Durability Criteria Research Articles

Trial Design of a Truss Bridge Prefabricated Using a Rectangular Steel Tube—Ultra-High-Performance Concrete Composite

In order to promote the development of bridge assembly technology and accelerate the application of rectangular steel-tube–concrete composite truss bridges, this study focuses on the Yellow River Diversion Jiqing Main Canal Bridge as the engineering example and conducts a numerical analysis of a rectangular steel-tube–concrete composite truss bridge. Based on the results of the analysis, structural optimization is achieved in three dimensions—structural design, construction methods, and force analysis—leading to the establishment of key design parameters for through-type ultra-high-performance rectangular steel-tube–concrete composite truss bridges. The results show that filling the hollow sections with ultra-high-strength concrete can significantly enhance the load-bearing capacity. Additionally, employing prestressed concrete components addresses the bending and tensile load capacity challenges of composite structures, thus maximizing the material strength advantages. The proposed preliminary design scheme incorporates prestressed PBL-reinforced tie rods filled with ultra-high-performance concrete with optimal design parameters, such as high span ratios, wide span ratios, and ideal segment lengths, are suggested to ensure that the strength, stiffness, and stability comply with relevant standards. While ensuring that the structure meets safety, applicability, and durability criteria, the preliminary design scheme reduces steel usage by 23.5%, concrete usage by 11.6%, and overall costs by 17.29% compared to the original design. The proposed design demonstrates distinct advantages over the original in terms of mechanical performance, construction efficiency, economic viability, and durability, highlighting its promising application potential.

Sustainable Geopolymer Concrete for Pavements: Performance Evaluation of Recycled Concrete Aggregates in Fly Ash-Based Mixtures

This study investigates the feasibility of incorporating recycled concrete aggregates (RCA) into fly ash-based geopolymer concrete for sustainable pavement applications. The research evaluates RCA’s physical and mechanical properties compared to virgin coarse aggregates (VCA) and assesses the performance of geopolymer concrete mixtures with up to 40% RCA replacement. Aggregate characterization revealed that RCA exhibited higher water absorption (4.39%), crushing value (20.9%), impact value (28.2%), and abrasion value (26.1%) compared to VCA, yet these values remained within acceptable limits for pavement applications. Geopolymer concrete specimens were tested for compressive strength, water absorption, abrasion resistance, and chloride ion permeability. Results indicated that increasing RCA content led to a gradual decrease in compressive strength, from 40.16 MPa to 33.52 MPa, while water absorption increased from 5.2% to 6.8%. Abrasion resistance declined as RCA content rose, and chloride ion penetrability increased from 1687 to 2196 coulombs. However, mixtures with up to 20% RCA replacement met the strength and durability criteria required for pavement construction. This study demonstrates the potential for utilizing RCA in geopolymer concrete pavements, offering a sustainable solution for waste management and resource conservation in the construction industry.

The reliability function of the case-hardened teeth of wheels of cylindrical gears

BACKGROUND: Methods for calculating the load capacity and reliability of gears, accepted as standardized both at the national and international levels, are based on the laws of distribution of random variables, considered as the only possible ones, which is not entirely true. As a result, the developed gears have either overestimated or underestimated reliability, which leads to their low competitiveness. Therefore, the development of methods for assessing the reliability of the case-hardened gears, taking into account the actual laws of distribution of random variables, remains relevant, as it will make it possible to design competitive transmissions. AIM: Improvement of the current approach to calculating the reliability function of case-hardened gears according to their strength performance criteria. METHODS: The improved approach to calculating the reliability function is based on improved classical methods for testing the load capacity of cylindrical gears for contact and bending stresses (GOST 21354-87 and ISO 6336). The methodology for calculating the reliability function according to the criterion of deep contact durability is based on the Lebedev-Pisarenko criterion, the formulae of which have been modified for application to gears by V.I. Korotkin. The implementation of the proposed methods was carried out in MathCAD software. RESULTS: The methods for calculating the reliability function of the case-hardened gears according to the criteria of contact and bending durability, which take into account the variable value of the misalignment in the gearing caused by the deformation of the shafts, the bearing rings and the housing (force misalignment), are proposed. In addition, the dependence of the calculation results of the reliability function of cylindrical gears on the method of setting the force misalignment in the gearing of teeth (constant or variable value) is shown. Validation of the improved approach was carried out using the data available in the scientific and technical literature on failures of the case-hardened gears. The scientific novelty of the research lies in the proposed method for calculating the reliability function of the case-hardened gears according to the criterion of deep contact durability, which performs the calculation under an unknown law of distribution of effective stresses using the Parzen-Rosenblatt method (the method is also used in methods for contact and bending durability criteria), as well as in taking into account the variable value of the force misalignment in the meshing. CONCLUSION: The practical significance of the research lies in the ability of probabilistic determination of the cause of gear failure according to six criteria (pitting, tooth breakage, tooth interior flank fracture of both the pinion and the wheel), which makes it possible to adjust the design, the manufacturing technology, and the operating requirements in order to ensure the required gear performance during its design.

