Pavement Construction Materials Research Articles

Evaluation of strength, wear, and skid resistance in pavement quality concrete with partial replacement of steel slag

ABSTRACT Sustainable pavement construction is essential for promoting ecological balance and reducing the environmental impact of infrastructure projects. This study investigates the viability of partially replacing conventional fine aggregate (river sand) with steel slag in proportions ranging from 10% to 100% by volume for pavement quality concrete (PQC). The mechanical properties of PQC were evaluated following IRC standards, with a focus on compressive strength, flexural strength, split tensile strength, and fatigue performance. Additionally, the study assessed the concrete’s abrasion resistance and skid resistance, critical for ensuring durability and road safety. The experimental results demonstrated that incorporating steel slag as a fine aggregate replacement significantly enhances the mechanical performance of PQC. A mix containing 40% steel slag exhibited optimal improvements in compressive, flexural, and tensile strengths, alongside superior resistance to wear and skid. These findings indicate that steel slag, when used in appropriate proportions, can enhance both the durability and safety of concrete pavements. The study highlights the potential of steel slag as a sustainable and resource-efficient alternative to conventional materials in pavement construction, contributing to environmental sustainability and improved infrastructure performance.

Characterization and Performance Evaluation of Eco-Friendly Angular-Shaped Fly Ash Aggregates as Base Material in Pavement Construction under Cyclic and Shear Loading

Characterization and Performance Evaluation of Eco-Friendly Angular-Shaped Fly Ash Aggregates as Base Material in Pavement Construction under Cyclic and Shear Loading

Strength and Durability Characteristics of Sustainable Pavement Base Course Stabilized with Cement Bypass Dust and Spent Fluid Catalytic Cracking Catalyst

This study explores the potential of a composite binder comprising cement bypass dust (CBD) and spent fluid catalytic cracking (FCC) catalyst for sustainable pavement base stabilization. Various CBD/FCC ratios (30:70, 50:50, 70:30) and binder contents (4%, 6%, 8%, 10%) were evaluated through laboratory testing. The 50:50 CBD/FCC mixture demonstrated optimal performance, achieving an unconfined compressive strength (UCS) of 15.6 MPa at 28 days with 10% binder content. The mix exhibited improved stiffness (E50 modulus up to 13,922 MPa) and resistance to degradation under wetting–drying cycles, attributable to synergistic cementitious and pozzolanic reactions. Microstructural analysis revealed a denser matrix, validating the enhanced performance. These findings suggest CBD and FCC, as promising materials for sustainable pavement construction, align with circular economy principles.

Experimental Investigation and Statistical Analysis of Recycled Asphalt Pavement Mixtures Incorporating Nanomaterials

Reclaimed Asphalt Pavement (RAP) materials are used as substitutes for new materials in asphalt pavement construction, leveraging the engineering and commercial benefits of the aged binders and aggregate matrixes in RAP. These asphalt mixtures impart significant variations in volumetric properties and asphalt mixture characteristics. The current study investigates the Marshall properties, moisture susceptibility, and rutting behavior of 24 recycled asphalt mixtures developed with nanosilica and nanoclay. RAP material percent, nanomaterial content, binder grade, and extra binder were considered the factors influencing asphalt mixture performance. The above factors were analyzed using the Response Surface Methodology (RSM) to predict the Marshall and volumetric properties. Also, this investigation covers the moisture susceptibility and rut characteristics of recycled nanomaterial-modified Hot Mix Asphalt (HMA) and Warm Mix Asphalt (WMA) mixes developed with Viscosity Grade 30 (VG-30) and Polymer-Modified Bitumen-40 (PMB-40). The chemical additive Zycotherm was used to develop WMA mixes. The test results indicate that adding RAP material at higher percentages and modifying the binder with nanomaterials affected moisture susceptibility with reduced moisture damage. Recycled nanosilica-modified HMA mixes developed with PMB-40 at higher RAP percentages reported higher tensile strength ratio (TSR) values in contrast with VG-30 mixes, indicating their greater susceptibility toward moisture-induced damage. The rutting potential of all of the recycled asphalt mixture combinations was enhanced by densely packed aggregate structures optimized with nanomaterials, total binder content, and RAP materials developed using the Marshall method. Overall, the nanosilica-modified recycled asphalt mixes developed with PMB40 at higher RAP percentages showed better performance in terms of strength and durability.

