Durability Test Research Articles

Innovative and environmentally friendly MICP surface curing: Enhancing mechanical and durability properties of concrete

Concrete curing is a critical factor influencing its mechanical properties and durability. Traditional curing methods, such as water curing and plastic film curing, have significant limitations, including high water consumption and environmental pollution. This study introduces Microbial Induced Carbonate Precipitation (MICP) as an innovative, environmentally friendly curing method for ready-mixed concrete, addressing the urgent need for sustainable construction practices. The feasibility of MICP surface curing is investigated through comprehensive mechanical and durability tests, coupled with microscopic analyses to understand the underlying mechanisms. The results demonstrate that MICP curing substantially enhances concrete performance. Compared to traditional water curing, the samples cured using MICP have increased compressive strength and splitting tensile strength by up to 31.69% and 24.66%, respectively. Additionally, MICP surface curing significantly reduced capillary water absorption, electric flux, and chloride ion migration coefficient by 12.83%, 15.50%, and 17.36%, respectively. It is found that the optimal concentration of Ca2+ in the MICP solution initially improves concrete performance, which then diminishes at higher concentrations due to bacterial activity inhibition. Spraying the MICP solution at appropriate intervals and increasing the number of treatments further improved concrete properties by ensuring a more extensive and dense deposition of CaCO3. Microscopic analyses, including XRD, TG, and SEM-EDS, revealed that MICP surface curing leads to the formation of vaterite and calcite, which densely cover and fill microscopic cracks and pores, ensuring adequate hydration and simultaneously enhancing the concrete's mechanical and durability properties. This study concludes that MICP surface curing provides superior performance than traditional methods and offers a more sustainable and environmentally friendly curing method.

Strength and Durability Studies on Concrete Utilizing Sewage Sludge Ash and Treated Sewage Water

The effects of incorporating sewage sludge ash and treated sewage water on the strength and durability of concrete, with the goal of evaluating their viability as sustainable alternatives in construction materials. The sewage sludge ash was used as a replacement material to cement after burning of sewage sludge with high temperature of 800oC. So obtained sewage sludge ash was analysed for chemical, physical and morphological properties. Burning sewage sludge at high temperatures imparts pozzolanic properties to the resulting ash, which, when used as a cement replacement, improves concrete's compressive and tensile strengths. Various SSA replacement levels (5%, 10%, 15%, 20%, and 25%) were tested, with 15% SSA showing the highest strength gains. SSA affects setting time and workability, but treated sewage water does not significantly impact concrete properties. Concrete with SSA showed superior strength compared to conventional mixes with both fresh and treated water. Durability tests revealed that while SSA concrete experienced minor efflorescence in saltwater, it resisted acid attacks better than conventional concrete, indicating its good durability.

Insight on physical–mechanical properties of one-part alkali-activated materials based on volcanic deposits of Mt. Etna (Italy) and their durability against ageing tests

In recent years, there has been a growing interest in one-part alkali-activated materials, which utilize solid-form alkali activators, within the construction industry. This approach is becoming popular due to its simpler and safer application for cast-in-situ purposes, as compared to the conventional two-part method. At this purpose, we have pioneered the use of volcanic deposits of Mt. Etna volcano (Italy) as precursor for the synthesis of a unique one-part formulation. This was done to assess its performance against both traditional and two-part alkali-activated materials. The study employed a comprehensive range of investigative techniques including X-ray powder diffraction, Fourier transform infrared spectroscopy, hydric tests, mercury intrusion porosimetry, ultrasound, infrared thermography, spectrophotometry, contact angle measurements, uniaxial compressive strength tests, as well as durability tests by salt crystallization and freeze–thaw cycles. The key findings on the studied samples are as follows: i) small size of pores and slow absorption-drying cycles; ii) satisfying compactness and uniaxial compressive strengths for building and restoration interventions; iii) high hydrophily of the surfaces; iv) lower heating dispersion than traditional materials; v) significant damage at the end of the salt crystallization test; vi) excellent resistance to freeze–thaw cycles. These newly developed materials hold promises as environmentally friendly options for construction applications. They offer a simplified mixing process in contrast to the conventional two-part alkali-activated materials, thus providing an added advantage to this class of materials.

