Durability Indicators Research Articles

Assessing durability properties of ultra-high performance concrete-class materials

Ultra-high performance concrete (UHPC) is a class of concrete materials that has received significant attention from the infrastructure community due to its favorable mechanical and durability performance. As the use of UHPC in infrastructure projects is becoming more common, there is an increasing interest in identifying appropriate testing techniques to assess the durability properties of UHPC-class materials. The dense microstructure of UHPC-class materials and the presence of a high concentration of fiber reinforcement have made it difficult to rely on existing standard testing approaches for concrete durability assessment. This study explores the application of various conventional-concrete durability test methods to UHPC, including electrical resistivity (American Association of State Highway and Transportation Officials (AASHTO) TP 119-22), freeze–thaw (ASTM C666), water absorption (ASTM C1585), and rapid chloride migration test (NT BUILD 492). The selected tests are meant to qualify and quantify the microstructural penetrability of UHPC to ions and fluids, a surrogate property commonly used as an indicator of durability. The findings from this study indicate that electrical resistivity can be used as a durability indicator for UHPC-class materials. Moreover, strong correlation between electrical resistivity and the chloride migration coefficient is identified, a potential benefit given that chloride migration can be used to estimate service lives of UHPC-class materials. Other tests, including freeze–thaw and water absorption, although identifying the favorable performance of UHPC relative to conventional concrete, were unable to provide insightful information through which the performance of individual UHPCs could be differentiated.

Retracted: A study on the strength and durability characteristics of fiber-reinforced recycled aggregate concrete modified with supplementary cementitious material

Recycled aggregate (RA) made from waste concrete is an environmentally friendly alternative to natural aggregate (NA) for concrete manufacturing. However, compared to NA concrete, concrete produced with recycled aggregates has poor characteristics. Supplementary cementitious materials (SCMs) can be used to enhance the poor properties of recycled aggregate concrete (RAC). Silica fume and fly ash are commonly used SCMs in the World, but their high usage led to a shortage of silica fume and fly ash. Still, the deficiency of these materials in large parts of the world is a challenge that requires exploring alternative feedstock materials for the construction industry in the coming years. Wheat straw ash (WSA) is an agricultural waste product that could be used as an alternative SCM due to its pozzolanic behavior to enhance the properties of RAC. In addition, concrete is brittle and needs reinforcement, for which polypropylene fibers (PPFs) can be used. The current research examines the mechanical characteristics of fiber-reinforced RAC, including compressive strength, splitting tensile strength, and ductility performance. Durability indicators, such as chloride diffusion, chloride penetration, acid resistance, and water absorption test, were also assessed. The results showed that concrete samples with 10% WSA, 50% RA and 1.5% PPFs had the highest compressive and splitting tensile strength, 60.2 MPa and 7.25 MPa, respectively, representing increases of 24.75% and 30.65%, as compared to plain samples at 56 days. In these samples, water absorption was reduced by 13% due to the finer WSA particles resulting in the lowest reduction in strength and mass recorded when exposing concrete samples to acidic media. The statistical analysis also validated that irrespective of WSA and PPFs, the concrete with 0% RA had the highest performance in strength and durability behavior. The study showed that WSA and PPFs might be employed in tandem to offset the poor behavior of RA, enhance the bond between fibers and concrete, and improve the mechanical strength and durability performance of RAC, thus demonstrating its suitability as a sustainable and economical construction material.