Design of optical performance for self-luminous pavement materials

The lower visibility in the nighttime environment makes higher accident risks during driving. Using self-luminous materials in pavement construction can effectively improve the luminance of load surface, thus significantly improve nighttime driving safety. This study has designed three types of self-luminous pavement materials (SLPM) with different optical properties by incorporating long-persistent luminescent aggregates into the mixture and using polymer binders with varying degrees of light transmittance, such as transparent polyurethane, transparent asphalt, and traditional asphalt. On this basis, utilizing digital image processing techniques to compare the optical performance differences among these three SLPM and established corresponding computational models based on the obtained data to enable efficient and accurate evaluation of the optical properties of pavement materials. The experimental results indicate that the durability performance of SLPM gradually diminishes over time, and this degree of attenuation is negatively correlated with the light transmittance of the binder. Specifically, a higher light transmittance of the binder results in a smaller decline in SLPM durability, whereas a lower transmittance leads to a more significant reduction. The optical performance calculation model established by this research can predict the reflective performance of SLPM through the optical parameters of aggregate, binders, and the doping amount of long persistent luminescent materials. In addition, the model can accurately calculate the minimum content of self-luminous materials according to the optical requirements required by the project, which can provide a reference for the performance evaluation of self-luminous pavement materials and the selection of optimal proportioning scheme.

A Critical Overview of Using Reclaimed Asphalt Pavement (RAP) in Road Pavement Construction

In view of the climate crisis, green technologies should be used to ensure sustainable structures in the construction industry. Road construction could also contribute to the creation of a circular economy, as it is partly responsible for several current environmental phenomena, such as greenhouse gas (GHG) emissions and depletion of natural aggregates and landfills. The use of Reclaimed Asphalt Pavement (RAP) is considered one of these recycling solutions, as it can be reused in road construction projects. Implementing it in practice is already a topic that should be included in the technical guidelines for road construction and maintenance. Therefore, this study is a critical overview of the worldwide experiences with the installation of RAP in road pavements published by different road authorities worldwide, aiming to prove the inconsistency in using these materials in pavement courses. The results of this review are analyzed to identify possible knowledge gaps regarding RAP content. It was shown that the use of RAP is different on all five continents. The main findings were that the RAP content in asphalt layers is still at a low level of about 30% and that the use of RAP materials in unbound layers in road pavement construction is not yet fully accepted. It is expected that the results of this study will help to improve further research on the performance of RAP and motivate more countries to develop appropriate guidelines for the use of RAP materials in road pavement construction.

The influence of olive kernel ash obtained from canning factory as a bitumen modifier

Today, the construction sector experiences significant pressure to use green and sustainable materials. In this framework, using biological components derived from agricultural products is the most interesting topic for the stability of asphalt pavement construction materials. Furthermore, the escalation in demand for transportation infrastructure has resulted in a rapid surge in the volume of traffic and premature degradation of asphalt pavements. The primary objective of this study is to assess the efficacy of olive kernel ash (OKA) obtained from olive canning factories in modifying the characteristics of asphalt. The investigation of this function has not been explored in prior research. To this end, a comprehensive analysis of morphological, Thermogravimetric, chemical, and phase separation was conducted, in addition to physical and rheological testing, over three distinct temperature ranges: high, intermediate, and low. The results showed that OKA is thermally stable and has a slow decomposition. Also, using OKA, compared to most biomass employed in bitumen, exhibits a satisfactory amount of phase separation. Despite the enhanced shear strength, the modified samples incorporating OKA do not encounter any operational challenges regarding transportation and pumping. The findings from the rheological experiments indicate that incorporating 20 % OKA in bitumen can increase the shear modulus up to 71 % and recovery percentage up to 20 %. Therefore, it significantly enhances the resistance to permanent deformation under high temperatures. The increase in molecular weight and asphaltene phase creates a resistant binder against high temperatures. Meanwhile, the fatigue life of modified samples containing 20 % OKA decreased to 59 %. However, applying the highest shear stress to the sample containing OKA experiences demonstrates its ability to resist this stress for longer. Also, it was found that regulating the OKA dosage in bitumen can maintain its acceptable resistance level to cracking at low temperatures. This phenomenon is due to the positive effect of OKA on the viscoelastic characteristics of bitumen. Based on our assessments, it has been observed that incorporating OKA up to 20 % in bitumen consistently enhances its performance capabilities at high temperatures. Nevertheless, while using this modified bitumen in cold regions, limiting its utilization to a maximum of 5 % is advisable.

