Crack Resistance Research Articles

Effect of Additives on Thermal Degradation and Crack Propagation Properties of Recycled Polyethylene Blends.

Additives, such as antioxidants (AOs), carbon black (CB) and compatibilizers (COs), are used in recycled polymer blends for different reasons. AOs slow thermal degradation, CB gives blends a black color and protect them against ultraviolet (UV) light, and compatibilizers improve compatibility between the different phases of the mixture and consequently enhance the mechanical properties of the final blend. In this paper, the three additives were added to recycled polyethylene (PE) blends to study their effect on the final properties and to determine the best formulations that help improve the mechanical properties of recycled PE blends. Stress Crack Resistance (SCR) was accessed by performing Notched Crack Ligament Stress (NCLS) and Un-notched Crack Ligament Stress (UCLS). On the other hand, Oxidative Induction Time (OIT) was used to determine the oxidation time of the blends and the effect of each additive on this property. Based on the results of this study, it was proven that adding carbon black and antioxidants delay the thermal degradation of recycled PE blends and consequently improve the OIT. Otherwise, resistance to stress cracking is improved only by adding a compatibilizer to the reference blend.

Resurface of rubber modified asphalt mixture with stress absorbing membrane interlayer: From laboratory to field application

The increasing concern over tire pollution, exacerbated by the improper disposal of waste tires, serves as the backdrop for this research, which aims to explore the efficacy of incorporating ground tire rubber (GTR) into asphalt mixtures enhanced with a stress-absorbing membrane interlayer (SAMI). In this study, three variations of Hot Mix Asphalt (HMA) were evaluated: a conventional mix, a rubber-modified asphalt mixture (RMA), and a trans-polyoctenamer rubber (TOR) modified asphalt mixture in the laboratory. The assessment focused on the high and low-temperature performance of the asphalt mix and binder. Key findings from the laboratory tests indicate that the integration of a SAMI layer and GTR as additives markedly boosts the crack resistance of the asphalt mixture. Despite a reduction in fracture energy across all three HMA types following long-term aging, the GTR-modified HMA maintained superior fracture energy relative to the conventional mix. Initially, the inclusion of GTR adversely affected the mixture's rutting resistance. However, after undergoing long-term aging, both the conventional and GTR-modified HMAs exhibited exceptional rutting and moisture damage resistance. Field noise assessments further demonstrated that GTR-enhanced pavements produced noise levels approximately 2 dB lower than those of standard asphalt pavements. Additionally, pavements lacking a SAMI layer manifested low-severity cracking, with an average cracking frequency occurring every 2 ∼ 6 m, whereas pavements equipped with a SAMI layer exhibited no cracking following two winter seasons. The rubber asphalt overlay may increase the leaching of 6PPD-quinone, but the SAMI layer helps reduce tire wear particle generation by preventing road cracking. Rubber asphalt overlay leaching tests resulted in 6PPD-quinone concentrations lower than currently available toxicity data (LC50 for Coho Salmon, 0.095 ug/L). In conclusion, the utilization of dry-processed rubber asphalt mixes alongside a SAMI layer in pavement construction not only has the potential to extend the service life of pavements but also contributes to the production of quieter road surfaces. This study underscores the environmental and functional benefits of incorporating rubber modifications into asphalt pavements, presenting a viable strategy for mitigating tire pollution through the reuse of waste tires in infrastructure.

Exploring Damage Patterns in CFRP Reinforcements: Insights from Simulation and Experimentation.