Optimizing plastic waste inclusion in paver blocks: Balancing performance, environmental impact, and cost through LCA and economic analysis

Rising waste plastic and cement used in construction raises environmental concerns. Substituting cement with recycled plastic waste (PW) in paver blocks offers an eco-friendly solution. However, a comprehensive life cycle assessment (LCA) economic and performance analysis is lacking. This study addresses this gap by evaluating the compressive strength and durability properties of PSPB while also conducting LCA and economic evaluations to identify the most optimal solutions for enhanced performance. Compressive strength tests determined that a 30% PW replacement yielded optimal results. The durability tests showed that PW paver blocks have significantly lower water absorption compared to conventional blocks, and they maintained a compressive strength of 20 MPa, which is acceptable for light traffic applications, even at elevated temperatures. LCA highlights that cement usage accounts for over 80% of climate change emissions for conventional blocks. Sensitivity analysis shows shipping distance, truck capacity, and energy use greatly affect environmental outcomes. Complete replacement of cement with PW is considered more environmentally friendly. Economic analysis indicates plastic pavers are 52% more cost-effective than cement-based ones. This research offers vital insights into the practicality, environmental impact, and financial sustainability of integrating PW into paver blocks.

Bis-cationic crosslinked anion exchange membranes based on carbazole-containing polyaromatics with excellent ionic conductivity for alkaline water electrolysis

As the core component in anion exchange membrane water electrolyser (AEMWE), anion exchange membrane (AEM) directly determines the electrolysis performance and long-term durability of AEMWE. Herein, we synthesized novel poly(carbazole-p-terphenylpiperidine) (PCTP-x) copolymers and then prepared a series of bis-cationic cross-linked AEMs (QPCTP-x-bpip) using the Menshutkin reaction between the cross-linker 4,4′-trimethylenebis(1-methylpiperidine) and the alkyl bromide on the polymer side chains. For comparison, non-crosslinked AEMs containing alkylpiperidinium side chains (QPCTP-x-pip) were prepared via a grafting reaction of alkyl bromide with 1-methylpiperidine. The bis-cationic crosslinked membrane exhibited high hydroxide conductivity of 190.0 mS cm−1, and demonstrated outstanding alkaline stability in a 1 M KOH solution at 80 °C, retaining more than 90 % of the initial hydroxide conductivity and tensile strength after 2200 h alkaline treatment. Meanwhile, the flexural carbazole backbone enhanced polymer solubility, enabling the utilization of QPCTP-20-pip as an anion exchange ionomer (AEI) in AEMWE. For the water electrolysis testing, AEMWE employing QPCTP-20-bpip as the AEM and QPCTP-20-pip as the AEI exhibited excellent performance, achieving a current density of 2910 mA cm−2 at 2.0 V using a 1 M KOH feed at 80℃. Moreover, the voltage increase during the in-situ durability test over 200 h was a mere 0.65 mV/h, demonstrating its promising potential for AEMWE applications.

Crystalline-Amorphous IrOx Supported on Perovskite Nanotubes for pH-Universal OER.

Designing catalysts with desirable oxygen evolution reaction (OER) performance under pH-universal conditions is of great significance to promote the development of hydrogen production. Herein, we successfully synthesized a crystalline-amorphous IrOx supported on perovskite oxide nanotubes to obtain IrOx@La0.6Ca0.4Fe0.8Ni0.2O3 with superior OER performance in whole pH media. The overpotential of the IrOx@La0.6Ca0.4Fe0.8Ni0.2O3 catalyst in media of pH 14, 7.2, and 1 has been demonstrated to be 120, 400, and 143 mV, respectively, with no significant element dissolution as well as double-layer capacitance decay after the durability test. Through comparative experiments with IrOx@CNT and the physical mixture of IrOx and La0.6Ca0.4Fe0.8Ni0.2O3, it is found that the strong metal-support interaction (SMSI) in IrOx@La0.6Ca0.4Fe0.8Ni0.2O3 makes IrOx exist in an amorphous state rich in Ir3+, which is closely associated with the surface-active species Ir-OH. Through the regulation of Ir by a perovskite oxide support at the heterointerface, the reaction breaks through the limitation of the adsorbate evolution mechanism (AEM) and converts to a lattice-oxygen-mediated mechanism (LOM), which was fully demonstrated by the addition of the probe tetramethylammonium cation (TMA+), a LOM reaction intermediate, to the electrolyte. This work fills the research gap of perovskite oxide supported Ir-based catalysts with heterogeneous structures, providing an excellent strategy for the structural design of efficient pH-universal OER catalysts for hydrogen production systems.

