Binder Content Research Articles

Effects of binder content on potato starch-derived porous carbon microspheres for high-performance supercapacitors

Potato starch-based carbon microspheres (PCMs) have successfully synthesized from potato starch by a simple strategy based on (NH4)2HPO4 and KOH activation. The PCMs presents a large specific surface area (SSA) of 2048 m2 g−1. The electrochemical behaviors of the PCMs with different binder content in 6 mol L−1 KOH were studied by impedance spectroscopy, cyclic voltammetry (CV), and galvanostatic charge-discharge (GCD). The results show that PCMs-85 (the binder content is 5 wt%) has a small equivalent series resistance (ESR), high specific capacitance, compacted density, and areal density. PCMs-85 exhibited good cycling durability of 100 % after 10,000 cycles at 1 A g−1 and delivered an energy density of 6.35 Wh L−1 and a volume power density of 167.38 W L−1. The corresponding capacitive performances of PCM-85-based symmetrical two-electrode supercapacitors are investigated in 6 mol L−1 KOH, 1 mol L−1 Na2SO4 and 1 mol L−1 TEA.BF4/AN electrolyte. The PCMs supercapacitor with 6 mol L−1 KOH electrolyte exhibits a mass-specific capacitance of 172 F g−1 with volumetric capacitances of 145 F cm−3 at 1 A g−1.

Life Cycle Assessment for the Use of Waste Plastics in Asphalt Concrete Mixes

Improper waste disposal poses the risk of contaminating natural water bodies and soil. The low recycling rate of plastics and their fate in landfills are significant global environmental concerns. Efforts to increase the use of recycled plastics worldwide aim to address the hazardous consequences of improper plastic treatment. One potential solution is incorporating plastics as binder or mixture modifiers in asphalt concrete (AC) mixtures, which repurposes waste plastics while reducing environmental impacts related to AC production. This study calculated the environmental impacts of repurposing waste plastics, specifically low-density polyethylene and polystyrene, into modifiers in AC mixes. Wet and dry processes were considered. The environmental impacts of plastic-modified AC mixes were compared with those of styrene-butadiene-styrene (SBS)-modified mixes. The life cycle assessment covered the following processes: (1) collection, sorting, and shredding of waste plastics; (2) transportation of waste plastics from landfill to recycling facility and then to the asphalt plant; (3) supply and transportation of virgin materials; (4) production of AC mixtures; (5) transport of material and equipment to site; and (6) onsite operations. The study concluded that waste plastic-modified mixes outperformed SBS-modified mixtures with regard to environmental performance, except for ozone depletion resulting from certain recycling process activities. The high-shear mixing in the wet process had a significant impact. Sensitivity analyses revealed the influence of binder content and material transportation on the overall environmental assessment.

Long-Term Drying Shrinkage Strain of Engineered Cementitious Composite Concrete Contains Polymeric Fibers

The lack of concrete tensile stress endurance led to the invention of engineered cementitious composite. However, the absence of gravel from the mixture in addition to the high binder content may lead to high shrinkage strain. Therefore, a radical solution to this problem is worth to be anticipated. The importance of this research lies in investigating the long-term drying shrinkage strain of the engineered cementitious composite since there is a lack of information regarding this behavior. Mixes of 30 and 60 MPa strengths were produced with polyvinyl alcohol fibers PVA-ECC and polypropylene fibers PP-ECC. The drying shrinkage strain of PVA-ECC mixes has been compared to PP-ECC mixes for both short term (0–28 days) and long term (0–360 days). Results indicated that all PVA-ECC mixes exhibited lower drying shrinkage strains than PP-ECC mixes. The ultimate drying shrinkage strain was recorded to be 1200 microstrain at 28 days. The increment in drying shrinkage strain after 28 days was 5.6% in PVA-ECC mixes when compared to that in PP-ECC mixes which was 6.77%. For high strength levels, the drying shrinkage strain at the age of 360 days declared a reduction of 3.5% for PVA-ECC compared to PP-ECC mixes. Also, it was lower for mixes with 60 MPa (6.3%) than for mixes with 30 MPa (7.6%). Therefore, despite the higher cement content for mixes with 60 MPa strength, the higher fiber volume fraction and the higher PVA solution percentage restricted the drying shrinkage strain increment. The research also addresses some mechanical tests of engineered cementitious composite concrete such as compressive strength, flexural strength, and strain capacity that may provide a strong relation to the drying shrinkage behavior of the different mixes. The scanning electron microscope images were involved in this research to declare the impact of fiber types on the microstructure of the ECC mixes.