Carbon Fiber Reinforced Polymers (CFRP) have become increasingly significant in real-world applications due to their superior strength-to-weight ratio, corrosion resistance, and high stiffness. These properties make CFRP an ideal material for reinforcing concrete structures, particularly in scenarios where weight reduction is crucial, such as in bridges and high-rise buildings. The transformative potential of CFRP lies in its ability to enhance the durability and load-bearing capacity of concrete structures while minimizing maintenance costs and extending the lifespan of the infrastructure. This research explores the impact of reinforcing structural elements with advanced composite materials on the strength and durability of concrete and reinforced concrete structures. By integrating Carbon Fiber Reinforced Polymer (CFRP) reinforcements, we subjected both rectangular and T-section concrete beams to comprehensive three-point bending tests, revealing a substantial increase in flexural strength by 45% and crack resistance due to CFRP reinforcement. The study revealed that CFRP reinforcement increased the flexural strength of concrete beams by 45% and improved crack resistance significantly. Additionally, the load-bearing capacity of the beams was enhanced by 40% compared to unreinforced specimens. These improvements were validated through finite element simulations, which showed a close alignment with the experimental data. Furthermore, an innovative simulation study was conducted using a finely tuned finite element numerical model within the Abaqus calculation code. This model accurately replicated the laboratory specimens in terms of shape, dimensions, and loading conditions. The simulation results not only validated the experimental observations but also provided deeper insights into the stress distribution and failure mechanisms of the reinforced beams. Novel aspects of this study include the identification of specific failure patterns unique to CFRP-reinforced beams and the introduction of an enhanced interaction model that more accurately reflects the composite behavior under load. In CFRP-reinforced beams, specific failure patterns were identified, including flexural cracks in the tension zone and debonding of the CFRP sheets. These patterns indicate the points of maximum stress concentration and potential weaknesses in the reinforcement strategy. The study revealed that while CFRP significantly improves the overall strength and stiffness, careful attention must be given to the bonding process and the quality of the adhesive used to ensure optimal performance. These findings contribute significantly to the understanding of material interactions and structural performance, offering new pathways for the design and optimization of composite-reinforced concrete structures. This research underscores the transformative potential of composite materials in elevating the structural integrity and longevity of concrete infrastructures.

Enhancing Hydraulic Lime Mortar with Metakaolin: A Study on Improving Restoration Materials for Historic Buildings.

This study investigates the enhancement of hydraulic lime mortar (HLM) using varying contents of metakaolin (MK) to improve its application in the restoration of historic buildings. Samples from historic structures were analyzed, and the effects of different MK contents on the physical and mechanical properties of HLM were examined. The reaction mechanism and microstructural changes were evaluated using XRD and SEM analysis. The results indicated that increasing MK levels in HLM led to a decrease in fluidity, with fluidity reducing by 4.8% at 12% MK. The addition of MK increased water consumption for standard consistency by 5.4% and shortened the final setting time by 10.2%. MK consumption promoted secondary hydration, enhancing compressive strength by up to 98.1% and flexural strength by up to 55.1%, and increasing bonding strength by 26.9%. The density of HLM improved with MK addition, slightly reducing moisture content by 4.5% and water absorption by 4.6%, while the water vapor transmission properties decreased by 50.9%, indicating reduced porosity. The elastic modulus of the mortar increased significantly from 2.19 GPa to 7.88 GPa with the addition of MK, enhancing rigidity and crack resistance. The optimal blend for restoration materials was found to be 9.0% MK and 25.0% heavy calcium carbonate and was characterized by moderate mechanical strength, enhanced early strength, commendable permeability, minimal risk of cracking, and ease of application. This blend is highly suitable for the rehabilitation of historic structures.

Improving Environmental Stress Cracking Resistance of High-Density Polyethylene Grades by Comonomer Addition and Nanocomposite Approach.

The aim of this paper is to determine the effect of polymer density, correlated to the comonomer content, and nanosilica addition on the mechanical and Environmental Stress Cracking Resistance (ESCR) characteristics of high-density polyethylene (HDPE). In this regard, five HDPE samples with similar Melt Flow Index (MFI) and molar mass but various densities were acquired from a petrochemical plant. Two polymerization reactors work in series and differ only in the amount of 1-buene comonomer fed to the second reactor. To ascertain the microstructure of the studied samples, GPC and SSA (successive self-nucleation and annealing) analyses were accomplished. All samples resulted having similar characteristics but slightly various SCB/1000 C=7.26-9.74 (SCB=Short Chain Branching). Consequently, meanwhile studied HDPEs reveal similar notched impact and stress at yield values, the tensile modulus, stress-at-break, and elongation-at-break tend to demonstrate different results with the SCB content. More significantly, ESCR characteristic varied considerably with SCB/1000 C extent, so that higher amount of SCB acknowledged advanced ESCR. Notably, blending HDPE sample containing higher amount of SCB/1000 C, with 3 wt.% of chemically modified nanosilica enhanced ESCR characteristic by 40 %. DFT (Density Functional Theory) calculations unveiled the role of the comonomer, quantitatively by binding energies and qualitatively by Non Covalent Interaction (NCI) plots.

