This study evaluates the effect of combining 12% rice husk ash (RHA) with varying percentages of RCC-15 spent catalyst (7%, 9%, 11%, and 13%) on the engineering properties of soft clay soil obtained from Cililin. Laboratory tests were conducted, including physical property characterization, compaction tests, and unconfined compressive strength (UCS) tests with curing periods of 0, 3, 7, and 14 days. The results show that the addition of RHA and RCC-15 improves soil compaction characteristics, indicated by an increase in maximum dry density and a reduction in optimum moisture content. Furthermore, the UCS values increased significantly with higher RCC-15 content and longer curing periods, reaching values between approximately 1.57 and 3.66 kg/cm² at 14 days. These improvements are attributed to mechanical densification and pozzolanic reactions between the stabilizing agents and soil minerals. This study emphasizes the synergistic application of agricultural and industrial waste materials for local soil stabilization, indicating that the combined use of rice husk ash and RCC-15 spent catalyst can enhance the engineering performance of soft clay while supporting sustainable and resource-efficient ground improvement practices.
Illegal parking in urban commercial corridors is commonly treated as a public-order problem. From a spatial perspective, however, it also reflects a shift in roadway function, where traffic space is temporarily converted into static space. This study examines that shift using longitudinal occupation (OL), effective width reduction (EWR), and a proposed composite measurement approach termed the Space Pressure Index (SPI). The case site is an approximately 200 m urban commercial segment where vehicles routinely park in parallel on both sides despite the absence of formal parking facilities. Data were collected through a four-day parking patrol survey covering two weekdays and two weekend days, supported by roadway-width measurements under two-sided parking conditions. The results show a clear time-dependent pattern: parking builds up and intensifies during peak commercial hours. Longitudinal occupation peaked at 120.7%, meaning that the cumulative equivalent length of parked vehicles exceeded the usable segment length during the busiest period. At the same time, two-sided parking reduced the effective width by 36.7% relative to the initial geometric width. When these two dimensions are combined, the SPI reached a maximum of 44.3%, indicating substantial functional conversion of movement space during the peak interval. Overall, the findings frame illegal parking in commercial areas as a measurable form of space competition with direct operational implications for corridor mobility. Compared with partial occupancy measures, the proposed OL-EWR-SPI approach offers a clearer segment-scale description of how roadway space is reallocated over time.
Excessive vibrations in heritage buildings located near heavy traffic often cause occupant discomfort despite adequate structural capacity. This study investigates the vibration mechanism and proposes a mitigation strategy with minimal intervention using Operational Modal Analysis (OMA) and Stochastic Subspace Identification (SSI). The identified fundamental frequency of the building is 3.09 Hz, which closely matches the dominant traffic-induced ground frequency (3.10 Hz), yielding a frequency ratio ≈ 1.0 and confirming soil–structure resonance as the governing mechanism. This resonance amplifies responses, particularly at intermediate floors. To mitigate the effect, a Multiple Tuned Mass Damper (MTMD) system with a total mass of 4 tons (≈0.54% of structural mass) is proposed. The MTMD effectively reduces dynamic amplification while remaining non-invasive, making it suitable for heritage structures. The results demonstrate that small-mass MTMD provides a practical and efficient vibration mitigation solution.
Concrete is a widely used construction material due to its strength and durability, but its quality is greatly influenced by its constituent materials and the environment. In West Kalimantan, people use scrap wire from building demolition as an additive in concrete, while clean water is limited, so peat water or seawater is often used as a mixer. This study aims to determine the effect of wire mesh usage and mixing water type on concrete compressive strength at 7, 14, and 28 days. Test specimens in the form of cubes were made with variations: normal concrete (clean water), concrete with peat water, concrete with seawater, and concrete with 1% wire mesh added to each type of water, and compressive strength testing was conducted using a compression testing machine. The results showed that peat-water concrete achieved the highest strength (119.50, 207.37, and 247.73 kg/cm² at 7, 14, and 28 days), seawater concrete produced the lowest (92.87, 182.27, and 225.90 kg/cm²), and the addition of 1% wire mesh increased early-age strength up to 186.57 kg/cm² at 7 days but its effect diminished at later ages. Thus, the type of mixing water plays a dominant role in concrete quality, while steel tie wire is more effective in increasing strength during the early stages of hardening.
