The impacts of oily wastewater on water quality, aquatic ecosystems and human health are a global problem. Therefore, the development of multifunctional oil-water separation materials, that are ...capable of organic pollutant removal, is of high importance and remains a significant challenge. Herein, we report a combination of 3D printing technology with hydrothermal method and liquid phase deposition to prepare a hierarchical TiO2/Cu2O porous lattice structure with 3D structure strengthening with oil-water separation performance and visible light catalytic degradation. Due to its micro-nano hierarchical structure, the as-prepared ceramic lattice structure exhibited very high levels of hydrophilicity and oleophobicity in aquatic environments. The 3D printed lattice structure achieved excellent oil-water separation performance, with the separation efficiency of the body-centered cubic lattice structure reaching 99.6%. Furthermore, organic pollutants dissolved in water can be decomposed by visible light irradiation after separation, improving the utilization rate of solar energy. The 3D printed lattice structure exhibited a compressive strength of 44.89 MPa and an absorption energy of 55.17 kJ m−3, indicating good mechanical strength and resistance to deformation. Overall, the use of 3D printing for structural strengthening of this multifunctional superhydrophilic and underwater superoleophobic lattice structure, is a promising method with a wide range of potential applications in environmental protection, particularly for the treatment of oily wastewater and the degradation of organic pollutants.
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•TiO2/Cu2O/CLS realizes the integration of structure and function.•Various oil/water mixtures can be separated with high separation efficiency.•The TiO2/Cu2O/CLS could purify the aqueous pollutant under visible light.•3D printing has broad potential application in environmental protection.
•The fatigue performance of carbon-FRCM and FRCM-strengthened RC beams were studied.•The fatigue degradation of FRCM was fabric slippage increase and stiffness reduction.•The fatigue life performance ...of carbon-FRCM was superior to rebar and inferior to CFRP.•The fatigue performance of RC beams was improved significantly by bonding carbon-FRCM.•A fatigue life prediction model for beams with bonded carbon-FRCM was proposed.
Fabric reinforced cementitious matrix (FRCM) systems can provide structural strengthening (SS) of aging reinforced concrete (RC) structures. Furthermore, impressed current cathodic protection (ICCP) has been integrated with FRCM systems to develop ICCP-SS intervention systems to help improve the long-term performance of FRCM-strengthened RC structures. However, there is a lack of research regarding the fatigue performance of FRCM composites and FRCM-strengthened RC members. This study investigated the effects of fabric layers in carbon-FRCM, anodic polarization in the process of ICCP, and cyclic loading conditions on the fatigue performance of FRCM composites in tension and FRCM-strengthened RC beams in flexure. Cyclic tensile loading tests of FRCM specimens and cyclic four-point bending tests of beam specimens were conducted. Cyclic tensile test results showed that the fatigue life performance of FRCM was superior to that of steel rebar and inferior to that of carbon fiber reinforced polymer (CFRP, a composite that commonly has an epoxy resin matrix). The anodic polarization of ICCP degraded the fatigue life of carbon-FRCM at a given stress level and fatigue strength after two million loading cycles. The cyclic bending test results indicated that the fatigue performance of the beams was largely dependent on the number of fabric layers in the FRCM and slightly influenced by the anodic polarization in the ICCP-SS. A new curve of the steel stress range versus the number of cycles (S-N curve) for FRCM-strengthened beams was obtained in this study and provided satisfactory fatigue life predictions.
RESUMO O objetivo deste trabalho foi avaliar a eficiência de um microconcreto para reforços estruturais, como ponte de aderência entre concreto velho e concreto novo. Foi avaliada a substituição da ...areia por um fíler, subproduto de britagem, a partir de um traço de referência. Os ligantes utilizados foram cimento Portland (85%) e sílica ativa (15%). A relação água/ligante e proporção entre cimento e sílica ativa foram obtidas de forma experimental, maximizando-se a utilização do aditivo superplastificante e obtendo-se condições aceitáveis de autoadensabilidade das misturas. Foram avaliadas as propriedades no estado fresco e endurecido, aderência do microconcreto em dois substratos e como ponte de aderência, simulando uma situação de reforço estrutural. Obtiveram-se boas propriedades de autoadensabilidade do MC, com aumento de 26% no espalhamento e 5% no tempo de escoamento do MC com 15% de substituição em relação ao MC de referência. Para 15% de substituição, observou-se aumento de 18% no módulo de elasticidade e redução de quase 9% na absorção total de água. Também se obtiveram bons resultados de aderência em substrato de concreto, demonstrados pela ruptura coesiva observada no ensaio de aderência. Em situação de reparo estrutural, o material mostrou-se satisfatório como ponte de aderência entre concretos.
