Reinforcement of Cement Stabilized Macadam

                                      

INTRODUCTION

Cement stabilized macadam (CSM) serves as a critical semi-rigid base layer in Chinese highway pavement structures. Over time, environmental factors and traffic loads contribute to cracking, reducing its service life. Despite the widespread use of CSM, limited studies have examined the performance of repaired specimens. Understanding the fracture behavior and damage evolution of CSM after repair is essential for improving pavement durability. This study investigates these aspects using experimental and microscopic methods to enhance repair strategies and performance evaluation.

LITERATURE BACKGROUND

Previous research highlights the vulnerability of CSM to cracking due to cyclic loading and environmental impacts. Traditional studies focused mainly on initial damage rather than post-repair behavior. Repair methods, such as the application of polymers, have shown promise in reinforcing the semi-rigid base layer. However, systematic investigations combining mechanical tests and microstructural analysis remain scarce. This study addresses these gaps by integrating fracture mechanics, acoustic monitoring, and microstructural evaluation to assess repaired CSM under various loading conditions.

METHODOLOGY

Three-point bending tests were conducted on both original CSM and repaired CSM (RCSM) specimens to analyze fracture characteristics. Acoustic emission (AE) techniques tracked real-time damage evolution, while digital image correlation (DIC) provided strain mapping and crack development visualization. Additionally, microscopic scanning tests were performed to examine the microstructure of RCSM specimens. Permeable polymer was used in the repair process to reinforce bonding and improve mechanical performance. Loading rates were varied to assess their influence on fracture behavior.

CRACK DAMAGE EVOLUTION

RCSM specimens exhibited staged cracking, indicating gradual damage accumulation rather than sudden failure. AE monitoring revealed that higher-energy events occurred earlier as loading rates increased, reflecting accelerated crack propagation. DIC analysis confirmed that crack development differed at the repaired interface depending on the loading rate. At lower rates, interface damage was more pronounced, while at higher rates, cracks tended to propagate away from the repaired surface. These observations highlight the importance of considering loading conditions in evaluating repaired CSM performance.

FRACTURE CHARACTERISTICS

Permeable polymer improved the fracture resistance of CSM, increasing the crack initiation load, peak load, and fracture energy. Three primary failure modes were observed in RCSM specimens: hydraulic gravel failure near the repaired interface, permeable polymer failure, and polymer-aggregate interface failure. The repair material effectively reinforced aggregate bonding, demonstrating enhanced structural integrity. The fracture response depended on both the loading rate and the quality of repair, emphasizing the role of materials selection and repair techniques in extending pavement service life.

MICROSTRUCTURAL ANALYSIS

Microscopic observations revealed that the permeable polymer effectively cemented aggregates within the semi-rigid base layer, contributing to improved load transfer and resistance to crack propagation. The repaired interface exhibited varying degrees of bonding strength, influenced by both material interaction and applied loads. Cracks were often localized at weaker regions in the polymer or at the interface, consistent with observed macroscopic failure patterns. These findings provide a fundamental understanding of microstructural behavior that can guide optimized repair strategies for CSM pavements.

CONCLUSION

The study demonstrates that permeable polymer repair enhances the mechanical performance and fracture resistance of CSM pavements. RCSM specimens show staged cracking, with failure modes depending on loading rates and interface bonding. Acoustic emission and DIC techniques effectively captured crack evolution, while microstructural analysis confirmed improved aggregate bonding. The findings support the use of polymers for semi-rigid base repair and provide valuable insights for designing durable pavement maintenance strategies, ultimately extending the service life of highway infrastructure.

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#CivilEngineering, #MaterialsScience, #RoadRepair, #PolymerTechnology, #ConstructionInnovation, #PavementReinforcement, #InfrastructureImprovement, #EngineeringResearch, #DurableRoads, #CrackRepair,

Legacy of Austro-Hungarian Military Buildings in Banja Luka #ArchitectureHistory

 

Introduction

The architectural and urban evolution of Banja Luka, Bosnia and Herzegovina, is deeply intertwined with its Austro-Hungarian past, particularly through the transformation of former military structures. These buildings, initially erected between 1878 and 1918 for administrative, residential, healthcare, and logistical purposes, played a crucial role in shaping the city’s physical and cultural identity. This paper explores the processes of replanning, reconstruction, and rebranding that have redefined these structures across different historical phases. By analyzing the continuity and change in the architectural function and meaning of these edifices, the study reveals how military heritage has been adaptively integrated into modern urban life. The research combines archival investigation with contemporary field observations, providing insight into the evolving relationship between built heritage and socio-political transformations. The introduction establishes the study’s aim to assess how the adaptive reuse of Austro-Hungarian military infrastructure contributes to Banja Luka’s sustainable urban and cultural development.