The Functionalization of Cotton Fabric Using Urtica dioica Microcapsules to Develop UV Protective Textiles

The World Health Organization (WHO) and the United Nations Environment Programme (UNEP) have highlighted the increased risk of skin cancer due to exposure to UV radiation. This emphasizes the importance of safeguarding the skin. Although sunscreens are commonly used for protection their high cost, the need for frequent reapplication, and pollution in coastal areas necessitate alternative solutions. Clothing also offers protection but requires additional application of dyes and finishes for prolonged effectiveness. The application of synthetic or natural dyes can enhance the UV protection properties of the fabric but Synthetic dyes contribute to pollution, while natural dyes lack durability. Addressing these challenges, this study focuses on providing a durable and sustainable solution for enhancing the UV protective properties of cotton fabric using Urtica dioica microcapsules based on RSM design. Urtica dioica plant extract serves as the core material for the microcapsules. Design Expert software 10 has been used for the study. It was observed through software that at 4.116% concentration of microcapsules, 3% concentration of binder and a curing temperature of 113.258 °C an optimum UPF with sufficient fabric properties can be achieved. On conducting the experiments on these optimum conditions UPF, tensile strength and bending length value were found to be 277.60, 14.89 N/cm2 and 2.00 cm respectively. Results indicate that cotton fabric demonstrates excellent UV protection properties even after the 20th wash cycle. This research contributes to the ongoing quest for fabric with UV protection, emphasizing both efficacy and sustainability compared to current synthetic alternatives available in the market.

Performance Investigation and Optimization of Composite Materials in Household Dehumidifiers

The efficiency of household dehumidifiers is affected by air temperature and the temperature used for regeneration. A regeneration temperature that is too high can lead to increased energy use, heat build-up in the desiccant wheel, and lower dehumidification efficiency. In this study, we developed a LiCl@Al-Fum composite material and evaluated it through physical characterization and module testing. The results show that the LiCl@Al-Fum composite with a 20% mass fraction is particularly effective as a desiccant material. Additionally, a 15% volume concentration of neutral silica sol was identified as the optimal binder concentration. A comparative analysis of the effects of glass-fiber desiccant wheels (GF DWs), aluminum desiccant wheels (Al DWs), and commercial desiccant wheels (CM DWs) on household dehumidifier performance revealed that the Al DWs outperformed the CM DWs, showing a 13% improvement in the dehumidification rate and a 12.56% increase in the DCPP. An increase in the dehumidifier structure led to increases in the dehumidification rate by 11.8%, 11.9%, and 10% and in the DCPP by 11.6%, 12.1%, and 10%, respectively. Moreover, the modifications resulted in a 3.85 °C, 3.34 °C, and 3.8 °C decrease in the temperature.

Fabrication and characterization of in-situ Ti(C, N) – CoCrFeNi cermets via mechanical alloying and spark plasma sintering

Ti(C, N) cermets were prepared by adding CoCrFeNiTi to g-C3N4 and using mechanical alloying and spark plasma sintering techniques. The evolution of microstructure and the systematic analysis of the influence of different binder content on mechanical properties were investigated. This result demonstrates that with an increase in binder content, the grain size of Ti(C, N) in the cermets decreases, and the formation of spheroidal small grains becomes more prominent while the occurrence of large grains decreases. Additionally, the relative density and hardness of Ti(C, N) metal ceramics have slightly decreased. The fracture toughness of Ti(C, N)/HEA cermet is codetermined by the intrinsic sintering property and deformability of HEA binders. The Ti(C, N) cermets (CH3) exhibits excellently bending strength and fracture toughness，which are 1941 MPa and 11.2 MPa m1/2 respectively. The study aims to enhance the mechanical properties and toughness of Ti(C, N) and proposes a novel approach for the synthesis of Ti(C, N) cermet.