Mechanism exploration of the modified asphalt binders with sustainable rapeseed-based derivatives using multi-scale evaluation method

Due to the concerns of sustainability, environment, and economy that are associated with non-renewable petroleum-based additives, there has been a growing interest in bio-additives derived from renewable feedstocks. This study aims to reveal the modification mechanism of three bio-additives derived from rapeseed on the base asphalt. The exploration of modification mechanism helped to explain the distinct rheological properties of bio-modified asphalt binders presented in a previous study. The effect of three bio-additives on the surface morphology, micro-mechanical properties, adhesivity, and chemical structure of base asphalt binders were investigated via Atomic Force Microscopy (AFM) and Fourier Transform Infrared spectrometer (FTIR) tests. The Electrostatic potential distribution and the orbital energy was analyzed via density functional theory (DFT) calculation to explore the inherit polarity of both the three bio-additives and asphalt components. Furthermore, molecular dynamic (MD) methods were used to evaluate the compatibility mechanism and aggregation tendency of asphalt components and bio-additives. The results showed that the electrostatic potential and the orbital energy of three bio-additives predominantly centered around the polar group. Specifically, AERO exhibited highest electrostatic potential distribution and lowest energy gap, indicating its heightened polarity. Moreover, the solution parameter difference value of bio-modified asphalt fell within 0.2 (J/m3)0.5, indicating great compatibility between asphalt and bio-additives, especially for ERO. Additionally, three bio-additives mitigated the aggregation of asphaltene within the asphalt due to their electrostatic interaction, especially notable in the cases of ERO and AERO. Furthermore, a cross-link network was formed within AERO-modified asphalt binders owing to its heightened polarity, fostering hydrogen bonding interactions internally and promoting the aggregation of saturate and resin factions around it. Consequently, this led to enhanced modulus and elasticity in the AERO-modified asphalt binders. Rapeseed derivatives as asphalt additives would be a sustainable and durable material for pavement construction and maintenance. It provides a theoretical basis for advancing the practical application of renewable vegetable oils in road engineering, which has exceptional economic and social benefits.

Geopolymer Cement in Pavement Applications: Bridging Sustainability and Performance

Sustainability and the quest for a more robust construction material cannot be divorced from each other. While Portland cement has revolutionized the construction sector, its environmental toll, particularly in greenhouse gas emissions and global warming, cannot be ignored. Addressing this dilemma requires embracing alternatives like geopolymer cement/geopolymer binder (GPC/GPB). Over the last few decades, considerable strides have been achieved in advancing GPC as a sustainable construction material, including its utilization in pavement construction. Despite these advances, gaps still exist in GPC optimal potential in pavement construction, as most studies have concentrated on specific attributes rather than on a comprehensive evaluation. To bridge this gap, this review adopts a novel, holistic approach by integrating environmental impacts with performance metrics. To set the stage, this review first delves into the geopolymer concept from a chemistry perspective, providing an essential broad overview for exploring GPC’s innovations and implications in pavement applications. The findings reveal that GPC not only significantly reduces greenhouse gas emissions and energy consumption compared to Portland cement but also enhances pavement performance. Further, GPC concrete pavement exhibits superior mechanical, durability, and thermal properties to ensure its long-term performance in pavement applications. However, challenges to GPC utilization as a pavement material include the variability of raw materials, the need for suitable hardeners, the lack of standardized codes and procedures, cost competitiveness, and limited field data. Despite these challenges, the process of geopolymerization presents GPC as a sustainable material for pavement construction, aligning with Sustainable Development Goals (SDGs) 3, 9, 11, and 12.

Preparation of geopolymer for in-situ pavement construction on the moon utilizing minimal additives and human urine in lunar regolith simulant

Constructing lunar pavements is of great significance for improving the transportation efficiency of materials and personnel transfer at lunar bases. Utilizing lunar regolith for the in-situ preparation of geopolymer is an effective means of supplying raw materials for lunar pavement construction. This present study prepared geopolymers for pavement material with lunar regolith simulant. The influence of NaOH on the compressive strength of geopolymers was understood by using different percentages of NaOH as alkaline activator. The effect of urine on the compressive strength of geopolymers by using artificial urine of different pH values as liquid phases. The results indicated that the addition of artificial urine slightly reduces the compressive strength of geopolymers, and the effects of pH and NaOH percentage are different. Microstructural analysis performed by Mercury Intrusion Porosimetry and Scanning Electron Microscope, indicated that choosing fine-particle lunar regolith simulant as precursor is more conducive to the preparation of high-strength geopolymers using human urine.

