Journal of Transactions in Systems Engineering

Performance Analysis of Recycled Concrete Aggregates Derived from Construction Waste

Mohammed. M. Saad — 2024-10-01

This paper highlights the potential advantages of incorporating aggregates derived from construction debris, particularly in the context of Libya, where the use of recycled concrete aggregate (RCA) is not yet widespread. This research aims to integrate recycling into state laws and procedures while demonstrating the practical applications of RCA. Three types of aggregates were examined such as natural aggregate (NA) as the reference, recycled concrete aggregate (RCA) from crushed old concrete blocks, and recycled terrazzo tiles (RTT). The characteristics of these aggregates were determined using various tests, including weight, volumetric, relative density (specific gravity), granular gradation, and Los Angeles abrasion (LA) tests. Results indicated a 15% reduction in specific gravity and a 20% decrease in volumetric weight for RCA compared to NA. The LA test revealed a higher abrasion percentage for the recycled aggregates, consistent with previous studies. To ensure a fair comparison, the same aggregate gradation and component proportions, based on the reference design mix, were used across all three mixes. The compressive strength of concrete made with these different aggregates was assessed through compression tests on cubes measuring 15 x 15 x 15 cm. A total of 12 specimens, with a combined volume of 0.0405 m3, were cast and cured by submerging them in water at 25°C for 3, 7, 14, and 28 days. The findings showed that the compressive strength of the NA mixture was higher than that of the mixes containing recycled materials. However, the compressive strength of the recycled aggregates is promising, with only a 21% decrease compared to the NA mixture, indicating potential for their use in construction.

Effect of Heat Treatment on Mechanical Properties and Corrosion Resistance of β Ti-18Mo-xCr (x = 3 & 7 wt.%) Alloy

Rosita Utari — 2024-10-05

β-Titanium alloys have gained significant attention for orthopaedic implants due to their superior mechanical properties, including high strength and a notably lower elastic modulus compared to conventional Ti-6Al-4V alloys. In this study, Ti-18Mo-xCr (x = 3 and 7 wt.%) alloys were developed to explore novel materials for biomedical applications. The alloys were produced using Vacuum Arc Remelting (VAR) followed by solution treatment and aging heat treatments. The elastic modulus was assessed using the Sonelastic tool, while corrosion resistance was evaluated via electrochemical polarization in a 0.9% NaCl solution. Surface morphology post-corrosion was analysed using SEM-EDS. The solution-treated alloys exhibited a significantly lower elastic modulus than those subjected to aging. Furthermore, the corrosion resistance of the aging-treated alloys was markedly inferior to both the solution-treated samples and the Ti-6Al-4V alloy, primarily due to β-phase stabilization during solution treatment. Prolonged aging further compromised corrosion resistance. Among all tested conditions, the Ti-18Mo-3Cr alloy aged at 500 °C demonstrated the lowest corrosion rate of 7.7373 × 10^-5 mm/year. These findings highlight the potential of Ti-18Mo-xCr alloys as candidates for next-generation orthopaedic implants, balancing mechanical properties and corrosion resistance.

Microstructural Evolution and Mechanical Properties Enhancement of Ti/SiC Metal Matrix Composites

Agus Pramono — 2024-10-06

Titanium's exceptional strength, low density, and outstanding corrosion resistance make it an ideal material for critical applications in power generation, the gas industry, sports equipment, and various industrial sectors. Under high-temperature conditions, titanium alloys must exhibit superior heat resistance and corrosion durability. However, enhancing titanium alloys with silicon carbide (SiC) through conventional powder metallurgy often results in issues such as porosity and the formation of silicides. To mitigate silicide formation, the hot-pressing technique has demonstrated excellent outcomes, achieving near-theoretical density without reaction zones. Nevertheless, increased sintering temperatures typically lead to a reduction in hardness. The highest hardness recorded was 92 HRB for a composite consisting of 70% titanium and 30% SiC at a sintering temperature of 900°C. By optimizing the sintering time, temperature, and applied pressure, denser Ti/SiC composites were produced.

The Effect of Temperature on the Pyrolysis PP and LDPE Plastic Waste: Implications for Pyrolysis Fuel Oil Characteristics

Fatah Sulaiman — 2024-10-10

The accumulation of plastic waste continues to rise, necessitating effective solutions for its management. Pyrolysis is a promising method for converting plastic waste into liquid fuel by breaking down long hydrocarbon chains into shorter ones. This thermochemical process occurs at high temperatures in the absence of oxygen, producing fuel that can be utilized. This study focuses on the experimental extraction of fuel oil from two types of plastic waste: polypropylene (PP) and low-density polyethylene (LDPE). Through pyrolysis, the study also investigates the effect of temperature variations on the properties and characteristics of the resulting fuel oil. A total of 750 grams of PP and LDPE plastic waste were used, with pyrolysis temperatures ranging from 250°C to 350°C for a duration of 2 hours. The fuel oil was analysed using density tests, combustion rate analysis, and gas chromatography–mass spectrometry (GC-MS). The results showed that the highest yield of fuel oil, 280 ml, was obtained from LDPE waste at a pyrolysis temperature of 350°C. The density of the produced fuel varied between 0.730–0.750 g/ml. GC-MS analysis revealed that the fuel oil consisted of hydrocarbon chains ranging from C7 to C12.

The Influence of Clay Soil Stabilization Using Nickel Slag on Unsoaked CBR Values

Rama Indera Kusuma — 2024-11-02

The subgrade soil is the most critical layer in road pavement structures, serving as the foundation supporting traffic loads. The strength of this subgrade also influences the required thickness of the pavement layers. In many road construction projects, the subgrade soil often exhibits a California Bearing Ratio (CBR) of less than 5%, indicating low bearing capacity and high swelling potential, necessitating soil stabilization. Nickel slag, a by-product of ferronickel smelting, contains high levels of silicate and lime, making it a suitable additive for soil stabilization. This study investigates the effect of nickel slag on soil characteristics by utilizing four different variations of slag content: 0%, 15%, 30%, and 45%, based on the dry weight of the soil. The soil samples were cured for 0, 3, and 7 days and subjected to liquid limit, plastic limit, and unsoaked CBR testing. According to the Unified Soil Classification System (USCS), the soil was classified as organic clay with medium to high plasticity (OH). The test results revealed that the unsoaked CBR value of the untreated soil was 2.9%. Upon stabilization, the maximum unsoaked CBR value increased to 22.65% with the addition of 45% nickel slag. Furthermore, the soil's plasticity index decreased from 18.25% to 8.64%, significantly reducing the soil's shrinkage potential. Nickel slag has proven to be an effective additive for enhancing subgrade soil properties, improving its bearing capacity, and reducing plasticity, making it a viable option for road pavement stabilization.