93887 research outputs found
Sort by
Assessment of GGBS-blended-Concrete Durability with Modified Water Permeability Method
No full textThe construction industry is increasingly embracing sustainable materials to mitigate environmental concerns and reduce the carbon footprint of conventional practices. Concrete, a vital material in modern infrastructure, is valued for its versatility and durability. However, Ordinary Portland Cement (OPC), the primary binder in conventional concrete, presents significant environmental challenges, including high carbon dioxide emissions and substantial energy consumption. With an annual growth rate of 2.5%, cement production exacerbates these issues, necessitating sustainable alternatives. Ground granulated blast-furnace slag (GGBS), a byproduct of the iron industry, is a promising supplementary material. Its use reduces cement consumption, enhances sustainability, and promotes eco-friendly construction practices. The application of OPC-GGBS-blended concrete improves not only environmental performance but also the durability of the resulting concrete. Durability, a critical property of concrete, is fundamentally linked to its permeation characteristics, which govern resistance to environmental degradation. Water permeability, a key durability parameter, is typically assessed using standards like DIN 1048 (Part 5). However, the traditional method is time-consuming, requires large equipment, and is limited in detecting penetration in low-strength concrete. To address these limitations, this study introduces a modified water permeability method, effective for all concrete types. Mixes were prepared with W/B ratios of 0.4 and 0.5, incorporating GGBS at 0%, 15%, 30%, 45%, and 60% levels. Results showed that GGBS improves resistance to water penetration, validating its contribution to durability. The modified method proved superior to conventional techniques, offering more efficient and accurate evaluation, thereby underscoring GGBS’s potential and the benefits of an improved testing approach
Corrosion Risk of RC Structures Against Combined Chloride Ingress and Carbonation Under Future Climate Projections
No full textThe deterioration of reinforced concrete (RC) structures is primarily caused by the corrosion of reinforcement due to chloride ingress or carbonation, with temperature playing a significant role in this process. This study presents a multi-physics modeling framework that integrates mass transport, electrochemical reactions, and material damage to simulate corrosion in RC structures. The model utilises experimentally validated parameters, including temperature-dependent chloride transport rates and binding capacities, to achieve enhanced accuracy. It was applied to assess the corrosion risk of RC structures in Hong Kong under various climate scenarios. Results showed that while higher temperatures accelerate chloride transport, they also increase chloride binding capacity, leading to only a slight reduction in corrosion initiation time with a 5°C rise. In tidal zones, climatic changes had a minimal impact, as corrosion was primarily driven by chloride. Surface layer carbonation caused an 8% reduction in corrosion initiation time. In marine atmospheric zones, corrosion began at low chloride levels due to partially carbonated concrete, reducing initiation time to less than half that of chloride ingress alone. This slow ingress resulted in localized corrosion and shorter intervals between initiation and first crack formation compared to tidal zones. This study provides a solid framework for evaluating corrosion risk in coastal structures
Site-specific mechanical weed management for specialty crops through AI-driven robotics
No full textWeed management is one of the most urgent and unresolved challenges in specialty crops in most regions in the United States. For crops like horseradish, which are largely cultivated in Illinois and Wisconsin, the weed issue is magnified because of the crop’s long growing season and sensitivity to chemical applications. Farmers in these states are responsible for more than 80% of the US horseradish market. However, for the current weed control practice, they rely on expensive manual labor, which is in short supply, or repeated application of unlabeled herbicides that degrade soil and lead to a herbicide-resistant weed population. Therefore, there is a need for a site-specific and environmentally responsible weeding solution that meets the practical realities of the horseradish growers. Thus, in an attempt to solve this problem, the mechanical weeding system was developed and deployed, which could identify and remove weeds in horseradish fields. An object detection model was developed to distinguish between weed and horseradish, which achieved an accuracy of more than 90%. A 2-row modular mechanical weeding system performed precisely during the lab-scale testing
Effect of Ultrafine Mineral Admixtures on Mechanical Properties of Engineered Cementitious Composites
No full textIn this study, to address the challenge of balancing the mechanical properties of traditional ECC with sustainability, the effects of substituting part of cement with ultrafine fly ash (UFA) and ultrafine ground granulated blast furnace slag (UGGBS) on the mechanical properties of ECC were investigated, and the differences in the roles of UFA and UGGBS were compared and analysed. The results showed that compared with UFA, UGGBS significantly improved the compressive strength and tensile strain of ECC, with a compressive strength of 92 MPa (73% higher than UFA-ECC), an ultimate tensile strain of 8.87% (4 times higher than UFA-ECC), and the formation of a finer multi-crack network. The rheological results showed that UGGBS improved the flowability by reducing the yield stress and plastic viscosity of the paste due to finer particles. In addition, ECC-UG had a higher PSH index, indicating superior toughness and crack saturation
Range and accuracy and of in-plane anisotropic thermal conductivity measurement using the laser-based angstrom method
No full textHigh heat fluxes in electronic devices must be effectively dissipated to prevent local hotspots, which are critical for long-term device reliability. In particular, advanced semiconductor packaging trends toward thin form factor products increase the need for understanding and improving in-plane conduction heat spreading in anisotropic materials. The 2D laser-based Ångstrom method, an extension of traditional Ångstrom and lock-in thermography techniques, measures in-plane thermal properties of anisotropic sheet-like materials. This method uses non-contact infrared temperature mapping to measure the thermal response to periodic laser heating at the center of a suspended sample. The spatiotemporal temperature data are analyzed via an inverse fitting algorithm to extract thermal conductivities in the in-plane orthotropic directions that best adhere to the governing heat conduction equation. Using this algorithm, we present an approach to simultaneously fit data across multiple heating frequencies, which improves measurement sensitivity because the thermal penetration depth varies with frequency. The accuracy of this technique is assessed by tuning experimental parameters such as sample dimensions and heating frequency. A standardized workflow is proposed for measuring unknown materials and for processing the data, including filtering out regions influenced by laser absorption and heat sink boundary effects. Numerical simulations validate the method across a wide range of thermal conductivities (0.1–1000 W m−1 K−1) and material thicknesses (0.1–10 mm), with accuracy demonstrated for anisotropy ratios up to 1000:1. Experimental measurements on isotropic and anisotropic materials agree well with the benchmark values. Ultimately, standardization of this technique supports the development of engineered anisotropic heat-spreading materials for thermal management and packaging applications
