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Sustainable Asphalt Mixtures Comprising Steel Slag Filler and SBS-Modified Binder: An Experimental Investigation
No full textUtilizing steel slag powder as a mineral filler in asphalt concrete mixtures has garnered increasing attention due to its attractive benefits in both sustainability and material properties. The paper aims to critically evaluate the replacement of mineral filler with steel slag to produce a sustainable mixture. The replacement was made at 3 varied contents, i.e., 0%, 50%, and 100%, and meanwhile working together with a modified asphalt binder using 4% styrene-butadiene-styrene polymer. All designed mixtures were tested for volumetric properties and Marshall stability; an indirect tensile test was performed to determine the moisture susceptibility of all the mixtures of optimized binder content. At last, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) analyses were performed to examine the crystal structure, microscopic attributes, and chemical composition of the steel slag particles and the limestone dust and compare their differences. The study showed that steel slag used for mineral filler can significantly enhance Marshall properties and moisture susceptibility of asphalt mixtures. Working together with the SBS-modified binder, the positive effect was further pronounced. SEM analysis revealed that steel slag has a rough, angular surface texture with a high porosity and specific surface area. EDX analysis confirmed the pozzolanic composition of steel slag. Doi: 10.28991/CEJ-2025-011-04-04 Full Text: PD
Optimization Framework for ASIAN and National Road Networks in Lao PDR Using the Stochastic Markov Model
No full textDeveloping effective road network management is crucial for the socioeconomic development of developing countries, particularly the Lao People's Democratic Republic (Lao PDR or Laos). The current road maintenance system in Lao PDR uses a traditional reactive maintenance approach, addressing road deterioration only after the condition reaches a critical state. This study proposes a stochastic Markov Decision Process (MDP) framework to enhance traditional road management practices. The proposed MDP framework shifts from a conventional reactive to a proactive strategy by considering probabilistic pavement performance and optimally allocating funding to rapidly deteriorating sections. This study enables decision-makers to determine the optimal intervention strategies based on different scenarios. The comparison of the ASIAN Road network, high technical design and construction, and the National Road network, standard technical design and construction, in different scenarios provides a workable framework for maintaining Laos, and other developing countries, road condition despite limited resources and sustainable development concerns. This comprehensive framework includes estimating deterioration rates, defining policies, conducting life-cycle cost (LCC) analysis, and determining optimal strategies that minimize LCC subject to financial and performance constraints. This study highlights significant improvements in decision-making, particularly in resource allocation, by creating innovative and preventive approaches that enhance the efficiency of road management systems and ensure sustainable maintenance practices in Lao PDR. Doi: 10.28991/CEJ-2025-011-05-023 Full Text: PD
Street Networks and Urban Sustainability by Quantifying Connectivity, Accessibility, and Walkability for Resilient Cities
No full textStreet networks are crucial in shaping the quality of urban life. Through their impact on mobility and social interaction, they play a critical role in shaping how people move around the city and determine the connectivity, accessibility, safety, and convenience of different areas. Thus, it is essential to develop a systematic understanding of street networks to create livable, sustainable, accessible, and equitable cities. The aim of this study is to analyze and develop the role of street networks in shaping urban mobility, connectivity, and accessibility, and thereby enhance sustainable urban living by creating people-centric cities. Quantitative techniques and measures are employed to examine urban structure metrics to understand both physical and spatial characteristics at micro and macro scales. Three primary parameters for the configuration of street patterns - grid pattern ratio (GPR), pedestrian route directness factor (PRD/PRF), and ped-shed (PS) and effective walking area (EWA) - are selected to compute the formational attributes of selected streets in Baghdad, Iraq. The evaluation employs different arithmetic methods linked with a Geographical Information System (GIS) to quantify and compare two examined areas, and the results reveal a contradiction in the spatial configuration of the sample street patterns. From these findings, the paper offers specific recommendations and urban design guidelines to improve the quality of similar urban areas. The paper concludes that in-depth knowledge of a street’s role in its urban context helps to optimize spatial configuration processes in the built environment
Driving Economic Value: Assessing the Financial Impact of Dynamic Message Signs on Freeways
No full textDynamic Message Signs (DMSs) are an integral feature of any Intelligent Transportation System (ITS), providing drivers with real-time information such as travel time, incidents, routes, and weather conditions. This study aims to estimate the economic impacts associated with DMS use for route choice, weather advisories, and work zone management on freeways. Several freeway locations with varying levels of traffic congestion were selected to ensure a comprehensive evaluation under diverse conditions. Travel time savings and speed reductions were used as performance metrics to assess Benefit-Cost Ratios (BCRs) for each application. The findings show that DMSs yield substantial economic advantages across all use cases. For route guidance messages with a 35% diversion rate, the BCR was 1.032, indicating a cost-effective investment. Weather advisory messages recommending speed reduction achieved a notably higher BCR of 6.0, reflecting strong safety and financial benefits. Work zone applications using Portable Changeable Message Signs (PCMS) projected a BCR of 1.22. This study offers a data-driven justification for DMS deployment and contributes to the literature by focusing on financial performance, supporting strategic investment decisions beyond qualitative or operational assessments
