Tensile Strength Ratio Research Articles

OPTIMIZATION OF DISSIMILAR WELDING PROCESSES BETWEEN Ti-4V-6Al TITANIUM ALLOYS WITH SS304 STAINLESS STEEL BY GAS TUNGSTEN ARC WELDING PROCESS

This study investigated the ultimate tensile strength (UTS) of dissimilar welding processes between Ti-4V-6Al titanium alloys with SS304 stainless steel by gas tungsten arc welding (GTAW) process. The intermetallic compounds of the welds were investigated by X-ray diffraction, and the Taguchi method was used in the experimental design. The welding process parameters are welding current (A), welding speeds (B), and Wire feeds (C). ANOVA analysed the S/N ratio of ultimate tensile strength to determine the optimal parameters for statistically significant factors. Analyse for process parameters on the response and the level of the indispensability factor, as well as predict and regression model for optimal tensile strength. The investigation revealed that the optimum parameters were A1B2C2, and the ultimate tensile strength was 285MPa. The ANOVA analysis found that welding current and welding speeds had significance on the ultimate tensile strength of the workpiece at a 95% confidence level. The investigation of intermetallic compounds of the welds with X-ray diffraction technical found that increased welding current tended to cause Ti3Cu and Fe4Cu3 compounds and affected the tensile strength of the weld to decrease.

Microstructure evolution and mechanical properties of Al/Mg–Li/Al laminate metallic composites via hot roll bonding and subsequent cryorolling

Hot roll (HR) bonded Al/Mg–Li laminated metallic composites (LMCs) were subsequent processed using room-temperature rolling (RTR) and cryorolling (CR), respectively. Afterward, the mechanical properties and the microstructure evolution of these LMCs under different rolling temperatures and reductions were studied. The results revealed that the Al/Mg–Li LMCs in the HR + CR1 group (a total reduction of 67 %) exhibited the best comprehensive mechanical properties, with the ultimate tensile strength and elongation ratio of 176.8 MPa and 10 %, respectively. The SEM and EBSD results revealed that the intermediate Mg–Li layer underwent an intense strain-induced phase transformation from the β-Li phase to the α-Mg phase during the RTR, while the strain-induced phase transformation during CR was inhibited due to the gradual atomic diffusion and insufficient driving energy. Therefore, the fraction of the β-Li phases in the Mg–Li layer was higher in HR + CR LMCs compared to HR + RTR LMCs, with the α-Mg phases in the former being evenly distributed in its β-Li matrix. Both β-Li and α-Mg phases in the Mg–Li layer held the stress and strain to ensure the ductility of the Mg–Li layer, which could consequently co-deform with the Al layers, thereby increasing the tensile strength and the elongation simultaneously in HR + CR LMCs. The XRD results revealed that during CR, multiple prismatic <a> slip systems and pyramidal <c+a> slip systems were activated in α-Mg phases, and the slip systems {110}<111>, {123}<111>, and {112}<111> were activated in β-Li phases simultaneously. The activation of a greater number of slip systems in both β-Li and α-Mg phases improved the overall ductility of the LMCs.

Evaluation of Properties of Asphalt Concrete Mixture Using Basalt Aggregate from Jeju Island

In this study, the engineering properties of basalt aggregate used for asphalt road pavement on Jeju Island were evaluated, and the characteristics of the asphalt mixtures used were evaluated to assess the suitability of Jeju Island basalt as road construction material. Chemical composition and surface morphology analysis of the basalt and granite aggregate, engineering characteristics analysis, and filler property evaluation were performed. Mix design was performed, and the basic properties of three asphalt mixtures for the surface, intermediate, and base layers were evaluated. Permanent deformation resistance was evaluated through a wheel tracking test, and moisture resistance was evaluated through a dynamic immersion test and a tensile strength ratio test. The optimum asphalt contents of the asphalt mixture using low-porosity basalt aggregate and high-porosity basalt aggregate were determined to be 5.7% and 5.9% in the surface layer, 5.3% and 5.4% in the intermediate layer, and 4.7% and 5.1% in the base layer, respectively. It was found that the basic properties of the asphalt mixtures satisfied Korean quality standards. The dynamic immersion test results of low-porosity basalt aggregate and high-porosity basalt aggregate were 20% and 10%, respectively, which fall far below the quality standard of 50%. The tensile strength ratios of the basalt asphalt mixtures for the intermediate layer were 0.69 and 0.40, and they were found to increase significantly to 0.87 and 0.80 after the application of a suitable anti-stripping agent. Therefore, it was concluded that in order to apply Jeju Island basalt to asphalt pavement, an appropriate anti-stripping material must be applied.

