Development of a Method for Accelerated Ageing of Cementitious Materials Used in Repositories for Nuclear Waste

The Swedish nuclear fuel and waste management company (SKB), is required to validate the service life prediction of the concrete structures in nuclear waste repositories. Considering the repository being in contact with water , the decalcification process of cementitious materials although being very slow can during the very long operational lifetime of the repository (up to 100000 years), cause the degradation of chemical and mechanical properties of the concrete structures. In order to predict the long-term service life of the structures without extrapolating short-term experimental results, methods that accelerate the leaching process of calcium from cementitious materials are required. In this work the development process of an electro-chemical migration method for acceleration of the calcium leaching from cementitious specimens is presented. The method enables ageing of cementitious specimens with sufficiently large sizes suitable for testing mechanical and transport properties. In this method, the cementitious specimen is placed in an electrochemical cell as a porous path way through which ions can migrate at a rate far higher than diffusion process. The results show that, by a careful adjustment of the experimental parameters such as the magnitude of electrical field and choice of anolyte and catholyte solutions, an effective leaching of calcium with an acceleration factor of >600 can be obtained. According to instrumental analysis the chemical and mineralogical properties of the treated specimens are comparable with the characteristics of the aged specimens in natural decalcification proces

Boosting electrical conductivity of textiles via fabrication of silver nano-ribbons using the fiber templates

This research has accomplished an exceptional achievement to synthesize metallic nano-ribbons. A simple and fast spray method has been used to fabrication the metallic ribbon-shape nanostructures on the cotton fabrics. In fact cotton fabrics can act as a good template directing the shape of nanostructures. The method to achieve this end has been reported and discussed. The SEM micrographs demonstrated the nano-ribbon fabrication. Evaluation the electrical conductivity disclosed that electrical resistance of fabrics containing the silver nano-ribbons has been decrease about 7640 times as compared to untreated one. In fact electrical resistance has been declined from 6.53×109.cm-1 on treated fabrics to 8.55 ×105.cm-1 on untreated fabrics. Consequently, applying this technique decreases the electrical resistance by four orders of magnitude. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2063

Nanowire fabrication on cotton surfaces: effect of the pretreatment

Anisotropic nanostructures such as nano-wires, nano-tubes, nano-rods, nanoribbons, nano-layers, etc. are extremely attracted due to their larger surface area as compared to nano-particles. This research has targeted at fabrication of the metallic nano-wires through a simple one-step pad-dry method. The effects of mercerizing as one of the most common and important finishing treatments on cotton fabrics have been investigated. Mercerized and un-mercerized fabrics with the same structures have been treated and compared. SEM micrographs confirmed fabrication of the nano-wires with a high aspect ratio on the fiber surfaces oriented parallel with fiber axes. An enhanced potentiality for growing nano-wires with higher level of orientation has been observed for mercerized fabrics compared to un-mercerized ones. As it is well known, mercerizing can cause some structural changes in cotton fibers. Reduction of crystallinity as a result of this process (mercerizing) leads to increasing the amorphous regions which have a good potentiality for growing nano-structured materials. The higher moisture regains, absorbency, smoother morphology, etc. caused by mercerizing can direct the better growth of nano-structures on mercerized fabrics. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2063

Ageing process of cementitious materials: Ion transport and diffusion coefficient

Risk assessment analysis concerning service life predictions of concrete structures in nuclear waste repositories requires broad knowledge about long-term concrete deterioration processes. It is well known that the degradation process of cementitious materials involves diffusion of internal and external ions, interaction between these ions and re-deposition of the interacted products. However, although diffusion properties play an important role in the deterioration process, there is a lack of reliable data on ion diffusivity in concrete, especially co-existing ions rather than chloride. The aim of this study is to further analyze multi-component ionic diffusion accompanied with surface complexation and selective adsorption. Natural diffusion cell and field immersion tests are used to analyze transport properties of ions present in groundwater surrounding nuclear waste repositories such as chloride, sodium, lithium and calcium ions, through cement paste. Analytical techniques such as Ion chromatography, potentiometric titration, inductively coupled plasma mass spectrometry and X-ray fluorescence methods are used. Results indicate that the ionic diffusion coefficients differ between different ions and the higher the concentration of the ions, the lower the diffusion coefficient will be