Experimental study on the improvement of bamboo properties using amide polymer repair material based on the principle of self-energy dissipation

Traditional bamboo and wood components have different holes due to their own and external factors, and the appropriate hole repair technology is the key to improve the component's energy dissipation capacity. In this paper, based on the principle of in-situ free radical polymerization and hollow glass microsphere (HGM) reinforced polymer, PAM hydrogel (PAMHG) with better deformation recovery ability and PAM/HGM amide polymer (AP) with better mechanical properties were prepared. Based on the principle of self-energy dissipation of components, AP is used to improve the deformation capacity of hollow bamboo. The ratio of PAMHG and AP was optimized by single factor test and orthogonal test. The performance of AP was verified by bending test, SEM, energy consumption analysis，durability test and statistical analysis of small diameter round bamboo. The size of the bamboo sample is 250 mm (L)×15 mm (D)×2.5 mm (t), in accordance with LY/T 3347–2023 " Testing methods for physical and mechanical properties of small diameter round bamboo " (China). The results showed that an appropriate amount of glycerol could effectively improve the volume stability of the hydrogel. HGM effectively improved the strength of the polymer, and when the mass ratio of HGM/PAM was 0.48, the maximum compressive strength was 0.8 MPa, which was 2.4 times higher than that of the undoped HGM, and at this time, the optimal polymer ratios were 25 g of AM, 1 g of MBA, 0.01 g of APS, 2 g of TEA, 2 g of Carbomer SF-1, a volume ratio of 1:1 of glycerol/deionized water that the dispersion medium was 70 ml, and HGM was 12 g. The average energy dissipation of grouted bamboo at ultimate load was 2.02 times that of the control group, and the highest bending strength and elastic modulus were 128.01 MPa and 11.24 GPa, which were 41.39 % and 39.75 % higher than that of the control group, respectively. The SEM results revealed that the AP partially prepolymerized solution could infiltrate into the cells and pores of the bamboo material to achieve filling, bonding, as well as reinforcing the bamboo tissue. In addition, the durability test shows that AP has good resistance to environmental pressure. The results of this paper can provide a reference for the restoration materials of bamboo and wood components.

Two-dimensional Boridene Nanosheets for Efficient Electrochemical Nitrogen Fixation under Ambient Conditions.

The carbon-free electrocatalytic nitrogen reduction reaction (NRR) is an alternative technology to the current Haber-Bosch method, that can be conducted under ambient conditions, and directly converting water and nitrogen (N₂) into ammonia (NH₃). However, the limited activity and selectivity of NH₃ electrosynthesis hinder the practical applications of NRR. In this study, we present a novel type of electrocatalyst called boridene nanosheets enriched with metal vacancies that are specifically designed for efficient electrocatalytic NRR under ambient conditions. Electrochemical testing in a 0.1 M phosphate-buffered saline (PBS) electrolyte demonstrates that boridene exhibits a high Faradaic efficiency of 66.7% for NH₃ production at -0.2 V vs. RHE, with a maximum NH₃ yield rate of 23.6 µg h-1 mg cat-1 at -0.4 V vs. RHE. Durability tests show that boridene maintains significant stability throughout multiple cycles of NRR. Mechanistic insights are obtained through in situ FTIR spectroscopy, revealing that boridene exhibits a preference for the distal pathway during the process of NRR. These findings highlight the potential of boridene as an efficient and stable catalyst for sustainable NH₃ synthesis.