EFFECTS IN DISCRETE AND CONTINUOUS STRENGTHENING OF MACHINES ELEMENTS

The work describes approaches to problem solving of operational and effective improvement of the technical and tactical characteristics of military and civilian machines: tanks, armored vehicles, diesel locomotives, turbo-expander power plants, autonomous power plants of strategic objects, etc. For this purpose, fundamentally new methods of strengthening of contacting machines elements are being developed. These methods combine the advantages of discrete and continuous strengthening methods, which have largely exhausted their capabilities by now. Qualitative features and advantages of proposed discrete-continuous strengthening methods require effective implementation. We are talking about the justification of progressive technical solutions based on the criteria of strength and durability. For this purpose, the methodology of multi-criteria synthesis in the expanded space of design and technological parameters will be improved. In addition, as a basis for substantiating advanced technological solutions, a set of related problems of analysis of the stress-strain state, friction and wear is formed. Therefore, based on the improved system approach, a much higher level of strength and durability of the reinforced structural parts is achieved than with traditional methods. The results of test problems solving are illustrated. In the result, micro-macromodels are generalized to determine the joint influence of structural and technological factors, microstructure, physical and mechanical properties of materials of reinforced layers on the contact interaction and stress-strain state of representative fragments of the system of discrete-continuous reinforced bodies. The results of analysis of combined influence of structural and technological factors, microstructure, physical and mechanical properties of materials reinforced layers have been established on the contact interaction and stress-strain state of test representative fragments of the system of discrete-continuously reinforced bodies. At the same time, a significant influence of reinforced layers properties was established on strength of contacting bodies.

Evaluation of Different Fly Ash-Blast Furnace Slag Formulations for Design of Geopolymers in Radioactivity Disposal Applications

Geopolymers in radioactive waste management have in recent times gained dominance in disposal module acceptance. Here is a comparative study on formulations prepared from industrial wastes to be utilized as radionuclide disposal barriers in near surface disposal facilities (NSDFs). Different tools such as isocalorimetry, compressive strength, chemical durability were utilized for screening the formulations. Water leaching of the samples shows that the release of the ions to the leachant is minimal. Durability studies in acids (H2SO4, HCl and HNO3) show that the samples are mostly acid resistant. X-ray tomography suggests low pore volume change over a period of 2 years. The study concludes that the NSDF requirement of low permeability of water and better chemical durability criterion is met by the optimized geopolymerization formulation.

Design and Development of an Automated PLC Electropneumatic Conveyor System Apparatus: An Industrial Process Simulator for Teaching Electrical/Electronics Technology Courses

The study was focused on the design and development of An Industrial Process Simulator for Teaching Electrical/ElectronicTechnology Courses . This project development research tried to achieve the following objectives: (1. To design and construct a valuable, innovative and inexpensive prototype for electrical and electronics instructional equipment; 2. Test the performance of the developed prototype in conformity to its design parameters and operational limitations; and 3. To determine the acceptability of the developed prototypes in terms of its functionality, aesthetics, economy, workability, durability, safety and instructional applicability). The five-point Likert’s scale was used to determine the descriptive meaning of the indicators of the variables used. Furthermore, the Weighted Average Mean (WAM) was used to interpret the equivalent meaning of the data gathered. Evaluation result shows that the project obtained an overall mean of 4.72 which means that the completed project is “HIGHLY ACCEPTABLE” to the evaluators based on the criteria of functionality, aesthetics, durability,workability economy, safety and instructional applicability