Electro-chemo-mechanical failure of solid-state electrolyte caused from intergranular or transgranular damage propagation in polycrystalline aggregates

Electro-chemo-mechanical failure of solid-state electrolytes (SEs) caused by the internal growth of lithium dendrites significantly impedes the application of solid-state batteries under high applied current density. The grain boundary is usually the key to the mechanical properties of polycrystalline ceramic SEs. Here, strength and width of grain boundary in SEs that are exampled by garnet-type Li7La3Zr2O12 are evaluated under the deposition of lithium by visualizing the stress field, damage accumulation and crack propagation. The enhancement of grain boundary strength triggers a dramatic increase stress when the ratio of tensile strength between grain boundary and grain (λ) is lower than 0.9. With the variation of λ, three damage processes are revealed as intergranular-damage, inter/transgranular-damage and transgranular-damage, leading to different propagation of cracks and the transformation of intergranular failure to transgranular failure. Furthermore, the width of the grain boundary is found to induce more transgranular-damage with its widening. A critical value of grain boundary width for the formation of displacement is obtained under various strengths, as δ = 21 nm for λ = 0.2, δ = 25 nm for λ = 0.5 and δ = 31 nm for λ = 0.9. The findings in this work indicate the coupling effect of grain boundary width and strength on the failure of SEs, providing an insightful perspective for the future design of solid-state batteries.

Effect of Natural Bitumen on the Performance of Hot Asphalt Mixture‏

Globally, for more than a century, large quantities of asphalt binder have been consumed in the production of asphalt mixtures. There are two types of natural asphalt (NA) deposits in the Heet region: rock asphalt and sulphur spring asphalt. NA from sulphur springs was used in this study to assess NA performance and determine the suitability of using NA in local asphalt mixtures. The NA was treated by heating it to 163 °C for several hours. NA was subjected to laboratory testing after industrial treatments, and it was found that the physical properties of NA can conform to Iraqi specifications by heating it for 20 hours. The results showed that treated NA is better suited to hot climates because it is less temperature sensitive than traditional petroleum asphalt. NA was discovered to be highly effective in improving mechanical properties. In addition, the NA mixture had the highest indirect tensile strength values and a tensile strength ratio of 81.2%, which was 0.37% higher than the TSR of the conventional mix. NA will play an important role in the production of flexible pavements and provide a significant economic benefit without compromising the overall performance of the mixture because it is less expensive than conventional asphalt and is available in large quantities in Iraq.

Evaluation of Bituminous Moisture Damage of High Silica Aggregate

Abstract Moisture damage (Stripping) in Hot Mix Asphalt (HMA) is the loss of adhesive bond between aggregate particles and bitumen due to water action. Most urban roads in Iraq have been exposed to moisture damage failure because of the high silica content in aggregate, this phenomenon led to a decrease in the service life of roads and an increase in maintenance cost. This study used two anti-stripping agents: hydrated lime and Wetfix-BE. Lime was added as a powder to the aggregate in a dosage of 2.0 % of the aggregate weight and Wetfix-BE, a liquid chemical adhesion promoter for hot and warm mix asphalt, was added to asphalt at in dosage of 0.5 % from the total weight of asphalt. The retained Marshall stability, tensile strength ratio, Texas boiling test, and static immersion test are calculated to determine the resistance to moisture damage. The results indicated that both Wetfix-BE and lime could increase Marshall retained stability, tensile strength, and resistance to moisture damage of mixtures, especially at higher condition temperatures. The bitumen modified with Wetfix-BE had better results than bitumen modified with lime for all tests at different temperatures.