This study evaluates the effectiveness of the Integrated Waste Management Facility (TPST) service in Sidodadi Sub-district, Wonomulyo District, Polewali Mandar Regency, using a spatial analysis approach based on the location–allocation method implemented in ArcGIS. The research is motivated by the high population density of Sidodadi, which has led to an increase in waste generation, while only a single TPST facility is currently operational. A quantitative descriptive method was applied, utilizing primary data from field observations and secondary spatial data, including building point data, road network data, and high-resolution satellite imagery. Spatial analysis was conducted by mapping waste generation at the building level, performing network-based distance analysis along the road network (as opposed to straight-line/Euclidean distance), and modeling TPST service coverage using a location– allocation model. The model parameters included a service distance cutoff of ≤ 1 km and facility capacity constraints based on the maximum number of households that can be served within a given facility. The results indicate that the existing TPST can serve approximately 600 households, corresponding to only about 15,84 % of the total residential buildings in Sidodadi Sub-district. Consequently, a significant proportion of densely populated residential areas remains outside the effective service coverage. This limited coverage is primarily influenced by insufficient facility capacity and service distances exceeding the defined cutoff. The study recommends the development of additional TPST facilities at strategically selected locations to increase service coverage percentage and enhance the efficiency and sustainability of waste management in Sidodadi Sub-district.
Construction projects operate under high uncertainty and remain vulnerable to cost, time, quality, and occupational safety issues. Although risk management is commonly applied, risk monitoring and control in practice often remain fragmented, with indicator tracking, follow-up actions, and reporting not always connected in a clear operational flow. This study aims to develop an initial design of a construction project risk monitoring and control framework that is practical, systematic, and easy to implement. The study adopts a design-study approach using secondary data derived from international standards and guidelines, scientific literature, and Indonesian construction risk management references, which were synthesized to identify the key process, information, and tool requirements of the framework. The proposed design integrates an iterative monitoring and control workflow, structured risk information including Early Warning Signs (EWS), Key Risk Indicator (KRI) grouping, metrics and thresholds, and action effectiveness evaluation, as well as semi-automated spreadsheet-based tools to support risk recording, evaluation, updating, and reporting. The contribution of this study lies in translating risk monitoring and control principles into a connected operational design that can support more consistent, traceable, and system-based project risk management practice. As a literature- and practice-based initial design, this framework is intended to serve as a foundation for further expert validation and implementation in construction projects.
Aluminum alloy AA1100 exhibits good corrosion resistance but suffers from low surface hardness and wear resistance, which can be improved through anodizing. However, limited studies have examined the combined influence of sulfuric–phosphoric acid electrolyte composition and aeration. This study investigates the effect of sulfuric–phosphoric acid electrolyte composition and aeration on oxide layer mass, thickness, and hardness during anodizing. Anodization was conducted using a total electrolyte concentration of 20% with varying sulfuric acid (15–20%) and phosphoric acid (5–0%) ratios at a current density of 3 A/dm², operating times of 15 and 30 minutes, and room temperature under aerated and non-aerated conditions. The results show that aeration significantly increased oxide layer formation, yielding an average oxide mass of 0.0173 g compared to 0.0106 g in non-aerated systems. The maximum oxide mass (0.0375 g) was obtained at 20% sulfuric acid with aeration for 30 minutes. The highest oxide layer thickness of 47.94 µm was achieved using a 19% sulfuric acid–1% phosphoric acid electrolyte under aerated conditions at 30 minutes. Meanwhile, the maximum surface hardness of 352.60 HVN was obtained at 15% sulfuric acid–5% phosphoric acid with aeration for 15 minutes. These findings demonstrate that electrolyte composition and aeration play a critical role in optimizing anodic oxide growth and mechanical properties of AA1100.