Enhancing Crack Resistance in Concrete Overlays by Shredded Rubber in Stress Absorbing Membrane Interlayer (SAMI)

Enhancing Crack Resistance in Concrete Overlays by Shredded Rubber in Stress Absorbing Membrane Interlayer (SAMI)

Revisiting Ag addition in 7xxx aluminum alloys: Insights into its impact on the microstructure and properties of an Al-Zn-Mg-Cu-Zr alloy with a Zn/Mg ratio of 4

In this study, the influence of minor Ag addition on the microstructure, mechanical and corrosion properties of an Al-Zn-Mg-Cu-Zr (7449) alloy with Zn/Mg ratio of 4 was systematically investigated using various materials characterization techniques, Slow Strain Rate Test (SSRT), Potentiodynamic Polarization (PDP) and Intergranular Corrosion (IGC) measurements. Microstructure characterization by Scanning Electron Microscopy (SEM) and Differential Scanning Calorimetry (DSC) showed that Ag partitioning in the eutectic Mg(Zn,Cu,Al)2 phase occurs resulting in an increase in its solvus line. After processing to the T4 condition, Ag was partially in solid solution with the excess forming an Ag-rich AlAgZnMgCu phase. Scanning-Transmission Electron Microscopy (STEM) showed evidence of quench-induced η-Mg(Zn,Cu,Al)2 precipitates at the grain boundaries (GBs) in the T4 condition with ∼3 at.% Ag in the Ag-modified alloy. STEM and Atom Probe Tomography (APT) confirmed that ∼1 at. % Ag was present in both the matrix and GB precipitates in the Ag-modified alloy after T76 aging. Furthermore, the frequently reported decrease in the PFZ width with Ag addition was not observed after T76 aging, with both alloys having a similar PFZ width. Despite higher hardness/strength in the T4 condition with Ag addition, no enhanced age hardening response and alteration of the precipitation kinetics was observed during artificial aging at 121 °C. In fact, Ag addition in a 7xxx alloy with Zn/Mg ratio of 4 was found to be detrimental to mechanical properties, stress corrosion cracking, pitting and IGC resistance after T76 aging, which is attributed to the presence of the Ag-rich AlAgZnMgCu phase.

Improving intergranular cracking and stress corrosion cracking resistance of highly sensitized AA5083 Al-Mg alloy via reversion heat treatment

This study systematically examines the impact of reversion heat treatments (220–280 ℃ for 1 h) on the microstructure evolution, electrochemical corrosion, intergranular cracking (IGC) and stress corrosion cracking (SCC) of a severely sensitized (175 ℃/100 h) AA5083 alloy. Increasing the reversion temperature gradually enhances the corrosion resistance by dissolving the β′-Al3Mg2 phase, with the optimal treatment identified as 280 ℃/1 h. The βˊ phase maintains its planar film shape and continuously covers the grain boundaries after reversion treatment below 240 °C, but spheroidizes at the triple junctions at 260 °C. The morphology of the βˊ phase is dictated by grain boundary diffusion and interface diffusion. Reversion treatments improve SCC resistance by dissolving the β′ phase and reducing yield strength, attributed to anodic dissolution and hydrogen embrittlement mechanisms. This research offers valuable insights into the practical benefits of reversion treatments for Al-Mg alloy marine applications, addressing safety concerns related to sensitization.