Effects of oil palm mesocarp fibers on the physical and mechanical properties of expansive soils

Palm fiber is one of the favorable materials used in stabilization of soft soil in geotechnical engineering projects, nowadays due to its sustainability, less damage of environment, biodegradability, availability and cost-effectiveness in a context of widespread appeal to the world for return to nature by protecting the earth. On the other hand, expansive soils are renowned for their swelling-shrinkage property and these volumetric changes resultantly cause huge damage to civil infrastructures. Likewise, subgrades consisting of expansive soils instigate serviceability failures in pavements across various regions worldwide. This paper presents results of the laboratory evaluation of expansive soils stabilized with oil palm mesocarp fiber (OPMF), with a view to determine its suitability as flexible pavement construction material. The mixtures were subjected to British Standard heavy (modified Proctor) compaction energy to determine their strength characteristics. The samples were subjected to different tests to ascertain their index properties. Varying proportions of OPMF from 1% to 4% were incorporated into the soil samples and the effects were observed based on compaction and California Bearing Ratio (CBR) results. The control samples without inclusion of OPMF achieved the highest Maximum Dry Densities (MDD), the MDDs reduced linearly as the OPMF content increased. Consequently, the CBR values decreased with increase in OPMF. The reduction in MDD ranged from 20.28g/cm3, 18.5 g/cm3, 15.65 g/cm3, 12.53 g/cm3 as the OPMF increased from 1%, 2% to 3%, 4%. and the optimum moisture content remained almost unaffected due to high-absorbent nature of the fibers. With the inclusion of the OPMF, the CBR value under soaked conditions dropped from 5% to 1.8% rendering them very unsuitable for pavement subgrade. It was concluded that the presence of fiber depreciated the engineering properties of the earth materials. Direct application of OPMF in any part of road pavement has been dissuaded.

Evaluating the effect of paper waste lignin in hot mix asphalt

Asphalt is a viscoelastic material which performs to resist rutting, fatigue cracking, and moisture susceptibility under different loading and temperature conditions. The use of innovative and renewable pavement construction materials is inevitable due to high axle loads, rapidly increasing traffic volumes, and varying climatic conditions. This study aims to assess the effect as well as the optimum dosage of paper waste lignin for use in hot mix asphalt (HMA). Lignin from the paper industry with dosage ratios of 5, 10, 15, and 20%, was utilized to study the effect of the addition of lignin to the asphalt binder. Virgin and lignin-modified binder samples, before and after the aging process, were subjected to physical testing through penetration, softening point, ductility, viscosity and specific gravity and rheological characteristics through dynamic shear rheometer (DSR), bending beam rheometer (BBR), and rational viscometer (RV). The fractional composition was assessed through saturates, aromatics, resins and asphaltenes (SARA) fractional composition technique. Statistical analysis was also performed to find correlation of different physical and rheological parameters. Furthermore, based on optimum dosage, the performance of asphalt mixtures was studied against rutting, fatigue cracking, and moisture susceptibility. The results indicated that the addition of lignin has improved the physical properties significantly. The amount of asphaltene decreased and aromatics increased in SARA fractional analysis. Moreover, the Colloidal Instability Index (CII) has also indicated a stable structure of the binder. The rheological characteristics are improved after modification. The asphalt mixture tests revealed that addition of lignin with optimum dosage (10%) has improved the performance against rutting, fatigue cracking and moisture susceptibility. Statistical analysis indicated good co-relation among different physical and rheological parameters. This study concludes that 10% dosage is the optimum dosage that can successfully replace the virgin asphalt binder for performance of hot mix asphalt.