Serang City, as the capital of Banten Province, has met the urban green open space standards, achieving a percentage of 59.64%. Serang City Square is one of the representations of public green open spaces in the area. This study aims to identify the extent to which Serang City Square fulfills its ecological, socio-cultural, aesthetic, and economic functions as a public green open space. This study is based on the direct perceptions of visitors and addresses a research gap, as perception-based evaluations of public green open spaces remain limited, particularly in the context of Serang City Square. This research is a quantitative descriptive study. Data were collected through a questionnaire survey and field observations. The questionnaire survey was conducted with 100 visitors of Serang City Square. Field observations were also carried out to complement the questionnaire data. The data were then analyzed using descriptive statistical and qualitative descriptive analysis techniques. The results indicate that Serang City Square has fulfilled most of its ecological and economic functions; however, some aspects of its social and aesthetic functions remain suboptimal. This is shown by the absence of children’s play areas, public perception of poor cleanliness and sanitation, and insufficient lighting that affects comfort and environmental aesthetics. These findings indicate the need for intervention by the Serang City Government to strengthen the functionality of Serang City Square as a public green open space.
The sustainability of rice fields is fundamental to maintaining regional food security, particularly in agricultural production centers such as Polewali Mandar Regency, West Sulawesi, Indonesia. Rapid population growth and spatial development have intensified pressure on productive agricultural land, increasing the risk of long-term decline in rice field availability. This study develops a spatial statistical modeling framework to predict the distribution of rice field conversion for the period 2026–2030 using an integration of Frequency Ratio (FR) and Spatial Multi-Criteria Analysis (SMCA) within a Geographic Information System (GIS) environment. Land cover data from 2010 and 2020 were used to identify historical conversion patterns and to construct predictive variables. Ten driving factors—including topography, slope, geomorphology, soil type, rainfall, accessibility, settlement characteristics, and spatial policy direction—were evaluated alongside protected agricultural zones as limiting constraints. Model validation using the Receiver Operating Characteristic (ROC) curve produced an AUC of 0.83 (success rate) and 0.75 (predictive rate), indicating good and reliable model performance. The projection results demonstrate continued pressure on rice field areas, particularly in zones influenced by infrastructure and settlement expansion. By providing spatially explicit predictions, this study offers a decision-support tool for proactive land-use regulation, agricultural protection policies, and strategic planning interventions aimed at safeguarding food self-sufficiency in the medium term.
In seismic-actively located West Bandung Regency it is crucial for evaluation of existing residential buildings seismic performance to mitigate potential earthquake losses. The purpose of this study was to study four standard two-storey reinforced concrete residential houses type A–D in West Bandung Regency using nonlinear static pushover analysis in SAP2000 and two main directions (X and Y). Performance points were established using the FEMA 440 equivalent linearization approach by crossing the capacity spectrum with the seismic demand spectrum, including stiffness degradation and effective damping due to nonlinear response. The seismic performance was analyzed in terms of some of the most common response indicators (spectral acceleration, spectral displacement, effective period or ductility, effective damping) and an empirical FEMA 356 plastic hinge assessment to establish the dominant mechanism of the damage. This shows a high directional dependency between spectral demand and displacement capacity among building types. The distribution of hinge states at the performance point is characterized by early–to-moderate damage types (A–B, B–IO, and IO–LS), with more severe states (LS–CP, CP–C, and isolated C–D) present in certain situations and localized. In conclusion the nonlinearity of the response is best characterized by a beam dominant mechanism indicating ductile behavior, however localized advanced hinge states indicate the requirement for targeted strengthening at critical members and directions.