ABSTRACT The objective of this work was to evaluate the efficiency of a micro concrete for structural strengthening, as an adhesion bridge between old and new concrete. Contributing to environmental preservation, the replacement of sand with a filler, a by-product of crushing stones, was evaluated based on a reference mixture. The binders used were Portland cement (85%) and silica fume (15%). The water/binder ratio and the proportion between cement and silica fume were obtained experimentally, maximizing the use of the superplasticizer additive, and obtaining acceptable conditions of self-compacting of the mixtures. The properties of micro concrete in the fresh and hardened state were evaluated, in addition to the adhesion provided by the micro concrete on concrete substrates and as an adherent material between old and new concrete, simulating a situation of structural reinforcement. As a result, good MC self-compacting properties were obtained, with an increase of 26% in scattering and 5% in MC flow time with 15% replacement in relation to the reference MC. There was also considerable gain in the physical properties of the mixtures. Still, for 15% replacement, there was an increase of 18% in the modulus of elasticity and a reduction of almost 9% in the total water absorption. Good adhesion results were also obtained on concrete substrates, demonstrated by the cohesive failure observed in the adhesion test. In addition, in a situation of structural repair, the material proved to be satisfactory for use as an adhesion bridge between old and new concrete.
The research proposes the combined use of a Glass Fiber Reinforced Cement Matrix (GFRCM) composite with an integrated fiber optic sensing system for innovative seismic retrofitting of masonry vaults. ...The need of eco-compatibility of bonding material with masonry support implies the use of Hydraulic Lime Mortar (HLM) as bonding matrix that, in contrast, is characterized by lower adhesion capacity respect to polymeric resins and not well-known carrying-load properties. Hence, monitoring of the operating features of the GFRCM reinforcement has been pursued with an advanced fiber optic sensing system realized through Fiber Bragg Grating (FBG) sensors. The use of FBG sensors is justified by a large number of advantages such as small sensor dimensions, low weight as well as high static and dynamic resolution of measured values, distributed sensing feature allowing to detect anomalies in load transfer between reinforcement and substrate. Specifically, the proposed retrofitting and monitoring technique is designed and applied to an old masonry pavilion vault. A nonlinear finite element model of the reinforced structure is developed in order to quantify the effectiveness of the GFRCM strengthening layer and to derive the convenient position of the optic fibers for a correct monitoring of the reinforced vault. An experimental campaign is carried out in order to verify the proper behavior of the proposed strengthening and sensing strategy.
•Flexural response of masonry beams strengthened with ECC sheets are investigated.•The experimental results are validated numerically.•Parametric study of flexural response of strengthened masonry ...beams has been done.•Optimum thickness of ECC sheet and bonding agents are recommended.
This study aims to develop and demonstrate the effectiveness of precast engineered cementitious composite (ECC) plates for strengthening of masonry beams by bonding them on tension face as well as both on tension and compression faces like sandwich beam. Two types of bonding materials have been used, i.e., epoxy and cement mortar for bonding the ECC plates with masonry beam. Experimental flexural response has been predicted for tension strengthened as well as sandwich beams. Detailed parametric study has been performed using ABAQUS commercial software package. The parametric study incorporates the effect of various parameters such as ECC thickness in compression and tension, epoxy and cement mortar as bonding agents, and bonding agent thickness on the flexural response of strengthened beams. All beams were tested under four-point loading systems. The numerical results obtained using ABAQUS are validated with experimental results. The present study results reveal that the application of precast ECC increases the strength and deformability of masonry beams and hence demonstrate its effectiveness as strengthening element for masonry structures. Furthermore, recommendations regarding optimum thickness of ECC strips/plates and bonding agents have been made for external strengthening of masonry beams with precast ECC strips.
Taking advantage of solid and liquid fire extinguishants in one material is desirable, especially for the selection of liquid phase components aimed at specific fire disaster situations. In this ...investigation, the feasibility of novel dry liquids with core-shell structure as fire extinguishants in liquid fuel fires was conducted. The microencapsulated functional materials were formed by the high-speed shearing method, which were then characterized for their liquid content, micromorphology, particle size, and fluidity. The surface tension of inner liquids and hydrophobicity of outer shell were the critical factors for the preparation and the addition of Gellangum enhanced the structural strength, and the formed gel-type particles reduced the rate of water loss by at least 50%. The fire extinguishing efficiency of gel-type dry liquids was obtained by the consumption and times of fire suppression compared to the dry powder and water mist, both in small and medium scale tests. The obtained results indicated that the performance of gel-type dry water is comparable to that of ultrafine dry powder in small-scale cyclohexane fire based on a total flooding ejection with a dosage of 44.3% lower than that of water mist as the consumption of ultrafine dry powder, gel-type dry water and water mist was 48.7g, 47.6g, and 85.4g, respectively. The efficiency of gel-type dry water in gasoline fire was increased from 13.4 to 27.7% with the increase in pressure from 0.5 to 1.0 MPa and fire power from 0.05 to 0.25 MW compared to the water mist with the dosages of gel-type dry water and water mist were 35.2g and 40.6g in small scale, meanwhile 262.7g and 363.3g in medium scale. The performance in diesel is 12.7% higher than that of gasoline fire under the same experimental conditions. The unique properties of gel-type dry liquids are due to their suspension characteristics and limited evaporation, and the mechanism of extinguishing is the result of comprehensive synergetic effects of cooling, dilution, homogeneous chemical, and heterogeneous inhibition.
