ABSTRACT This study investigates the combined effects of metakaolin (MK) and steel fibres (SF) on the mechanical and durability properties of M30-grade concrete. An experimental programme was designed comprising six concrete mixes with varying MK replacement levels (5%, 10%, 15%, 20%, and 25%) and a constant 1% SF dosage. The experimental results showed that the mix containing 15% MK and 1% SF produced the highest compressive strength at both 7 days (37.06 MPa) and 28 days (58.13 MPa), with increases of 59.7% and 69.9% compared to the conventional M30 mix. Significant improvements were also observed in split tensile and flexural strengths, with increases of 106.1% and 129% at 7 days, and 98.2% and 129% at 28 days, respectively. Durability tests showed a 29.9% reduction in water absorption, a 28.7% decrease in chloride permeability, and a 156.1% increase in electrical resistivity for the optimal mix compared to the control. The UPV results rated the 15% MK + 1% SF mix as ‘Excellent’, with a pulse velocity of 4.781 km/sec. This research highlights that a 15% MK replacement level, combined with 1% SF, offers the best balance of strength and durability, making it a promising approach for enhancing the performance of concrete in construction applications.

ABSTRACT Orthotropic Steel Decks (OSDs) are widely used in modern bridge construction for their lightweight and high-strength properties, yet they face significant fatigue challenges under dynamic loading. This paper presents an experimental investigation into OSD fatigue performance using a sequential, multi-position loading protocol. Focusing on strain and deflection measured through strain gauges and linear potentiometers, a scaled-down specimen was developed to analyse stress distributions and identify fatigue-prone areas. The findings revealed significant strain concentrations at rib-to-deck connections, identifying them as key locations for early plastic deformation and fatigue damage initiation. Additionally, rib-to-diaphragm (RTD) connections exhibited elevated fatigue sensitivity, indicating complex load transfer mechanisms and non-uniform stress distribution across the deck. The main highlight of this paper lies in its sequential loading protocol and detailed monitoring strategy, which accurately approximate the spatial variability of in-service traffic compared to conventional single-point static approaches. By comparing these findings with existing research, the paper highlights the specific fatigue challenges associated with dynamic traffic loading and contributes to a deeper understanding of fatigue-resistant mechanisms in long-span steel bridges. These insights provide a useful basis for informing the development of monitoring and fatigue-assessment strategies for long-span OSD structures.

ABSTRACT Permeability is a fundamental parameter governing the long-term durability of concrete structures, as it controls the ingress of water and aggressive ions, such as chlorides and sulphates, which initiate deterioration mechanisms including microcracking, expansive reactions, and reinforcement corrosion. This review synthesises the primary mechanisms influencing concrete permeability, with emphasis on pore structure evolution, microcrack formation, and mix design parameters. Strategies for permeability mitigation, including optimised aggregate grading and incorporation of supplementary cementitious materials, are critically examined in relation to durability enhancement. A comprehensive evaluation of Non-destructive Testing (NDT) techniques, Acoustic Emission (AE), Electrical Resistivity (ER), Resonance Frequency Testing (RFT), and Ultrasonic Pulse Velocity (UPV), is presented, highlighting their underlying principles, sensitivity to permeability-related parameters, and applicability under laboratory and field conditions. A comparative case study analysis demonstrates how environmental exposure, moisture conditions, and specimen characteristics influence the interpretation of NDT results. The findings underscore that no single technique is sufficient for reliable permeability assessment; instead, integrated multi-method approaches, supported by appropriate calibration, provide improved diagnostic confidence. This review offers a structured framework to support informed selection and implementation of permeability evaluation strategies in both new construction and existing infrastructure.

ABSTRACT Utilisation of high-strength concrete in modern infrastructure requires materials that combine high load-carrying capacity with improved ductility and serviceability. This study provides an extensive experimental programme carried out to evaluate the influence of SF on the mechanical properties of flexural beam testing supported by a numerical simulation and microstructural characteristics of high-strength M60 grade concrete. SFs were added at volume fractions of 0.75%, 1.0% and 1.25% to identify optimal dosage. Standard tests were conducted to evaluate compressive strength, split tensile strength and flexural strength at a curing age of 7, 28 and 56 days, while full-scale reinforced concrete beams are tested under monotonic loading to investigate load vs deflection behaviour, stiffness degradation, crack development and ductility. In addition, microstructural analysis was performed using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction to investigate fibre–matrix bonding and hydration processes. The results indicated that addition of SFs significantly improved tensile and flexural performance at an optimal dosage of 1.0% fibre content. SFRC beams showed delayed crack initiation, reduced crack width and improved ductility compared to conventional high-strength concrete beams. The numerical simulation showed closed agreement with the experimental results, confirming the validity of the developed finite element model.

ABSTRACT Concrete structures are prone to degradation due to various internal flaws and external stresses, with crack formation being one of the most critical challenges affecting their strength and durability. Traditional methods of condition assessment are often limited by their inability to systematically detect and differentiate between crack types. In this study, a hybrid methodology is proposed in which manual crack assessment is complemented by classical image processing techniques, specifically, Otsu-Thresholding and Canny Edge Detection. Through this integration, the process of crack evaluation is automated and enhanced, allowing for more consistent identification and classification of cracks. The methodology is applied to real-world examples, where its effectiveness is demonstrated in detecting crack patterns at multiple scales and associating them with their underlying structural causes. It is shown that the proposed approach may provide a practical and resource-efficient tool for improving the consistency and reliability of structural assessments.

