Insight on characterization through porosity-to-lime index of a stabilized soil for the long-term

The strength of lime-cemented soils has received significant attention in previous studies. However, limited research has focused on studying soil mixtures for extended durations beyond 365 days, which is essential for understanding shear strength, microstructure, unconfined compressive, and matric suction. Consequently, there is a need to explore the long-term behavior and unsaturated properties of soil specimens cured for up to 500 days using appropriately hydrated lime, considering the semi-empirical porosity/lime index. By investigating various curing times ranging from 15 to 500 days, as well as employing different compaction energies (standard, intermediate, and modified) and lime content ranging from 3% to 9% by weight, this study aims to characterize the evolution of resistance and unsaturated properties of lime-cemented soils. The semi-empirical porosity/lime index is employed to guide the characterization and analysis of the mixtures' resistance properties. By developing equations to estimate the resistance of these mixtures, the study contributes to reducing lime consumption (and reducing CO2 emissions during its production) and optimizing curing time, leading to environmentally friendly geotechnical projects. Due to the utilization of the porosity/lime ratio, lime consumption can be minimized, and curing time can be fixed, resulting in a significant reduction in energy requirements, which is beneficial for the environment. The outcomes of this research have profound implications for the design and construction of sustainable structures such as dams, pavements, and slope protection systems, ensuring their long-term stability, resilience, and ecological balance

Effect of an Aftermarket Additive in Powertrain Wear and Fuel Consumption of Small-Capacity Motorcycles: A Lab and Field Study

Metal conditioners (MC) are friction, wear, and heat-reducing agents between metal components in motion and are mainly used in engines and transmission boxes as aftermarket additives. Laboratory and field tests were conducted to assess the performance of a commercial MC. Laboratory tribotests revealed the MC’s potential to reduce wear and friction in lubricated steel contacts. Field studies were performed on two new motorcycles (160 cc) under urban driving conditions for 15,000 km. The physico-chemical properties of the used oils were similar and within the acceptable limits provided in the literature. The FTIR results showed that specific components in the MC formulation do not allow for a direct comparison between oils and their mixtures with MC. Regarding engine wear, MC provided overall aluminum and iron metal parts protection, mainly in the first 7000 km of engine break-in, but a higher wear of copper-containing parts, although at levels below the warning limits. Accurate measurements of engine components demonstrated there were changes of less than 0.05% in the cylinder, piston, and transmission system pieces, except for gear #5. The lubrication of the crown, pinion, transmission chain and gear #5 with the MC significantly increased their wear resistance. The motorcycle driven with MC maintained higher average fuel economy improvements (+1 km/L), representing a 2.5% gain compared to the other motorcycle. Although only two motorcycles were tested, the laboratory and field results suggested that mixing MC with the fully formulated oil (10W-30) reduces wear and friction during the break-in period

Effect of an Aftermarket Additive in Powertrain Wear and Fuel Consumption of Small-Capacity Motorcycles: A Lab and Field Study

Metal conditioners (MC) are friction, wear, and heat-reducing agents between metal components in motion and are mainly used in engines and transmission boxes as aftermarket additives. Laboratory and field tests were conducted to assess the performance of a commercial MC. Laboratory tribotests revealed the MC’s potential to reduce wear and friction in lubricated steel contacts. Field studies were performed on two new motorcycles (160 cc) under urban driving conditions for 15,000 km. The physico-chemical properties of the used oils were similar and within the acceptable limits provided in the literature. The FTIR results showed that specific components in the MC formulation do not allow for a direct comparison between oils and their mixtures with MC. Regarding engine wear, MC provided overall aluminum and iron metal parts protection, mainly in the first 7000 km of engine break-in, but a higher wear of copper-containing parts, although at levels below the warning limits. Accurate measurements of engine components demonstrated there were changes of less than 0.05% in the cylinder, piston, and transmission system pieces, except for gear #5. The lubrication of the crown, pinion, transmission chain and gear #5 with the MC significantly increased their wear resistance. The motorcycle driven with MC maintained higher average fuel economy improvements (+1 km/L), representing a 2.5% gain compared to the other motorcycle. Although only two motorcycles were tested, the laboratory and field results suggested that mixing MC with the fully formulated oil (10W-30) reduces wear and friction during the break-in period