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•A novel functional material with microencapsulation structure for fire extinguishant is prepared.•Dry liquid is powder macroscopically with internal liquid content is as high as 90%.•Dry liquid is suitable for extinguishing liquid fuel fires compared with dry powder.•Structural stability of dry liquid could be achieved by Gellangum addition.
•Development of a dual-functional intervention method for reinforced concrete beams.•Experimental programme on simply supported beams repaired by ICCP-SS method.•Analysis on the structural responses ...of simply supported beams with C-FRCM strengthening.•Comparison of test results with existing design methods.•Recommendation of changes on the design methods for cross-section capacity prediction.
Chloride ions in marine environment can cause corrosion of steel reinforcement in reinforced concrete (RC) structures and result in structure deterioration. This study investigates a dual-functional intervention method, i.e. impressed current cathodic protection – structural strengthening (ICCP-SS) method, using carbon fibre reinforced polymer (CFRP) as both the anode material for impressed current cathodic protection and strengthening material for structural strengthening system. The effectiveness of the ICCP-SS method on the improvement of durability of RC structures is considered in a long-term timeframe. An experimental programme comprising nine simply supported beams is presented in this paper. The beams experienced 360-day accelerated corrosion and 180-day cathodic protection, followed by four-point bending tests. Flexural behaviour and capacities of the degraded beams repaired by using ICCP technology, structural strengthening technology and ICCP-SS technology were obtained. After the tests, the steel reinforcement bars inside concrete were taken out and cleaned to measure the section reduction due to corrosion. Results showed that the ICCP-SS technology can prevent the corrosion of the steel reinforcement effectively and increase the capacities of the beams at the same time. Finally, the appropriateness of existing design approaches for the intervened beams was also discussed in the paper. The ICCP-SS intervention method is found to be beneficial for the durability of RC structures in marine environment.
Fiber-reinforced polymer (FRP) composites have been widely used for strengthening or constructing structures due to their excellent corrosion resistance and high tensile strength. An emerging hybrid ...structural member form with FRP composites-which consist of a steel section as internal reinforcement, an external FRP wrap/tube, and concrete filled between them (referred to as FRP-confined steel-reinforced concrete (FCSRC) systems)-has attracted increasing research interest. To date, the concept has been adopted to strengthen/repair steel structures or used as new hybrid structural members (e.g., hybrid columns or beams, including buckling restrained braces (BRBs)). The FRP confinement and composite action between the three components in FCSRCs result in the excellent performance of the hybrid member. This paper presents a state-of-the-art review of FCSRCs for structural applications. The gaps in knowledge and future research opportunities on FCSRC structural members are also identified.
Dieser Aufsatz gibt einen Überblick über jüngste Arbeiten zur Entwicklung und Anwendung von Formgedächtnislegierungen auf Eisenbasis (Fe‐SMA), den sog. Memory‐Stählen, für Verstärkungs‐ und ...Instandsetzungsmaßnahmen an Stahlkonstruktionen. Zunächst werden Studien zu den Materialeigenschaften von Fe‐SMA bezüglich Formgedächtniseffekt und Pseudoelastizität erörtert. Anschließend wird der Einsatz von Fe‐SMA als vorgespannte Verstärkungsmaßnahme bei Stahlkonstruktionen erläutert. Hierbei wird auf Verstärkungen von Stahlträgern, Verbindungen und die Reparatur von Ermüdungsrissen eingegangen. Es werden verschiedene Verstärkungslösungen wie mechanisch verankerte oder geklebte Fe‐SMA sowie Studien über das Verhalten von Fe‐SMA‐Stahlverbindungen diskutiert. Ein Anwendungsfall wird anhand einer 113 Jahre alten Stahlbrücke vorgestellt. Zusätzlich wird die Anwendung von Fe‐SMA für Rohrkupplungen gezeigt. Abschließend werden innovative Untersuchungen aus der laufenden Forschung zum Thema additive Fertigung von Fe‐SMA (4D‐Druck) erörtert.
Translation
Memory‐steel for smart steel structures – a review on recent developments and applications
This study comprehensively examines recent advancements in the development and utilization of iron‐based shape memory alloy (Fe‐SMA), commonly known as memory‐steel, within the retrofitting of steel structures. The discussion is structured into several key areas. Initially, a thorough analysis of the material properties of Fe‐SMA is presented, focusing on aspects such as shape memory effect and super‐elasticity. Subsequently, the application of Fe‐SMA in prestressed strengthening of steel structures is elucidated, encompassing its role in reinforcing steel girders, connections, and addressing fatigue crack repairs. Various strengthening methodologies are explored, including the utilization of mechanically anchored or adhesively‐bonded Fe‐SMA. The study delves into an in‐depth examination of the behavior exhibited by Fe‐SMA‐to‐steel bonded joints. Notably, the research highlights the practical application of Fe‐SMA in strengthening a 113‐year‐old steel bridge. Furthermore, innovative applications of Fe‐SMA as pipe couplers are introduced, showcasing its versatility in diverse structural contexts.
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