Microporous Polyurethane Elastomer’s Comprehensive Properties Affected by Flame Retardant EG/APP

The mechanical characteristics, creep resistance, fatigue resistance, and other comprehensive properties of flame retardants/microporous polyurethane elastomers (FRs/MPUE) have not been systematically researched. Because of this, we used expandable graphite (EG) and ammonium polyphosphate (APP) to conduct this study on FRs/MPUE composites. The thermal degradation and flame retardant characteristics, tensile strength, compressive creep, and dynamic and static stiffness ratio of FRs/MPUE were studied. The findings demonstrated that the optimum synergistic flame retardant effect occurred when the ratio of EG to APP was 2:1. The LOI of MPUE reached 30.5%. The vertical combustion grade achieved V-0. The stage of thermal decomposition was the most stable. However, compared with pure MPUE, the tensile strength was slightly decreased, and the compressive creep and dynamic and static stiffness ratio were slightly increased. The MPUE’s LOI value was more than or equal to 26% when the EG to APP ratio was 2:1 to 1:2. The tensile strength was basically the same as that of pure MPUE. The compression creep was less than 5%, which met the B1 flame retardant requirements and creep resistance performance indicators of floating floor vibration-damping pads.

Effect of design parameters on degree of blending and performance of recycled hot-mix asphalt incorporating fine reclaimed asphalt pavement particles

Due to the rich binder content and high economic benefits of fine reclaimed asphalt pavement (RAP) particle, more and more attention has been paid to the effective design of recycled hot-mix asphalt (HMA) incorporating this material. This research explored the effect of design parameters on degree of blending (DoB) and performance of recycled HMAs incorporating fine RAP particles. Six groups of mixes were designed, including one no blending group, four experimental groups, and one full blending group. The different parameters of preheating temperature, compaction effort, asphalt content (AC), and blending duration, were involved in this research. It can be found that the recycled HMAs incorporating fine RAP particles under the traditional design proved to the risks in water stability and low-temperature performance. By rising the preheating temperature, decreasing compaction effort and increasing AC, or extending the blending duration, more RAP binder would be activated and blended with the virgin binder, and the poor rheological performance of recycled HMAs can be restored. The different design parameters have different effects on the performance. Besides, the actual contribution of DoB to performance was quantified. With an increase in DoB by 10%, the tensile strength ratio, shear strength, fracture energy, fracture strength, and abrasion loss percentage of recycled mixes can improve by around 15%∼28%, 0.15–0.34 MPa, 180–1969 J·m2, 0.25–0.34 MPa, and 7–18%, respectively. In addition, design incorporating fine RAP particles generally can bring significant advantages in energy consumption and CO2 emission.

Polymer cement mortar strengthened RC beams with/without silica fume as repair material

Polymer cement mortar (PCM) overlaying methods leads to brittle interfacial debonding before its classical failure causing a sudden decrease of the load-carrying capacity. For a reliable design procedure for the practitioner, a need exits to prevent the interfacial debonding. The proposed modified 5 % silica fume (M) PCM overlay is intended to delay debonding because it increased the concrete-PCM bond (confirmed in our previous study). Fourteen RC beams (size-150x150x1440 mm, a/d – 3.5) using C40 concrete (mix proportion – 1:2.1:2.6) were prepared and strengthened with rebar (2D6 and 2D10), CFRP grid with changing stiffness (low, medium and high), and CFRP strand sheet (50 mm and 150 mm width) as strengthening reinforcement that embedded with normal (N) PCM and MPCM overlay of thickness 20 mm to investigate the effectiveness of silica fume. Four-point bending test were made at room temperature to evaluate the flexural performance. Compared to NPCM, MPCM with all cases of strengthening reinforcement enhanced the crack numbers, ductile behavior, peak load (12–25 %) and debonding load (3–33 %), proving MPCM as ideal cementitious matrix for strengthening. The flexural strengthening configuration using MPCM and reinforcement amount (area x tensile strength) ratio of 0.5 between strengthening and main bar proved to be more efficient as this configuration delayed the debonding failure, shifted fracture to classical mode and confirmed uniform shear stress transfer at the overlay-concrete interface. Conclusively, MPCM overlay nearly achieved a full-strength composite action which is effective to prevent the debonding that benefits practitioners.