Historical Context of Austro-Hungarian Military Architecture

During the Austro-Hungarian period, Banja Luka underwent significant military and infrastructural expansion that profoundly influenced its urban landscape. The empire’s military planning prioritized strategic control, efficient logistics, and administrative oversight, leading to the construction of barracks, hospitals, railway systems, and housing for officers and soldiers. These facilities not only served military purposes but also introduced new architectural typologies and urban planning principles reflective of Central European design standards. The military jurisdiction extended beyond mere defense, influencing public health, mobility, and governance structures in the region. Consequently, these developments laid the foundation for modern Banja Luka’s spatial organization. The architectural character of the buildings, marked by symmetry, functionality, and durable materials, reflected the empire’s authority and modernization agenda. Understanding this historical framework is essential to interpreting how these once-militarized spaces evolved into civic assets, influencing subsequent reconstruction and adaptive reuse efforts in the post-imperial period.

Post-Imperial Transition and Urban Replanning

Following the dissolution of the Austro-Hungarian Empire in 1918, Banja Luka’s military complexes underwent a gradual shift in function and ownership. The interwar period and subsequent Yugoslav era introduced new administrative and civic uses for former military buildings, integrating them into the broader urban framework. Urban planners and architects began repurposing barracks and hospitals into public institutions such as schools, museums, and government offices, aligning with national reconstruction priorities. This phase marked a critical transition from spaces of control to spaces of service and community engagement. The city’s spatial development policies emphasized modernization while retaining the functional essence of these robust structures. Adaptive planning ensured that the urban core expanded around these architectural anchors, blending historical integrity with new infrastructural demands. This period of transformation laid the groundwork for future redevelopment initiatives that would further redefine the role of Austro-Hungarian heritage in shaping Banja Luka’s identity.

Transformation between 1945–1991

The socialist period between 1945 and 1991 brought significant political and economic changes that influenced Banja Luka’s approach to urban development. During this era, former military zones were systematically restructured to meet public needs, reflecting socialist ideals of communal accessibility and functional urbanism. Many Austro-Hungarian military buildings were converted into administrative centers, educational institutions, and housing facilities, integrating historical structures into the social fabric. The state-driven urbanization policies promoted adaptive reuse as a cost-effective and symbolic act of reclaiming authority from past regimes. This transformation phase demonstrated the potential of architectural continuity within new ideological contexts, where the utilitarian value of heritage outweighed purely aesthetic considerations. The process also preserved key architectural features, ensuring that the city’s layered history remained visible. Thus, the mid-20th century marked a crucial period of large-scale adaptation that strengthened Banja Luka’s identity as a city built upon reinterpreted historical foundations.

Post-1995 Reconstruction and Rebranding

The post-1995 period, following the Bosnian War, introduced a renewed focus on reconstruction and cultural redefinition. Banja Luka’s urban planners and heritage experts sought to rebrand former Austro-Hungarian military buildings as integral components of the city’s cultural renaissance. Policies encouraged the conversion of abandoned or damaged structures into public institutions, art centers, and educational venues, symbolizing resilience and continuity. International and local collaborations facilitated funding for restoration and adaptive reuse projects, emphasizing both architectural preservation and functional reintegration. This era also saw the emergence of heritage tourism, where rebranded military buildings became cultural landmarks representing the city’s historical endurance. The rebranding process extended beyond architecture, contributing to a broader narrative of identity reconstruction in post-conflict Bosnia and Herzegovina. Ultimately, this transformation reinforced Banja Luka’s position as a model for sustainable urban recovery grounded in the adaptive reuse of its architectural legacy.

Adaptive Reuse and Heritage Management

The adaptive reuse of Austro-Hungarian military buildings in Banja Luka illustrates the effectiveness of sustainable heritage management practices. By repurposing existing structures instead of demolishing them, the city achieved both environmental and cultural benefits. The conservation approach prioritized maintaining architectural integrity while adapting interior functions to meet modern urban needs. Schools, museums, cultural centers, and administrative offices now occupy spaces once dedicated to military logistics, reflecting a balanced integration of past and present. This dynamic reuse also revitalized neighborhoods surrounding former military zones, stimulating local economies and community engagement. The process required multidisciplinary collaboration among architects, historians, urban planners, and policymakers to ensure that heritage preservation aligned with contemporary development goals. The successful execution of these projects highlights how adaptive reuse can serve as a strategic tool for sustainable growth, where historical memory and modern functionality coexist harmoniously within a living urban landscape.