RESEARCH ON THE FORMULATION OF NANOPARTICLES CONTAINING MANGIFERIN USING SELF-ASSEMBLY METHOD

Background: The use of natural-origin active compounds in disease treatment is currently a prevailing trend. Mangiferin, a major component found in mangoes, is present in relatively high proportions. However, mangiferin's disadvantages include low solubility and poor permeability. There are numerous methods available to improve solubility and permeability, among which selfassembly is noteworthy. Self-assembly involves the combination of certain molecules or macromolecules to form three-dimensional networks or other structures with new characteristics, phospholipids and chitosan are often used as raw materials for the self-assembly process to create nanoparticles. This method offers advantages such as high efficiency, simple implementation, short execution time, high retention efficiency, and increased permeability through biological membranes. Objectives: To develop a formulation and process for producing nano mangiferin using the selfassembly method with phosphatidylcholine and chitosan. Materials and methods: The solubility of mangiferin in high-proof ethanol was investigated, followed by an assessment of the influence of formulation factors and processes on the characteristics of nano-sized mangiferin particles. Results: The average solubility of mangiferin in 96% ethanol was approximately 0.5529±0.0003 mg/mL. The mole ratio of mangiferin to Lipoid S100 was 1:1, and the mass ratio of Lipoid S100 to chitosan was 20:1. A stirring speed of 1.000 revolutions per minute, reflux temperature of 70°C, reflux time of 2 hours. homogenization speed of 1,000 revolutions per minute, and homogenization time of 15 minutes produced the smallest nanoparticles (103.44±0.46 nm), with a low polydispersity index (0.281±0.009≤ 0.3) and zeta potential (31.95±0.08 mV ≥ +30 mV), encapsulation efficiency of 82.42±0.53%; loading capacity of 32.97±0.95%. Conclusions: A successful formulation of nanosized mangiferin particles was achieved using the self-assembly method, resulting in particles that meet the criteria of small size, uniformity, and durability. Moreover, nearly 100% mangiferin release was achieved after 60 minutes, indicating the promising potential for developing highly bioavailable oral formulations.

High-quality recycled concrete aggregates developed through an integrated thermomechanical approach

This study demonstrates an integrated thermomechanical treatment process to produce high quality recycled concrete aggregate (RCA) for structural concrete. RCA is mechanically treated after 90 min of heating at 250 °C in this process. The material properties of RCA produced through 15 combinations of charges and drum revolutions are compared using a statistical method. The highest ranking of an RCA identifies it as a high-quality class. Concrete composed of 100% RCA (recycled aggregate concrete, RAC) has 1.7% higher compressive strength than natural aggregate concrete (NAC). RAC has tensile and flexural strengths of 0.95 and 1.03 in fraction of NAC. RAC meets durability criteria such as UPV greater than 4.4 km/s, rapid chloride ion penetration test (RCPT) less than 1000 C, electrical resistivity greater than 208 Ohm-m, and sorptivity closer to NAC. Water absorption and abrasion resistance are similar to or superior to those of NAC. Coherent and uniform surface morphology of RCA enhances the ITZ microstructure in RAC.