Building better, for longer, with less: a “holistic” approach to material and structural concept and design with Advanced Cement Based Materials
No full textThe paper presents, as the summary of a more than a decade long research performed by the author’s research group, an approach which combines, in a holistic life cycle thinking framework, higher and longer lasting material performance with enhanced structural functionality. The signature high resilience material concept also features the possibility of engineering the structural performance over time through its self-healing capacity, i.e. the ability of the material to self-repair cracks without external intervention but thanks to its suitably designed composition. Concretes are no longer regarded as providers of passive protection, whose degradation over time has to be delayed as much as possible, but become active players in shaping their own performance as a function of the requirement in the operating scenario. The conceptual design approach, suitably nestled into a life cycle thinking framework, represents a key driver for advanced materials innovation uptake in concrete construction industry. The overall performance assessment does no longer rely on the merely misleading concepts of material unit volume cost and environmental impact at its time of generation but is framed appropriately into a structural functional unit context all along its service life. The research results have demonstrated that up to 70% less amount of material can be used to achieve the same or higher structural and durability performance, with maintenance from five to ten times less frequent all along the reference service life period. This represents a breakthrough innovation in the approach of concrete construction industry to the use of advanced cement based materials, overcoming the current situation where Advanced Cement Based Materials are very often promoted only through their extremely high compressive strength, whereas their higher durability is simply accepted as a bonus but has hardly been quantified as true benefit in design, construction, maintenance and use stage of buildings and structures
Magnetic Technologies for a Carbon Conscious Concrete
No full textConcrete has long been a cornerstone of civil infrastructure due to its strength, versatility, and cost-effectiveness. However, as global construction demands increase, so do concerns about the environmental impact of concrete production, particularly its significant carbon footprint. In recent years, numerous advanced materials and innovative methods have been explored to enhance concrete performance while minimizing its ecological impact. These advancements include the incorporation of alternative cementitious materials, self-healing agents, and 3D printing technologies. Among the emerging techniques, the use of magnetic fields to improve concrete properties has garnered considerable attention, as evidenced by the growing body of research over the past two decades. Magnetic technologies typically involve applying an external magnetic field to modify the behavior and properties of concrete, which can influence either the magnetic components within concrete itself or materials incorporated into the concrete mixture. Laboratory-scale research has demonstrated that such magnetic techniques can significantly enhance various aspects of concrete performance, such as its rheological properties, mechanical strength, and long-term durability. However, despite these promising findings, several challenges remain in translating these techniques from controlled laboratory settings to large-scale real-world applications. Key obstacles include scalability, cost-effectiveness, and achieving consistent results under varying environmental conditions. This presentation will focus on magnetic techniques for enhancement in properties of concrete, focusing on three key areas: (1) real-time rheology control of cementitious materials through magnetic field manipulation (set-on-demand), (2) magnetic-based crack filling for concrete (flow-on-demand), and (3) the orientation of magnetic fibers for structural performance enhancement. By examining these areas, this presentation aims to provide a comprehensive understanding of the potential and challenges of magnetic technologies, offering insights into their future integration into sustainable construction practices and paving the way for a more carbon-conscious concrete industry
Multi-scale assessment of the structural performance of 3D printed concrete
No full text3D concrete printing (3DCP) has sparked a lot of interest in the concrete research community worldwide, because of the many possibilities that exist in design and fabrication of complex structures. Among other aspects, the determination of index properties governing the structural performance has been a major challenge for 3DCP. Unlike conventional concrete, where standard specimens can be mould cast to determine the response to different types of loading, the presence of interlayer joints in 3DCP leads to uncertainties regarding the representative volume element that should be considered for testing. As a result, there exist a number of methodologies around the world for assessment of the strength and modulus of 3D concrete, and no distinct standardization strategy has been universally accepted. This presentation explores the assessment of compressive loading performance of 3D printed concrete, from small scale specimens to full scale wall panels. The results indicate that there is a significant difference in performance at different scales, which is further complicated by the inclusion of infill material in the cavities of the 3D printed segments
Cement for net-zero future: Energy-Resource-Carbon Neutral and Multifunctional
No full textOrdinary Portland Cement (OPC)-based concrete, a cornerstone of modern infrastructure, is a major contributor to CO₂ emissions, resource depletion, and waste generation. OPC production accounts for 8% of global CO₂ emissions and consumes over 6 billion tons of raw materials annually, while concrete production uses 30 billion tons of aggregate and generates 2.2 billion tons of C&D waste yearly. This study introduces a novel manufacturing process that mitigates these impacts by utilizing waste streams as energy sources and raw materials while sequestering carbon as high-value CNTs. The resulting cement will enable next-generation concrete for resilient, net-zero infrastructure and advanced technologies like structural health monitoring, renewable energy integration, and smart urban systems