Effects of microencapsulated phase change materials on chloride ion transport properties of geopolymers incorporating slag and, metakaolin, and cement-based mortars

The addition of microencapsulated phase change materials (MPCMs) to geopolymers is a technological alternative for meeting the thermal comfort and energy efficiency requirements of buildings. However, current research is limited to the effects of MPCM addition on mechanical and thermal performances of geopolymers. New MPCM applications, therefore, require additional research on durability indicators (chloride diffusivity, porosity, absorption, etc.). The objective of this research is to examine the effects of MPCM addition on sodium chloride ion transport properties of geopolymer mortars based on a combination of blast furnace slag and metakaolin, and Portland cement based mortars. Twelve different mortars (three cement-based and nine geopolymer-based) are studied by varying the MPCM content (0%, 5% and 10%, respectively) within two types of mortar: a geopolymer mortar (GPM) and a cement mortar (CM). With this aim in view, a series of characterizations are conducted, including determination of total porosity by water saturation, analysis of pore structure distribution by mercury intrusion porosimetry (MIP), measurement of electrical resistivity, capillary water uptake, stationary-state migration coefficient “Dss” and non-stationary-state migration coefficient “Dnss”, and determination of chloride ion binding capacity. The results show that MPCM addition increases total porosity, which in turn increases capillary water absorption and decreases GPM and CM electrical resistivity. Conversely, MPCM addition also reduces critical diameter and pore connectivity, due of the agglomeration effect. MPCMs also increase chloride ion binding capacity. Both effects results in decreased stationary state migration coefficient. Finally, the study shows that the chemical reaction of GPM with chloride ions delays chloride penetration in stationary state conditions. However, the same is not true for the non-stationary state method. This demonstrates the technical limitations of this method for the characterization of GPM in comparison to CM.

A Novel Method of Self-Healing Concrete to Improve Durability and Extend the Service Life of Civil Infrastructure

Concrete civil infrastructure often suffers severe damage to its internal structure due to insufficient durability in high and cold complex environments, affecting the service life of the infrastructure. Therefore, a novel method based on nanofillers for self-healing concrete is proposed to optimize the durability mix proportion of high-performance concrete in complex high and cold environments, which improves the strength recovery rate of concrete. Moreover, a concrete durability prediction model based on particle swarm optimization-least squares support vector machine (PSO-LSSVM) and improved NSGA-II (nondominated sorting genetic algorithm II) algorithm was proposed to quickly and accurately determine the optimization scheme of self-healing concrete mix proportion. First, the model employs PSO-LSSVM to achieve highly accurate predictions of relative dynamic elastic modulus and chloride ion permeability coefficient, which are key indicators of the concrete durability. Subsequently, the predicted regression functions for concrete durability are utilized as fitness functions, and the improved NSGA-II algorithm is employed to obtain the optimal mix ratio for durable concrete. Finally, the Pareto frontier solution set is processed using the ideal point method selection approach to determine the optimal concrete mix ratio scheme. To assess the self-healing ability of the proposed concrete, a concrete durability test study is conducted. Experimental research shows that the durability of the proposed self-healing concrete has been significantly improved. The optimized PSO-LSSVM model demonstrates excellent generalization capability. The coefficient of determination between the predicted and actual values in the test dataset is 0.9357, and the root-mean-square error is 0.10267. Building upon this, the enhanced concrete durability prediction model based on the NSGA-II algorithm proves to be highly effective in predicting the optimal concrete mix proportion scheme. The predicted values of chloride ion permeability coefficient and relative dynamic elastic modulus of the proposed model differ from the actual experimental values by 1.29% and 0.59%, significantly better than the other prediction models.

Coins from the multi-stratified medieval site of Reccopolis: analysis of long-term numismatic records

ABSTRACT The relationship between numismatic research and archaeological stratigraphy is one of the most significant resources for defining the economic and social mechanisms of the Middle Ages. A numismatic assemblage comprising 146 coins – mostly unpublished – recovered from the late sixth-century Visigothic settlement of Reccopolis in Guadalajara, Spain, is the focus of this study. Through characterisation of the deposits and monetary finds it has been possible to establish a contextual interpretation in which indicators of durability, continuity and rituality in the use of currency can be observed. In connection with this, a substantial number of coins have been found concentrated in specific sectors of the site, especially in the neighbourhood of the church, where the foundational value of some hoards has been reinterpreted. This study establishes a constant connection between chronological dating and stratigraphic contextualisation, exploring the complex periods of continuity in use of certain specimens, while also stressing the importance of interpreting coinage within wider material assemblages.