An NPK plant is a facility that produces NPK fertilizer through a manufacturing process specifically designed to create fertilizer with a special formulation. However, in the production process, the feeding of raw materials is still done manually, resulting in low productivity and high operational costs. Based on production performance tests conducted on September 15, 2024, the manual system only achieved an average of 1.34 tons/hour, or 47% of the production target of 3 tons/hour. Therefore, a transportation system is needed to transport the materials, given the limitations of human labor capacity in terms of material handling and employee safety. This study aims to design an automatic feeding system to maximize production capacity up to 3 tons per hour. The system design begins with analyzing losses due to low productivity of the manual system, analyzing factory requirements, designing the main components of the feeding system, such as the hopper, weigher, and conveyor belt, equipped with an on-off control-based system to ensure consistent raw material flow. Technical design was carried out through visualization using AutoCAD and Visio software, solid flow simulation using Altair EDEM software, and economic feasibility analysis by calculating the Return on Investment (ROI) and Payback Period (POT). The calculation results show that this feeding system has a ROI of 40.8% and a POT of 2.05 years, indicating that the designed system is economically viable for implementation.
The use of synthetic textile dyes causes environmental problems, namely the waste produced is still colored and difficult to degrade. Methyl orange is a synthetic dye in the textile industry which has low solubility in water, is difficult to degrade, has the potential to be carcinogenic and is toxic. To overcome this, adsorption can be carried out using activated carbon from reeds. This research aims to find out how active carbon of reeds is absorbed in methyl orange using the batch method with Langmuir isotherm analysis. Research methods include pretreatment of reeds, manufacture and activation of reeds carbon, testing the characteristics of activated carbon, adsorption process, and analysis of adsorption results using a UV-Vis spectrophotometer. The research was carried out by varying the concentration of methyl orange solution, adsorption time, and mass of activated carbon used. From the research, optimum conditions were obtained for the methyl orange adsorption process using reed activated carbon for 120 minutes with an activated carbon mass of 0.3 grams, a final concentration of 7.328 ppm was obtained with an initial concentration of 10 ppm, and a % adsorption of 26.72%.
Coffee is one of the most widely produced and consumed agricultural commodities in Indonesia, with production rates increasing each year. This growing demand results in an increasing volume of spent coffee grounds, which are typically discarded as waste. One sustainable approach to managing this waste is by converting it into bio-briquettes, a form of solid fuel. This study aims to evaluate the physicochemical characteristics of coffee ground-based briquettes using different types of adhesives in accordance with the Indonesian National Standard (SNI 01-6235-2000) and to determine which adhesive yields the highest briquette quality. Three types of adhesives were tested: tapioca starch, sago starch, and polyvinyl alcohol (PVA), each mixed with carbonized coffee grounds in a 1:10 ratio. The briquettes were analyzed based on key performance indicators, including moisture content, ash content, volatile matter, density, fixed carbon, and calorific value. The carbonization process was applied prior to briquette formation to improve fuel quality. The results showed that the briquette using PVA as an adhesive exhibited the best overall performance, with a density of 0.449 g/cm³, ash content of 4.360%, moisture content of 1.480%, volatile matter of 33.974%, fixed carbon of 59.743%, and a calorific value of 6.861 cal/g. These findings suggest that PVA-based briquettes offer promising potential in reducing biomass waste and supporting the development of renewable energy in Indonesia.
Indonesia has significant maritime potential, particularly in salt production. However, national salt production has not yet met domestic demand, especially for industrial-grade salt, which requires a minimum NaCl content of 97%. Crude salt produced using traditional methods often contains only 88-94% NaCl and includes impurities such as Ca, Mg, and sulfate. This research aims to produce recrystallized salt that meets industrial standards and to determine the optimal conditions in a laboratory-scale simulator. The experimental method was conducted by simulating evaporation on a recrystallization table. Salt solutions were prepared from crude salt with varied concentrations of 22%, 25%, and 30%. The observed parameters included solution density, evaporation rate, and the content of NaCl, total hardness, and sulfate in the salt product. The results showed that recrystallization significantly increased the NaCl content and reduced impurities. Optimal conditions were achieved with a 22% salt solution, where crystal formation produced recrystallized salt with an NaCl content of 99.33%, total hardness of 0.47%, and sulfate content of 8.56 ppm. This quality has the potential to meet industrial salt standards. This study can serve as a reference for industrial salt production on a larger scale.