Impact of Nonrecyclable Plastics on Asphalt Binders and Mixtures

Low-density polyethylene (LDPE) and polystyrene (PS) were evaluated for incorporation as binder additives to enhance the potential performance of asphalt concrete (AC) mixtures, as well as addressing global rising concerns over nonrecyclable plastics accumulation. Incorporation of LDPE and PS in asphalt binder resulted in an increase in its complex moduli over a range of temperatures and frequencies, as determined using frequency sweep (FS) and linear amplitude sweep (LAS) tests. AC performance tests were conducted, including the Hamburg wheel-tracking test (HWTT) to assess potential rutting, the Illinois flexibility index test (I-FIT) to determine cracking potential, the indirect tensile strength test (ITS) to assess moisture susceptibility, and the dynamic modulus for structural capacity. Two control AC mixes were designed, utilizing aggregates from different sources. For each AC mix, the aggregate blend and binder content were kept constant, with only the binder type changed. LDPE and PS were added through a wet process in one mix. Dry and wet processes were used in the other mix. Waste plastics–modified AC mixes, in both wet and dry processes, exhibited reduced rutting potential. However, the cracking potential and moisture damage susceptibility varied, depending on the modified AC mix. The addition of waste plastics had no impact on AC dynamic modulus. The results for waste plastics–modified AC mixes were compared with those for styrene-butadiene-styrene (SBS)–modified AC mixes. While waste plastics modification provided improvement over the control mixes, the performance fell short of that of the double-pump SBS-modified mix.

The Design of a Novel Alkali-Activated Binder for Solidifying Silty Soft Clay and the Study of Its Solidification Mechanism.

In order to overcome the problems of the high economic and environmental costs of a traditional ordinary portland cement-based binder, this study used self-combusted coal gangue (SCCG), granulated blast furnace slag (GBFS) and phosphorous slag (PS) to prepare a novel SCCG-GBFS-PS (SGP) ternary alkali-activated binder for solidifying silty soft clay (SC). Firstly, the parameters of the SGP ternary binder were optimized using orthogonal experiments. Then the effects of the SGP ternary binder content (mass ratio of the SGP ternary binder and the SGP-solidified soil), initial water content of SC (mass ratio of SC' water and SC) and types of additives on the unconfined compressive strength (UCS) of the SGP-solidified soil were analyzed. Finally, the hydration products and microstructure of the SGP-solidified soil were analyzed to investigate the solidification mechanism of the SGP ternary binder. The results showed that the optimal mass ratio of GBFS and PS is 2:1, and the optimal alkali activator content (mass ratio of Na2O and the SGP ternary binder) and modulus of alkali activator (molar ratio of SiO2 and Na2O of alkali activator) were 13% and 1.3, respectively. When the SGP ternary binder content was 16% and the initial water content of SC was 35%, the SGP-solidified soil met the requirement of UCS for tertiary cured soil. The incorporation of triethanolamine and polyvinyl alcohol improved the UCS, while the incorporation of Na2SO4 significantly deteriorated the UCS of the SGP-solidified soil. The C-S-H gels and C(N)-A-S-H gels generated by hydration of the SGP-solidified soil were interspersed, interwoven and adhered to each other to form a network-like space structure that played the roles of skeleton, bonding soil particles and filling pores, which improved the macroscopic properties of the SGP-solidified soil. The results of this study provide a reference for the design and development of a solid waste-based binder for solidifying SC.

Quaternary blended eco high performance concrete utilizing high volumes of siliceous additives

