Search Results (176)

As a novel prefabricated structural element, the pre-tensioned, prestressed concrete T-beam with polygonal tendons layout demonstrates advantages including reduced prestress loss, streamlined construction procedures, and stable manufacturing quality, showing promising applications in medium-span bridge engineering. This paper conducted a full-scale experiment and numerical simulation research on a 30 m pre-tensioned, prestressed concrete T-beam with polygonal tendons practically used in engineering. The full-scale experiment applied symmetrical four-point bending to create a pure bending region and used embedded strain gauges, surface sensors, and optical 3D motion capture systems to monitor the beam’s internal strain, surface strain distribution, and three-dimensional displacement patterns during loading. The experiment observed that the test beam underwent elastic, crack development, and failure phases. The design’s service-load bending moment induced a deflection of 18.67 mm (below the 47.13 mm limit). Visible cracking initiated under a bending moment of 7916.85 kN·m, which exceeded the theoretical cracking moment of 5928.81 kN·m calculated from the design parameters. Upon yielding of the bottom steel reinforcement, the maximum of the crack width reached 1.00 mm, the deflection in mid-span measured 148.61 mm, and the residual deflection after unloading was 10.68 mm. These results confirmed that the beam satisfied design code requirements for serviceability stiffness and crack control, exhibiting favorable elastic recovery characteristics. Numerical simulations using ABAQUS further verified the structural performance of the T-beam. The finite element model accurately captured the beam’s mechanical response and verified its satisfactory ductility, highlighting the applicability of this beam type in bridge engineering. Full article

This research focuses on improving the characteristics of recycled concrete and utilizing solid waste resources through the combination of industrial waste pre-impregnation and the carbonation process. A novel pre-impregnation–carbonation aggregate method is proposed to increase the content of carbonatable components in the surface-bonded mortar of recycled coarse aggregate by pre-impregnating it with carbide slag slurry (CSS). This approach enhances the subsequent carbonation effect and thus the properties of recycled aggregates. The experimental results showed that the method significantly improved the water absorption, crushing value, and apparent density of the recycled aggregate. Additionally, it enhanced the compressive strength, split tensile strength, and flexural strength of the recycled concrete produced using the aggregate improved by this method. Microanalysis revealed that CO₂ reacts with calcium hydroxide and hydrated calcium silicate (C-S-H) to produce calcite-type calcium carbonate and amorphous silica gel. These reaction products fill microcracks and pores on the aggregate and densify the aggregate–paste interfacial transition zone (ITZ), thereby improving the properties of recycled concrete. This study presents a practical approach for the high-value utilization of construction waste and the production of low-carbon building materials by enhancing the quality of recycled concrete. Additionally, carbon sequestration demonstrates broad promise for engineering applications. Full article

Hydraulic concrete is a critical infrastructure material, with its surface condition playing a vital role in quality assessments for water conservancy and hydropower projects. However, images taken in complex hydraulic environments often suffer from degraded quality due to low lighting, shadows, and noise, making it difficult to distinguish defects from the background and thereby hindering accurate defect detection and damage evaluation. In this study, following systematic analyses of hydraulic concrete color space characteristics, we propose a Dual-Branch Luminance–Chrominance Attention Network (DBLCANet-HCIE) specifically designed for low-light hydraulic concrete image enhancement. Inspired by human visual perception, the network simultaneously improves global contrast and preserves fine-grained defect textures, which are essential for structural analysis. The proposed architecture consists of a Luminance Adjustment Branch (LAB) and a Chroma Restoration Branch (CRB). The LAB incorporates a Luminance-Aware Hybrid Attention Block (LAHAB) to capture both the global luminance distribution and local texture details, enabling adaptive illumination correction through comprehensive scene understanding. The CRB integrates a Channel Denoiser Block (CDB) for channel-specific noise suppression and a Frequency-Domain Detail Enhancement Block (FDDEB) to refine chrominance information and enhance subtle defect textures. A feature fusion block is designed to fuse and learn the features of the outputs from the two branches, resulting in images with enhanced luminance, reduced noise, and preserved surface anomalies. To validate the proposed approach, we construct a dedicated low-light hydraulic concrete image dataset (LLHCID). Extensive experiments conducted on both LOLv1 and LLHCID benchmarks demonstrate that the proposed method significantly enhances the visual interpretability of hydraulic concrete surfaces while effectively addressing low-light degradation challenges. Full article