ABSTRACT Bolted joints are critical to engineering structures and their integrity is essential for safety and functionality. Traditional monitoring methods are often expensive and intrusive, necessitating the development of more efficient approaches. Preload loss in pretensioned bolts is inevitable in practice, making the reliable detection of loosening vital for structural reliability. This study presents a novel structural health monitoring (SHM) method based on vibration and percussive audio-emission signals generated during controlled percussion. A single bolted lap joint was subjected to percussion, and the resulting audio and vibration signals were recorded and analyzed in both the time and frequency domains to assess bolt tightness. As the bolt torque increased from 0 Nm to 25 Nm, significant variations were observed in signal characteristics. For the vibration signals, the Signal Energy, Peak-to-RMS ratio, and kurtosis changed by 48.84%, 61.02%, and 90.15%, respectively. For audio signals, the corresponding variations were 39.53%, 44.77% and 80.79%. Fast Fourier Transform (FFT) analysis showed a correlation between bolt tightening levels and frequency amplitudes, with slight frequency increases in both signal types with an increase in bolt torque. The results demonstrate that percussion-induced signals effectively reflect bolt tightness. Comparative analysis of vibration and audio responses highlights the potential of this multi-modal approach to enhance the reliability of bolted joint SHM applications.

ABSTRACT This study aims to critically investigate the development of self-compacting ultra-high-performance geopolymer concrete (SCUHPGC), with a particular focus on the influence of the type of alkaline activator and curing regime on mechanical performance, embodied CO2 emissions, and cost efficiency. A detailed comparative analysis was conducted between ambient-cured mixtures activated by a sodium hydroxide (SH)-sodium silicate (SS) mixture versus combined-cured mixtures (a 90°C hot water followed by 250°C dry-air curing) activated by calcium carbide residue (CCR). The ambient-cured SH-SS-activated mixtures were designed using a ternary binder, achieving a slump flow diameter of 740 mm and a compressive strength of 132.7 MPa. The CCR-activated mixtures reported in the literature consisted of a binary binder. It was reported that under combined curing conditions, the plain CCR-activated mixture achieved a slump flow diameter of 700 mm and a compressive strength of 130.4 MPa. The total carbon dioxide equivalent (CO2-e) emissions and production cost of the ambient-cured SH-SS-activated SCUHPGC were lower than the corresponding total CO2-e emissions and production cost of the combined-cured CCR-activated SCUHPGC by approximately 15.9% and 13.5%, respectively. The ambient-cured SH – SS-activated SCUHPGC demonstrates superior efficiency, combining ultra-high mechanical performance with a lower environmental impact.

ABSTRACT Managing bridges with substandard structural capacity presents an ongoing challenge for asset owners as infrastructure ages and vehicle loads increase. Many legacy structures do not conform to current design standards or adequately accommodate contemporary freight demands. Conventional strengthening techniques include externally bonded steel plates, concrete or steel jackets, and external post-tensioning. Since the early 2000s, fibre-reinforced polymer (FRP) systems, particularly carbon fibre-reinforced polymer (CFRP), have been adopted in Australia as an alternative strengthening method due to their high strength-to-weight ratio, corrosion resistance, and ease of installation. Recent advancements in research and material technology have led to increased industry recognition of CFRP systems. The Queensland Department of Transport and Main Roads (TMR) identified a portfolio of bridges requiring strengthening to accommodate current freight loads and selected CFRP as a potential solution. Given its limited prior application within TMR projects, a research-based pilot was initiated to evaluate feasibility, define performance criteria, and establish quality assurance protocols. This paper presents the pilot project’s implementation. The Routh Creek pilot project demonstrated the effectiveness of the CFRP strengthening in accordance with relevant standards. The field implementation demonstrated that vacuum-assisted installation and rigorous surface preparation procedures supported by robust quality assurance and environmental controls can ensure adequate bond performance despite environmental challenges. It also highlighted the significance of climate-adapted material handling, skilled workforce mobilisation and contingency planning. The technical challenges, mitigation strategies, and recommendations for future applications of CFRP in bridge strengthening are discussed.

ABSTRACT A model was developed to predict construction risks for bridges by coupling the analytic hierarchy process (AHP) with an optimised Extreme Learning Machine (ELM) neural network. Firstly, by using the AHP method, 22 factors were identified to comprehensively represent risks during bridge construction. These factors were formulated in a two-level hierarchical structure. Secondly, a risk assessment system was formulated. Thirdly, an ELM neural network model was built to automate the risk prediction process and minimise the subjectivity associated with the traditional expert assessment system. The ELM model was optimised by the Sparrow Search Algorithm (SSA). Finally, the AHP-SSA-ELM model was tested on 50 bridge construction cases, and showed a 96% agreement with the expert assessment. This means that the proposed model can be used confidently to assess risks during bridge construction in complex environments. The model is accurate, practical, and efficient. It will inform risk management to avoid social and economic losses during bridge construction.

ABSTRACT This study proposes a comprehensive methodology for the structural health assessment of ageing infrastructure with limited available documentation. The case study involves a reinforced concrete structure constructed in 1971, for which only architectural drawings with a limited technical document are available. An initial finite element model (FEM) is developed based on geometric information inferred from the available drawings and standard material assumptions. To overcome uncertainties arising from the absence of structural and reinforcement details, a suite of non-destructive tests, Schmidt hammer rebound tests and Profometer are employed. The experimental results are used to update and calibrate the FEM, enabling a more accurate representation of the in-situ condition. The refined model is then used to evaluate structural performance and compare results against current design codes. This integrated approach highlights the value of combining limited documents with in-situ testing to support informed decision-making in the assessment and management of ageing concrete. When reassessed against AS 1170 and AS 3600 provisions, the structure failed to meet key performance requirements, particularly in lateral resistance and reinforcement capacity, highlighting the need for retrofit.