Highly-Branched PtCu Nanocrystals with Low-Coordination for Enhanced Oxygen Reduction Catalysis.

Low-coordination platinum-based nanocrystals emanate great potential for catalyzing the oxygen reduction reactions (ORR) in fuel cells, but are not widely applied owing to poor structural stability. Here, several PtCu nanocrystals (PtCu NCs) with low coordination numbers were prepared via a facile one-step method, while the desirable catalyst structures were easily obtained by adjusting the reaction parameters. Wherein, the Pt1Cu1 NCs catalyst with abundant twin boundaries and high-index facets displays 15.25 times mass activity (1.647 A mgPt -1 at 0.9 VRHE) of Pt/C owing to the abundant effective active sites, low-coordination numbers and appropriate compressive strain. More importantly, the core-shell and highly developed dendritic structures in Pt1Cu1 NCs catalyst give it an extremely high stability with only 17.2% attenuation of mass activity while 61.1% for Pt/C after the durability tests (30 000 cycles). In H2-O2 fuel cells, Pt1Cu1 NCs cathode also exhibits a higher peak power density and a longer-term lifetime than Pt/C cathode. Moreover, theoretical calculations imply that the weaker adsorption of intermediate products and the lower formation energy barrier of OOH* in Pt1Cu1 NCs collaboratively boost the ORR process. This work offers a morphology tuning approach to prepare and stabilize the low-coordination platinum-based nanocrystals for efficient and stable ORR.

Phase-changing NIPAM-AM/ATO hydrogels for thermochromic smart windows with highly adaptive solar modulation

Improving the solar regulation and reducing the response temperature of thermochromic smart windows are pivotal importance for energy-saving buildings. However, these two strategies are challenging to be integrated into one window. Herein, a novel composite hydrogel based on N-isopropylacrylamide (NIPAM) doped with antimony-doped tin oxide (ATO) nanoparticles and acrylamide (AM) was developed for producing a high-performance smart window, which successfully achieved enhanced solar energy regulation and reduced response temperature. This smart window was fabricated by combining a reversible thermoresponsive hydrogel (TAH) that acted as a thermochromic material with a ATO multilayer film that performed as a transparent heater. The as-prepared smart window could modulate solar light over a range from ultraviolet (UV) to infrared (IR) radiation and achieved active responses to high-temperature weather. The smart window showed high luminous transmittance (Tlum, 82.92 %) together with an excellent solar modulation performance (ΔTlum = 73.31 %, ΔTIR = 38.26 %, and ΔTsol = 60.74 %), and a lower critical solution temperature of 32 °C. Even after 120 high- and low-temperature cyclic durability tests, the smart windows still exhibited a high solar modulation capability. In outdoor demonstrations, the as-prepared smart window exhibited a promising temperature regulation ability under strong solar irradiation. Therefore, the present universal modification framework provided some insights for the future design of energy-saving windows.

Optimized determination of vehicle durability test specification correlated with user-targeted fatigue life using the multi-index decision-making approach

Optimized determination of vehicle durability test specification correlated with user-targeted fatigue life using the multi-index decision-making approach

Investigation of functionalized graphene oxide incorporated superabsorbent polymers for enhanced durability, hydration, microstructure and mechanical strength of modified concrete

ABSTRACT This study focuses on enhancing cementitious materials by incorporating silanized graphene oxide (SGO) and superabsorbent polymers (SAPs), aiming to improve their mechanical and durability properties. The primary goal is to evaluate the effects of SGO/SAP composites on the hydration, absorption, shrinkage, and overall performance of concrete. The composites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) to understand their microstructure. Mechanical and durability tests revealed that adding SGO/SAP composites significantly increased the mechanical strength and water absorption capabilities of the concrete. The compressive strength, split tensile strength, and flexural strength of the SGO/SAP-modified concrete were measured at 57 MPa, 4.90 MPa, and 8.25 MPa, respectively. Shrinkage tests demonstrated the composite hydrogel’s excellent water-holding capacity at 0.3 wt.% SGO/SAP, facilitating internal curing in concrete structures. FE-SEM analysis indicated a reduction in microcracks due to the presence of SGO/SAP. The improvements are attributed to the synergistic effects of SGO and SAP, which enhance water retention, dispersion, and interfacial bonding within the cementitious matrix. The microstructural studies confirmed the exceptional stability of the SGO/SAP-modified mix, emphasizing its potential as an additive to improve concrete properties. This research underscores the significant potential of SGO and SAP in advancing the performance of cement-based materials, highlighting their applicability in infrastructure development and construction for creating more durable and high-performing concrete structures.