Analysis of the destruction of a die insert used in the industrial process of hot die forging to produce a yoke forging

The article performs an analysis of the destruction of forging dies (with two impressions for a double system) used in the industrial process of forging on a hydraulic hammer to produce a yoke forging with a complex geometry. A detailed analysis was performer on one of the lower dies made of non-standard hot chromium-molybdenum-vanadium tool steel, selected for the tests due to its premature damage (a crack) and relatively low durability equalling only 1200 forgings, that is 600 forged elements. Based on the performed complex studies (surface scanning, microhardness tests, microscopic tests, numerical modelling, impact strength trials) it was demonstrated that the most dangerous destruction mechanism for the analyzed process is mechanical cracking and thermo-mechanical fatigue. As a result of the tool working under extreme conditions (high cyclic mechanical impact loads as well as thermal loads), the most intensive damage of the roughing pass, caused by thermal fatigue and abrasive wear, takes place in the areas of complex geometry as well as intensive flow of the forging material on the radii of the roundings. In turn, in the case of the finishing pass, we observe mechanical fatigue cracking of the tool in the areas of stress and high pressure concentration. The results of FEM modelling combined with the results of a microstructural analysis made it possible to determine the causes of the formation of cracks in the working area of the die, which included cyclic high thermal and mechanical loads as well as abrasive wear as a result of intensive flow of the forging material. Within the conducted studies, directions of further investigations were also proposed in order to improve the durability of the examined tool. Additionally, the observed high tendency of the tool material to crack, based on thermal expansion and impact tests and the determination of the crack resistance coefficient K1C, led to the proposal of an alternative material with higher impact strength.

Low-temperature performance and micro-structure of warm mix recycled composite aged asphalt

Given the cold winters in Inner Mongolia, the low-temperature performance of asphalt pavement is one of the key factors affecting the service life of roads. This study focuses on commonly used SBS modified asphalt and investigates the coupling effect of adverse factors such as solar radiation, high temperature, and precipitation on road surface asphalt. The objective is offer insights for improving the applicability and service life of warm mix recycled asphalt in cold regions. By using indoor simulation aging equipment, asphalt subjected to hot oxygen aging, composite water aging, and composite ultraviolet aging was prepared to investigate the low-temperature performance of warm mix recycled asphalt. Additionally, to explore the synergistic effect of new asphalt, regenerant, and warm mix agent on the regeneration of aged asphalt, this study analyzes the low-temperature performance and microstructure changes of recycled asphalt through bending beam rheometer (BBR) test, atomic force microscopy (AFM) test, and infrared spectroscopy (FTIR) test. The results show that as the degree of aging increases, the low-temperature crack resistance performance of asphalt deteriorates. Additionally, after the regeneration of aged asphalt, the damping ratio and dissipation energy ratio of warm mix recycled asphalt slightly enhances compared to hot mix recycled asphalt. Furthermore, the incorporation of a warm mix agent enhances the asphalt’s fluidity, viscosity, surface toughness, and further its low-temperature performance. The AFM test results show that the synergistic effect of warm mix agents and regeneration effectively restores the microstructure and surface roughness of asphalt. Moreover, the warm mix agent improves the dispersion uniformity of the SBS modifier in asphalt, helping prevent the agglomeration of asphalt slurry. Qualitative and quantitative analysis of asphalt through FTIR test demonstrates that the mechanisms of warm mix agents and regeneration on new and aged asphalt are a physical process. New asphalt and regeneration supplement the internal lightweight components of aged asphalt, enabling the restoration of most asphalt without affecting the structure of SBS modified asphalt. This project provides a theoretical basis for the engineering applicability of high content warm mix recycled asphalt (composed of 50 % aged asphalt) in large temperature range areas.

Improved Tensile Strength and SCC Resistance via Nonisothermal Creep Aging under a High Stress Level

Compared with conventional isothermal creep aging (ICA), non‐ICA (NICA) does not involve a prolonged holding stage, but only has heating and cooling stages. During the NICA process, the precipitates nucleate and grow up in the early part of heating stage, resulting in fluctuations in creep rate and an increase in strength. The coarsening of precipitates in the later part of the heating stage can lead to significant increase of creep rate. Upon approaching the peak temperature, the dissolution of the precipitates occurs in conjunction with a partial coarsening of the remaining precipitates, causing a reduction in strength. However, the secondary precipitation during the cooling stage facilitates a significant strength enhancement in a relatively shorter period. In contrast to the ICA, the targeted NICA treatment gives an increase in ultimate strength while improves the stress corrosion cracking resistance. Moreover, the time required for NICA to obtain ultimate strength is only 13.9% of that of the ICA treatment. A large amount of creep strain can be generated during the NICA process, which is equivalent to 630% of that of creep age forming treatment.

