MULTISCALE FIBER-REINFORCED SUSTAINABLE CONCRETE WITH HIGH-VOLUME FLY ASH AND PORCELAIN AGGREGATE

The construction industry is increasingly focused on sustainable materials that reduce environmental impact while maintaining high mechanical performance. One promising strategy involves incorporating industrial waste materials into concrete, such as high-volume fly ash (FA) as a cement substitute and recycled porcelain aggregate (PA) as fine aggregate. This study investigates a novel sustainable concrete system enhanced with multiscale fibers to overcome the strength limitations typically associated with high replacement levels. The goal is to develop an eco-friendly material capable of meeting structural performance requirements while promoting circular economy principles.

Optimization of Fly Ash and Porcelain Aggregate Replacement

A key objective of the research was to determine the optimal proportions of FA (0–50 %) and PA (0–100 %) required to achieve a target compressive strength of 45 MPa. Through experimental testing and numerical modeling, the study demonstrated that even at maximum replacement levels, the concrete achieved a compressive strength of 44.3 MPa at 28 days. This finding confirms that significant reductions in cement and natural sand consumption are possible without severely compromising structural performance, making the mixture highly sustainable.

Role of Multiscale Fiber Reinforcement

To further enhance performance, the optimized mixture incorporated multiscale fibers consisting of 1 % steel fibers (macro-scale) and 0.1 % graphene nanotubes (nano-scale). This hybrid reinforcement strategy creates a hierarchical strengthening mechanism across different length scales. Steel fibers improve crack resistance and load transfer at the macro level, while graphene nanotubes refine the microstructure and inhibit microcrack propagation at the nanoscale, producing a synergistic improvement in overall material behavior.

Mechanical Performance Enhancement

The addition of multiscale fibers significantly improved key mechanical properties. Compressive strength increased by 13.3 %, while flexural strength and direct tensile strength improved dramatically by 145.8 % and 44.4 %, respectively. These results indicate that fiber reinforcement is particularly effective in enhancing tensile-related properties, which are typically weak in conventional concrete. Such improvements broaden the applicability of sustainable concrete for structural components subjected to bending, tension, and dynamic loads.

Impact Resistance and Energy Absorption

One of the most striking outcomes of the study was the substantial increase in impact resistance. The energy absorption capacity at the initial cracking stage rose from 98.1 J to 5790.8 J after fiber incorporation. This enhancement is attributed to multiscale crack-bridging mechanisms, where fibers arrest crack growth at different stages and scales, thereby delaying failure and dissipating energy. Such behavior is critical for infrastructure exposed to repeated or sudden loading, including pavements, industrial floors, and protective structures.

Microstructural Characteristics and Engineering Applications

Microstructural analyses using ICP-MS, XRD, and STA tests revealed that graphene nanotubes and fly ash contributed to pore refinement, enhanced pozzolanic reactions, and improved bonding within the cement matrix. The combined effects of waste material utilization and multiscale reinforcement produced a dense, durable microstructure with superior mechanical performance. Consequently, this advanced sustainable concrete is well suited for applications requiring high tensile strength and impact resistance, particularly rigid pavements and heavy-duty infrastructure systems.

#EcoFriendlyMaterials
#HighPerformanceConcrete
#RigidPavement
#ImpactResistance
#CompressiveStrength
#FlexuralStrength
#TensileStrength
#ConstructionInnovation
#CircularEconomy
#CivilEngineering
#SustainableInfrastructure
#AdvancedMaterials

BOREHOLE PRESSURE SHEAR TESTER (BPST) FOR IN-SITU EVALUATION OF WEATHERED GEOMATERIALS

Accurate characterization of weathered geomaterials—comprising residual soils and weathered rocks—is essential for ensuring the stability and safety of civil engineering structures. These materials exhibit transitional behavior between soil and rock, making their mechanical properties difficult to assess using conventional techniques. Laboratory testing is often impractical because obtaining undisturbed samples from weathered layers is extremely challenging. Consequently, reliable in-situ testing methods are crucial for capturing true field conditions and improving geotechnical design accuracy.

Limitations of Conventional Field Testing Methods

Traditional field tests are typically developed either for soils or for intact rock masses, leading to significant shortcomings when applied to intermediate geomaterials. Weathered layers possess heterogeneous structures, variable stiffness, and complex failure mechanisms that standard tests cannot fully capture. As a result, existing techniques may produce unreliable estimates of deformation and shear strength, potentially compromising engineering decisions for foundations, slopes, and underground structures.