Ex-situ and in-situ post-photosynthesis of silver nanoparticles on polyamide fabric using daylight irradiation

Silver nanoparticles (AgNPs) have been ex-situ post-synthesized in an aqueous solution and in-situ synthesized on polyamide fabric through a simple chemical reduction method by using silver nitrate (AgNO3), stannous chloride (SnCl2) and cetyltrimethylammonium bromide (CTAB) under daylight irradiation. SnCl2 and CTAB act as reducing and stabilizing agents in the colloidal silver nanoparticles solution respectively. Post in-situ synthesis of Ag NPs have been carried out on polyamide fabric by spraying solution of AgNO3, CTAB and SnCl2 on the fabric and then irradiating under daylight for 2 h. Ag NPs solutions and Ag NPs loaded polyamide fabrics are characterized by UV-vis spectroscopy, dynamic light scattering (DLS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Appearing a strong plasmon resonance peak at 400 nm in UV-visible spectrum, XRD patterns and SEM images are found to clearly confirm the formation of silver nanoparticles. The UV-vis spectra also confirm no Ag NPs formation without daylight irradiation

A Deep Reinforcement Learning-Based Controller for Magnetorheological-Damped Vehicle Suspension

This paper proposes a novel approach to controller design for MR-damped vehicle suspension system. This approach is predicated on the premise that the optimal control strategy can be learned through real-world or simulated experiments utilizing a reinforcement learning algorithm with continuous states/actions. The sensor data is fed into a Twin Delayed Deep Deterministic Policy Gradient (TD3) algorithm, which generates the actuation voltage required for the MR damper. The resulting suspension space (displacement), sprung mass acceleration, and dynamic tire load are calculated using a quarter vehicle model incorporating the modified Bouc-Wen MR damper model. Deep RL's reward function is based on sprung mass acceleration. The proposed approach outperforms traditional suspension control strategies regarding ride comfort and stability, as demonstrated by multiple simulated experimentsComment: 19 pages , 9 figures , 5 table

Electrochemical migration technique to accelerate ageing of cementitious materials

Durability assessment of concrete structures for constructions in nuclear waste repositories requires long term service life predictions. As deposition of low and intermediate level radioactive waste (LILW) takes up to 100 000 years, it is necessary to analyze the service life of cementitious materials in this time perspective. Using acceleration methods producing aged specimens would decrease the need of extrapolating short term data sets. Laboratory methods are therefore, needed for accelerating the ageing process without making any influencing distortion in the properties of the materials. This paper presents an electro-chemical migration method to increase the rate of calcium leaching from cementitious specimens. This method is developed based on the fact that major long term deterioration process of hardened cement paste in concrete structures for deposition of LILW is due to slow diffusion of calcium ions. In this method the cementitious specimen is placed in an electrochemical cell as a porous path way through which ions can migrate at a rate far higher than diffusion process. The electrical field is applied to the cell in a way to accelerate the ion migration without making destructions in the specimen's micro and macroscopic properties. The anolyte and catholyte solutions are designed favoring dissolution of calcium hydroxide and compensating for the leached calcium ions with another ion like lithium

Photochemical reduction of silver nitrate to nano silver using stannous chloride, ctab and daylight irradiation

Silver nanoparticles (NPs) were synthesized and stabilized by a simple method in aqueous solution, by the reduction of silver nitrate with stannous chloride (SnCl2.2H2O) and cetyl trimethyl ammonium bromide (CTAB)through day light irradiation. Thereby, the silver nanoparticles were colloidally stabilized by CTAB as a surfactant. The synthesis of silver NPs with different size were possible by changing the reaction conditions such as reagent ratio. The silver NPs were characterized by Dynamic Light Scattering (DLS) and UV-visible spectroscopy. A very strong plasmon resonance peak at 400-500 nm in the UV-visible spectra is a clear consequence of the silver NPs production. The synthesized silver NPs showed good stability by using CTAB. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2063