Performance evaluation of recycled concrete aggregates with geosynthetics as an alternative subbase course material in pavement construction

This study investigates the feasibility of using recycled concrete aggregates (RCA) as subbase materials in roads through laboratory experiments. Various physical tests were conducted on the soil subgrade and RCA subbase, followed by cyclic plate load tests to assess the impact of geosynthetic reinforcement on the bearing capacity of RCA materials. The ultimate bearing capacities of different RCA configurations ranged from 186 to 480 kPa, similar to previous studies on natural and recycled aggregates. The geocell-reinforced section exhibited excellent performance, with a measured ultimate bearing capacity of 480 kPa. The Geocell-Geogrid and Geocell-Geotextile sections showed the highest bearing capacity ratios at 2.58 each, indicating superior performance. Reinforced RCA infills demonstrated improved settlement values under repeated loading, with the geocell-geogrid section effectively reducing permanent settlement. The study concludes that RCA can be a substitute for natural aggregates in road subbase materials, mitigating the environmental impact of construction and demolition waste.

Life cycle assessment and pavement performance of recycled aggregates in road construction

Integrating environmental goals in the construction of infrastructure has attracted great attention over the past two decades. The use of construction and demolished waste materials (C&D) as a base layer for pavement structures gained popularity as a sustainable alternative to virgin aggregates (VA). An experimental testing program was designed to investigate several recycled materials as a potential replacement to VA in flexible pavements base layer. The testing program included routine tests, matric suction, static, and repeated load triaxial tests to measure the general engineering properties and evaluate the material performance under static and cyclic loading. The results of the laboratory testing program were employed to predict the pavement performance utilizing different combinations of C&D waste as a base layer for flexible pavement structures using the AASHTOWare Pavement ME Design at different climate conditions. The sustainability of using C&D material as a partial or full replacement of VA base material in pavement construction was evaluated by using the life cycle assessment (LCA) approach. The results showed that all the C&D materials yielded a much thinner base layer compared to the natural VA achieving the same pavement performance. Moreover, the reduction in the thickness is more significant in cold and wet climatic conditions rather than the hot and dry climatic conditions. LCA results revealed that the VA base layer had the highest environmental impact on all tested categories. VA materials, used as a base layer, show 65% higher global warming potential compared to C&D materials as a base layer in all climatic conditions.

The effect of paving block from plastic waste material in the urban drainage: Study case in residential areas

Large expanses of green, open land are frequently converted as a result of population growth and quick development. This phenomenon causes the decreasing of water infiltration area which has an impact on increasing runoff coefficient. In the urban drainage problem, paving blocks are often used as road pavement construction materials to reduce surface runoff. The aim of this research is to study the characteristic of flow in the paving block made from plastic waste material. The research conducted in the laboratory testing utilizing a rainfall simulator by several variations in slope of 0% to 15%. The findings indicate that paving blocks made from plastic waste have less runoff coefficient than asphalt and/or concrete pavement. There is a correlation between the slope of the land and the runoff coefficient value which the runoff coefficient value increasing as the slope of the land increases. That finding is then applied in urban drainage problem located in the Cipamokolan Village region in Bandung City with the help of SWMM program for drainage calculation. As a result, the runoff discharge is decreasing by implementing the paving block made from plastic waste.

Advancing Pavement Sustainability with Recycled Materials

The increasing environmental concerns and depletion of natural resources have catalyzed the exploration of sustainable alternatives in civil engineering practices, particularly pavement construction. This study evaluates the efficacy of using recycled materials—crushed concrete aggregate (CCA), reclaimed asphalt pavement (RAP), and recycled plastics—as viable substitutes for traditional pavement materials. By examining mechanical properties, environmental impacts, and real-world implementations, the research highlights the potential of these materials to meet or exceed the performance standards of traditional pavements. Mechanical testing shows that recycled materials provide comparable or enhanced performance metrics, while life cycle assessments reveal significant reductions in carbon emissions, resource consumption, and ecological toxicity. Case studies from diverse geographical contexts further validate the practical applicability and effectiveness of recycled materials. The study concludes with recommendations for standardizing material processing, updating policies, and continuing research to address long-term durability and environmental concerns. This paper contributes to the literature on sustainable civil engineering by providing a pathway for the increased adoption of recycled materials in pavement construction, thus aligning with global sustainability objectives.