Multiscale textured solar absorber coatings for next-generation concentrating solar power

A high-temperature stable solar absorber is crucial for next-generation (Gen3) concentrating solar power (CSP) plants, to enable high temperature operation, maximize power generation efficiency, and thereby reduce the levelized cost of energy. This study presents novel, fractal-textured solar absorber coatings whose multiscale feature scales effectively match the visible region of the solar spectrum, leading to superb absorptive properties. Single and bimetallic oxide coatings of copper, cobalt and manganese were prepared on Inconel 625 substrates using electrodeposition. The effect of electrodeposition parameters and annealing temperature are systematically studied to optimize the morphology and properties of the oxide coatings. Multiscale textured bimetallic coatings of copper manganese oxide and copper cobalt oxide demonstrate a superior absorptance of 0.985, a remarkably low emittance <0.45 and an exceptional optical efficiency of ∼96 % under Gen3 CSP operating conditions, surpassing previously reported values in the literature by about 5 %. Durability tests confirmed the coatings’ steadfast endurance of mechanical and environmental stress, making them suitable for long-term application in harsh CSP environments.

A Janus Platinum/Tin Oxide Heterostructure for Durable Oxygen Reduction Reaction.

Designing efficient and durable electrocatalysts for oxygen reduction reaction (ORR) is essential for proton exchange membrane fuel cells (PEMFCs). Platinum-based catalysts are considered efficient ORR catalysts due to their high activity. However, the degradation of Pt species leads to poor durability of catalysts, limiting their applications in PEMFCs. Herein, a Janus heterostructure is designed for high durability ORR in acidic media. The Janus heterostructure composes of crystalline platinum and cassiterite tin oxide nanoparticles with carbon support (J-Pt@SnO2/C). Based on the synchrotron fine structure analysis and electrochemical investigation, the crystalline reconstruction and charge redistribution at the interface of Janus structure are revealed. The tightly coupled interface could optimize the valance states of Pt and the adsorption/desorption of oxygenated intermediates. As a result, the J-Pt@SnO2/C catalyst possesses distinguishing long-term stability during the accelerated durability test without obvious degradation after 40000 cycles and keeps the majority of activity after 70000 cycles. Meanwhile, the catalyst exhibits outstanding activity with half-wave potential at 0.905V and a mass activity of 0.355AmgPt -1 (2.7 times higher than Pt/C). The approach of the Janus catalyst paves an avenue for designing highly efficient and stable Pt-based ORR catalyst in the future implementation.

Integration of Multifunctionality in a Colloidal Self‐Repairing Catalyst for Alkaline Water Electrolysis to Achieve High Activity and Durability

Self‐repairing catalysts are useful for achieving alkaline water electrolyzers with long lifetimes under intermittent operation. However, rational methodologies for designing self‐repairing catalysts have not yet been established. Herein, hybrid cobalt hydroxide nanosheets (Co‐ns), with a high deposition (repairing) rate, and β‐FeOOH nanorods (Fe‐nr), with high oxygen evolution reaction (OER) ability, are electrostatically self‐assembled into composite catalysts. This strategy is developed to integrate multifunctionality in self‐repairing catalysts. Positively charged Co‐ns and negatively charged Fe‐nr form uniform composites when dispersed in an electrolyte. These composites are electrochemically deposited on a nickel electrode by electrolysis at 800 mA cm−2. Co‐ns form a conductive mesoporous assembly of CoOOH nanosheets as a support. Fe‐nr are then distributed on the CoOOH nanosheets as active sites for the OER. Because of the high deposition rate of Co‐ns, the amount of Fe‐nr deposited increases 22 times compared to when Fe‐nr is deposited alone, and the OER current density increases 14 times compared to that of Co‐ns alone. The composite self‐repair catalyst shows the highest activity and durability under an accelerated durability test (ADT), and its degradation rate decreases from 84 μV cycle−1 (Fe‐nr only) to 60 μV cycle−1 (composite catalyst) under ADT conditions without repair.