Performance of compressed earth bricks reinforced with sugar industrial by-products bagasse and molasse: Mechanical, physical and durability properties

Because sustainable development is a major concern, many studies focus on reducing greenhouse gas emissions during the manufacturing of building materials. Therefore, in this study, we aim to produce lightweight eco-friendly compressed earth bricks (CEB) using industrial sugar by-products, sugarcane bagasse fibers (SCB) and molasse (SCM), as soil stabilizers to diminish the employment of cement. First, we investigated the physical, chemical, and mineralogical composition of the sugar by-products and the used soil. Then, we produced three types of CEB: bricks with soil and SCM (5 wt% and 10 wt%), bricks with soil and SCB (0.5 wt%, 0.75 wt%, and 1 wt%), and bricks with soil, SCB and SCM (this mixture considered two variable parameters: 5 wt% and 10 wt% of SCM, with varying SCB concentrations at three distinct levels: 0,5 wt%, 0.75 wt% and 1 wt%).The results showed that the incorporation of SCM as a stabilizer instead of cement in CEB enhanced both the dry and wet compressive strength, reaching 11.128 MPa and 9.897 MPa, respectively, which represent more than three times the results for the reference soil brick. As to the soil-SCB matrix, the incorporation of SCB decreased the compressive strength by about 36 % (from 3.338 MPa corresponding to reference brick composed only with soil to 2,142 MPa related to bricks stabilized with 1 wt% of SCB). Finally, for the composite soil-SCB-SCM, the highest value obtained was 9.309 MPa related to 10 wt% of SCM and 0.5 wt% of SCB. Moreover, the durability properties including dry abrasion, erosion, and capillarity tests were investigated and compared. The results indicated that SCM has satisfactory durability criteria while bricks stabilized with only SCB showed low resistance, especially to the capillarity test.

Optimizing durability and performance in high-volume fly ash-based alkali-activated mortar with palm oil fuel ash and slag: A response surface methodology approach

While extensive research has been conducted on the production of binary or ternary binders incorporated into alkali-activated mortars (AAMs), significant efforts continue to be directed towards determining the optimal blends that not only address strength requirements but also durability criteria. The present study seeks to optimize highly durable AAMs subjected to harsh conditions that would most likely occur in the mortar during service, through both experimental and optimization modeling. A ternary binder system was developed with a high proportion of fly ash (FA) at 50%, 60%, and 70%, combined with ground granulated blast furnace slag (GBFS) and palm oil fuel ash (POFA) at varying levels from 0% to 30%. Visual inspection, compressive strength loss, and microstructure tests were used to evaluate the performance of the proposed AAMs with exposure to freezing-thawing cycles, wet-dry cycles, and an acidic environment for up to one year. Results indicated that the acid, wet-dry, and freezing-thawing resistances of the proposed mortar were satisfactory at the binder level (60% FA, 10% POFA, and 30% GBFS). Furthermore, the response surface methodology model's accuracy and robustness were attained, with mean absolute percentage error (MAPE) and scatter index (SI) values less than 0.11. It is recommended that a ternary binder of high-volume FA incorporating POFA and GBFS should be used in AAMs to minimize environmental problems, enhance durability performance, and reduce natural resource depletion.

New electrochemical method for the determination of the barrier properties of corrosion protective coatings

A novel electrochemical method evaluates the durability of corrosion protective coatings by measuring the galvanic current between a coated AZ31 Mg alloy and a Pt auxiliary electrode in a 2 M NaCl solution. In this work an organo-inorganic sol-gel film was used. The durability criterion, tsat, was selected as the time where the galvanic current reached 1 mA. Validated using EIS, the method showed 82 % accuracy. However, this difference was not deemed statistically significant. Under the conditions used in this study, results from the new method align with traditional EIS, establishing its viability as a simple and straightforward tool for assessing the barrier properties of corrosion protective coatings.

ASSESSING RAINWATER HARVESTING OPTIONS IN TERESA, RIZAL: INCORPORATING USER PREFERENCES WITH MULTI-CRITERIA DECISION ANALYSIS