Investigations on the Environmental Characteristics and Cracking Control of Plateau Concrete

In the present study, first, the environmental challenges and cracking characteristics during the construction of plateau concrete on the Sichuan–Tibet route were revealed. Then, using a multi-field coupled shrinkage model with hydration temperature humidity constraints, the early and long-term cracking risks in the core of plateau pier bodies were investigated. Later, the effects of tensile strength, pouring interval age and adiabatic temperature rise on the cracking risk were analyzed. Finally, various control measures for high-altitude concrete cracking were proposed. The results indicated that the complex environment of the plateau led to different forms of cracks in the pier body, especially vertical cracks in the straight sections. The long-term risk of core cracking in the plateau pier body is significantly greater than the risk of early cracking. This risk was strongly influenced by factors such as the concrete tensile strength, pouring interval age and adiabatic temperature rise, which should be given more attention. Deformation compensation can significantly enhance the peak and residual deformation capacities of plateau concrete, with peak values greater than 900 με and residual deformation greater than 200 με at day 60, as well as its resistance to cracking. Strategies such as adopting radiant cooling techniques, improving construction techniques and implementing effective management measures can all play a vital role in improving the cracking resistance of highland concrete.

Influence of preparation parameters on rheological properties and relation analysis of waste rubber modified bitumen mastic

Waste rubber modified bitumen has gained significant attention as a sustainable and innovative material in the field of pavement engineering. This study aims to evaluate the performance of rubber modified bitumen mastic by considering its rheological properties, specifically focusing on preparation parameters, i.e., rubber content, mesh number, and filler to bitumen ratio. From the experimental results, the rheological properties of rubber modified bitumen mastic were significantly influenced by preparation parameters. Increasing the rubber powder content in bitumen mastic results in higher viscosity. Increasing the rubber content improves high-temperature rutting resistance to a certain extent, however, excessive rubber powder content would result in weakened high-temperature performance improvement. The rutting factor decreases gradually with an increase in the rubber mesh number. A ratio of filler to bitumen of 0.95 exhibits the best resistance to rutting at high temperatures. Higher rubber content and larger mesh number correspond to stronger low-temperature crack resistance in bitumen mastic. As the ratio of filler to bitumen increases, the low-temperature deformation capacity gradually decreases, resulting in weaker low-temperature crack resistance. Based on the grey relation analysis, the ratio of filler to bitumen has the greatest impact on the high and low-temperature rheological properties of bitumen mastic, followed by the rubber content. The rubber mesh number has a relatively lower impact. It is crucial to control the ratio of filler to bitumen to avoid excessive values. When possible, a higher rubber powder content should be used while meeting process requirements. These findings provide valuable insights into the design and optimization of rubber modified bitumen mastic, which can contribute to the development of sustainable and high-performance bitumen mixtures, promoting the use of recycled rubber in pavement engineering.

Effect of Post-Cured through Thickness Reinforcement on Disbonding Behavior in Skin-Stringer Configuration.

An experimental investigation of interlaminar toughness for post-cured through-thickness reinforcement (PTTR) skin-stringer sub-element is presented. The improvement in the crack resistance capability of skin-stringer samples was shown through experimental testing and finite element analysis (FEA) modeling. The performance of PTTR was evaluated on a pristine and initial-disbond of the skin-stringer specimen. A macro-scale pin-spring modeling approach was employed in FEA using a non-linear spring to capture the pin failure under the mixed-mode load. The experimental results showed a 15.5% and 20.9% increase in strength for the pristine-PTTR and initial-disbond PTTR specimens, respectively. The modeling approach accurately represents the overall structural response of PTTR laminate, including stiffness, adhesive strength, crack extension scenarios and progressive pin failure modes. This modeling approach can be beneficial for designing damage-tolerant structures by exploring various PTTR arrangements for achieving improved structural responses.

