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A Mathematical Model for CO2 Capture via Mineral Carbonation Using Hydrated Lime
No full textThe construction sector contributes to approximately 37% of global GHG emissions. To mitigate this impact, this study develops a mathematical model to analyze CO2 capture via hydrated lime carbonation. The model integrates reaction kinetics, diffusion and heat balance, considering the effects of liquid water saturation, the influence of porosity on diffusion and the heat generated by both the reaction and water evaporation. For a specific case, the carbonation front and temperature gradient along the reactor are analyzed. Then, the model is validated, demonstrating promising results for optimizing future carbonation processes
Serpentine Activation and CO2 Mineralization: A Pathway to Sustainable Cementitious Materials
No full textSerpentine, a naturally occurring magnesium-rich mineral, has a significant capacity to bind carbon dioxide (CO₂). This study explores the activation and CO₂ mineralization with serpentine, investigating its potential as a supplementary cementitious material (SCM). The findings of this research could play a crucial role in assisting the cement industry in reducing its carbon footprint while promoting greater sustainability
Mix Designs of Low Modulus of Elasticity of Mass Concrete and Cushion Concrete Used in Yusufeli Dam Body
No full textThe construction of the Yusufeli Dam and Hydroelectric Power Plant on the Coruh River has been completed and the dam, which has a total water storage volume of approximately 2,2 billion cubic meters, has become the highest dam in Turkey and the fifth highest dam in the world with a height of 275 meters in the double-curvature concrete arch dam type. During the design process of the mass concrete body of the Yusufeli Dam, relatively low deformation modulus zones were encountered in some slope rock soils where the thin arch structure would create pressure. It was taken into consideration that these partially weak soil conditions would create structural risks in terms of the interaction of the rigid arch dam structure with the foundation, and instead of conventional mass concrete, a special concrete design defined as “cushion concrete” with low elasticity modulus and high unit deformation capacity was developed and implemented in the dam. The aim of this study is to present the theoretical basis, material properties and field application of this special concrete design developed to provide elastic compliance by reducing stress concentrations between the dam body and the foundation in the low rigidity foundation zones encountered during the construction of the Yusufeli Dam and to prevent crack formation under high elastic deformation. The changes on the left side required significant changes in the design of the low modulus rock material dam, requiring a larger left embankment concrete structure. However, the preservation of the less rigid base rock with the more rigid body concrete was deemed necessary on a transition zone basis, and the transition in question was called “Cushion Concrete”. The cushion concrete has a larger base area than the dam structure. With less deformable concrete on the more flexible rock mass, the cushion concrete tends to act as a rigid beam on a flexible foundation. Therefore, while significant benefits can be obtained from the cushion concrete structure acting as a rigid transition between the dam and the foundation, in return, the cushion concrete structure has to be constructed with a low E modulus value and maximum possible flexural stress capacity in the concrete. Analyses have determined that the maximum elasticity modulus of approximately 19 GPa and a slow-loading tensile strain capacity of 150x10-6 units are important design criteria in the “cushion concrete” design (1,2). In addition, in regional areas where the strain exceeds the concrete capacity, it has been suggested to add synthetic fiber reinforcement to the cushion concrete structure. It is thought that such fiber reinforcement will increase the tensile strength by 50% and, more importantly, increase the concrete ductility and tensile strain capacity by 100% (7). The absolute extent of the cushion concrete zones that will require fibre reinforcement was determined depending on the resulting final geotechnical conditions and the zones that can be improved by consolidation injection. All mixtures and experimental results obtained regarding the alternatives of the cushion concrete prepared in the laboratory are given in the relevant Tables in this article (11)
Durability of reinforced concrete exposed to stray currents from DC-driven track systems under constant and varying voltages
No full textReal-world conditions near a light rail system were simulated to examine the effect of stray electric currents on the corrosion of reinforced concrete and the service life of these elements. Field measurements were conducted near the track to estimate typical stray electric voltages. These voltages were then applied to concrete specimens in a controlled laboratory environment under two different conditions: variable voltage, as measured in the field, and with a constant voltage of 9 V. Two types of concrete were tested: normal-strength concrete (approximately 30 MPa) and medium-strength concrete (approximately 60 MPa). Crack times were recorded for both to assess their differences. Additionally, the effect of cover thickness on the amount of corrosion products and time of cracking was examined
Recycling waste glass powder in lightweight aggregate concrete: Towards lightweight, sustainable and durable marine engineering structures
No full textThis study investigates the feasibility of incorporating waste glass powder (GP) as a sustainable supplementary cementitious material in structural lightweight aggregate concrete (SLAC) for marine applications. The effects of GP replacement (0–40%) on the fresh, mechanical, and durability properties were evaluated. Results showed that while GP reduces early-age strength, long-term mechanical stability is maintained, with GP20 achieving the highest elastic modulus. GP incorporation significantly improves durability, including reduced chloride migration, lower water absorption, and higher electrical resistivity. Corrosion resistance of steel bars under chloride exposure was enhanced, as indicated by higher open-circuit potential values (OCP). Microstructural analysis revealed that GP refines the pore structure and densifies the aggregate–matrix interface. These findings support the use of GP in producing low-carbon, durable SLAC for marine infrastructure