Influence of Corn Cob Ash-Silica Fume Blend on the Mechanical and Durability Properties of Concrete

— This research explored the feasibility of corn cob ash-silica fume blend in the production of pozzolanic cement to produce High-Performance Concrete. The cement in concrete was partially replaced by corn cob ash-silica fume blend in 5,10,15 and 20% by weight of cement and was compared to a control mix of 0% replacement. An intelligent mix design, Densified Mix Design Algorithm (DMDA), was used to effectively reduce both water and cement content. In order to create high strength and workability, a polycarboxylate-based super plasticizing admixture was utilized in conjunction with a low water binder ratio of 0.35. Compressive strength was appraised to determine the mechanical properties at days 3,7,14,28 and 56 to determine the optimum percentage replacement and compared to the control at the specific ages. With the optimum percentage replacement, the flexural test was investigated at 28 days. Water absorption and electrical resistivity tests were also investigated as potential indicators of durability. All of the blends that included corn cob ash and silica fume produced a higher strength than the control except 15 and 20%, with 10% replacement yielding a cube strength of 61 MPa at day 56.

Durability assessment of industrial by-product and marine resource-based ultra-high-performance concrete

The increasing demand for concrete and the associated environmental impacts such as depletion of natural resources (e.g., fresh water, river sand, and coarse aggregates) have prompted the development of seawater and sea-sand concrete (SWSSC). On the other hand, incorporating industrial by-products in concrete as supplementary cementitious materials (SCMs) can offset the cement carbon footprint. Utilizing seawater, sea sand, and industrial wastes in ultra-high-performance concrete (UHPC) fabrication can lead to a sustainable as well as durable construction material, especially suited for marine infrastructure development. This experimental work investigates the durability properties of ultra-high-performance seawater and sea-sand concrete (UHP-SWSSC) with partial substitution of cement by ground granulated blast furnace slag and silica fume as SCMs. Five mixes were developed with varying proportions of SCMs as cement replacement (0% as control mix, 25% and 50% by mass) and water-to-binder ratio (0.15, 0.2 and 0.25). In addition to mechanical behaviour through standard axial compression tests on cube specimens, several durability indicators such as water absorption, sorptivity, the permeability of chloride ions, and volume of permeable voids were measured over time. Results reveal that the incorporation of SCMs in UHP-SWSSC although improves the mechanical properties marginally, significantly enhances the durability performance. In comparison to the control mix, 53%, 75%, and 95% reductions in the volume of permeable voids, rate of water absorption and non-steady state chloride migration coefficient were observed in a 50% SCM replaced mix, respectively. Addition of ground slag and silica fume induced a relatively compact matrix through refinement of the microstructure, which made the resulting concrete nearly impermeable to ion movements. An optimum water-to-binder ratio of 0.2 was established, below which neither the strength nor the durability characteristics improved further.

Performance, Mechanical Properties and Durability of a New Type of UHPC-Basalt Fiber Reinforced Reactive Powder Concrete: A Review.

The advent of reactive powder concrete (RPC) has brought about the era of ultra-high performance concrete (UHPC), and the incorporation of fiber has brought about more possibilities for its application. Basalt fiber reinforced reactive powder concrete (BFRPC), as the product of the combination of RPC and fiber, has become a new engineering material that has received much attention from scholars in recent years. Compared with traditional UHPC, BFRPC is superior in corrosion resistance, material compatibility, cost performance, environmental protection, and other aspects; therefore, it is destined to have a wide range of applications in the future. In this article, we extensively reviewed the literature on basalt fiber reinforced RPC in the past decade from the perspective of work performance, mechanical properties, and durability. Moreover, we summarized the research progress and achievements on BFRPCs in the following points: (1) The performance of BFRPCs is mainly influenced by three factors: the frictional resistance between fine aggregates, the consistency of the cement slurry, and the three-dimensional random interweaving of basalt fibers; (2) the mechanical properties of BFRPC are mainly influenced by curing conditions, the design of the RPC matrix proportional mix, and the addition of basalt fibers up to a threshold; (3) thanks in part to RPC's density and the filling and bridging of fibers, BFRPC exhibits uniform and good performance in durability indicators. However, there are still some problems in the current development of BFRPC, such as inconsistent test conclusions among different scholars and a lack of scenarios in which to apply BFRPC. This paper also puts forward the prospect from the aspects of theoretical research and practical application, and provides a reference for subsequent related work.