This research examines the optimal feasibility of incorporating siliceous additives as an adjunct material for cement in the formulation of environmentally sustainable high-performance concrete (Eco-HPC). Siliceous materials, including Nano silica (NS), Rice Husk Ash (RHA), and Fly Ash (FA), were fine-tuned within the cementitious system in order to achieve the amplified performance of Eco-HPC by reducing the required cement content from 370 kg/m3 to 273 kg/m3. This is achieved by employing the Modified Andreasen and Andreasen (MA&A) particle packing model, with ‘q’ (distribution factor) as ‘0.3’. The Levenberg Marquardt algorithm (curve fitting) was utilized to validate the packing density of each concrete blends. Initially, the dry NS agglomerates are synthesized into stabilized aqueous dispersion through High shear mixing (10 min/1750 rpm) followed by probe sonication (15 min/(1/3) s/s) with anionic surfactant dosage of 0.1 g/10 g. Incorporating secondary siliceous binders into the cement matrix led to an enhancement in the packing density, increasing from 0.94 (nullary) to 0.96 (quaternary) which in turn alters the reactivity and cohesiveness of the matrix. Compressive strength values for Binary (NS2), Ternary (RN15, FN20), and quaternary mix (FRN25) were observed as 57.42 MPa, 56.83 MPa, 55.34 MPa, and 52.58 MPa, respectively, for primary binder contents of 362 kg/m3, 314 kg/m3, 296 kg/m3, and 273 kg/m3 without compromising durability parameters. An assessment on reduced carbon dioxide emissions indicated that increasing the cement replacement percentages in Eco-HPC by up to 30% for binder contents of 358 kg/m3, 296 kg/m3, 259 kg/m3, and 273 kg/m3 resulted in a reduction of CO2 emissions by 2.98%, 18%, 27%, and 23.33%, respectively. Among the twelve formulated mixes, FRN25, FRN20, FRN15 and FN30 are identified as Eco-HPC mix through a computational framework which integrates the packing density, carbon emission, strength and diffusion coefficient.

Porous asphalt mixture performance in cold regions: Case study of Chicago

Porous Asphalt Mixtures (PAMs) improve resilience of flexible pavements in the context of climate change. PAM application in coastal cities like Chicago is of interest; however severe winters compromise the durability of PAMs given their susceptibility to freeze-thaw. This work aimed to evaluate the to-date experience with PAMs in Chicago, exploring benefits and limitations to be considered for future projects in the Southern Lake Michigan region. Full-depth PAM cores were obtained from seven sections, constructed in different years. Tests were conducted to assess the evolution of surface texture, internal structure, and multi-scale material properties. Regarding surface texture, consistent change over time was observed, such as loss of the “channel” structure, and increase in mean profile parameters because of raveling. Also, binder content varies with time within different layer depths. An aging gradient in terms of stiffness from top to bottom within the layer does not necessarily occur. However, binder ductility shows drastic and consistent reduction throughout the layer as aging increases. Analysis of internal structure using a CT scan revealed that there is also a lack of homogeneity in the air void and particle size distributions. Finally, this study suggests that full-depth PAM viscoelastic behavior is sensitive to saturation level, and this is a relevant subject to be considered, since partial saturation may be a condition often observed in the field.

Aging Resistance Evaluation of an Asphalt Mixture Modified with Zinc Oxide

The phenomenon of the oxidation and aging of asphalt binders affects the strength and durability of asphalt mixtures in pavements. Several studies are trying to improve the resistance to this phenomenon by modifying the properties of the binders with nano-particles. One material that shows promise in this field is zinc oxide (ZnO), especially in improving ultraviolet (UV) aging resistance. Few studies have evaluated the effect of these nano-particles on the thermo-oxidative resistance of asphalt binders, and, on hot-mix asphalt (HMA), studies are even more scarce and limited. Therefore, in the present study, the resistance to thermo-oxidative aging of an HMA manufactured with an asphalt binder modified with ZnO was evaluated. An asphalt cement (AC 60–70) was initially modified with 0, 1, 3, 5, 7.5, and 10% ZnO (percentage by weight of asphalt binder; ZnO/AC in wt%), and then exposed to aging in Rolling Thin-Film Oven tests (RTFOT) and a Pressure Aging Vessel (PAV). Penetration, viscosity, and softening point tests were performed on these binders, and aging indices were calculated and evaluated. Samples of HMAs were then manufactured using these binders and designed by the Marshall method, determining the optimum asphalt binder content (OAC) and the optimum ZnO/AC ratio. Control (unmodified) and modified HMA were subjected to short-term oven aging (STOA) and long-term oven aging (LTOA) procedures. Marshall, Indirect Tensile Strength (ITS), and resilient modulus (RM) tests were performed on these mixtures. LTOA/STOA results of the parameters measured in these tests were used as aging indices. In this study, ZnO was shown to increase the thermo-oxidative aging resistance of the asphalt binder and HMA. It also contributed to an increase in the resistance under monotonic loading in the Marshall and ITS tests, and under repeated loading in RM test. Likewise, it contributed to a slightly increasing resistance to moisture damage. The best performance is achieved using ZnO/AC = 5 wt%.