Development of the Borehole Pressure Shear Tester (BPST)

To address these limitations, this study introduces the Borehole Pressure Shear Tester (BPST), an innovative device that combines the principles of pressuremeter testing and borehole shear testing. The BPST applies controlled horizontal pressure and shear forces directly within a borehole, enabling simultaneous assessment of deformation characteristics and shear strength parameters. This integrated approach provides a more comprehensive understanding of the mechanical behavior of weathered geomaterials compared to single-mode testing methods.

Testing Procedure and Measurement Capabilities

The BPST operates by expanding against the borehole wall while applying tangential shear displacement, replicating realistic stress conditions encountered in situ. This allows direct measurement of deformation modulus and shear resistance under controlled loading paths. By capturing both normal and shear responses in a single test, the device reduces uncertainty associated with extrapolating parameters from separate tests and improves efficiency in field investigations.

Experimental Validation on Residual Soils

Empirical tests conducted on residual soils at simulated high relative densities and varying overburden stresses demonstrated the effectiveness of the BPST. The measured deformation moduli and shear strength parameters showed strong agreement with results obtained from conventional triaxial compression and direct shear tests. This correlation confirms the accuracy and reliability of the device for characterizing intermediate geomaterials under realistic field conditions.

Implications for Geotechnical Design and Infrastructure Safety

The introduction of the BPST represents a significant advancement in geotechnical site investigation. By enabling accurate in-situ evaluation of weathered layers, the device enhances predictive modeling, supports safer foundation design, and reduces uncertainty in stability assessments. Its ability to characterize materials that fall between soil and rock categories makes it particularly valuable for projects involving slopes, tunnels, deep foundations, and infrastructure built on weathered terrain.

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#ShearStrength

#DeformationModulus

#SiteCharacterization

#EngineeringGeology

#InfrastructureSafety

#FieldTesting

#SoilMechanics

#GeotechnicalInnovation

#SlopeStability

#SubsurfaceEngineering

SOFT ACTOR-CRITIC REINFORCEMENT LEARNING FOR ROBUST ACTIVE STRUCTURAL VIBRATION CONTROL

Active structural control systems are among the most effective technologies for suppressing vibrations in civil engineering structures subjected to dynamic loads such as earthquakes and wind. However, conventional active control methods often suffer from performance degradation due to time delays, measurement noise, and changing operational conditions. To overcome these limitations, data-driven control strategies based on reinforcement learning have emerged as promising alternatives. This study introduces advanced soft actor-critic (SAC)–based control approaches designed to enhance adaptability and robustness in complex real-world environments.

Challenges in Traditional Active Control Systems

Traditional controllers, such as linear quadratic Gaussian (LQG) control, rely on predefined system models and fixed parameters. In practical applications, uncertainties such as sensor noise, communication delays, and environmental variability can significantly reduce their effectiveness. These issues may lead to instability or loss of control performance during critical events. Consequently, there is a growing need for intelligent control strategies capable of learning from real-time data and adapting to evolving structural conditions.

Parameter Real-Time Regulator Strategy

The first proposed SAC-based approach introduces a parameter real-time regulator that dynamically adjusts controller parameters using feedback from the environment. By continuously updating its control policy, this strategy maintains effective vibration suppression even when system characteristics change. The regulator demonstrates strong adaptability, particularly in scenarios where external disturbances or structural properties vary over time, making it suitable for practical structural control applications.

Independent Data-Driven Controller

The second strategy replaces conventional control algorithms entirely with an independent reinforcement learning controller. This SAC-based controller learns optimal control actions directly from environmental interactions without relying on prior system models. As a result, it can handle highly nonlinear behavior and unknown dynamics. Experimental results indicate that this approach significantly improves displacement control compared to traditional methods, though its performance in acceleration mitigation varies depending on operating conditions.

Hybrid Compensator Strategy

The third strategy combines reinforcement learning with traditional control methods through a compensator mechanism. Instead of replacing the baseline controller, the SAC algorithm adjusts the control signal in real time to compensate for uncertainties, delays, and noise. This hybrid approach leverages the stability of classical control and the adaptability of machine learning. Among the tested methods, the compensator demonstrates the most effective reduction in structural responses, achieving the highest improvements in both drift and acceleration control.