Rapid prediction of cementitious initial sorptivity via surface wettability

The tendency of cementitious systems to absorb and transmit liquid through capillary pores is often characterized by initial sorptivity, which is an important indicator of long-term durability. However, sorptivity measurements, which are based on the continuous mass change of specimens exposed to water, are labor-intensive (up to 6 h of continuous measurements). Here, we exploit the fundamental surface-wetting characteristics of cementitious systems to estimate their sorptivity in a rapid fashion, i.e., in a matter of few minutes. In a series of 63 distinct paste systems of varying w/c ratios (0.4–0.8), subject to a range of curing periods (1–7d), we establish strong correlations (adjusted R2 ≥ 0.9) between the initial sorptivity (~6 h) and dynamics of drop spreading (contact angle ~0.5 s, drop residence time <10 min). These results elucidate rapid pathways in estimating initial sorptivity and durability of a broad variety of hydrated cementitious matrices.

Comparison of the Vortex Chamber Supercharger Characteristics for Grain Pumping with Other Types Superchargers

Problem. Among the superchargers used in pneumatic transport, jet pumps have the best reliability and durability indicators. However, their use in these systems is limited due to the large specific energy consumption indicators for pumping. Vortex chamber superchargers allow to increase the pressure of the medium at the outlet of the pump, in comparison with classic direct-flow jet pumps, but their characteristics during operation in undrained mode have not yet been investigated. Goal. The goal of this work is to analyze the characteristics of vortex chamber superchargers for pumping grain and compare the main integral parameters with the parameters of existing pneumatic devices of other types. Methodology. The study was carried out by comparing the experimental and calculated super-chargers characteristics with the technical characteristics of industrial pneumatic transport units based on direct-flow jet pumps and grain loaders. Results. As a result of the comparison, it was found that the mass flow rate for the solid medium (grain) for the vortex chamber supercharger exceeds the achievable (theoretical) rate of the direct-flow jet pump by 1.1 times and is 15% inferior to the grain loader. Originality. Improving the efficiency indicators of the vortex chamber supercharger allows for expanding the range of pneumatic device usage for grain over-loading. The distance of transportation can be increased to 220 m due to exceeding the indicators of the relative drop in comparison with direct-flow jet devices with an increase in the process efficiency. Compared to suction grain loaders, the vortex chamber supercharger can create a larger pressure drop, but with reduced efficiency. Practical value. The creation of a vacuum in a grain transfer unit is limited to 1 atm, unlike a jet supercharger, which can operate at almost any created pressure drop, which increases the transportation distance.

Political economy of financial development: empirical evidence from Ethiopia

PurposeThe main purpose of this study is to examine the political economy of financial development in Ethiopia, specifically, to test the empirical relevance of the interest group theory of financial development in the context of Ethiopia.Design/methodology/approachThe autoregressive distributive lag model to co-integration is applied to Ethiopia’s time series data from 1990 to 2020 to identify the long- and short-run effects of the political regime characteristics on financial development of the country.FindingsThe findings reveal that the degree of democracy in the political system (a proxy for narrow elites) was found to have a significant positive effect on financial development in the long run but has negatively affected financial development in the short run. Similarly, the political regime durability indicator shows a positive and statistically significant effect both in the long run and short run. The macroeconomic policy indicators which are used as control variables in this study reveal significant effects on the financial development of Ethiopia. Generally, the finding supports the interest group theory of financial development.Originality/valueThis paper is the original work on the effect of political regime characteristics on financial development in Ethiopia. Thus, it brings substantial value to studying determinants of financial development as it goes beyond the conventional determinants by considering the role of political power in the process of financial development.