Engineering properties-based parameters used for moisture damage evaluation of asphalt mixtures: a review

Moisture-induced damage has been known as a major premature distresses in asphalt pavement. Numerous review papers have been made to provide the progression in study on moisture damage of asphalt pavement. However, mechanical properties of asphalt mixtures used as a parameter for moisture susceptibility evaluation were not reviewed in detail. To make the review of moisture-induced damage in asphalt pavement more comprehensive, this paper reviews research studies on moisture damage of asphalt pavement in view of mechanical properties as a parameter during the past 50 years. These parameters include tensile strength ratio (TSR), cohesion ratio (CR), dynamic modulus ratio (DMR), resilient modulus ratio (RMR), and shear strength ratio (SSR). TSR and CR are only relevant at bottom of asphalt concrete (AC), while SSR can be used to describe moisture damage at different AC depths. DMR and RMR are concentrated on the impact of moisture damage via performance characteristics of asphalt mixtures.

A possible mechanism for the difference in ballistic performance between sapphire and spinel

The contradictory finding that sapphire has advantages in most mechanical properties but is inferior to spinel in ballistic performance has been re-examined. The ballistic performance of sapphire and spinel against armor-piercing-incendiary (API) projectiles of caliber 7.62 mm was explored through experiments and numerical simulations. During the parameterization of the Johnson-Holmquist 2 (JH2) model, several assumptions concerning the material constants were suggested. The observed agreement between experiments and numerical simulations validated the simulation method. On this basis, a parametric study was carried out in which some of the JH2 parameters for sapphire were modified to those for spinel. The results showed that ceramics with lower tensile strength and lower Poisson's ratio tend to form a larger fracture cone, which contributes to higher ballistic resistance by spreading the load over a larger area. This work would offer new insight into the complex relationship between mechanical properties and ballistic performance.

Anomalous tensile strength and thermal expansion, and low thermal conductivity in wide band gap boron monoxide monolayer

Most recently the formation of boron monoxide (BO) in the two-dimensional (2D) form has been confirmed experimentally (J. Am. Chem. Soc. 2023, 145, 14660). Motivated by the aforementioned finding, herein we theoretically explore the key physical properties of the single-layer and suspended BO. Density functional theory (DFT) results reveal that BO monolayer yields a large indirect band gap of 3.78 (2.18) eV on the basis of HSE06(PBE) functional. Ab-initio molecular dynamics results reveal the remarkable thermal stability of the BO monolayer at 1000 K. The thermal and mechanical properties at room temperature are furthermore investigated using a machine learning interatomic potential (MLIP). The developed MLIP-based model close to the ground state could very precisely reproduce the DFT predictions for the mechanical properties of the BO monolayer. The elastic modulus, tensile strength and lattice thermal conductivity of the BO monolayer at room temperature are predicted to be 107 GPa, 25 GPa and 5.6 ± 0.5 W/mK, respectively. At the room temperature the BO monolayer is noticeably predicted to yield an ultrahigh negative thermal expansion coefficient, by almost 17 folds larger than that of the single-layer graphene. The presented results reveal the large indirect electronic band gap, decent thermal and dynamical stability, anomalously low elastic modulus to tensile strength ratio, ultrahigh negative thermal expansion coefficients and low lattice thermal conductivity of the BO monolayer.

Comparative performance of DG mixes and SMA mixes with waste crumb rubber as aggregate replacement

This research paper presents a comparative study on the performance of asphalt mixes containing waste crumb rubber as an aggregate replacement. Two different mixes namely Dense Graded (DG) and Stone Matrix Asphalt (SMA) with different ratios of waste crumb rubber WCR (0.5%, 1.0%, 1.5%, and 2.0% by weight of aggregate) were produced. The performance tests including, Marshall stability, Marshall Quotient (MQ), tensile strength, tensile strength ratio, and deformation strength in Kim test were carried out on DG and SMA asphalt mixtures. The analyses of test results show that the performance of DG-mixtures is better than SMA-mixtures in term of Marshall stability, and Marshall Quotient and lower indirect tensile strength, and Deformation Strength than SMA mixes. The moisture susceptibility and temperature susceptibility can be reduced by the inclusion of waste crumb rubber in the DG asphalt mixture. A waste crumb rubber content of 0–1.0% by weight of aggregate is recommended for the aggregate replacement of the performance of asphalt concrete mixtures similar to that investigated in this study.