Water scarcity has emerged as a critical global challenge, necessitating the exploration of alternative water sources. Rainwater harvesting (RWH) presents a promising solution, given its abundance and ease of collection. Despite the Philippines' ample rainfall, RWH remains underutilized, capturing merely 6% of the annual precipitation. To bolster RWH adoption, this study aims to investigate residents' preferences for alternative water systems, with a specific focus on cost-effectiveness and reliability. By addressing these factors, we aim to identify key strategies for promoting and implementing RWH to mitigate water scarcity and foster sustainable water management practices in the Philippines. Preferences of rural residents (n = 185) in Teresa, Rizal on RWH alternative was then evaluated using a multi-criteria decision analysis. The main criteria assessed were reliability, cost, adoption factors, and benefits. The analysis involved assessing and converting the scores into Yield After Spillage (YAS) to establish rainfall reliability. The study employed Multi-criteria Decision Analysis (MCDA) to compare and evaluate various alternatives based on different factors, which were subsequently ranked under different scenarios. The study found that Alternative P10, a 1,000L plastic tank with a 20L first flush, exhibited the highest utility score among the assessed alternatives, with a score of 0.617. Notably, Alternative F30, featuring a 3,000L ferrocement tank with a 200L first flush, closely followed with a utility score of 0.614. The study employed the Jonckheere-Terpstra test and Kendall's tau with a significance level of 0.05 to determine the significance of these criteria concerning increasing income. The criteria of price, maintenance, and durability were identified as statistically significant (p-values: 0.007, 0.031, and 0.005, respectively) as residents' income increased. Consequently, residents with higher incomes placed greater importance on Alternative F50, a 5,000L ferrocement tank, due to its alignment with these influential criteria. Moreover, given the potential impacts of changing rainfall patterns and growing water demands, implementing larger storage tanks, like Alternative F50, is advisable to enhance future water sustainability in Teresa, Rizal.

Cement-Stabilized Granular Volcanic Ash Materials for Construction of Low-Traffic Roads in Yemen

Granular volcanic ash (GVA) is a volcanic activity material with low density, high porosity, and other undesirable properties that must be improved prior to use in any construction. This material can be considered an alternative for use in road building, given its availability in many locations and in large quantities in Yemen. This article aims to investigate the potential use of GVA for the construction of roads in Yemen when treated with cement stabilizer. Two types of GVA materials with different colors were selected and referred to as red and black GVA materials. Tests performed included the unconfined compressive strength (UCS), compaction, indirect tensile strength (ITS), wetting–drying durability test, and ultrasonic pulse velocity (UPV) test for samples curried for 7 and 28 days. For each GVA–cement mixture, the cement content varied as 2%, 5%, and 8% by dry weight of GVA. Test results revealed that the compaction energy applied during sample preparation led to a significant reduction in the finesse modulus for red and black coarse GVA materials, with reductions of 10% and 23%, respectively. In addition, the cement content and curing period had a significant effect on UCS, ITS, and UPV for cement-treated GVA. The applicable quantity of cement required stabilizing GVA and achieving the base course specification for strength and durability criteria in flexible pavement with low traffic is 8% cement.

Investigation of the surface of light-curing dental materials after pre-polymerization heating

Despite the great variety and wide application of light-cured composite restorative materials for the treatment of hard tissue diseases, the issue of longevity of restorations remains relevant to this day. One of the criteria for the long-term durability of a composite restoration is the finish of the restoration. Poor polishing and surface roughness significantly reduce theservice life of the restoration and provide a good environment for biofilm adhesion, loss of luster of the restoration, and caries recurrence. Thus, methods affecting the reduction of surface relief in restorations remain a current issue. Aim. To evaluate the surface roughness and porosity of composite filling materials after pre-polymerization heating. Materials and methods. Sixty composite samples were prepared in the form of 1 mm thick, 1.2 cm diameter disks. The samples were divided into 2 groups depending on the presence of pre-polymerization heating. Atomic force microscopy (AFM) was used to measure the roughness and to visualize the surface morphology of the samples. Porosity was measured using a vacuum sputtering unit, and a scanning electron microscope was used to obtain micrographs of the sample. Results. The use of pre-polymerization heating of composite filling materials in dental practice will allow dentists to significantly reduce the expression of the relief of the composite restoration by reducing the roughness and pore volume in the matrix of the composite filling material, which will certainly optimize the finishing of the restoration. Conclusions. Pre-polymerization heating has a positive effect on the surface topography of the composite restoration, reducing its roughness and porosity, which improves the stage of finishing: obtaining a dry gloss, ensuring the duration of color stability, as well as reducing the adhesion of microorganisms to the filling material, thereby increasing the longevity of the composite restoration.