INTEGRATION OF ADVANCED METHODS AND MODELS IN THE METHODOLOGY OF ENGINEER-ING CALCULATION OF TORSION SHAFTS OF LIGHT ARMORED VEHICLE SUSPENSION SYSTEMS (REVIEW ARTICLE)

The requirements for the tactical and technical characteristics of the suspension systems of light armored vehicles are constantly growing, taking into account the increase in the intensity of their loads. It is necessary to improve the suspension system, in particular the torsion shafts, which are the most responsible and loaded in the suspension system of light armored vehicles. The existing traditional methods of calculating the torsion shafts of the suspension systems of light armored vehicles do not meet modern requirements. Today, there is a contradiction between the real indicators of strength and durability and those that should be provided for light armored vehicles of the new generation, and especially for future ones. In addition, this contradiction is deepened by the lack of in-depth scientific methods and models of the stress-strain state that would adequately reflect the processes and states in the torsion shafts of the suspension systems of light armored vehicles, and would also become the basis for developing measures to increase their strength and durability. The analysis of literaure showed the absence of a systematic connection of structural solutions, technological modes and load conditions in the calculations of torsion shafts of suspension systems of light armored vehicles. The necessity of creating such a system approach in calculations is shown. Conclusions were made about the need to integrate advanced methods and models in a single methodology for calculating torsional shafts of suspension systems of light armored vehicles. The necessity of linking stress-strain state methods with constructive, technological, and operational factors and developing a suitable specialized software-module complex for carrying out relevant research is shown. Keywords: light armored vehicle; performance characteristics; torsion shaft; suspension systems; stress-strain state; strength; durability; elastic-plastic deformation; contact interaction

Machine learning models to predict the residual tensile strength of glass fiber reinforced polymer bars in strong alkaline environments: A comparative study

The long-term durability of glass fiber reinforced polymers (GFRPs) in strong alkaline environments is of utmost importance in marine infrastructure construction. The residual tensile strength, as one of the important durability indicators, can be characterized by the tensile strength retention (TSR). However, accurate prediction of the TSR is a challenging task. Therefore, the main objective of this study is to develop a generalized, accurate, and optimized TSR prediction model from machine learning (ML) perspective. To this aim, seven machine learning models were developed using the diameter of the bar (db), the volume fraction (Vf) of the E-glass fibers, the pH of the alkaline solution, the conditioning temperature (temp) and the duration of immersion (T) as input variables. A database containing 150 sets of samples, divided into training and testing sets, was created for model building and comparison. Evaluated against three performance evaluation metrics (including RMSE, R2, and VAF) and the Taylor diagram, the final generalization performance of the models was found to be the extreme gradient boosting (XGBoost), long short-term memory (LSTM), support vector regression (SVR), random forest (RF), extreme learning machine (ELM), backpropagation neural network (BPNN), and generalized additive model (GAM) from highest to lowest. In addition, the relative sensitivity of the five input variables was assessed by the one variable at a time (OVAAT) method, and pH and temp were identified as the top two most significant variables in TSR prediction. This study also explored the effect of the training set/test set division ratio on the model, an aspect that has not been investigated in previous studies, and identified 8:2 as the optimal division ratio. The findings of this study could be of real benefit to long-term durability studies of GFRP bars, and also expand the application of machine learning in civil engineering.