Estimating tensile strength ratio of asphalt mixtures using Surface Free Energy (SFE) and Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR)

Moisture damage often leads to pavement failure, particularly as pavements age. The widely adopted AASHTO T283 test evaluates asphalt mixtures’ susceptibility to moisture damage but has shortcomings, time-consuming procedures, and lack of representation of realistic aging effects. Given the adoption of AASHTO T283 by state agencies, this study aimed to establish correlations with reliable and practical tests, especially Surface Free Energy (SFE)’s work of cohesion (Wc) and Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR) tests’ carbonyl and sulfoxide indices, to estimate AASHTO T283′s Tensile Strength Ratio (TSR%). Three asphalt binders (PG 52–34, PG 64–22, and PG 76–22) were assessed at oxidation levels (original, short-term, and long-term). Analysis of Variance (ANOVA) and linear regression analysis were conducted to assess the relationship between SFE and FTIR-ATR with TSR%. Results showed PG 52–34 mixtures had the highest TSR%, while PG 76–22 mixtures had the lowest, decreasing with higher oxidation. PG 52–34 had higher Wc values than PG 76–22, reducing with higher oxidation. FTIR-ATR measured higher carbonyl and sulfoxide index values for PG 52–34 and lower values for PG 76–22. ANOVA and linear regression analysis highlighted correlations between TSR%, SFE, and FTIR-ATR, with the combined effects of Wc, carbonyl, and sulfoxide indices showing the strongest relationship. The findings demonstrate that SFE and FTIR-ATR measurements showed potential in predicted TSR% for the asphalt mixtures. Particularly, predicted TSR% values differed the highest from actual TSR% for PG 52–34 without aging and at short-term aging but achieved accurate predictions with small absolute differences under long-term aging conditions.

Effect of recycled vegetable oil on the performance of nanomarl-modified asphalt mixtures

In response to the demand for a greener approach to pavement infrastructure and the economic benefits associated with alternative materials, the modification of neat binders has been a consistent focus. This research aimed to enhance the characteristics of asphalt binders and mixtures by incorporating recycled vegetable oil (RVO) and nanomarl. RVO was added to 60/70 penetration bitumen at concentrations of 1%, 3%, and 5% by weight, while nanomarl was kept constant at 5% by weight of the bitumen. Various physical, rheological, and microstructural properties of the modified binders were evaluated, including penetration, softening point, viscosity, rutting resistance, fatigue resistance, creep, stiffness, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Furthermore, the moisture susceptibility and rutting resistance performance of asphalt mixtures incorporating these modified binders were investigated through analyses of tensile strength ratio and Hamburg wheel tracking. The test results revealed that the incorporation of RVO in bitumen led to a gradual increase in the penetration value of the modified bitumen. Simultaneously, the softening point and viscosity of the modified bitumen decreased, indicating that the addition of oil rendered the modified bitumen softer. However, the inclusion of nanomarl in RVO-modified bitumen improved its viscoelastic behavior and positively influenced its rheological properties under both unaged and aged conditions. Specifically, the addition of 5% nanomarl resulted in reduced penetration value, increased softening point, viscosity, rutting resistance, fatigue resistance, creep stiffness, and improved relaxation behavior at low temperatures. The most favorable outcomes were observed when incorporating 1% RVO with 5% nanomarl. Moreover, SEM and FTIR analysis demonstrated successful blending of the additives into the bitumen, without any evidence of phase separation. This indicates a homogeneous distribution of the additives within the bitumen matrix.Practical application: The modification of bitumen with waste or recycled oils for the production of asphalt mixture has been successfully studied in numerous researches. However, this study introduces a novel approach by synergistically combining recycled vegetable oil (RVO) modification with the incorporation of nanomarl particles into asphalt mixture. The innovation aspect lies in the integration of two sustainable and environmentally friendly components, RVO and nanomral, to enhance asphalt performance. The findings offer a blueprint for incorporating sustainable materials and approaches in road construction projects. Pavement engineers can adopt the use of RVO modification and nanomarl particles to create longer-lasting and environmentally friendly asphalt pavements. In regions with challenging climatic conditions, the use of this modified asphalt can lead to improved infrastructure resilience. Roads built with these materials can better withstand temperature fluctuations. The integration of RVO and nanomarl particles offers improved performance, cost-effectiveness, reduced environmental impact, and also opens avenue for further exploration and optimization of asphalt mixtures incorporating innovative additives.