Subsidence of Artificial Reefs with Bamboo Foundations on a Soft Seabed

The design of artificial reefs must be based on the criteria of both durability and serviceability. In this respect, the seabed subsidence rate related to the weight of the reefs and of their foundation system should be limited. The horizontal drift of the reefs during their life should be small too. In this study, pertaining to the behavior of artificial reefs made of microsilica concrete and realized with foundations in bamboo near the international airport of Hong Kong, 1-year monitoring data and calculations of reef foundation settlements are shown and discussed to assess the performance of the adopted mixed foundation and to deduce the nature of the long-term subsidence. The subsidence related to the settlements of the foundations was monitored using a Multibeam Echo Sounder System. It was found that the observed subsidence rate cannot be justified by the primary consolidation of the soils forming the seabed. Indeed, secondary consolidation seems to play an important role. Overall, after one year of service, the artificial reefs are considered to be effective in terms of limitation of both subsidence and drift.

Experimental study on strength, durability, hydraulic and toxicity characteristics of soil treated with mine tailings based geopolymers for sustainable road subgrade application

This article explores the utilization potential of three distinct mine tailings (MT) viz.; red mud (RM), iron tailings (FeT), and zinc tailings (ZT) as geopolymer binders to stabilize the soil for road subgrade application. The strength and durability of soil treated with various MT-based geopolymers are examined through a succession of unconfined compressive strength (UCS), California bearing ratio (CBR) and alternate wetting-drying tests respectively. Furthermore, permeability tests are also conducted to examine the hydraulic response of soil amended with MT-based geopolymers. Finally, leaching study is performed to examine the geo-environmental implications of various geopolymer specimens. The experimental results reveal that the UCS of untreated soil is increased from 0.39 MPa to 5.24 MPa, 5.13 MPa and 3.78 MPa with the use of RM, FeT, and ZT-based geopolymers respectively. The study further shows a 26-fold, 19-fold, and 15.8-fold increase in the soaked CBR values of soil when it is stabilized with RM, FeT, and ZT-based geopolymers respectively. In contrast to untreated soil, soil stabilized with MT-based geopolymers exhibit excellent weathering resistance to alternate wetting-drying cycles showcasing its exceptional durability under challenging environmental conditions. Irrespective of the MT content, curing environment, and the alkali activator concentrations, soil treated with MT-based geopolymers is found to satisfy both the strength (i.e. UCS = 0.75–1.5 MPa and CBR > 5%) as well as durability criteria (i.e. % loss in mass < 10%) specified by Indian Road Congress for subgrade soil. Moreover, the leaching study shows the concentrations of toxic elements (Zn, Cd, Fe, Pb, Ni etc.) to be within the permissible limits specified by USEPA thereby dispelling any environmental concerns associated with the use of MT-based geopolymers.

Endurance and durability in biodiesel powered engines

The use of fatty acids methyl esters either in mixtures with fossil diesel or in pure state in diesel engines is correlated to a series of technical problems which are to be taken into account in order to not spoil the important environmental and social advantages that this kind of biocombustibles reports. Throughout this work, in agreement with this fundamental premise and on the basis of the technical criteria of durability and resistance that so much affect engines, the most critical aspects of biodiesel use as well as their immediate consequences are introduced. Special emphasis is done on certain phenomena that condition the engine utility life, like the lubricating oil dilution and the deposits formation, as well as the storage and oxidative stability and finally the low temperature behaviour related to engine operation in greater or smaller degree incompatible with biodiesel (fatty acid methyl esters). To sum up, a study in depth will be realized about some of the most problematic aspects referred to biodiesel use, analysing its entire technical dimension and contributing possible solutions. In general, this work tries to be a guide, which allows to identify the most sensible areas within the engine, as well as the suitable means and solutions for the correct use of biodiesel in compression ignition engines (diesel engines).