The Corrosive Effects of Aftermarket Oil Additives on High-Leaded Tin Bronze Alloy

Aftermarket additives are used to enhance the performance of internal combustion engines in specific aspects such as reducing wear, increasing power, and improving fuel economy. Despite their advantages, they can sometimes cause corrosion-related problems. This research evaluated the corrosiveness of four aftermarket additives on the corrosion of a high-leaded tin bronze alloy over 28 days at 80 °C in immersion tests. Among the evaluated products, three showed corrosive effects ranging from intermediate to severe. Notably, the visual appearance of the surfaces often did not indicate the underlying corrosive damage. Therefore, the assessment of corrosiveness was based on chemical characterizations conducted on both the drained oils and the bronze surfaces. The study found minimal oil degradation under the testing conditions, indicating that the primary cause of corrosion was the interaction between the specific additives and the metal elements of the alloy, rather than oil degradation itself. A direct correlation was observed between the dissolution of lead and copper and the adsorption of S and Cl-containing additives on the surfaces, respectively. The corrosive impact of Cl-containing additives in aftermarket formulations was significantly reduced when mixed with engine oil SAE 10W-30 (at a 25:1 ratio), suggesting a mitigated effect in combined formulations, which is the recommended usage for engines

Effect of Porosity/Binder Index on Strength, Stiffness and Microstructure of Cemented Clay: The Impact of Sustainable Development Geomaterials

Searching for alternative material options to reduce the extraction of natural resources is essential for promoting a more sustainable world. This is especially relevant in construction and infrastructure projects, where significant volumes of materials are used. This paper aims to introduce three alternative materials, crushed ground glass (GG), recycled gypsum (GY) and crushed lime waste (CLW), byproducts of construction industry geomaterials, to enhance the mechanical properties of clay soil in Cartagena de Indias, Colombia. These materials show promise as cementitious and frictional agents, combined with soil and cement. Rigorous testing, including tests on unconfined compressive strength (qu) and initial stiffness (Go) and with a scanning electron microscope (SEM), reveals a correlation between strength, stiffness and the novel porosity/binder index (η/Civ) and provides mixed design equations for the novel geomaterials. Micro-level analyses show the formation of hydrated calcium silicates and complex interactions among the waste materials, cement and clay. These new geomaterials offer an eco-friendly alternative to traditional cementation, contributing to geotechnical solutions in vulnerable tropical regions

Efecto de la nitruración por plasma a baja temperatura sobre la corrosión y las propiedades de la superficie del acero inoxidable dúplex UNS S32205

El acero inoxidable dúplex UNS S32205 se nitruró con plasma a 380 ° C durante 10 h usando una mezcla de gases de 25% N 2 -75% H 2 . El espesor de la capa nitrurada fue de 4,5 ± 0,5 µm, compuesta principalmente por precipitados de austenita expandida con nitrógeno y nitruros de hierro. Hubo un aumento en la dureza superficial alrededor de 2,6 y 3,8 veces en la capa nitrurada formada sobre las fases de austenita y ferrita, respectivamente, en relación con las muestras sin tratar. Los parámetros de textura de la superficie sesgo ( S sk ), altura máxima de pico ( S p ) y relación de aspecto de textura ( S tr) fueron los parámetros más adecuados para estudiar los cambios topográficos posteriores al tratamiento. Las curvas de polarización cíclica revelaron una mejora en las propiedades de corrosión localizada después del tratamiento de nitruración. Las muestras nitruradas mostraron un mayor potencial de corrosión por picadura y de repasivación en comparación con el material sin tratar. Las fases ferríticas y los límites de grano fueron más susceptibles a la corrosión en las muestras nitruradas. Las curvas potenciodinámicas de las muestras nitruradas exhibieron una ladera en la transición de pasivo a transpasivo. Esta característica ya fue observada por otros investigadores, pero no ha sido bien investigada. Los estudios potenciostáticos demostraron que se produjeron picaduras metaestables en esta transición.The duplex stainless steel UNS S32205 was plasma nitrided at 380 °C for 10 h using a gas mixture of 25% N2-75% H2. The thickness of the nitrided layer was 4.5 ± 0.5 ?m, composed mainly of nitrogen-expanded austenite and iron nitrides precipitates. There was an increase in surface hardness around 2.6 and 3.8 times in the nitrided layer formed on the austenite and the ferrite phases, respectively, in relation to the untreated samples. The surface texture parameters skewness (Ssk), maximum peak height (Sp) and texture aspect ratio (Str) were the most appropriate parameters for studying the topography changes after treatment. An improvement in the localized corrosion properties after the nitriding treatment was revealed by the cyclic polarization curves. The nitrided samples showed higher pitting corrosion and repassivation potentials compared to the untreated material. The ferritic phases and grain boundaries were more susceptible to corrosion in the nitrided samples. The potentiodynamic curves of the nitrided samples exhibited a hillside on the passive-to-transpassive transition. This feature was already observed by other researchers, but it has not been well investigated. Potentiostatic studies demonstrated that metastable pitting took place on this transition.Q2Grupo de Investigación en Diseño, Análisis y Desarrollo de Sistemas de Ingeniería -GIDA