Experimental study on the shear and slip behaviors of perfobond strip connectors with low elastic modulus material wrapped perforated rebars

Adopting Ultra-high performance concrete (UHPC) endows steel-UHPC composite beams with numerous benefits, including high cracking capacity, high durability, light self-weight, etc. However, the cracking load of the steel-UHPC composite beams under negative moments reaches only 13–40 % of their ultimate load, with cracking properties being the primary constraint to the development of steel-UHPC composite beams. This study proposed a novel uplift-restricted and slip-permitted (URSP)-PBL connector to improve the crack resistance in the negative moment regions of continuous steel-UHPC composite beams. A total of ten push-out tests were conducted to investigate the behaviors of the URSP-PBL connector. The effects of perforated rebar diameter, rubber thickness, and row numbers on the URSP-PBL connector were investigated by evaluating the failure mode and the load-slip relationship of the push-out specimens. Additionally, numerical analyses were carried out to investigate the effect of various parameters on the mechanical properties of the connector. Based on the analysis results, a load-slip curve model of the URSP-PBL connector was established as a reference for the promotion of the URSP-PBL connector in steel-UHPC composite structures.

Upcycling process of mill scale waste into high-value ceramic products

Ceramic industry consumes large amounts of raw materials, including costly and environmental impact iron based-pigments. Steel rolling (SR) and wire drawing (WD) waste, rich in iron (>67 wt %), present a viable alternative. This study aims to develop high value stoneware pastes for tableware products by substituting commercial pigments with SR and WD. The influence of incorporation content (3, 5 and 10 wt %) and pre-treatments (sieving at 250, 150 and 63 μm, and grinding followed by sieving at 63 μm) on the samples properties was assessed including weight loss, firing shrinkage, apparent density, flexural resistance, and water absorption. The laboratory scale results revealed that darker hues, ranging from grey to reddish, were obtained when SR and WD were incorporated in the stoneware paste (beige colour). The smaller the particle size, more homogeneous is the developed colour, which is intensified as higher is the incorporation level.The prototypes (plates) were characterized in terms of thermal shock, edge impact, cracking and microwaves resistance, water absorption, and leaching behaviour, demonstrating that they met the industrial requirements. Thermal shock resistance was enhanced and the levels of leached Fe, Pb, Cd, Ni, Cr, Mo, V, Zn, and Cu, were below permissible limits (EU Ceramic Directive 84/500/EEC, Decree-Law n°152/2017, Decree-Law n°236/98 and WHO Guidelines for Drinking-Water Quality) confirming their effective immobilization. Concluding, this work shows the viability of using mill scale waste as a valuable secondary raw material in stoneware pastes acting as a chromophore agent. Dark colours are obtained while preserving the product technical characteristics, promoting sustainable production and reducing landfilled waste.

Compressive Bearing Capacity and Ductility of Slurry-Infiltrated Fiber Concrete Blocks with Two-Dimensional Distributed Steel Fibers

Slurry-infiltrated fiber concrete (SIFCON) has excellent potential for application as a new material with good crack resistance, impact resistance, and seismic performance. In this paper, SIFCON blocks were cast in a single pour using the custom-made two-dimensional directional steel fiber placement device, followed by compressive testing. Based on the test results, the effects of fly ash substitution rate, steel fiber aspect ratio, and steel fiber volume fraction on the compressive bearing capacity and ductility of SIFCON blocks were investigated. The results indicate that the custom-made device in this paper effectively achieves the directional placement of steel fibers, offering a cost-effective solution that optimizes the construction process. Regarding the test results, it was observed that the compressive bearing capacity of SIFCON blocks decreases linearly with increasing fly ash substitution rate, while the addition of fly ash improves the ductility of the blocks. Notably, a 31% decrease in bearing capacity was noted when the fly ash substitution rate increases from 0% to 40%, whereas the ductility ratio increased by 99% for the same substitution rate range. Furthermore, the results revealed a positive correlation between the bearing capacity and ductility of SIFCON blocks with higher steel fiber aspect ratios and volume fractions. Specifically, the bearing capacity increased by 19% and 33% with steel fiber aspect ratio increments from 33 to 70 and volume fraction increases from 10% to 14%, respectively. Additionally, the ductility ratio of the test blocks increased by 104% when the aspect ratio of the steel fibers increased from 33 to 70, and by 37% when the volume fraction of steel fibers rose from 10% to 14%.