Conclusion

The study of Banja Luka’s Austro-Hungarian military architecture reveals a profound narrative of transformation, resilience, and innovation. Through systematic replanning, reconstruction, and rebranding, the city has successfully converted former symbols of military power into vibrant cultural and social spaces. Each phase—from imperial construction to post-socialist renewal—demonstrates the evolving relationship between architecture, identity, and governance. The adaptive reuse of these heritage structures not only preserved their historical significance but also infused them with new relevance in a rapidly modernizing urban environment. Banja Luka’s approach exemplifies how heritage management can balance preservation with progress, fostering both cultural continuity and urban revitalization. As a result, the city stands as a compelling model for post-conflict and post-industrial regions seeking sustainable strategies for heritage-based development. The integration of historical infrastructure into contemporary urban life underscores the enduring value of architectural legacy in shaping civic identity and collective memory.

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#ArchitectureHistory, #BanjaLuka, #HeritageConservation, #AustroHungarian, #CulturalHeritage

CO2 Impact on Steel Slag Materials | #CarbonCapture

Introduction

Steel slag, a by-product generated during steel manufacturing, poses significant environmental challenges due to its disposal issues. However, it also presents an opportunity for carbon utilization through carbonation curing. By exposing steel slag to carbon dioxide, its properties can be enhanced while simultaneously reducing CO2 emissions. This study explores how varying CO2 concentrations influence the curing process, focusing on the carbon uptake, mechanical strength, and microstructural transformations of compact steel slag. The investigation aims to optimize the use of industrial flue gas as a sustainable means of CO2 sequestration and material strengthening.

Experimental Design and CO2 Concentration Range

The research examined a broad spectrum of CO2 concentrations, ranging from 0.04% (representing ambient atmospheric levels) to 27% (simulating industrial flue gas conditions). Compact steel slag samples were subjected to these environments for carbonation curing. The experimental setup allowed observation of how differing CO2 levels influence carbonation kinetics and hydration processes. Through controlled exposure and precise measurement, the study assessed both chemical and physical responses within the material. This range provided a realistic perspective on the potential use of actual industrial emissions for efficient steel slag treatment and carbon capture.

CO2 Uptake and Carbon Sequestration Efficiency

Results revealed that even at a relatively low CO2 concentration of 4%, steel slag demonstrated substantial carbon absorption, achieving a CO2 uptake of 7.3%. This outcome highlights the material’s inherent ability to act as an effective carbon sink. As CO2 concentration increased, the rate and extent of carbon sequestration also improved proportionally. The study confirms that carbonation curing is not only an environmentally beneficial process but also a practical approach for industrial-scale carbon capture, utilizing waste by-products from steel production to mitigate greenhouse gas emissions effectively.

Mechanical Strength Development

Mechanical testing showed a significant improvement in the compressive strength of compact steel slag following carbonation curing. Under 4% CO2 concentration, the material achieved a strength of 42.03 MPa after 72 hours of curing. Higher CO2 concentrations further enhanced this strength, suggesting a direct relationship between carbon uptake and material densification. The increased formation of calcium carbonate compounds within the matrix contributed to pore refinement and improved bonding between particles. This enhancement demonstrates that carbonation not only supports environmental sustainability but also leads to the production of durable and high-performance construction materials.

Microstructural Transformations

Microstructure analysis revealed distinct crystal morphology changes as CO2 concentration increased. Initially, the calcium carbonate formed primarily as aragonite, but at higher CO2 levels, it transitioned into the thermodynamically stable calcite form. This transformation indicated improved material stability and densification due to enhanced carbonation. The change from aragonite to calcite crystal structures provided evidence of effective CO2 interaction with steel slag components. These microstructural modifications directly influenced mechanical performance and durability, proving that higher CO2 environments facilitate the development of stronger and more compact materials.

Role of Carbonation and Hydration Mechanisms

Both carbonation and hydration reactions contributed to the overall consolidation of steel slag during curing. At lower CO2 concentrations, hydration dominated, leading to the formation of calcium silicate hydrates that bind particles together. As CO2 levels increased, carbonation became the primary mechanism, forming dense calcium carbonate matrices that improved strength and stability. This interaction between hydration and carbonation created a synergistic effect, optimizing the material’s performance. Understanding the balance between these two processes is essential for tailoring curing conditions to maximize both carbon capture and mechanical enhancement.

