture energy from the indirect tensile strength test (IDT), and the asphalt aging was assessed with the rolling thin-film oven (RTFO) test and the pressure aging vessel (PAV) test. The rheology properties of asphalt were estimated by a dynamic shear rheometer (DSR). Based on the test results: (1) The dry-processed rubberized asphalt mixture presented better resistance to cracking, as the fracture energy was enhanced by 29-50% compared to that of conventional hot mix asphalt (HMA); and (2) the high-temperature anti-rutting performance of the rubberized pavement increased. The dynamic modulus increased up to 19%. The findings of the noise test showed that at different vehicle speeds, the rubberized asphalt pavement greatly reduced the noise level by 2-3 dB. The pavement M-E (mechanistic-empirical) design-predicted distress illustrated that the rubberized asphalt pavement could reduce the IRI, rutting, and bottom-up fatigue-cracking distress based on a comparison of prediction results. To sum up, the dry-processed rubber-modified asphalt pavement has better pavement performance compared to the conventional asphalt pavement.

14.
Sensors (Basel) ; 23(4)2023 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-36850779

RESUMEN

Vibratory compaction status has a significant influence on the construction quality of subgrade engineering. This study carried out field experiments to study the propagation characteristics of the vertical vibration wave in the soil field along the traveling direction of the vibratory roller. The propagation coefficients of the peak acceleration at different positions and compacting rounds are compared in both the time and frequency domains. The compaction status is estimated in the form of dynamic modulus of deformation (Evd) obtained by plate load tests. The experiment results show that the propagation coefficient of peak acceleration is affected by the traveling speed, excitation amplitude, and frequency of the vibratory roller, as well as the compacting rounds. An exponential relationship between the wave amplitudes of the fundamental mode and higher-order modes is revealed. The amplitude of the fundamental wave is maximum at the speed of 3 km/h, whereas the amplitudes of higher-order waves have a maximum of 1.5 km/h. The influences of compaction rounds on the average value of Evd are also investigated to provide a practical reference for engineering construction.

15.
Materials (Basel) ; 16(2)2023 Jan 09.
Artículo en Inglés | MEDLINE | ID: mdl-36676360

RESUMEN

This study investigates the engineering and mechanical properties of basalt fiber-reinforced (FRF) concrete, giving special attention to residual flexural strength and dynamic modal parameters. These properties, which have not been thoroughly investigated elsewhere, are a precursor to structural design applications for dynamic compliant structures (i.e., bridges, offshore platforms, railways, and airport pavement). Accordingly, the standard notched flexural tests have been carried out to assess the basalt fiber-reinforced concrete's residual flexural strength with an additional 0.125%, 0.25%, 0.375%, and 0.5% of volume fraction of basalt fiber. In addition, dynamic modal tests were then conducted to determine the dynamic modulus of elasticity (MOE) and damping of the FRF concrete beams. The results indicate that concrete's toughness and crack resistance performance are significantly improved with added fiber in basalt fiber reinforced concrete, and the optimum fiber content is 0.25%. It also exhibits the highest increment of compressive strength of 4.48% and a dynamic MOE of 13.83%. New insights reveal that although the residual flexural performance gradually improved with the addition of basalt fiber, the damping ratio had an insignificant change.

16.
Materials (Basel) ; 16(2)2023 Jan 12.
Artículo en Inglés | MEDLINE | ID: mdl-36676508

RESUMEN

The dynamic modulus is a key property determining the short- and long-term performance of asphalt pavement, and its strong dependence on confining pressure and material density (mixture compactness) has been clearly indicated in the literature. It is always challenging to reproduce three-dimensional in situ stress conditions in the laboratory. To alleviate this difficulty, in this study, a convenient experimental setup was developed, in which the lateral confinement was made present and variable as a concomitant reaction of the surrounding materials to the vertical loading. Three dense-graded mixtures were prepared to a set of four different densities and then subjected to the confined dynamic modulus test. The results indicated a significant dependence of the confined modulus on the three factors of temperature, frequency, and compactness and that the mixture with coarser gradation demonstrated a less sensitivity to these parameters. A mathematical model was developed for the dynamic modulus master curve unifying these factors by means of horizontal shifting due to the time-temperature superposition principle (validated against the variable confinement at different compactness) and the vertical shift factor as a function of reduced frequency and compactness. The adequacy of the model was demonstrated using the experimental data, and its potential application in field pavement compaction was discussed.