Effect of Low-Temperature Plasma Nitriding on Corrosion and Surface Properties of Duplex Stainless Steel UNS S32205

El acero inoxidable dúplex UNS S32205 se nitruró con plasma a 380 ° C durante 10 h usando una mezcla de gases de 25% N 2 -75% H 2 . El espesor de la capa nitrurada fue de 4,5 ± 0,5 µm, compuesta principalmente por precipitados de austenita expandida con nitrógeno y nitruros de hierro. Hubo un aumento en la dureza superficial alrededor de 2,6 y 3,8 veces en la capa nitrurada formada sobre las fases de austenita y ferrita, respectivamente, en relación con las muestras sin tratar. Los parámetros de textura de la superficie sesgo ( S sk ), altura máxima de pico ( S p ) y relación de aspecto de textura ( S tr) fueron los parámetros más adecuados para estudiar los cambios topográficos posteriores al tratamiento. Las curvas de polarización cíclica revelaron una mejora en las propiedades de corrosión localizada después del tratamiento de nitruración. Las muestras nitruradas mostraron un mayor potencial de corrosión por picadura y de repasivación en comparación con el material sin tratar. Las fases ferríticas y los límites de grano fueron más susceptibles a la corrosión en las muestras nitruradas. Las curvas potenciodinámicas de las muestras nitruradas exhibieron una ladera en la transición de pasivo a transpasivo. Esta característica ya fue observada por otros investigadores, pero no ha sido bien investigada. Los estudios potenciostáticos demostraron que se produjeron picaduras metaestables en esta transición.The duplex stainless steel UNS S32205 was plasma nitrided at 380 °C for 10 h using a gas mixture of 25% N2-75% H2. The thickness of the nitrided layer was 4.5 ± 0.5 μm, composed mainly of nitrogen-expanded austenite and iron nitrides precipitates. There was an increase in surface hardness around 2.6 and 3.8 times in the nitrided layer formed on the austenite and the ferrite phases, respectively, in relation to the untreated samples. The surface texture parameters skewness (Ssk), maximum peak height (Sp) and texture aspect ratio (Str) were the most appropriate parameters for studying the topography changes after treatment. An improvement in the localized corrosion properties after the nitriding treatment was revealed by the cyclic polarization curves. The nitrided samples showed higher pitting corrosion and repassivation potentials compared to the untreated material. The ferritic phases and grain boundaries were more susceptible to corrosion in the nitrided samples. The potentiodynamic curves of the nitrided samples exhibited a hillside on the passive-to-transpassive transition. This feature was already observed by other researchers, but it has not been well investigated. Potentiostatic studies demonstrated that metastable pitting took place on this transition.Q2Grupo de Investigación en Diseño, Análisis y Desarrollo de Sistemas de Ingeniería -GIDA