Stress Concentration Factors in Tubular T-Joint Braces Under Compressive Loads Using Artificial Neural Networks
No full textStress concentration factors (SCFs) are often calculated using formulas based on experimental testing and finite element analysis (FEA). While maximum SCF could occur at any location along the brace axis of the tubular T-joint’s brace, only the SCFs at the crown and saddle points can be determined from the available formulae, which can result in imprecise fatigue life determination. The current study presents a methodology to determine the SCFs in T-joints using FEA and ANN. ANNs are more effective than conventional data-fitting techniques at modelling intricate phenomena. In this work, parametric equations to estimate the SCFs of the T-joint’s brace under compressive loading were developed. Utilizing parametric equations allows for rapid estimates of SCFs, in contrast to time-consuming FEA and expensive testing. The equations are based on an artificial neural network’s training weights and biases (ANN). 625 finite element simulations were performed on tubular T-joints with various dimensions under compressive loads to determine the SCFs at the brace of the T-joint. These SCFs were then used to train an ANN. The weights and biases of the ANN were subsequently used to derive equations for calculating SCFs based on dimensionless parameters. The equations can estimate the SCF of a T-joint brace with less than 7% error and a root mean square error (RMSE) of less than 0.19
Revolutionizing Recycled Aggregate Concrete: A Dual Approach Using HCl Treatment and Silica Fume
No full textDebris from building and demolition projects, as well as the shortage of natural resources, have become more pressing issues on a global scale in recent times. Even though concrete, the utmost adaptable building material, is a vital factor in the development of the infrastructural and industrial sectors, it has been claimed that it is not an environmentally friendly material due to its potential for profound environmental influence beyond its use and critical resource-consumption nature. Nevertheless, it will continue to be the dominant building material utilized globally. The present research aims to investigate the synergistic effects of the treatment of recycled concrete aggregate (RCA) by hydrochloric acid (HCl) and the replacement of cement by silica fume (SF) on the mechanical properties of produced concrete. Four groups of concrete mixes were prepared: (1) untreated recycled concrete aggregate (URCA), (2) HCl-treated recycled concrete aggregate (TRCA), (3) URCA with SF replacement, and (4) TRCA with SF replacement. The HCl treatment was applied at four molarities (0.2M, 0.4M, 0.6M, and 0.8M), while SF was used to replace cement by weight at four ratios (5%, 10%, 15%, and 20%). The results were evaluated in terms of the 7, 14, and 28-day compressive strength. The findings indicated that TRCA mixes significantly outperformed URCA mixes in terms of the mechanical properties, namely the 28-day compressive strength, in which the optimal mix was that with 100% TRCA by 0.4M HCl combined with 5% SF replacement. The results also demonstrated that 0.6M HCl treatment significantly enhanced the quality of RCA by removing weakly adhered mortar, leading to a nearly 21% rise in the 28-day compressive strength compared to URCA with complete replacement. Indeed, adding further SF enhanced the performance, as using 75% of TRCA+10% SF achieved the highest compressive strength of 38.7 MPa at 28 days, equalling around 25% improvement over the URCA with the same replacing level. Doi: 10.28991/CEJ-2025-011-05-08 Full Text: PD
Advancing Seismic Performance: Experimental Behavior of Hybridized Steel-FRP Composite Bars
No full textThis study investigates the structural performance of reinforced concrete (RC) columns reinforced with hybrid Steel-FRP Composite Bars (SFCBs), offering a sustainable alternative to conventional steel and fiber-reinforced polymer (FRP) reinforcement. Eight large-scale RC columns, measuring 400 × 400 mm in cross-section and 1850 mm in height, were tested under combined cyclic and axial loading to simulate seismic conditions. The experimental variables included SFCB diameters (14 mm, 18 mm, 22 mm), axial load ratios (20%, 30%, 40%), and stirrup spacing (80 mm, 100 mm, 150 mm). The results indicate that SFCBs can effectively replace traditional steel reinforcement, providing comparable load-bearing capacity while significantly improving durability. Columns reinforced with SFCBs demonstrated superior initial stiffness and achieved higher drift ratios than steel-reinforced columns, exceeding the limits set by international design codes (ACI 440.2R, CSA S806-12, Eurocode 8) with maximum drift ratios of up to 6.5%. Increasing the SFCB diameter from 14 mm to 22 mm enhanced peak load capacity by 14%–20% and improved drift ratios by up to 113%. However, higher axial load ratios and wider stirrup spacing were found to reduce ductility. Specifically, increasing the axial load ratio from 20% to 40% decreased ductility by 13.46%, while increasing stirrup spacing from 80 mm to 150 mm reduced ductility by 8.90%. These findings underscore the potential of SFCBs to enhance the performance of RC columns in seismic and corrosive environments, offering a durable and sustainable solution for modern infrastructure. To the authors' knowledge, this study represents the first comprehensive investigation into the behavior of SFCB-reinforced RC columns under combined cyclic and axial loading, providing valuable insights for the design of resilient concrete structures