The curing process of a concrete sample has a significant influence on hydration and its strength. This means that inadequate curing conditions lead to a loss of concrete quality and negative consequences in structural engineering. In addition, different state-of-the-art (SOTA) curing surface treatments and hydration periods have a significant effect on durability. This paper introduces an innovative non-destructive method to detect the development of the hydration process under different treatment conditions. Hyperspectral imaging is a non-contact measurement technique that provides detailed information on hydration characteristics within an electromagnetic wavelength range. A comparative laboratory measurement was conducted on twelve concrete samples, subjected to three curing treatments and four curing surface treatments, over a hydration period from the 1st to the 56th day. Additionally, artificial neural networks and convolutional neural networks have achieved classification accuracies of 67.8% (hydration time), 83.3% (curing regime), and 87.6% (surface type), demonstrating the feasibility of using neural networks for hydration monitoring. In this study, the results revealed differences in near-infrared spectral signatures, representing the type of curing treatment, curing surface, and hydration time of the concrete. The dataset was classified and analyzed using neural networks. For each hydration treatment, three different models were developed to achieve better prediction performance for hyperspectral imaging analysis. This method demonstrated a high level of reliability in investigating curing surface treatments, curing treatments, and hydration time. A recommended method for using hyperspectral imaging to evaluate the cured quality of concrete will be developed in future research. Full article

Particulate matter (PM) originating from road dust is an increasing concern in urban air quality, particularly as non-exhaust emissions from tire–pavement interactions gain prominence. Existing models often focus on meteorological and traffic-related variables while oversimplifying pavement surface characteristics, limiting their applicability across diverse spatial and traffic conditions. This study investigates the influence of concrete pavement macrotexture—specifically the Mean Texture Depth (MTD) and surface wavelength—on PM₁₀ resuspension. Field data were collected using a vehicle-mounted DustTrak 8530 sensor following the TRAKER protocol, enabling real-time monitoring near the tire–pavement interface. A multivariable linear regression model was used to evaluate the effects of MTD, wavelength, and the interaction between silt loading (sL) and PM₁₀ content, achieving a high adjusted R² of 0.765. The surface wavelength and sL–PM₁₀ interaction were statistically significant (p < 0.01). The PM₁₀ concentrations increased with the MTD up to a threshold of approximately 1.4 mm, after which the trend plateaued. A short wavelength (<4 mm) resulted in 30–50% higher PM₁₀ emissions compared to a longer wavelength (>30 mm), likely due to enhanced air-pumping effects caused by more frequent aggregate contact. Among pavement types, Transverse Tining (T.Tining) exhibited the highest emissions due to its high MTD and short wavelength, whereas Exposed Aggregate Concrete Pavement (EACP) and the Next-Generation Concrete Surface (NGCS) showed lower emissions with a moderate MTD (1.0–1.4 mm) and longer wavelength. Mechanistically, a low MTD means there is a lack of sufficient voids for dust retention but generates less turbulence, producing moderate emissions. In contrast, a high MTD combined with a very short wavelength intensifies tire contact and localized air pumping, increasing emissions. Therefore, an intermediate MTD and moderate wavelength configuration appears optimal, balancing dust retention with minimized turbulence. These findings offer a texture-informed framework for integrating pavement surface characteristics into PM emission models, supporting sustainable and emission-conscious pavement design. Full article

This research focuses on the impact of a pozzolanic additive (zeolite) on the durability properties of concrete and the evaluation of the surface finish of the final product (concrete). Durability is one of the key characteristics of concrete that ensures the performance of concrete structures, landscaping elements, and products over their lifetime and beyond. To reduce CO₂ emissions, replacing part of traditional cement with pozzolanic additives is necessary. We tested concrete mixes in which up to 20% of cement was replaced with a pozzolanic additive. Concrete flow and entrained air content were measured. The following properties of hardened modified concrete were determined: density, ultrasonic pulse velocity, water absorption, freeze–thaw resistance, and mechanical properties after 7 and 28 days of curing. The compressive strength values were normalised and expressed in MPa/g to obtain a deeper insight into the effect of a pozzolanic additive on the mechanical properties of concrete. The test results showed that the pozzolanic additive selected for testing reduced the flowability, density, and ultrasonic pulse velocity; increased entrained air content; and reduced the porosity of concrete. The compressive strength results at 28 days (normalised and expressed in MPa/g) showed that all specimens modified with up to 20% zeolite had a higher compressive strength than that of the reference specimen (from 0.0138 to 0.0164). Freeze–thaw resistance results showed that 15% was the optimum content of zeolite additive that could replace cement in the mix to obtain concrete with appropriate durability properties. Concrete surface finish evaluation tests showed that 15% of the pozzolanic additive is recommended to obtain a good-quality surface finish of exposed concrete. Full article