Moisture diffusion and tensile properties of epoxy-based and polyurethane-based flax-glass hybrid FRP under hygrothermal and weathering environments

This research presents tensile modulus and strength of flax-glass hybrid FRP (HFRP) flat coupons with different fibre volume fractions and fabric stacking sequences under constant hygrothermal (50 °C and 95% RH) and cyclic weathering (water spray-ultraviolet radiation) environments for six months. Two types of polymer (i.e., epoxy (EP) and polyurethane (PUR)) were employed in HFRP. Fourier transformed infrared spectroscopy (FTIR) was performed to identify the changes in functional groups of flax fibres and polymer matrix after exposures. The glass transition temperature (Tg) of polymer matrix was measured by differential scanning calorimetry (DSC), which was used to study the influence of environmental exposure on Tg. The 3D diffusion coefficients of EP-based flax FRP and glass FRP laminates were determined based on experimental moisture uptake and Fick's law. A coupled mass diffusion-stress analysis based on finite element (FE) model was conducted to simulate the moisture diffusion and swelling behaviour of HFRP. The results showed that hygrothermal and weathering exposures hardly affected tensile modulus of HFRP regardless of the matrix type. After the environmental exposure, EP-based HFRP experienced lower retention ratio of tensile strength (65.4–88.0%) compared to PUR-based HFRP (80.7–94.1%) because of higher moisture absorption in the EP-based HFRP. The influence of fabric stacking sequence on tensile strength reduction varied with different fibre volume fractions in EP-based HFRP, which was explained by the combined effects of the internal stress and damage propagation at flax-glass interface.

The investigation of surface free energy components and moisture sensitivity damage of asphalt mixes modified with carbon black using the sessile drop method

Asphalt pavement is vulnerable to moisture damage when water infiltrates the asphalt-aggregate interface and weakens their bond. To prevent this problem, researchers have explored the use of additives to increase resistance against moisture damage. The moisture sensitivity of asphalt mixtures can be assessed by measuring their basic properties related to the mechanism of moisture damage. One effective approach to this is using the surface free energy method, which calculates bond energies between different materials’ surfaces and identifies the most appropriate combination of asphalt and aggregate. High cohesion or adhesion bonding is crucial for the proper performance of asphalt mixtures, such as moisture damage resistance. This study aimed to investigate the effect of carbon black additive on moisture damage resistance using surface free energy methods, comparing results with the Tensile Strength Ratio (TSR) test. Modified asphalts containing 4, 8, 12, and 16% carbon black were tested, with natural base asphalt as a control sample. The study used surface free energy theory to determine moisture sensitivity parameters of asphalt mixtures by obtaining surface free energy components of the raw materials and testing the ratio of tensile strength. Results showed that adding 8% carbon black to the asphalt mixture improved moisture sensitivity, and increasing additive content up to 16% reduced it but still provided better results than samples made with pure asphalt. The study concluded that the surface free energy method can determine the suitable combination of asphalt and aggregate materials for resistance against moisture damage.