17.
J Orthop Sports Med ; 5(4): 398-405, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-38161622

RESUMEN

Rotator cuff injury is the leading cause of shoulder pain. Hyperlipidemia is responsible in depositing lipids in tendons and reduce the healing upon injuries or tears. In this study, we created rotator cuff injury and repair models in swine and studied the changes in biomechanical properties of infraspinatus tendons in hyperlipidemic swine. The infraspinatus tendons from control group, hyperlipidemic injury and repair group of animals were collected and tested ex-vivo. The ultimate tensile strength (UTS) and modulus of elasticity increased in the tendons from the contralateral side on both the injury and repair models and were higher than the injury side. The presence of large number of fibrous tissues in the surgical site of repair and increased water content was observed in addition to the fatty infiltration which would have contributed to the decreased mechanical properties of the injured tendons following repair. Meanwhile the tendons of the contralateral side in both the injury and repair model showed adaptation to chronic load as observed in the modulus and viscoelastic properties. This is a pilot study that warrants detailed investigation in a larger sample size with longer duration following tendon injury and repair to gain better understanding on the effect of hyperlipidemia in the healing of rotator cuff tendon injury.

18.
Materials (Basel) ; 15(14)2022 Jul 10.
Artículo en Inglés | MEDLINE | ID: mdl-35888279

RESUMEN

One of the main difficulties with employing recycled asphalt pavement (RAP) in hot mix asphalt (HMA) is bitumen aging; hence, the percentage of RAP in the HMA is limited. This research evaluates the rheological properties of the RAP binder and the performance of HMA containing high RAP content using waste engine oil (WEO) from an Electrical Power Plant as a rejuvenator. The rheological and microstructural properties of the RAP binder and rejuvenated RAP binder were determined in the laboratory. Both the recycled and rejuvenated recycled mixes were tested for Marshall stability, indirect tensile strength, dynamic modulus (E*), and flow number tests. The RAP binder was recovered using two different processes: rotavapor distillation followed by centrifugation (RCRD) and column distillation without centrifugation (RNCCD). The optimal WEO percentages for the RCRD and RNCCD recovery procedures were 0.5% and 3%, respectively. The Marshall test results revealed that adding WEO to the recycled mix enhanced its stability and flow compared to the control mix. The rejuvenated mix containing recovered binder from the RCRD recovery process was found to be better than the rejuvenated mix containing recovered binder from the RNCCD recovery process. The rejuvenated recycled mixes outperformed the recycled mix in terms of moisture resistance, which was evidenced by tensile strength ratio values of 0.88, 0.90, and 0.91 for the control and 0.5% and 3% WEO modified mixes, respectively. Finally, the results of dynamic modulus and flow number testing revealed that the rejuvenated mixes had a modest drop in both the dynamic modulus and flow number compared to the non-rejuvenated mix.

19.
Materials (Basel) ; 15(12)2022 Jun 18.
Artículo en Inglés | MEDLINE | ID: mdl-35744385

RESUMEN

To develop a mechanistic-empirical pavement design system for Norwegian conditions, this paper evaluates the influence of the adoption of different models and shifting techniques on the determination of dynamic modulus master curves of asphalt mixtures. Two asphalt mixture types commonly used in Norway, namely Asphalt Concrete (AC) and Stone Mastic Asphalt (SMA) containing neat bitumen and polymer-modified bitumen, were prepared by the roller compactor, and their dynamic moduli were determined by the cyclic indirect tensile test. The dynamic modulus master curves were constructed using the standard logistic sigmoidal model, a generalized logistic sigmoidal model and the Christensen-Anderson-Marasteanu model. The shifting techniques consisted of log-linear, quadratic polynomial function, Arrhenius, William-Landel-Ferry and Kaelble methods. The absolute error, normalised square error and goodness-of-fit statistics encompassing standard error ratio and coefficient of determination were used to appraise the models and shifting methods. The results showed that the standard logistic sigmoidal model and the Williams-Landel-Ferry equation had the most suitable fits for the specimens tested. The asphalt mixtures containing neat bitumen had a better fit than the ones containing polymer-modified bitumen. The Kaelble equation and log-linear equation led to similar results. These findings provide a relevant recommendation for the mechanistic-empirical pavement design system.

20.
Materials (Basel) ; 15(5)2022 Feb 27.
Artículo en Inglés | MEDLINE | ID: mdl-35269021

RESUMEN

To characterize the dynamic modulus (E*) of the asphalt mixtures more accurately, a comparative study was shown in this paper, combining six ML models (BP, SVM, DT, RF, KNN, and LR) with the novelly developed MBAS (modified BAS, beetle antennae search) algorithm to check the potential to replace the empirical model. The hyperparameter tuning process of the six ML models by the proposed MBAS algorithm showed satisfactory results. The calculation and evaluation process demonstrated fast convergence and significantly lower values of RMSE for the five ML models (BP, SVM, DT, RF, and KNN) to determine the E* of the asphalt mixtures. Comparing the performances of the six ML models in the prediction of the E* by the statistical coefficients and Monte Carlo simulation, the RF model showed the highest accuracy, efficiency, and robustness.

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