Concrete surface crack detection plays a crucial role in infrastructure maintenance and safety. Deep learning-based methods have shown great potential in this task. However, under real-world conditions such as poor image quality, environmental interference, and complex crack patterns, existing models still face challenges in detecting fine cracks and often rely on large training parameters, limiting their practicality in complex environments. To address these issues, this paper proposes a crack detection model based on adaptive feature quantization, which primarily consists of a maximum soft pooling module, an adaptive crack feature quantization module, and a trainable crack post-processing module. Specifically, the maximum soft pooling module improves the continuity and integrity of detected cracks. The adaptive crack feature quantization module enhances the contrast between cracks and background features and strengthens the model’s focus on critical regions through spatial feature fusion. The trainable crack post-processing module incorporates edge-guided post-processing algorithms to correct false predictions and refine segmentation results. Experiments conducted on the Crack500 Road Crack Dataset show that, the proposed model achieves notable improvements in detection accuracy and efficiency, with an average F1-score improvement of 2.81% and a precision gain of 2.20% over the baseline methods. In addition, the model significantly reduces computational cost, achieving a 78.5–88.7% reduction in parameter size and up to 96.8% improvement in inference speed, making it more efficient and deployable for real-world crack detection applications. Full article

The prefabricated concrete channel, constructed by integrating factory-based prefabrication with on-site assembly, offers enhanced quality, reduced construction time, and minimized environmental impact. To promote its application in water conservancy projects, an innovative concrete joint combining semi-grouting sleeves and shear-resistant steel plates was proposed. Its seismic performance was assessed through a 1:3 scale low-cycle reversed loading test, focusing on failure mode, hysteretic behavior, skeleton curves, stiffness degradation, ductility, and energy dissipation. Results show that the joint primarily exhibits bending–shear failure, with cracks initiating at the sidewall–base slab interface. Also, the sidewall and base slab are interconnected through semi-grouting sleeves, while the concrete bonding is achieved via grouting and surface chiseling at the joint interface. The results indicated that the innovative concrete joint connection exhibits satisfied seismic performance. The shear-resistant steel plate significantly improves shear strength and enhances water sealing. Compared with cast-in-place specimens, the prefabricated joint shows a 16.04% lower equivalent viscous damping coefficient during failure due to reinforcement slippage, while achieving 16.34% greater cumulative energy dissipation and 52.00% higher ductility. These findings provide theoretical and experimental support for the broader adoption of prefabricated channels in water conservancy engineering. Full article

To address the challenges of low automation in tunnel wet-spraying jumbos and the heavy reliance on manual expertise for ensuring the spraying quality, this study proposes a novel task planning method for tunnel spraying operations. First, the tunnel surface to be sprayed is aligned with the designed contour using a vehicle navigation method, enabling the estimation of the overbreak and underbreak volumes. These volumes are then utilized to hierarchically plan the spraying tasks (e.g., patching, filling, and surface smoothing). A concrete coating thickness prediction method is developed, incorporating static and dynamic coating accumulation models with key process parameters—spraying flow rate Q, air pressure P, and spraying distance H—as independent variables. Based on the required thickness for each task layer, operational parameters such as the spraying duration t and nozzle movement speed v are optimized. By analyzing the spray gun action combinations and integrating hierarchical task planning with parameter optimization, a Planning Domain Definition Language (PDDL) domain file and problem file are designed to generate the spray gun action sequences and paths via a planner. The experimental results demonstrate that the overbreak volume on the sprayed tunnel surface is reduced to approximately 3 cm after applying the planned sequences. The proposed method autonomously generates the task hierarchies and the corresponding spray gun actions based on the 3D morphology of the tunnel surface, effectively ensuring the spraying quality while significantly reducing the dependence on manual intervention. This approach provides a practical solution for enhancing automation and precision in tunnel spraying operations. Full article