USE OF STEEL FIBER AND COPPER SLAG IN CONCRETE PAVEMENT

This study explores the utilization of steel fiber as a reinforcement material in concrete pavement construction. The investigation delves into the mechanical and structural properties of steel fiber-reinforced concrete (SFRC) and its impact on the performance of pavement structures. Various proportions of steel fibers are incorporated into the concrete mix, and the resulting mixtures are subjected to comprehensive testing, including compressive strength, flexural strength, and fatigue resistance. The study aims to assess the potential enhancement in the durability and load-bearing capacity of concrete pavements through the incorporation of steel fibers. The findings indicate that the addition of steel fibers contributes to increased tensile strength and crack resistance, addressing common issues such as reflective cracking and fatigue failure in concrete pavements. Moreover, the study investigates the economic viability and sustainability aspects associated with the use of steel fiber in concrete pavements, considering its influence on lifecycle costs and environmental impact. The outcomes provide valuable insights for engineers and practitioners seeking optimized solutions for durable and resilient concrete pavement construction. Keywords: Steel fibers, Concrete pavement, Reinforcement, Mechanical Properties, Durability,Structural Performance, Compressive strength, Flexural Strength,Fatigue resistance, Reflective Cracking,Sustainability.

Field Studies on Expansive Soil Stabilization with Nanomaterials and Lime for Flexible Pavement

The long-term performance of pavement is greatly influenced by the subgrade soil-bearing capacity. The areas with lower bearing capability experience higher construction costs due to soil replacement. Soil stabilization is one of the engineering measures that may be used to improve soil properties. The improvement in the soil properties varies depending on the soil type and type and dosage of the stabilizer. The primary objective of this study is to determine the impact of the different types of stabilizers on different types of black cotton soil. In the present study, black cotton soil was treated with Terrasil (0.5, 0.75, and 1 kg/m3), Zycobond (0.5, 0.75, and 1 kg/m3), and lime (0, 2, and 3%). The influence of varying dosages of Terrasil, Zycobond, and lime showed a significant improvement in the FSI, CBR, and UCS. In this study, attempts were made to investigate the field performance of chemically treated black cotton soil. A 100 m trail section with chemical- and lime-treated subgrade was constructed and analyzed using the dynamic cone penetration test. Finally, the mechanical design indicated that the chemical stabilization layer could be helpful to reduce asphalt layer thickness by 30 mm and cost. It is anticipated that this study will be useful to perceive, visualize, and understand the advantages of chemically treated black cotton soil. Overall, it is a step toward sustainable construction, which will reduce the demand for natural materials by optimizing pavement design and the use of existing unsuitable materials (black cotton soil) in flexible pavement construction.

Exploratory Field and Laboratory Investigation on the Use of Noncontact Digital Ski Sensor in the South Korea Expressway Network

In the case of asphalt pavement construction, better smoothing and reliable material performance acquisition are essential. In South Korea, the next-generation asphalt pavement-smoothing technology, known as the noncontact digital ski (NCDS), started to be used in expressway construction in 2018, making this system an essential tool in the paving industry. The present work thoroughly assessed how employing the NCDS system affected the response of the pavement material at low temperatures. Portions of paved roads with and without NCDS were assessed for the international roughness index (IRI, m/km). The development of thermal stress propagation was then examined using the bending beam rheometer on asphalt samples from the road. Based on straightforward visual and statistical analysis, it was discovered that using NCDS produces significantly lower IRI and reduced thermal stress, which raises the possibility that using NCDS has the potential for better low-temperatures predictions.

Investigation of the Fatigue Performance of Sustainable Asphalt Pavement

Selecting suitable materials for sustainable asphalt pavement construction can be a challenging task, particularly due to the significant issue of fatigue damage in flexible pavement. The fatigue performance of gap-graded asphalt mixes (GGCP) was assessed through four-point bending beam fatigue testing, examining the impact of incorporating 6% Calcium carbonate (CaCO3) and 2% treated palm oil fuel ash (TPOFA) on fatigue cracking. The testing was conducted at various stress levels (800, 1000, and 1200 kPa) and a temperature of 5°C. Additionally, the asphalt mixtures underwent acceleration ageing and moisture conditions, which varied during the study. The experimental findings indicated that higher stress levels resulted in a decrease in the fatigue life of asphalt mixtures due to ageing effects. Moreover, moisture conditioning was found to diminish the fatigue life of the asphalt mixture. Comparatively, the fatigue model incorporating a plateau value and fatigue life demonstrated greater accuracy when compared to previous regression models.