Evaluation of binders in twin-screw wet granulation – Optimization of tabletability

The influence of hydroxypropyl cellulose type (HPC-SSL SFP, HPC-SSL), concentration (2 %, 3.5 %, 5 %) and filler (lactose, calcium hydrogen phosphate (DCP)/microcrystalline cellulose (MCC)) on twin-screw wet granulation and subsequent tableting was studied. The aim was to identify the formulation of the highest tabletability which still fulfills the requirements of the disintegration. Lactose combined with 5 % binder enabled a higher tabletability and a faster disintegration than DCP/MCC. It was found that tabletability of lactose formulations can be increased by higher binder concentration and higher compression pressure while tabletability of DCP/MCC formulations can be only increased by higher compression pressure. It was observed that batches containing DCP/MCC failed the disintegration test, if the highest binder concentration and the highest compression pressure were used. To ensure a fast disintegration, the compression pressure or at least the binder concentration had to be low. Changing the disintegrant and its localization improved the DCP/MCC formulation, resulting in faster disintegration than lactose tablets. However, it also resulted in a lower tabletability. In this study best tablets were achieved with 3.5 % or 5 % binder and lactose as filler. These tablets presented the highest tabletability but still disintegrated in less than 500 s.

Shrinkage characteristics of sustainable mortar and concrete with alkali-activated slag and fly ash Binders: A focused review

Alkali-activated binders are emerging as promising sustainable alternatives to ordinary Portland cement (OPC) due to their lower environmental footprint. They offer competitive mechanical properties and enhanced durability, making them attractive options for a wide range of construction and infrastructure applications. This paper is a focused review of key findings related to the shrinkage characteristics of mortar and concrete with alkali-activated slag and fly ash binders. Shrinkage induces nonuniform deformations in mortar/concrete, leading to the development of internal tensile stresses and the formation of cracks. Such cracks may be sufficiently large to facilitate the penetration of harmful substances, which may compromise the integrity of structural elements. Several studies indicated that the combination of fly ash and slag precursors in appropriate proportions produces mortar with favorable shrinkage cracks when compared to mortar with individual binders. This article discusses the influence of the following factors on shrinkage characteristics: binder type, binder proportions, water/binder ratio, binder content, aggregate content, alkaline activator type, and concentration. The article compares the shrinkage of mortar/concrete prepared using mostly alkali-activated slag and fly ash binders and compares their shrinkage response to OPC. Shrinkage types evaluated include chemical shrinkage, autogenous shrinkage, and drying shrinkage. Shrinkage responses reported in this article include the sample curing method and environment as they are known to influence durability, strength, and shrinkage characteristics. In general, mortar/concrete with alkali-activated fly ash and slag experience higher shrinkage rates than conventional concrete with OPC binders. The study further explores shrinkage mechanisms and methods to mitigate shrinkage in alkali-activated binders.

A Study of ZSM-5 Molecular Sieve Shaping for an Innovative Cyclohexene Hydration Process

The development of the zeolite molecular sieves (ZSM-5) molding technique is essential for the cyclohexene hydration reaction distillation process in both industrial and research settings. The reactive distillation process can solve many of the drawbacks associated with the existing technique of manufacturing cyclohexanol via cyclohexene hydration, such as high catalyst digestibility, low conversion rate, and operational challenges. This study developed a series of molded ZSM-5 catalysts with various binder types and contents were constructed. The suggested pseudo-boehmite and hydroxypropyl methylcellulose were chosen as binders for extrusion molding of ZSM-5. The effects of binders on the strength reliability were investigated by strength tests and statistical analysis of the Weibull function. The effects of binders on the physical structure, acidity, and catalytic performance of ZSM-5 were investigated by X-ray diffraction, scanning electron microscopy, physical adsorption of N2, and desorption of NH3. The findings demonstrate that the addition of binder has no effect on ZSM-5's crystal structure. The experiment's results showed that the molded catalyst could be used for the hydration process with over 95% selectivity and a yield of 10.45% cyclohexanol. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Experimental Investigations of Bituminous Concrete Using Dissimilar Trash Which Improve the Results

Abstract: Bituminous mixture is an admixture of coarse aggregate, fine aggregate and fill. CRMB is based on a unique technology that permits homogeneity. CRMB is suited for use in heavy load traffic lanes, air fields. In this study, Crumb Rubber Modified Bitumen (CRMB-60) blended with normal asphalt binder VG-30 with various different percentages of crumb rubber in different proportions with constant optimum binder content i.e. 5% which shows improved characteristics when compared with regular bitumen. The cost for Bituminous course for CRMB-60 came out to be Rs 68.23 Lacs per Km which was 20.81% economical than the bituminous work done by normal VG- 30 bitumen. The Marshall Mix design using CRMB 55 with 0.04 % Zycosoil chemical, reflects the significant rise in stability, unit weight and flow values for better compaction and enhancing the workability conditions.