Corrosion inhibitors play a crucial role in the corrosion protection of rebars in reinforced concrete structures under harsh service conditions. However, conventional corrosion inhibitors often suffer from low efficiency and environmental concerns. This study investigates a low-cost and environmentally friendly lotus leaf extract (LLE) as a corrosion inhibitor and examines its effects on carbon steel rebar corrosion under various conditions. The structure and composition of LLE were characterized using SEM, FTIR, and LC-MS. The effects of LLE on rebar corrosion behavior under different environmental conditions were investigated using electrochemical tests, Mott–Schottky analysis, and XPS. The main findings indicate that LLE is rich in polar chemical bonds and functional groups, which facilitate adsorption and film formation on the rebar surface. In a 3.5% NaCl solution, rebar corrosion is primarily influenced by the solution pH, and low concentrations of LLE exhibit effective corrosion inhibition. In a simulated concrete pore solution, higher concentrations of LLE promote the formation of a passivation film in a chloride-alkaline environment. Studies on pre-passivated rebar indicate that LLE effectively protects the passivation film, with the optimal LLE concentration for passivation film protection and adsorption film quality being 0.5 wt%. This study contributes to the application and development of novel LLE-based corrosion inhibition technology for carbon steel rebar. Full article

Fair-faced concrete has garnered substantial attention in recent years owing to its aesthetic appeal and eco-friendly attributes. However, as a construction material, its long-term performance is highly dependent on its service environment, particularly ultraviolet (UV) radiation. This research focuses on examining the influence of UV exposure and managing the admixtures employed in concrete and investigating the effects of UV radiation on the appearance quality, pore distribution, and micro-composition of fair-faced concrete. Results indicate that UV radiation enhances moisture evaporation, increases surface and bulk porosity, and accelerates carbonation and early hydration reactions, forming more calcite on the surface. These factors degrade the appearance quality of fair-faced concrete. To mitigate UV-aging damage, two common anti-UV admixtures, nano-silica (NS) and water-based fluorocarbon paint (FC), were evaluated. Results show that both admixtures effectively improve the UV-resistance of fair-faced concrete, particularly when combined. The FC+NS group reduced the surface glossiness loss rate from 28.63% to 12.95% after 28 days of UV exposure, with surface porosity and maximum pore diameter recorded at 0.157% and 3.66 mm, respectively, indicating excellent appearance quality. These findings underscore the potential of these admixtures, both individually and in combination, to enhance the UV resistance of fair-faced concrete, sustaining its durability under prolonged UV exposure. Full article

The utilization of aeolian sand (AS) as a substitute for river sand (RS) in ultra-high-performance concrete (UHPC) offers a sustainable solution to address natural sand resource shortages while enhancing AS utilization. This study systematically evaluates the influence of AS content (0–100% RS replacement by mass) on the workability, mechanical properties, and microstructure of UHPC under different curing regimes. All mixtures incorporate 0.65% by volume of straight steel fibers to ensure adequate fiber reinforcement. The results reveal that the spherical morphology, smooth surface nature, and fine particle size of AS enhance the matrix fluidity and reduce the early autogenous shrinkage of UHPC. By employing steam curing at 90 °C for 2 d followed by standard curing for 7 d (M3), UHPC samples with a 60% and 80% AS substitution achieve a compressive strength of 132.4 MPa and 130.8 MPa, respectively; a flexural strength exceeding 18 MPa; a porosity below 10%; and a gel pore content exceeding 60%. The steel fiber reinforcement contributes significantly to the flexural performance, with the fiber–matrix interface quality maintained even at high AS replacement levels. These findings highlight the feasibility of AS as an alternative fine aggregate in UHPC. Full article