Advanced Geogrid Reinforcement Strategies for Superior Bearing Capacity and Settlement Control in Square Shallow Foundations
No full textRecently, many research studies on square-shaped soil foundations have failed to achieve acceptable results due to their low resistance, in addition to the expected settlement of these foundations when constructed on weak granular soil. This study aims to overcome the low resistance and excessive settlement of square shallow foundations on weak granular soils by developing advanced geogrid reinforcement strategies to enhance load-bearing capacity and control settlement. A series of scaled laboratory experiments were conducted on simulated weak soil profiles, varying three key parameters—the depth of geogrid reinforcement layers, the width of each geogrid layer, and the number of layers—while quantifying performance through the Bearing Capacity Ratio (BCR) and Settlement Reduction Ratio (SRR); these empirical results were complemented by theoretical derivations of novel mathematical models to predict reinforced foundation behavior under diverse difficulty conditions. Experimental outcomes reveal that multilayer geogrid systems substantially elevate BCR and diminish settlement, with optimal configurations achieving up to a 60% improvement in bearing capacity and a 50% reduction in settlement compared to unreinforced foundations, and that deeper placement and additional layers yield significant yet progressively smaller gains. The proposed approach uniquely employs insulating geogrid layers to prevent water ingress and moisture infiltration—preserving structural integrity and imparting anti-settlement properties—and introduces high-precision predictive models; furthermore, the multilayer arrangement creates a barrier against moisture migration, reducing long-term settlement risks under fluctuating groundwater conditions, and cost analysis indicates that the optimal configurations deliver superior performance with minimal additional material investment, offering a cost-effective and geotechnically sound solution for foundation engineering
Structural and Soil Deformations in Non-Invert and Circular Tunnels: A Centrifuge and Numerical Analysis
No full textNon-invert tunnels are often chosen to reduce initial construction costs compared to circular tunnels, but they frequently require expensive maintenance. Despite their widespread use, limited research has quantified the differences in material requirements (steel and concrete) between these two designs. This study compares the internal forces and material demands of circular and non-invert tunnels using centrifuge model tests and numerical analysis. A combined approach using 40g centrifuge testing and parametric analysis in OPTUM G2 assesses bending moments, lining shear forces, and shear stress distributions. Three tunnel diameters (9 m, 12 m, and 16 m) are analyzed across depth ratios (H/D = 10, 7, 5, and 1), covering eight reinforced concrete lining designs. Results show that circular tunnels have more uniform stress distributions in the lining and surrounding soil, leading to lower bending moments and shear forces. In contrast, non-invert tunnels exhibit stress concentrations near the lower fulcrum corners and spring line. Due to their uniform stress distribution, circular tunnels become more material-efficient than non-invert at greater depths and larger diameters, reducing steel use by up to 36% despite requiring up to 19% more concrete. Non-invert tunnels, however, use less material at shallow depths, saving up to 14% in steel and 23% in concrete
The ITB Unit Hydrograph Method: A Novel Approach to User-Defined Unit Hydrograph Development (Part II)
Get PDFThis paper is the second part of a comprehensive two-part series on the ITB Unit Hydrograph (ITB-UH) Method, titled The ITB Unit Hydrograph Method: A Novel Approach to User-Defined Unit Hydrograph Development. Building on the foundational concepts introduced in Part I, this paper delves into advanced applications of the ITB-UH Method, emphasizing its adaptability, calibration capabilities, and real-world utility. The ITB-UH Method introduces novel derivations for the Peak Rate Factor (Kp) and Peak Discharge (Qp), along with a time-step normalization approach that enables flexible adjustments to unit rainfall durations and a systematic calibration process. These innovations significantly enhance the method's versatility and accuracy in modeling flood discharge across diverse hydrological conditions. The practical applicability of the ITB-UH Method is demonstrated through real-world flood discharge calculations in the Pinamula River, located in Buol District, Central Sulawesi Province. Three illustrative examples highlight the method's versatility: (1) analyzing flood hydrographs at a 1-hour time step to showcase its practical applicability for flood management; (2) recalculating flood hydrographs with a finer 0.5-hour time step to demonstrate its adaptability to varying temporal resolutions; and (3) refining model parameters to improve alignment with observed flood hydrographs, underscoring the method's capacity for calibration and optimization. To evaluate the method's performance, robust metrics such as the Nash–Sutcliffe Efficiency (NSE), Percentage Bias (PBIAS), and Index of Agreement (IA) are employed. These metrics confirm the ITB-UH Method's accuracy and reliability, with results consistently aligning closely with observed data. Collectively, the findings underscore the ITB-UH Method's suitability across diverse hydrological settings and its potential to enhance both the verification of existing SUH methods and the development of user-defined hydrographs. By enabling more accurate and effective flood management, the ITB-UH method represents a significant advancement in hydrological modeling, with broad implications for water resource management and infrastructure planning worldwide. Doi: 10.28991/CEJ-2025-011-05-015 Full Text: PD