Conclusion

The study demonstrates that carbonation curing of steel slag under varying CO2 concentrations offers a dual advantage—effective carbon sequestration and improved material properties. Even low CO2 environments significantly enhance performance, while higher concentrations promote greater strength and structural stability. The transition from aragonite to calcite and the balance between hydration and carbonation highlight the process’s scientific and industrial potential. Utilizing industrial flue gas directly for curing opens promising avenues for sustainable construction materials and carbon management, transforming steelmaking waste into a valuable resource for environmental and engineering applications.

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#CO2,#SteelSlag,#CarbonCapture,#Sustainability,#GreenBuilding,#MaterialsScience,#ClimateAction,#Carbonation,#EcoMaterials,#FlueGas,

Bridge Health Monitoring #SHM

 

Introduction
Bridges play a pivotal role in ensuring national mobility and supporting economic activity, making their structural health a critical concern. Structural health monitoring (SHM) systems are essential for maintaining bridge safety and durability. However, sensor faults, environmental noise, and transmission issues can compromise the quality of SHM data. To mitigate these challenges, anomaly detection methods are widely employed. Despite their popularity, there is no comprehensive evaluation comparing these techniques. This review addresses that gap by systematically analyzing recent research in SHM anomaly detection.

Motivation and Research Gap
Existing reviews on bridge SHM anomaly detection are limited in scope and often fail to synthesize comparative insights. Most studies overlook real-time performance and multivariate data analysis, which are crucial for practical deployment. Moreover, previous work rarely provides a structured framework to classify detection methods comprehensively. These limitations highlight the need for a systematic review that evaluates different approaches across multiple dimensions. Understanding these gaps motivates the development of a more thorough taxonomy and evaluation methodology.

Methodology
This systematic literature review (SLR) analyzes 36 peer-reviewed studies published between 2020 and 2025, selected from eight reputable databases. Studies were evaluated using a four-dimensional taxonomy, including real-time capability, multivariate support, analysis domain, and detection method. Detection methods were further categorized into distance-based, predictive, and image-processing approaches. The review also assessed five key performance dimensions: robustness, scalability, real-world feasibility, interpretability, and data dependency. This methodology ensures a holistic comparison of contemporary anomaly detection techniques.

Taxonomy of Detection Methods
The review introduces a novel four-dimensional taxonomy to organize anomaly detection methods. Distance-based methods rely on similarity measures but are sensitive to environmental and dimensional variations. Predictive models balance performance with interpretability, making them practical in certain contexts. Image-processing techniques dominate the field, achieving high accuracy but requiring significant computational resources. Each category is evaluated in terms of real-time application and support for multivariate analysis. This taxonomy helps researchers identify suitable approaches for different SHM scenarios.

Comparative Evaluation
A detailed comparative evaluation revealed distinct strengths and weaknesses among methods. Image-processing methods are most frequently applied (22 studies) but face scalability challenges. Predictive models provide a balanced trade-off between interpretability and accuracy. Distance-based methods are less common due to sensitivity issues. Only 11 studies demonstrate real-time anomaly detection capabilities, while multivariate analysis remains underutilized. Time-domain signal processing dominates, whereas frequency and time-frequency methods are rarely applied, despite their potential advantages.

Challenges and Future Directions
Current SHM anomaly detection approaches face challenges in scalability, robustness, interpretability, and practical deployment. Existing models often lack adaptability and fail to handle multi-modal or uncertain data efficiently. Future research should focus on developing adaptive, interpretable frameworks suitable for real-world monitoring. Standardized evaluation protocols and cross-environment testing are necessary to validate performance. Combining predictive, distance-based, and image-processing strategies may enhance accuracy and reliability. The field needs innovation to ensure SHM systems remain practical and effective.

Conclusion
This review systematically examined recent studies in bridge SHM anomaly detection, highlighting trends, strengths, and gaps. Image-processing methods dominate but require computational optimization. Predictive and distance-based approaches offer trade-offs between accuracy and interpretability. Real-time and multivariate analysis remain underexplored. Future work should focus on adaptive, scalable, and interpretable models with multi-modal capabilities. Implementing such frameworks will enhance bridge safety and ensure reliable monitoring across diverse environments.

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#BridgeMonitoring, #StructuralHealth, #SHM, #CivilEngineering, #AnomalyDetection, #SmartInfrastructure, #BridgeSafety, #StructuralIntegrity, #EngineeringResearch, #InfrastructureHealth,