Investigating the performance and durability of high mechanical milling nano pulverised refused SCMs

This study investigated the performance and durability of high-mechanical-milling nano-pulverized industrial reject supplementary cementitious materials (SCMs). The research utilized industrial reject (IR-1), specifically Ground Blast Furnace Slag (GBFS), as the SCM. As-received IR-1 GBFS was milled for 90 minutes to achieve nano-sized particles, and its properties were compared with the un-milled, or before-milled (BM) material. Three pozzolanicity tests were conducted to compare the before milled (BM) and after-milled (AM) materials. Additionally, M30 grade concrete mixes were developed with cement partially replaced by 30 %, 35 %, and 40 % using both BM and AM IR-1 materials. Mechanical performance, including compressive strength, flexural strength, and split tensile strength, along with durability tests such as water absorption, sorptivity, and rapid chloride penetration, were conducted for the BM and AM IR-1 blended concretes. The results showed that AM IR-1 blended concrete achieved the required design strength at a 30 % cement replacement level. Furthermore, the AM IR-1 blended concrete exhibited 40 % higher compressive strength, 39 % higher flexural strength, and 29 % higher split tensile strength compared to the control concrete. Durability testing also revealed significant improvements in AM IR-1 blended concrete, with reductions of 19.65 % in water absorption, 24.71 % in sorptivity, and 38 % in chloride penetration. This study demonstrates that industrial waste, such as GBFS, can be effectively utilized as a sustainable alternative to traditional materials in the construction industry. Additionally, nano-pulverization treatment significantly enhances the pozzolanicity and overall performance of materials that may not meet the physicochemical standards specified in IS 3812-(Part 1):2017 and ASTM C618–19.

Vapor-feed direct methanol fuel cells using pure methanol

This work optimizes the performance of the direct methanol fuel cell (DMFC) to increase its efficiency and strengthen its validity in portable power generation. Specifically, this work focuses on optimizing vapor-feed supply techniques and incorporating water management layers (WMLs) to analyze their effect on methanol crossover. The significance of the vapor-feed supply technique is to enhance the reaction kinetics of the methanol oxidation reaction (MOR) and enable the use of pure methanol (MeOH) as a fuel. Pure methanol is the ideal fuel for the DMFC as it has the highest possible energy density compared to dilute concentrations. However, use of pure methanol is hindered by methanol crossover, which is regarded as the largest technical barrier to commercializing DMFCs. This study measured methanol crossover through a CO2 sensor attached to the cathode outlet and added hydrophobic WMLs to the cathode to alleviate the methanol crossover. The hydrophobic WMLs increased the mass transfer resistance to generate a pressure gradient that encourages water backflow for use in both the proton exchange membrane (PEM) and anode reactions. The influence of vapor flow rate and fuel concentration will also be explored to show their impact on performance and methanol crossover. Likewise, long-term consumption and durability tests were conducted with and without a WML to dictate the WML’s superior fuel efficiency, total efficiency, energy density, and reduced methanol crossover using pure methanol. The addition of the WML increased the energy density of the vapor feed DMFC, using pure methanol, from 705.9 Wh kgMeOH-1 to 867.7 Wh kgMeOH-1 and lowered the crossover current density by 14.8 % when discharged at a constant 200 mA cm−2.