НЕРАЗРУШАЮЩИЙ КОНТРОЛЬ ЭЛЕКТРООБОРУДОВАНИЯ ЭЛЕКТРОПРИВОДОВ

A strategy is proposed for using control methods of a different nature, which allows increasing the service life, maintaining durability, reliability and safety indicators of electromechanical systems of electrical equipment of electric drives

β-CaSiO3 and colloidal n-SiO2 based blended cement composites- their properties, regression analysis and micro-characterization studies

This paper examines the effect on mechanical properties such as compressive strength, flexural strength, and dynamic modulus of elasticity (DYE) of different proportions of wollastonite (β-CaSiO3) and colloidal nano-silica (n-SiO2) partially replacing cement. Durability indicators (water absorption, sorptivity and sulphate treatment test) were also examined to ascertain the quality of hardened paste mixes with respect to the control mix. The regression models were found for mechanical properties using different parameters from the results obtained, and statistical relations were established and validated. Regression analysis shows the significance of every parameter considered and model for the prediction of mechanical strengths. Finally, the results were substantiated by the microstructural characterization by FESEM. β-CaSiO3 and colloidal n-SiO2 replaced cement by 15%, and 1.5%-6% with an offset of 1.5%, respectively at low (0.25), medium (0.40) and high (0.55) water/binder (w/b) ratio. FESEM micrographs showed dense Calcium-silicate-hydrate (CSH) gel and stratlingite (CASH) was formed by blended cement paste mixes containing β-CaSiO3 and n-SiO2. n-SiO2 at 3% and CaSiO3 at 15% replacements of cement (NS3 mix) was the optimum replacement level for the cement paste mix. Analysed regression model suggests that the models and parameters were found significant and can also be used for prediction (based on R2 values and p-value).

Correlating Durability Indicators to Resistivity and Formation Factor of Concrete Materials

Concrete pavement durability in the United States is an important characteristic that owners are considering in new construction and rehabilitation projects, and many are including durability tests in the next generation of their specifications. Specifically, focus has fallen on electrically based testing owing to its rapid testing time and economical testing equipment. Results from electrically based tests have also been shown to be good inputs to service life models and can correlate with a wide range of other material properties used to understand how ions and fluid are transported through concrete. This study aimed to correlate the two most common electrically based test results (resistivity and formation factor) with more established and involved tests of transport properties, such as rapid chloride migration and water absorption. The major difference between these two tests resides in the conditioning solution, which is typically limewater for resistivity and an alkali-concentrated solution for the formation factor. Based on the results, both electrical resistivity and formation factor were deemed acceptable tools for mixture approval and acceptance, though formation factor demonstrated higher correlations with the other transport properties and, therefore, was preferrable for performance modeling. Overall, concrete resistivity and formation factor measurements at ages beyond 28 days could be used to indicate the durability of a concrete material during its lifespan. During the investigation, the authors observed that compressive strength measurements were independent of the type and volume of the conditioning solution.

Introducing fiber to enhance the mechanical properties and durability of polymer-modified cement-based coating

Polymer-modified cement-based coatings are widely used in the field of concrete protection. However, in harsh environments such as the ocean, the core durability indicators such as anti-UV aging resistance and anti-chloride corrosion of the coating need to be further improved. In this study, the polypropylene (PP) fiber was introduced into the composite coating with silicone-modified polyacrylate (SPA) emulsion and calcium sulphoaluminate (CSA) cement as the main body. And the influences of PP fiber on the mechanical properties, UV aging resistance and chloride penetration were mainly discussed. Results showed that PP fiber not only significantly improved the tensile strength of the coating as expected (increment > 60%), but also showed the obviously positive effect on the bonding strength and wear resistance. For UV aging conditions, PP fiber could reduce the loss rate of elongation at break of the coating. For chloride corrosion, the chloride penetration resistance of the coating was also significantly improved by 48.92%. The enhancement was attributed to PP fiber itself and its effects on the coating, resisting the external stress, promoting the break of bubbles and reducing microporosity. In addition, the application was also attached to this study to verify the performance of the coating.

Life cycle impact of concrete incorporating nylon waste and demolition waste.