Performance of High-Dose Reclaimed Asphalt Mixtures (RAPs) in Hot In-Place Recycling Based on Balanced Design.

This study endeavors to employ a balanced design methodology, aiming to equilibrate the resistance to rutting and cracking exhibited by hot in-place recycling asphalt mixtures containing a high dose of reclaimed asphalt pavement (RAP). The primary goal is to ascertain the optimal amount of new binder necessary for practical engineering applications, ensuring a balanced rutting and crack resistance performance of recycled asphalt mixtures. The investigation mainly employed wheel-tracking tests and semi-circular bending tests to assess the rutting and cracking performance of recycled asphalt mixtures with a different dose of RAP (in China, it is common to use RAP with 80% and 90% content as additives for preparing hot in-place recycling asphalt mixtures), and varying quantities of new binders (10%, 20%, and 30% of the binder content in the total RAP added). The results indicated that the addition of new binder reduced the resistance to rutting of the recycling asphalt mixtures but improved their resistance to cracking. Furthermore, for the recycling asphalt mixture with 80% RAP content aged for 5 days, the optimal new binder content is 1.52%, while the mixture with 90% RAP content requires 1.23% of new binder. After 10 days of aging, the optimal new binder content for the recycling asphalt mixture with 80% RAP content is 1.55%, while the mixture with 90% RAP content requires 1.28% of new binder.

Analysis of the compactibility of bituminous mixtures for reflective crack relief interlayers (RCRI)

The physical properties determining the strength parameters of bituminous mixtures are strongly influenced by the processes of placement and compaction. The effectiveness of this process depends on the compactive effort and is directly related to the mixture temperature. This research focused on the assessment of compactibility of mixtures designed for reflective crack relief interlayers (RCRI) which, in most cases, are applied in thin layers. The materials analysed for compactibility in this research included AC – asphalt concrete, AC AF – asphalt concrete “anti-fatigue”, SMA – stone mastic asphalt and SMA-MA – stone mastic asphalt rich in bitumen mastic. The gyratory compactor method was used to determine the compaction slope K, the locking point LP and the compaction densification index CDI. All the tested mixtures were fine-graded, i.e., contained grains up to 8 mm in diameter, each mixed with a different type of bituminous binder. The values of CDI show a substantially greater input of energy required for compaction of high-polymer modified mixtures, as compared to mixtures of the same design, yet containing the 50/70 bitumen. Locking point analysis showed that SMA and SMA-MA mixtures attain 98% relative compaction before reaching the locking point at which the aggregate skeleton starts to resist further compaction. This is quite the opposite as with the AC and AC AF mixtures. Among the tested mixtures the best compaction behaviour was observed in the case of SMA-MA 8 50/70, and this over a wide range of working temperature (100–160C°) and pressures (150 kPa, 600 kPa). The design of the mixture SMA-MA as an anti-fatigue layer assumes an increase in the content of filler and binder, as compared to conventional SMA. This composition is bound to reduce the resistance to compaction, i.e., provide a better compaction behaviour as compared to a conventional SMA mixture.