The conservation of experimental building materials that were introduced during the 20th-century currently represents one of the main challenges in building restoration. Fair-faced concrete is especially affected by durability problems and requires careful assessment to implement effective conservation methods, even more so when the building has artistic and expressive value. In addition, the literature in this field is still limited and case studies are very rare. In this paper, the Partisan Ossuary Monument, a brutalist monument at the Certosa of Bologna, was studied and analysed in order to find the most effective restoration techniques, especially for its concretes, which have a particularly expressive texture. The aim was to combine both the preservation of the aesthetics and functional quality of the building with the use of existing technologies in this field. Firstly, archive research was carried out to discover the original building techniques and the materials used. The literature on the Monument was studied to unveil the expressive role given to the concretes’ surface finishing. Then, after an on-site investigation, all the materials used in the Monument and the degradation processes were analysed and mapped out. Significant samples of the Monument were manually collected whilst limiting invasiveness. Then, diagnostic tests were carried out to identify the causes of degradation and to comprehend the nature of certain superficial finishes. Several techniques were used, i.e., X-ray diffraction, optical microscopy, and FT-IR spectrometry. Finally, guidelines were drafted for possible future restoration, merging all the results from the previous phases of this study with compliance with heritage structures’ restoration requirements. Many technologies commonly used for the repair of concrete structures could not be applied to this Monument due to its features. Hence, new solutions were studied and proposed. The results obtained may contribute to an increased awareness of the need to restore 20th-century heritage buildings in order to limit degradation and partial reconstruction. Many concrete heritage buildings of this period suffer from the same problems, and this paper could offer an important starting point for future research. Full article

This study evaluated the environmental sustainability of partially replacing natural aggregates with electric arc furnace (EAF) slag in concrete and porous asphalt mixtures. Both the Equilibrium Leaching Test (EN 12457-4) and the Dynamic Surface Leaching Test (DSLT, CEN/TS 16637-2) were applied to analyse the leaching behaviour of the asphalt mixtures. The results showed that the incorporation of EAF slag led to the release of chromium (Cr), molybdenum (Mo), and vanadium (V), while the type of bitumen affected the dissolved organic carbon (DOC) release. However, when compared to EAF slag leaching, asphalt mixtures exhibited significantly reduced leaching, particularly Cr (by 70%) and V (by 60%). These results indicate that metal leaching follows a diffusion-controlled release mechanism, showing higher concentrations for the porous asphalt compared to the asphalt concrete. The cumulative leaching values at 64 days reached 2.54 mg·m⁻² for Cr, 3.29 mg·m⁻² for Mo, and 28.67 mg·m⁻² for V, far from the limits set by the Dutch Soil Quality Decree (SQD) of 120, 144, and 320 mg·m⁻², respectively. Therefore, this study demonstrated that EAF slag is a viable alternative for sustainable road construction, reducing natural resource consumption and promoting the circular economy. Full article

The research presented in this article seeks to identify the possible causes of reinforcement shadows (RS) on the surface of concrete test specimen produced under laboratory conditions. Different hypotheses about RS were selected based on factory practices and simulated in the study. The test specimens were cast horizontally in contact with steel form-facing surfaces coated with a water-soluble release agent. In addition, two scenarios were analysed during specimen production: reinforcing mesh was fixed using plastic spacers or tie wire. The analysis of the reinforcement shadows was based on visual inspection, taking photos, surface moisture content measurements, and colour variation analysis using the Natural Colour System. It was concluded that RS, which are typically characterized by darker lines, can be defined by the percentage of black colour present in the shadowed area compared to the percentage of black colour in the surrounding area. This percentage can be quickly assessed on a factory scale using digital colour readers that provide timely information. The reduced concrete cover thickness from 35 mm to 10 mm revealed light horizontal dark lines on the exposed surface. It was hypothesised that the gap of less than 10 mm between the reinforcing bars and the steel form-facing plate, along with the sieving effect of the fresh concrete, can retard the cement paste hydration process, resulting in unhydrated ferrite phases that contribute to the dark colour of the unhydrated cement. The release agent sprayed on the steel form-facing surface straight through the reinforcing mesh created a RS effect of the reinforcement on the exposed concrete surface. The absence of a release agent under steel rebars decreased the wettability at the interface between the formwork and fresh concrete, resulting in dark lines during the curing process. It is important to avoid such cases when manufacturing precast reinforced concrete elements. Quantitatively assessing RS and proposing a standardized method for calculation and categorization could be a new research direction in the future. Full article