The large consumption of natural resources by the construction industry and resultant pollution have inspired the necessity to investigate the potential of eco-friendly materials, such as recycled aggregates and recycled fibers. In this study, the effect of different percentages of recycled coarse aggregate (RCA) and nylon waste fibers (NWFs) was investigated on engineering performance and performance-related carbon emissions of high-performance concrete (HPC). Engineering performance indices include compressive strength (CS), splitting tensile strength (STS), water absorption (WA), and chloride ion penetration (CIP). The environmental impact of designed mixes was evaluated using a cradle-to-gate life cycle assessment approach on the HPC mixes. The results showed that the incorporation of 0.25-0.5% yielded maximum STS for all percentages of RCA. The use of NWF helped overcome the negative impact of RCA on the STS of HPC. The use of the 0.1-0.25% volume of NWF was beneficial to the permeability-related durability indicators of HPC. CS-related emissions were minimum for concrete mixes incorporating 0.1-0.25% NWF with 0% and 50% substitution levels of RCA. While STS-related emissions were lowest for HPC incorporating 0.5% NWF with 50% and 100% substitution levels of RCA.

Analysis of the effectiveness of methods for ensuring the reliability of a communication satellite transponder

Objectives . Since the launch of satellite communication systems in practical use, approaches towards enhancing their operational quality and durability have been developing in the direction of increased reliability of airborne transponders. This is mainly achieved by increasing redundancy and using components with a lower failure rate. In this regard, the creation of new technologies and new materials is a particularly promising direction. However, since durability testing of complex systems can take several years, the problem of ensuring an effective combination of redundancy methods and elements having a reduced failure rate remains challenging. The purpose of the work is to analyze the effectiveness of methods for ensuring the reliability of a communication satellite transponder based on a proposed methodology for determining the durability index using a mathematical model of the probability of failure-free operation. Methods . In order to describe the complex structure of a satellite communication system transponder, a logical- probabilistic method is used, in which the dependence of the system reliability indicators on the reliability indicators of the transponder elements is formulated as a logical function of operability. Mathematical models of system reliability are created on this basis including for redundant systems. Graphs and analytical methods are used to compare different systems. Results . The influence of various methods for ensuring the redundancy of transponder devices and the use of more reliable components on the reliability and durability indicators is considered. A gamma-percentage resource-based technique for determining the durability indicator based on the constructed mathematical models of the probability of failure-free operation is presented along with a comparative analysis of measures to increase the gamma-percentage resource of the transponder. Conclusions . The presented method for determining the durability index using a mathematical model of the probability of no-failure operation can be used to determine the time interval within which redundancy increases the probability of no-failure operation as compared with a decrease in the failure rate of elements. On this basis, the most effective combination of redundancy methods and approaches for reducing the failure rate of elements can be identified.

Life Cycle Assessment (LCA) of 3D Concrete Printing and Casting Processes for Cementitious Materials Incorporating Ground Waste Tire Rubber

Ordinary concrete is an indispensable construction material of modern society which is used for everything from mundane road pavements to building structures. However, it is often used for non-load-bearing applications (for instance, insulating lightweight building units) where mechanical strength is not a priority. This leads to an avoidable depletion of natural aggregates which could instead be replaced by alternative waste materials capable of conferring to the material the desired performance while ensuring a “green” route for their disposal. Furthermore, the automation of production processes via 3D printing can further assist in the achievement of a more advanced and sustainable scenario in the construction sector. In this work, performance and environmental analyses were conducted on a 3D-printable cementitious mix engineered with ground waste tire rubber aggregates. The research proposed a comparative study between rubberized concrete mixes obtained by 3D printing and traditional mold-casting methods to achieve a comprehensive analysis in terms of the mix design and manufacturing process. To evaluate the environmental performance (global warming potential and cumulative energy demand) of the investigated samples, Life Cycle Assessment models were built by using the SimaPro software and the Ecoinvent database. The Empathetic Added Sustainability Index, which includes mechanical strength, durability, thermo-acoustic insulation, and environmental indicators, was defined to quantify the overall performance of the samples in relation to their engineering properties and eco-footprint.