Identification of asphalt binder tests for detecting variations in binder cracking performance

Asphalt binders are vital components in the construction of roadways, and their quality significantly impacts the performance and durability of asphalt mixtures. However, it is possible for binders to exhibit different performance with identical Performance Grade (PG) due to variations in source, refining processes, and modifiers (if any). This paper presents a comprehensive study aimed at identifying candidate tests to detect variances in the quality of the binders in terms of cracking resistance. Eight PG 64–22 asphalt binders were selected and subjected to multiple laboratory tests, including X-ray fluorescence (XRF), Dynamic Shear Rheometer (DSR), Poker chip, and Bending Beam Rheometer (BBR) tests. The binders were then incorporated into asphalt mixtures, and their cracking resistance was evaluated using the IDEAL cracking test (IDEAL-CT) and Overlay test (OT). The study findings revealed that phase angle test, poker chip test, and Glover–Rowe (G–R) parameter test emerged as promising candidates to detect variations in the quality of binders of the same grade based on their cracking resistance. Notably, phase angle and G-R tests, both utilizing DSR, offered valuable supplementary assessments to the traditional PG grading system, proving crucial in evaluating cracking resistance. Furthermore, the poker chip test, an affordable alternative to DSR, demonstrated its effectiveness in evaluating binder quality for cracking performance. In conclusion, the identified candidate tests provide valuable insights into evaluating the quality of asphalt binders. By incorporating these tests into mix design and evaluation processes, engineers can make informed decisions to optimize the performance and durability of asphalt pavements.

Enhancing self-healing of asphalt mixtures containing recycled concrete aggregates and reclaimed asphalt pavement using induction heating

Given the growing demand for sustainable road construction materials, this research aims to evaluate the synergistic effects of incorporating recycled concrete aggregate (RCA) and reclaimed asphalt pavement (RAP) in asphalt mixtures. Induction heating was also utilized to enhance the self-healing ability of asphalt mixtures, with the intention of prolonging their lifespan and mitigating environmental impacts. This research assessed the pavement performance of recycled asphalt mixtures (RAM) with different RCA and RAP dosages. The induction heating performance, cooling performance, and effective heating depth of RAM were tested. Lastly, the cumulative healing efficiency of the RAM was evaluated under multiple "fracture-healing" conditions. Findings indicated that the inclusion of RCA and RAP negatively influenced the water stability, high-temperature deformation resistance, and crack resistance at low temperatures of the RAM. However, when the RCA content was 20 % and the RAP content did not exceed 20 %, the road performance of the RAM met the requirements. The contents of the RCA and RAP had no discernible effect on the RAM's induction heating capability. Moreover, when the RCA content was 20 % and the RAP content did not exceed 10 %, the effective heating depth of the RAM could reach 50 mm. Using fracture energy recovery rate as the healing index, after three cycles of "fracture-healing", the RAM with 20 % RCA achieved the highest cumulative healing efficiency of 291 %. The cumulative healing efficiency of recycled asphalt mixtures with 20 % RCA and 10 % RAP was close to that of normal asphalt mixtures. This research contributes to reducing the consumption of non-renewable resources, minimizing environmental impact, and maintaining or even improving the performance of asphalt pavements by optimizing the use of RCA and RAP.

Evaluating the Suitability of the Gurson—Tvergaard—Needleman Plasticity Model for Crack Resistance Curve Analysis

Evaluating the Suitability of the Gurson—Tvergaard—Needleman Plasticity Model for Crack Resistance Curve Analysis