Cathodic Protection of Reinforced concrete infrastructure using MMO-Coated Titanium Alloy Bars
No full textASTM B1009 titanium alloy bars (TiABs), which are chemically and mechanically equivalent to Grade 5 titanium, have recently gained attention as dual-purpose materials for near-surface-mounted retrofit (NSMR) of concrete. These bars offer both structural reinforcement and corrosion protection when used as anodes in impressed current cathodic protection (ICCP) systems. While TiABs without mixed metal oxide (MMO) coating provide inherent corrosion resistance as an ICCP anode, their effectiveness in ICCP applications may be limited. This study evaluates the electrochemical behavior of iridium-based MMO coatings on TiABs that are designed as ICCP anodes. Open circuit potential (OCP) measurements showed that both uncoated and coated metals stabilized at similar potentials, while uncoated bars initially exhibited more active behavior. Additionally, linear polarization resistance (LPR) results revealed that MMO-coated TiABs exhibit approximately three times higher reactivity compared to bare TiABs. Electrochemical impedance spectroscopy (EIS) further confirmed that MMO-coated TiABs possess significantly greater conductivity, making them a superior option for use as anodes in ICCP systems. Studies on long-term performance also show that MMO coated bars are better suited for the dual-purpose application
Rethinking Concrete Slabs: Modular CFRP-Reinforced Systems for Sustainable Construction
No full textA significant portion of concrete in building construction is allocated to traditional solid slabs, resulting in excessive material use and substantial CO2 emissions. Modular ribbed CFRPreinforced floor slab systems offer an efficient alternative, significantly reducing material use while maintaining structural performance. However, fabricating such ribbed structures is challenging, particularly regarding complex formwork and labor-intensive processes. Innovations in 3D concrete printing provide a solution by enabling the straightforward production of novel, load-adapted concrete structures, disrupting conventional construction practices. This paper presents a concept for a modular floor slab system that integrates topology-optimized design principles with digital manufacturing methods. Slender, bi-directionally oriented ribs are 3D-printed onto a thin precast base slab, creating lightweight, geometrically adaptable slab modules. These modules are designed with detachable dryjoint connections for mechanical assembly through post-tensioning, which ensures reusability. A prototype comprising five integrated modules validated the efficacy of digitally fabricated slab system. This demonstration successfully bridges ecological responsibility with cutting-edge digital fabrication techniques, establishing a groundbreaking paradigm for sustainable construction practices
Hydrophobic Modification for the Design of High-Performance and Ultra-High Performance Cementitious Composites
No full textThis paper presents a novel method for designing high-performance and ultra-high-performance concrete (HPC/UHPC) through hydrophobic and nanomaterial modification. Three-dimensional hydrophobization of cementitious matrices is achieved by incorporating water-based emulsions of silico-organic compounds containing active hydrogen. The approach enables high-strength matrices with superior flexural performance via fiber reinforcement, further improved by uniformly distributed small air voids that promote multi-cracking and strain-hardening behavior. Incorporating aluminum oxide (Al₂O₃) nanofibers with 1% silica fume (or metakaolin) produces UHPC-grade strength and ductility while reducing chemical shrinkage and simplifying composition. Developed with Type V and I cements at W/CM \u3c 0.3, the composites reached compressive strengths up to 195 MPa, exhibited high flowability, and showed excellent strain-hardening when reinforced with 2% synthetic macrofibers (PVA and HDPE), with HDPE yielding greater ductility. This synergy of hydrophobic modification, nanoengineered matrix, and synthetic fibers offers a cost-effective, sustainable alternative to conventional HPC/UHPC, exceeding durability and environmental performance benchmarks
Transforming Agricultural Residues into High-Performance SCMs through Mechanochemical Activation
No full textDespite the abundance of ashed agricultural residues and their potential as supplementary cementitious materials (SCMs), given a high silica content (up to 90 wt.%), their high water demand limits their use. This challenge compromises both the fresh-state workability and mechanical performance of supplemented concrete – a pivotal challenge for countries in the Global South with large agricultural sectors and low production of other industrial SCMs. To address this limitation, we investigate two innovative mechanochemical methods and their effects on the fresh-state workability issues of these ash-based SCMs. This presentation will share our latest results describing how the mechanochemical activation of rice hull ash influences the silica atomic coordination and improves both the workability and compressive strength of supplemented cementitious materials. Improvements in workability lead to a near 6-fold increase in compressive strength at 28 days, reaching ~8,000 psi at replacement levels of 20 wt.%. By enabling the manufacturing of high-performance SCMs from agricultural residues, our findings offer a viable pathway to utilize abundant agricultural ashes in global concrete production, addressing environmental and SCM supply challenges in the Global South
OxCem: A Novel Carbon-Negative Cement Based on Oxalic Acid and Steel Slag
No full textThe proper disposal of steel slag remains a challenging issue. This study explores a novel carbon-negative cement, utilizing the reaction between steel slag and oxalic acid. The mechanical properties, phase composition, and microstructure of OxCem were investigated through compressive strength tests, TG analysis, XRD, and MIP test. The results indicate that the optimal EAF/OA ratio is 3.5, achieving a 28-day compressive strength of 34.7 MPa. The strength enhancement of the paste is attributed to the influence of the reaction products, ferrous oxalate and calcium oxalate, on the pore structure