Performance Evaluation Under Uncertainty

To assess robustness, the control environment was augmented with random time delays and noise, simulating realistic operating conditions. Seven performance criteria were used to evaluate effectiveness. Results show that all SAC-based strategies maintain stable and efficient control, whereas the traditional LQG controller loses effectiveness under severe disturbances. Strategy C (hybrid compensator) achieves the best overall performance, reducing peak inter-story drift by up to 84.50% and peak acceleration by 63.45%. These findings highlight the strong potential of reinforcement learning for next-generation intelligent structural control systems.

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#DataDrivenControl

#AIinEngineering

#InfrastructureSafety

#ControlSystems

#IntelligentInfrastructure

#StructuralHealth

#RobustControl

#EngineeringInnovation

#SeismicProtection

#FutureEngineering

FOAMED GLASS AGGREGATE AS A LIGHTWEIGHT SUSTAINABLE GEOMATERIAL FOR GEOTECHNICAL INFRASTRUCTURE

Foamed glass aggregate (FGA) is an innovative lightweight geomaterial manufactured from recycled glass through a sinter-foaming process. As sustainability becomes a central priority in civil engineering, FGA has emerged as a promising alternative to conventional granular fills. Its highly porous cellular structure results in extremely low density, excellent thermal insulation, and efficient drainage performance. These characteristics make FGA particularly suitable for applications such as embankments, backfills, retaining structures, and foundation systems where weight reduction and environmental benefits are essential.

Production Mechanisms and Microstructural Formation

The engineering performance of FGA originates from its manufacturing process, in which glass particle size, sintering temperature, and foaming agent dosage interact to create a controlled cellular microstructure. During sintering, gas released from the foaming agent becomes trapped within softened glass particles, forming interconnected pores. The resulting pore size distribution, connectivity, and wall thickness determine the aggregate’s mechanical strength, density, and durability. Understanding these production parameters is crucial for tailoring FGA to specific geotechnical requirements.

Influence of Porosity on Engineering Properties

The intrinsic porosity of FGA governs its macroscopic behavior. High void content produces low unit weight and strong thermal insulation, while pore connectivity enhances drainage capacity. However, excessive porosity may reduce strength and increase compressibility. The study highlights the concept of intra-void ratio as a key parameter controlling deformation resistance, load-bearing capacity, and thermal conductivity. This relationship underscores the need to balance lightweight characteristics with structural performance.

Compaction Behavior and Strength Characteristics

Unlike natural soils, FGA exhibits unique compaction responses due to its rigid cellular particles and low particle crushing resistance. Variations in particle size distribution, specific gravity, and pore structure significantly influence compaction efficiency and resulting strength. The material’s degradation behavior under load is also linked to pore wall integrity and internal structure. These factors determine whether FGA can function effectively as a load-bearing geomaterial in infrastructure projects.

Limitations of Conventional Soil Classification

Traditional soil classification systems and compaction methods were developed for natural granular materials and may not accurately represent FGA behavior. The research emphasizes that applying standard soil mechanics approaches can lead to misleading design assumptions. Instead, a new unified classification framework based on intrinsic structural parameters—such as apparent specific gravity, bulk density, and intra-porosity—is recommended. Such a system would better capture the engineered nature of FGA and support reliable design practices.

Implications for Sustainable Infrastructure Design

By integrating principles from materials science, chemistry, and geotechnical engineering, this study positions FGA as a multifunctional engineered aggregate capable of balancing weight reduction, strength, and durability. Its use of recycled glass contributes to circular economy goals while improving infrastructure resilience. As research advances, FGA has the potential to become a cornerstone material for next-generation sustainable construction, offering environmentally responsible solutions for transportation, foundation, and earthwork applications.

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#CivilEngineering
#EngineeredAggregates
#InfrastructureDesign
#SoilMechanics
#PorousMaterials
#EcoFriendlyMaterials
#FoundationEngineering
#EmbankmentDesign
#ResilientInfrastructure
#FutureConstruction

NON-DESTRUCTIVE ESTIMATION OF UNSATURATED HYDRAULIC CONDUCTIVITY USING TIME-LAPSE GEOPHYSICAL METHODS

Accurate estimation of soil unsaturated hydraulic conductivity is essential for understanding vadose zone flow, groundwater recharge, contaminant transport, and broader subsurface hydrological processes. Conventional point-scale measurements are typically invasive, labor-intensive, and limited in spatial and temporal coverage, making them inadequate for capturing natural field heterogeneity. To address these limitations, non-destructive geophysical techniques offer a promising alternative for continuous, large-scale monitoring of soil moisture dynamics and hydraulic behavior.