EVALUATION OF ROAD SURFACE OPTIONS BASED ON THE ANALYTICAL HIERARCHY METHOD

Purpose. The purpose of this work is to conduct a comprehensive analysis of various types of road surfaces, including asphalt concrete, cement concrete, and pavement, with the aim of determining the most optimal option for a specific project based on criteria of productivity, durability, cost, and environmental impact. Methodology. The methodology involves the selection of construction materials and rational construction methods, taking into account weather conditions, climatic factors, and economic factors that influence the quality and durability of road surfaces. To evaluate road surface options while considering the importance of various criteria, the Analytical Hierarchy Method (AHP) is utilized. The process includes creating a hierarchy of criteria, assessing their significance, pairwise comparative analysis, calculating weight coefficients, and evaluating alternatives. Based on this analysis, the optimal road surface option is determined for a specific project or task. Findings. At this stage of the decision-making process involving the comparison of road constructions, we considered ten primary requirements and three widely used types of road surfaces: asphalt concrete, cement concrete, and pavement. Through a comprehensive analysis of various road surface options, the most optimal choice for a specific project was determined based on criteria of productivity, durability, cost, and environmental impact. Originality. A scientific approach was employed, which involved the selection of road surface construction and rational construction methods, taking into account weather conditions, climatic factors, and economic factors influencing the quality and durability of the road surface. This approach also considered the significance of various criteria to determine the optimal road surface option for a specific project or task. Practical value. The business model encompasses the stages of project design, implementation of construction work, and outlines a sequence of steps for creating, developing, and ensuring the efficient operation of industrial enterprises. The selection of the optimal road surface construction allows industrial enterprises to generate profits in the shortest possible time with minimal investments.

Utilization of recycled concrete aggregates for pavement base courses – A detailed laboratory study

Pavement construction and maintenance have become prevalent globally due to increasing traffic volumes and higher vehicular axle weights, driven by population growth and technological advancements. However, the extensive reliance on natural resources raises concerns about their long-term availability and sustainability. An emerging trend in construction involves the application of alternative materials, such as demolished waste and industrial by-products, as substitutes for natural materials like aggregates. This study examined strength properties, including unconfined compressive strength (UCS), flexural strength, elastic modulus, indirect tensile strength (ITS) and the performance aspects of durability, shrinkage, and fatigue. Cement stabilized recycled concrete aggregate (CSRCA) mixes were prepared by varying the percentage of natural coarse aggregate (NCA) and recycled concrete aggregate (RCA) from 0% to 100% and cement content from 3% to 7%. The experimental findings demonstrated that the cement content had a more significant impact on the strength and performance characteristics of CSRCA mixes than RCA content. The mixes with RCA replacement up to 50% and a cement content of 5% satisfy the strength and durability criteria recommended by IRC 37. A higher proportion of RCA was found to have a detrimental effect on mechanical properties and fatigue characteristics. It was found that the CSRCA mixes with 50% RCA replacement to NCA can be used as a base layer instead of a conventional cement-treated base (CTB) for flexible pavement.

Electrochemical cycling durability of platinum overlayers formed by self-terminating electrodeposition

Platinum thin films comprising nominally 1 to 20 atomic overlayers were formed on a gold-coated substrate using the self-terminating electrodeposition (STED) method. The platinum overlayer loading and morphology were characterized using X-ray Photoelectron Spectroscopy (XPS), Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES), Field Emission Scanning Electron Microscopy (FESEM), Cyclic Voltammetry (CV) and Chronoamperometry (CA). The durability of these platinum overlayer samples was estimated by subjecting the samples to ex-situ electrochemical potential cycling. The extent of platinum overlayer growth is lower than expected till four STED cycles and then increases non-linearly, leading to increased roughness. The shifts of platinum redox peaks in CVs and Pt4f signals in XPS spectra indicate surface-alloying of gold and platinum. After the durability test, the morphological evolution of platinum overlayers conforms with the extent of platinum dissolution estimated from CVs. Our results reveal that more than four STED cycles are needed to form platinum overlayers that meet the US Department of Energy (DOE) criteria for durability.