Rock Wool Fiber-Reinforced and Recycled Concrete Aggregate-Imbued Hot Asphalt Mixtures: Design and Moisture Susceptibility Evaluation

Designing asphalt mixtures for pavement construction by controlling the moisture-mediated damage remains challenging. With the progression of time, this type of damage can accelerate deterioration via fatigue cracking and rutting unless inhibited. In this study, two types of hot asphalt mixtures (HAMs) were made by incorporating recycled concrete aggregates (RCAs), which were reinforced with rock wool fibers (RWFs). The first specimen was a normal mixture with a completely virgin aggregate, and the second one was a sustainable mixture with 30% RCAs. The proposed mixes were thoroughly characterized to assess the impact of RWF incorporation at various contents (0.5, 1, 1.5, and 2%) on moisture resistance. The optimal asphalt concentration (OAC) and volumetric parameters of the mixes were determined using the Marshall technique. The moisture susceptibility of the obtained HAMs was evaluated in terms of the tensile strength ratio (TSR). The results revealed that the moisture resistance, Marshall stability, flow, and volumetric parameters of the HAMs were improved due to the reinforcement by RWFs, indicating a reduction in the moisture sensitivity and an increase in TSR%. In addition, the HAMs designed with 1.5% RWFs displayed the highest TSR% (11.37) and Marshall stability compared to the control mix. The observed improvement in the moisture resistance and Marshall attributes of the prepared HAMs was ascribed to the uniform distribution of the RWFs that caused a well-interconnected structure and tightening in the asphalt concrete matrix. It is asserted that the proposed HAMs can be nominated for the construction of durable high-performance pavements.

Effects of a two-phase mixing process on warm-mix asphalt by factorial analysis

Warm-mix asphalt (WMA) was produced using a two-phase mixing process without additives, with bitumen–emulsion-coated aggregates and with bitumen at different mixing temperatures (MTs). The asphalt samples were prepared with 8% ground granulated blast-furnace slag fillers determined from hot-mix asphalt (HMA) analysis, with different bitumen-to-emulsion ratios and different MTs. Using the factorial design technique, the effects of the selected factors on Marshall performance parameters were investigated using interaction plots and main effect plots. The analysis from contour plots revealed that WMA prepared at 120°C with a bitumen-to-emulsion ratio of 80:20 performed best, with indirect tensile strength, tensile strength ratio, retained stability, rutting tests and ravelling loss values all meeting the standard code limits. Compared with HMA, the chosen WMA had a 37% lower ravelling loss.

The Multi-Objective Optimization Design and Hydrothermal Performance Evaluation of Anhydrous Calcium Sulfate Whisker and Polyester Fiber Compound Modified Asphalt Mixture in Hot-Humid Areas.

In hot and humid climates, asphalt pavements frequently encounter environmental factors such as elevated temperatures and rainfall, leading to rutting deformations and potholes, which can affect pavement performance. The primary objective of this study was to enhance the hydrothermal characteristics of asphalt mixtures through an investigation into the impact of anhydrous calcium sulfate whisker (ACSW) and polyester fiber (PF) on the hydrothermal properties of asphalt mixtures. In this paper, a central composite concatenation design (CCC) was employed to determine the optimal combination of ACSW and PF contents, as well as the asphalt aggregate ratio (AAR). Each influencing factor was assigned three levels for analysis. The evaluation indexes included dynamic stability, retained Marshall stability, and tensile strength ratio. Using the analysis methods of variance and gray correlation degree analysis, the hydrothermal properties of the asphalt mixture were examined in relation to the contents of ACSW, PF, and AAR based on the CCC results. Consequently, the optimal mix design parameters for composite modified asphalt mixture incorporating ACSW and PF were determined. The results indicated that the asphalt mixtures with hydrothermal qualities exhibited optimal performance in terms of 4.1% ARR, 11.84% ACSW, and 0.4% PF. The interaction between AAR and ACSW content had a greater effect on the dynamic stability and tensile strength ratio of the asphalt mixture, whereas the incorporation of ACSW and PF had a greater effect on the retained Marshall stability of the asphalt mixture. Among the three contributing factors, AAR exhibited the strongest relationship with the hydrothermal characteristics of the asphalt mixture, followed by the ACSW content; the correlation of PF content was the lowest. Therefore, to enhance the hydrothermal characteristics of the asphalt mixture, it is important to conduct a full evaluation of the constituents of ACSW and PF, along with the AAR in hot-humid regions.