Integrated Geophysical Framework

This study introduces an innovative framework that integrates time-lapse ground penetrating radar (GPR) and electrical resistivity tomography (ERT) with an improved instantaneous profile (IIP) inversion approach. By combining electromagnetic and electrical measurements, the method captures changes in soil moisture and pore-water distribution over time. This integrated approach enables the indirect estimation of hydraulic conductivity without disturbing the soil structure, providing high-resolution spatial and temporal insights into subsurface flow processes.

Validation with Laboratory-Based Models

To ensure reliability, the conductivity estimates obtained from geophysical data were validated against laboratory-derived soil water characteristic curve (SWCC) models, specifically the van Genuchten–Mualem (VGM) and Childs–Collis-George (CCG) formulations. These widely accepted models relate soil water retention properties to hydraulic conductivity. The comparison demonstrates that the proposed method can produce results consistent with established theoretical predictions, reinforcing its suitability for practical hydrological applications.

Constitutive Relationships with Electrical Properties

The research further developed parsimonious logarithmic constitutive models linking hydraulic conductivity to relative permittivity and bulk electrical conductivity for two soil types. These relationships leverage measurable geophysical properties to infer hydraulic behavior, enabling rapid estimation across large areas. By translating electrical and dielectric measurements into hydraulic parameters, the approach bridges geophysics and soil physics, facilitating non-invasive subsurface characterization.

Model Performance and Uncertainty Analysis

Predictive performance was evaluated using root mean square error (RMSE) and coefficient of variation (CV) metrics. The models achieved an overall RMSE of 0.32 mm/min, indicating strong agreement with laboratory references. Uncertainty analysis revealed low variability in intermediate moisture conditions, with CV values around 2.5–5.4%, while higher variability (7.1–8.6%) occurred near saturation. This pattern reflects increased complexity in fully saturated soils due to thin-film flow and surface conduction effects.

Implications and Future Research Directions

The findings demonstrate that time-lapse geophysical monitoring can provide spatially explicit, non-destructive estimates of unsaturated hydraulic conductivity, particularly in drained to partially saturated conditions. However, model confidence decreases near saturation, highlighting the need for further refinement. Future work should focus on field-scale validation, joint inversion of multiple geophysical datasets, and improved modeling of saturation effects to enhance transferability across diverse soil environments. This approach holds significant potential for advancing hydrological modeling, agricultural management, and environmental monitoring.

#VanGenuchtenModel

#EnvironmentalEngineering

#SoilPhysics

#GroundwaterResearch

#GeotechnicalEngineering

#FieldHydrology

#EarthScienceResearch

#WaterResources

#CivilEngineering

 

BRIDGE DIGITAL TWINS AND THE ROLE OF LOAD TESTING IN LIFECYCLE MANAGEMENT

Bridge digital twins represent a transformative approach in bridge engineering, enabling the creation of virtual replicas that mirror the physical structure throughout its lifecycle. Originating from advancements in other industries, digital twin technology integrates real-world data with computational models to support monitoring, analysis, and decision-making. In bridge applications, digital twins promise enhanced safety, predictive maintenance, and optimized asset management, making them a critical component of next-generation infrastructure systems.

Concept of Digital Twins in Bridge Engineering

A bridge digital twin combines geometric information, material properties, sensor data, and operational conditions into a unified virtual model. By linking physical bridges with Building Information Modeling (BIM) and Finite Element (FE) models, engineers can simulate structural behavior under varying loads and environmental influences. This integration enables continuous assessment of performance, allowing infrastructure owners to move from reactive maintenance toward proactive management strategies.

Load Testing as the Birth of the Digital Twin

The study emphasizes that bridge load testing marks the “birth” of the digital twin. During this phase, controlled loads are applied to the actual bridge to measure structural responses such as deflection, strain, and vibration. This process provides high-quality empirical data that cannot be obtained at later stages with the same reliability. Consequently, load testing offers a unique opportunity to calibrate digital models so that they accurately represent real structural behavior.

Updating BIM and Finite Element Models

Accurate digital twins depend on well-calibrated BIM and FE models. Load test data enables engineers to validate assumptions regarding stiffness, boundary conditions, and material properties. By updating these models with measured responses, discrepancies between theoretical predictions and actual performance can be minimized. This calibration ensures that the digital twin remains a trustworthy tool for structural analysis, safety evaluation, and performance forecasting.