Influence of printing parameters on the durability of 3D-printed limestone calcined clay cement mortar: overlap between filaments and nozzle offset

Large-scale cement-based Additive Manufacturing (AM), also known as 3D Concrete Printing (3DCP), is a promising technique to innovate the construction industry. The durability properties of printed specimens have been studied and compared to those of cast samples in the literature. However, no study has evaluated and quantified the influence of printing parameters on the durability of 3DCP specimens. Aspects such as nozzle offset and the overlap between printed filaments, among others, may influence the porosity of the samples and, therefore, the durability properties. This paper aims to investigate the influence of printing parameters on the durability of 3D manufactured mortar samples. The effects of the printing height and overlap between filaments on the durability properties were analysed in the X, Y and Z axes. An experimental investigation of 39 samples was conducted. Printed and cast specimens were subjected to a curing process for up to 90 days in a water tank at a temperature of 20 °C. Durability tests (oxygen permeability, electrical resistivity, and porosity) were performed at 7, 28 and 90 days. Relationships between the printing variables and durability properties with time were derived. Based on this study, it is concluded that the long-term properties of concrete are significantly sensitive to the overlap between filaments and the nozzle offset. In general, the durability properties were enhanced by modifying the printing parameters. In particular, an overlap of 4 mm showed the most promising results in this regard.

Effects of soil composition and curing conditions on the strength and durability of Cr3+-crosslinked biopolymer-soil composites

Stabilized soil composites incorporating Cr3+-crosslinked xanthan gum (CrXG), a self-stiffening cation-crosslinked biopolymer, have recently emerged as sustainable construction materials for earthen structures. However, the influence of curing conditions and soil composition in altering the mechanical properties of CrXG–soil composites has so far received limited attention. This study investigates the effects of fine contents and curing conditions on the time-dependent strength development and durability of CrXG-soil composites. CrXG-soil composites, ranging from poorly graded sand to clayey silty sand, are subjected to unconfined compressive strength (UCS) and durability tests under various curing conditions, including wet, submerged, and dry conditions. Microscopic structural changes are characterized using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The results showed that the UCS of CrXG-soil composite increases nonlinearly, reaching up to 4.8 times the initial wet UCS after 28 days of curing, closely aligning with predictions from a hyperbolic model. Notably, CrXG-soil compositions with a clay-sand mixture (CSM) containing 15 % fine content (CSM15) demonstrated consistent strength parameters across all curing conditions in UCS tests. CSM15 also maintains a 90 % of durability index after eight dry-wet cycles and a dry UCS of 300 kPa after 130 days of atmospheric weathering. Microscopic-scale analysis confirms the stable agglomeration of CrXG-clay matrices between sand grains, with the peak wavelength of the major functional group remaining constant, even under multiple cycles. These findings contribute to a deeper understanding of CrXG–soil composites, offering valuable insights into optimizing soil compositions and enhancing the technical feasibility of applying these composites as a sustainable surface protection strategy for earthen structures, such as levees and road slopes.

Development and evaluation of STRC coating for cooling asphalt pavement and mitigating urban heat island effects

To mitigate the negative impacts of urban heat island (UHI) effects on modern cities, this study developed and evaluated a novel cool coating, solar thermal reflective coatings (STRC), for reducing asphalt pavement temperatures. Firstly, the optical properties were characterized using UV-Vis-NIR spectroscopy, and the thermal performance of eight STRC formulations was assessed using a custom-built testing apparatus. Subsequently, the microstructure and elemental composition were examined using scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). Finally, the optimized coating was applied to asphalt concrete, and its long-term performance and stability were confirmed through durability tests, including water immersion test, temperature variation endurance test, and radiation cycle test. The results showed that chromium sesquioxide (Cr₂O₃), a critical pigment of STRC, exhibited a high near-infrared reflectance of 54.76 % and a lower visible reflectance of 10.22 %. Among the eight STRC formulations, STRC5 demonstrated balanced performance with a visible reflectance of 35.69 % and a near-infrared reflectance of 71.85 %. The microstructure of STRC5 was uniform with minimal surface defects. When STRC5 was applied to asphalt concrete, it achieved significant cooling effects, maintaining a mean temperature of 49.51 °C compared to 60.07 °C for uncoated samples, resulting in a maximum temperature difference of 10.56 °C after 4 h of light exposure. Durability test results confirmed the long-term performance and stability as the coating withstood extreme temperature fluctuations from −20 °C to 60 °C and 72 h of water immersion. In conclusion, STRC5 demonstrated great potential to effectively cool asphalt pavement and mitigate UHI effects.