Cadmium (Cd) is a heavy metal with high toxicity that can enter the body through contaminated food chains, so wastewater containing cadmium needs to be treated before being discharged into the environment. This study uses adsorption methods to reduce Cd(II) concentration in artificial wastewater by utilizing modified sengon wood sawdust cellulose as a bioadsorbent. Adsorption tests were conducted in batch mode at room temperature with constant stirring, and the results were analyzed using AAS. The objective of this study was to determine the optimum adsorption conditions using Response Surface Methodology (RSM) and to determine the adsorption capacity of the modified bioadsorbent based on the Freundlich or Langmuir adsorption isotherm models. The variations in bioadsorbent dose in this study were 2, 4, and 6 g/L; adsorption time variations were 30, 60, and 90 minutes; pH variations were 3, 4, and 5. Based on the design expert 13 RSM software, the optimum adsorption conditions for citric acid-modified bioadsorbent are a bioadsorbent dose of 3.957 g/L, time of 31.655 minutes, and pH of 4.968. For the EDTA-modified bioadsorbent, the optimum conditions were a bioadsorbent dose of 3.836 g/L, time of 30 minutes, and pH of 4.708. The results of the adsorption isotherm modeling indicate that the citric acid-modified and EDTA-modified bioadsorbents are more suitable for the Freundlich isotherm model due to their higher determination coefficient (R²). Thus, the adsorption capacities for the citric acid-modified and EDTA-modified bioadsorbents were determined to be 1.7828 mg/g and 1.5776 mg/g, respectively.
Coffee consumption in Indonesia has been increasing over time. As a result of the high consumption and production, coffee waste often ends up in landfills. One potential solution to this problem is converting coffee waste into reusable products. Coffee grounds waste can be utilized as renewable energy in the form of briquettes. In this research, coffee grounds are used as briquette material. Briquettes are made by the carbonization method. Temperature plays a crucial role in determining the quality of briquette. This study aims to identify the optimum carbonization temperature, with variations of 350°C, 400°C, and 450°C. Each briquette sample was analyzed according to the Indonesian National Standard SNI 01-6235-2000. The results show that all carbonization temperatures produced briquettes with high calorific values (>5000 cal/g), that is 6981 cal/g at 350°C, 7037 cal/g at 400°C, and 7043 cal/g at 450°C. However, the resulting briquettes did not meet the standard criteria for density, fixed carbon, and volatile matter.
Aluminum is a type of metal that is widely used in the industrial and household fields. This study aims to analyze the effect of variations in sulfuric acid and oxalic acid concentrations, as well as aeration systems, on the surface characteristics of aluminum 1100 through the anodizing process. The anodizing process is one of the surface treatment processes that is carried out with the aim of improving or improving the properties of a metal, including resistance to wear, increasing hardness, and aiming to beautify the appearance itself. This anodizing test is with sulfuric acid-oxalic acid electrolyte solution, electrolyte concentration 16%, at room temperature with a current density of 3/dm2 in time intervals of 20 minutes and 30 minutes. The data obtained from the test results showed that the oxide layer was formed maximally in the aeration system with a concentration of 13.5+2.5 and a time interval of 30 minutes of 0.0411 gr. This shows that the addition of oxalic acid and oxygen can accelerate the formation of the oxide layer. At electrolyte concentrations of 16+0, 15.5+0.5, 15+1, 14.5+1.5 and 14+2, there was an increase in the difference in oxide mass by 0.0337 gr, 0.0335 gr, 0.0366 gr, 0.0390 and 0.0411 gr.