Microstructure and mechanical properties of continuous carbon fiber-reinforced SiC ceramic composite fabricated by direct ink writing

The direct ink writing (DIW) technique is considered efficient for manufacturing complex-shaped Cf/SiC composites. However, the SiC slurry with high load has poor flow ability and covering-fibers properties, resulting in numerous gaps between the ceramic matrix and fibers. This study utilized DIW to manufacture Cf/SiC composites and improved the slurry's printing ability by adjusting the binder content. Moreover, the printing parameters, such as the angle between the fiber nozzle and slurry nozzle and the slurry nozzle size, were optimized to enhance the accuracy of the body structure and the filling effect of the slurry on the fiber gaps. The results showed that a binder content of 0.4 wt% produced excellent thixotropic, viscoelastic, and shear thinning behavior in the slurry. By using a fiber nozzle angle of 60° and a nozzle diameter of 1.55 mm, the slurry effectively filled the gaps between the fiber bundle and matrix, reducing the number and size of pores in the SiC matrix. These improvements greatly enhance the density, strength, and fracture toughness of the Cf/SiC composites. Therefore, this research demonstrated that optimizing the printing parameters not only improved the structural accuracy of the printed bodies but also greatly enhanced the properties of the ceramic matrix composites.

Automating the determination of low-temperature fracture resistance curves of normal and rubberized asphalt concrete in single-edge notched beam tests using convolutional neural networks

As materials undergo large-scale yielding or exhibit large sizes of fracture process zone in the crack tip region, multi-parameter fracture concepts should be employed to describe the complex crack-tip stress-strain fields. Fracture resistance curves (R-curves) are an established tool in characterizing the entire fracture process of such materials. However, for complex materials such as bituminous mixtures, the development of these curves is subject to experimental and computational intricacies. In this research, a framework is developed to automate the construction of R-curves for normal and rubberized asphalt concrete (AC) mixtures. AC mixtures are produced using PG58–22 and PG58–28 binders. Limestone and siliceous aggregates are used, and three binder contents are considered for the mixtures. Single-edge notched beam (SE(B)) fracture testing is conducted on AC beams with two different notch patterns. A convolutional neural network (CNN) model is developed and trained over 1260 test images with varying temperatures, notch geometries, and setups. The CNN model was used to detect the growing crack on the beam surface and each crack-detected image was sent to an image processing framework to measure the crack length. Crack extension increments were calculated and synchronized with test time and magnitude of load, load-line displacement, and cumulative fracture energy, and the R-curve could be constructed. A training accuracy of 0.91 was obtained for the model and a loss of below 0.10 as a result of a hyperparameter tuning indicating reliable classifications by the CNN architecture. The R-curves showed desirable agreement for control mixtures at temperatures of 0 °C and −15 °C. As the mixtures are rubberized, the R-curves showed favorable agreement in the crack blunting phase, transition zone, as well as the unstable propagation phase at −20 °C. Cohesive energy magnitudes were compared for the two methods with a Pearson coefficient of 0.81 while fracture rate and fracture energy magnitudes showed favorably close magnitudes with coefficients of 0.89 and 0.98 respectively.

Fatigue Performance Evaluation of Fiber-Reinforced Asphalt Mixtures with Four-Point Bending Beam and Uniaxial Fatigue Tests

This study aimed to evaluate the fatigue cracking potential of aramid fiber–reinforced asphalt mixtures. Three fiber-reinforced asphalt mixtures (FRAMs) were prepared employing a singular aggregate type (diabase stone), one binder type (PG76-22), and two distinct combinations of aramid fibers at varying dosages. Two types of fiber were used at different dosages by weight of mix: polyolefin/aramid (PFA) fibers at a dosage 0.05% and sasobit-coated aramid (SCA) fibers at dosages of 0.01% and 0.02%. Additionally, an unreinforced (control) mix was also produced for comparison purposes. Each of the mixtures was produced at a batch plant, adhering to the fiber manufacturer’s recommended mixing methods, while maintaining a constant binder content of 5.5% based on the total mix weight. Four-point beam (4PB) fatigue, uniaxial fatigue (UF), and Texas overlay tests (OT) were performed to characterize the fatigue and reflective cracking behavior of FRAM. The 4PB test results suggest that FRAM improved the fatigue life at lower strain levels (400 µε and 600 µε); however, at higher microstrain (800 µε) level, FRAM exhibited lower fatigue life than the control mix. Damage characteristic curves obtained from the UF tests showed better fatigue tolerance for reinforced mixtures, regardless of microstrain level. For cycles to failure under tensile loading, UF and OT test results indicated lower fatigue life of reinforced mixtures compared with the control mix. Therefore, under flexural loading the fiber-reinforced asphalt mixtures tend to improve the fatigue life. However, for direct tension load, reinforced mixtures tend to deteriorate the fatigue life when comparing cycles to failure at constant strain amplitude.