Application During the Operational Phase

Once established, the digital twin supports the bridge throughout its service life. During operation, it can be continuously updated with monitoring data to detect anomalies, assess damage, and evaluate the effects of aging or environmental changes. This capability allows engineers to predict future performance, schedule maintenance efficiently, and extend service life while maintaining safety standards. Thus, the digital twin becomes an active management system rather than a static model.

Case Study of a Post-Tensioned Concrete Bridge

The concept is demonstrated through modeling and load testing of a real post-tensioned concrete bridge. Post-tensioning introduces complex stress distributions and structural behavior, making accurate modeling particularly important. The case study illustrates how field measurements obtained during testing can refine computational models and establish a reliable digital twin. This example confirms the feasibility and practical value of integrating testing, modeling, and digital technologies in modern bridge engineering.

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#InfrastructureInnovation

#StructuralAnalysis

#EngineeringSimulation

#SmartBridges

#AssetManagement

#StructuralSafety

#InfrastructureLifecycle

#FutureOfConstruction

 

ANISOTROPIC SHEAR BEHAVIOR OF BAMBOO SCRIMBER FOR STRUCTURAL APPLICATIONS

 Bamboo scrimber (BS) is a high-performance engineered bamboo material gaining recognition as a sustainable alternative to conventional structural materials. Produced through the densification and resin impregnation of bamboo fibers, BS exhibits excellent strength, durability, and resource efficiency. Despite its promising mechanical properties, the anisotropic nature of bamboo—stemming from its fibrous structure—leads to direction-dependent behavior that is not yet fully understood, particularly under shear loading. This knowledge gap presents a critical challenge for the reliable structural design of BS components subjected to shear forces.

Experimental Investigation of Shear Properties

To address this challenge, the study conducted an extensive experimental program involving 250 shear tests performed under five distinct loading orientations. This comprehensive testing approach enabled the systematic evaluation of how fiber alignment and loading direction influence shear performance. By capturing a wide range of conditions, the experiments provide a robust dataset for characterizing the mechanical response of BS, ensuring that the findings are representative of practical structural applications.

Failure Modes and Directional Response

The tests revealed multiple failure modes, each strongly dependent on the loading orientation relative to the bamboo fiber direction. Observed mechanisms included fiber pull-out, matrix cracking, interfacial debonding, and shear sliding along weak planes. These distinct failure patterns demonstrate that BS does not exhibit uniform behavior but instead responds differently depending on the direction of applied load. Understanding these mechanisms is essential for predicting structural performance and preventing brittle or premature failures in real-world applications.

Quantification of Anisotropic Shear Strength and Modulus

Analysis of the experimental data showed pronounced anisotropy in both shear strength and shear modulus. Average shear strengths ranged from 12.93 to 37.63 MPa, while shear modulus values varied between 213.6 and 606.3 MPa across orientations. These wide ranges confirm that BS possesses highly direction-dependent mechanical properties. Such variability underscores the necessity of incorporating orientation-specific parameters into structural design calculations to ensure safety and efficiency.

Statistical Modeling and Design Values

To translate experimental findings into practical engineering parameters, the study employed both Normal and Weibull statistical models to derive directional design values. The resulting characteristic shear strengths ranged from 6.33 to 32.58 MPa, reflecting conservative estimates suitable for structural design. The use of probabilistic models enhances reliability by accounting for material variability and uncertainty, supporting performance-based design methodologies for engineered bamboo structures.

Comparative Performance and Structural Design Implications

When compared with traditional construction materials such as concrete, timber, and laminated bamboo, BS demonstrates superior specific shear strength, highlighting its potential for lightweight yet high-capacity structural elements. Based on these findings, the study proposes design recommendations that explicitly consider directional shear behavior, enabling engineers to utilize BS effectively in shear-critical components. These insights contribute to the advancement of sustainable construction and support the development of standardized guidelines for engineered bamboo structures.

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#StructuralEngineering
#PerformanceBasedDesign
#EcoFriendlyMaterials
#BambooEngineering
#HighStrengthMaterials
#RenewableConstruction
#MechanicalProperties
#AdvancedBuildingMaterials
#LightweightStructures
#CivilEngineeringResearch
#SustainableInfrastructure