The direct disposal of tofu industrial wastewater without treatment can have negative impacts on the environment due to its organic content. One effort that can be done is to process tofu liquid waste using the adsorption method. Nowadays, coffee shops are growing rapidly in indonesia, resulting in a lot of coffee grounds waste which can be used as raw material for activated charcoal because of its carbon content. In addition to coffee grounds, other waste in the form of fly ash is also used as an adsorbent because of its silica content. This study aims to determine the optimization of the composition of coffee grounds and fly ash adsorbents in the purification of tofu industry liquid waste and to determine the optimum contact time so that liquid waste is obtained in accordance with quality standards. Observation parameters include acidity (ph) and chemical oxygen demand (cod). Coffee grounds charcoal is activated using 0.1 n h₃po₄ solution then mixed with fly ash in a ratio of 20:80; 30:70; 50:50; 70:30; and 80:20. The adsorption process is carried out in batches for 60, 90, and 120 minutes. The results of the study showed the optimum composition of the adsorbent 20:80 and contact time 120 minutes with a final cod of 2,761 mg/l, ph 6.21, and a cod reduction of 80.46%.
The growth and development of the population have significantly accelerated economic progress within society. Consequently, many new businesses have emerged, including commercial laundry services. One of the substances found in laundry wastewater, phosphate can cause eutrophication, which disrupts the balance of aquatic ecosystems. One method that can be developed to address this issue is adsorption technology. The aim of this research was to lower the phosphat content and to meet the Regulation of the Minister of Environment of the Republic of Indonesia No. 5 of 2014. The increasing number of coffee shops generates coffee grounds that have the potential to be processed into activated carbon. Additionally, fly ash a by-product of coal combustion contains silica and can be used as an adsorbent. The activated carbon is activated using 0.1 N NaOH and combined with fly ash in various compositions: 2:8, 4:6, 5:5, 6:4, and 8:2. Besides the variation in composition, contact time is also varied 30 minutes, 60 minutes, 90 minutes, 120 minutes, and 150 minutes. The observed parameters include pH and phosphate concentration at each contact time. The research results show that the optimal composition is 0.2AC:0.8FA with the highest phosphate removal efficiency of 60.3% at 150 minutes contact time and a pH of 7.1. However, the final phosphate concentration has not yet met the quality standard of 2 mg/L set by the Regulation of the Minister of Environment of the Republic of Indonesia No. 5 of 2014.
The initial generation capacity of 30 MW at the Geothermal Power Plant (GPP) decreased to 11.88 MW due to reduced steam supply from production wells. This mismatch between the original system design and current operating conditions affected components such as the steam ejector, which experienced a reduction in motive steam flow from 1.96 kg/s to 1.66 kg/s. As a result, the mixing chamber became inefficient in entraining flow of non- condensable gases (NCG), causing suboptimal pressure ratios (P3/P5), turbulence, and backflow. This study aims to redesign the mixing chamber of the steam ejector to enhance the extraction NCG. Using compressible flow theory and CFD simulation with Ansys Fluent 2025R1, the redesigned geometry improved the entrainment ratio from 0.27 to 0.31 and increased the NCG suction rate from 0.45 kg/s to 0.52 kg/s. The pressure ratio P3/P5 rose from 0.04 to 0.07, approaching optimal conditions. Further analysis revealed that under increased motive flow (1.687 kg/s), the ejector achieved an entrainment ratio of 0.32, and under lowered condenser pressure (8.1 kPa), the entrainment reached 0.34. These two optimal conditions demonstrate the redesigned chamber’s adaptability under varied operational scenarios. The performance improvement contributed to an additional power output of 41.68 kWh, approaching the plant’s installed capacity and improving system reliability. From economic perspective, the optimization is also feasible, yielding a net present value (NPV) of Rp6.46 million and demonstrating high profitability and practical applicability.
