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The output of C&D waste is increasing year by year, among which low-quality recycled brick aggregates (RBAs) have not been well utilized and brought environmental burden. The durability of steam-cured concrete (HCC) is often compromised due to the detrimental effects of this curing regime on the long-term performance and microstructure development of the concrete material. To address this issue, this study investigates the potential of incorporating RBAs to improve the long-term durability of HCC. The results demonstrate that the incorporation of a small amount of RBA (10–20%) not only enhances the 28-d strength of HCC by 2.5–11.3%, but also improves its impermeability by mitigating heat damage effects. The combined application of fine and coarse RBA was found to effectively balance the negative effects of coarse RBA on the performance of HCC. Furthermore, the utilization of RBA in HCC was shown to have economic and environmental benefits. The results of this study demonstrate a simple and effective approach to improve the long-term durability of HCC while promoting the high-value utilization of solid waste.
Since 2016 ISO Technical Committee (TC) 265 is working on standardization the whole CCS-process chain. Around 30 countries are working together to provide international guidelines. As ISO 27913 was the first standard finished within these activities it is already in the stage of first revision.
The objective of ISO 27913 is “to provide specific requirements and recommendations on certain aspects of safe and reliable design, construction and operation of pipelines intended for the large-scale transportation of CO2 that are not already covered in existing pipeline standards such as ISO 13623, ASME B31.8, EN 1594, AS 2885 or other standards. Existing pipeline standards cover many of the issues related to the design and construction of CO2 pipelines; however, there are some CO2 specific issues that are not adequately covered in these standards. The purpose of this document is to cover these issues consistently. Hence, this document is not a standalone standard, but is written to be a supplement to other existing pipeline standards for natural gas or liquids for both onshore and offshore pipelines.”
This contribution shall provide information on the content, the current stage of the revision process, encourage to contribute to this standard and make listeners aware to consider the influence of ISO standard on documents currently in draft.
Since 2016 ISO Technical Committee (TC) 265 is working on standardization the whole CCS-process chain. Around 30 countries are working together to provide international guidelines. As ISO 27913 was the first standard finished within these activities it is already in the stage of first revision.
The objective of ISO 27913 is “to provide specific requirements and recommendations on certain aspects of safe and reliable design, construction and operation of pipelines intended for the large-scale transportation of CO2 that are not already covered in existing pipeline standards such as ISO 13623, ASME B31.8, EN 1594, AS 2885 or other standards. Existing pipeline standards cover many of the issues related to the design and construction of CO2 pipelines; however, there are some CO2 specific issues that are not adequately covered in these standards. The purpose of this document is to cover these issues consistently. Hence, this document is not a standalone standard, but is written to be a supplement to other existing pipeline standards for natural gas or liquids for both onshore and offshore pipelines.”
This contribution shall provide information on the content, the current stage of the revision process, encourage to contribute to this standard and make listeners aware to consider the influence of ISO standard on documents currently in draft.
Two-dimensional covalent organic frameworks (COFs) based on phosphinine and thiophene building blocks have been synthesized with two different side groups. The materials are denoted as CPSF-MeO and CPSF-EtO where CxxF correspond to the covalent framework, whereas P and S are related to heteroatoms phosphorous and sulfur. MeO and EtO indicate the substituents, i.e. methoxy and ethoxy.
Their morphologies were studied by scanning electron microcopy and X-ray scattering. The absence of crystalline reflexes in the X-ray pattern reveal that both materials are amorphous and can be considered as glasses. Furthermore, N2 adsorption measurements indicate substantial Brunauer–Emmett–Teller (BET) surface area values pointing to the formation of three-dimensional pores by stacking of the aromatic 2D layer. An analysis of the porosity of both COFs showed a mean radius of the pores to be of ca. 4 nm, consistent with their chemical structure. The COFs form nanoparticles with a radius of around 100 nm. The thermal behavior of the COFs was further investigated by fast scanning calorimetry. These investigations showed that both COFs undergo a glass transition. The glass transition temperature of CPSF-EtO is found to be ca. 100 K higher than that for CPSF-MeO. This large difference in the glass transition is discussed to be due to a change in the interaction of the COF sheets induced by the longer ethoxy group. It might be assumed that for CPSF-EtO more individual COF sheets assemble to larger stacks than for CPSF-MeO. This agrees with the much larger surface area value found for CPSF-EtO compared to CPSF-MeO. To corroborate the results obtained be fast scanning calorimetry dielectric measurements were conducted which confirm the occurrence of a dynamic glass transition. The estimated temperature dependence of the relaxation rates of the dielectric relaxation and their absolute values agrees well with the data obtained by fast scanning calorimetry. Considering the fragility approach to the glass transition, it was further found that CPSF-MeO is a fragile glass former whereas CPSF-EtO behaves as a strong glass forming material. This difference in the fragility points also to distinct differences in the interaction between the 2D COF molecules in both materials.
Despite the advances in hardware and software techniques, standard numerical methods fail in providing real-time simulations, especially for complex processes such as additive manufacturing applications. A real-time simulation enables process control through the combination of process monitoring and automated feedback, which increases the flexibil- ity and quality of a process. Typically, before producing a whole additive manufacturing structure, a simplified experiment in form of a bead-on- plate experiment is performed to get a first insight into the process and to set parameters suitably. In this work, a reduced order model for the transient thermal problem of the bead-on-plate weld simulation is devel- oped, allowing an efficient model calibration and control of the process. The proposed approach applies the proper generalized decomposition (PGD) method, a popular model order reduction technique, to decrease the computational effort of each model evaluation required multiple times in parameter estimation, control and optimization. The welding torch is modeled by a moving heat source, which leads to difficulties separating space and time, a key ingredient in PGD simulations. A novel approach for separating space and time is applied and extended to 3D problems allowing the derivation of an efficient separated representation of the tem- perature. The results are verified against a standard finite element model showing excellent agreement. The reduced order model is also leveraged in a Bayesian model parameter estimation setup, speeding up calibrations and ultimately leading to an optimized real-time simulation approach for welding experiment using synthetic as well as real measurement data.
Despite the advances in hardware and software techniques, standard numerical methods fail in providing real-time simulations, especially for complex processes such as additive manufacturing applications. A real-time simulation enables process control through the combination of process monitoring and automated feedback, which increases the flexibility and quality of a process. Typically, before producing a whole additive manufacturing structure, a simplified experiment in the form of a beadon-plate experiment is performed to get a first insight into the process and to set parameters suitably. In this work, a reduced order model for the transient thermal problem of the bead-on-plate weld simulation is developed, allowing an efficient model calibration and control of the process. The proposed approach applies the proper generalized decomposition (PGD) method, a popular model order reduction technique, to decrease the computational effort of each model evaluation required multiple times in parameter estimation, control, and optimization. The welding torch is modeled by a moving heat source, which leads to difficulties separating space and time, a key ingredient in PGD simulations. A novel approach for separating space and time is applied and extended to 3D problems allowing the derivation of an efficient separated representation of the temperature.
The results are verified against a standard finite element model showing excellent agreement. The reduced order model is also leveraged in a Bayesian model parameter estimation setup, speeding up calibrations and ultimately leading to an optimized real-time simulation approach for welding experiment using synthetic as well as real measurement data.
Currently, mandatory requirements and recommendations for the detection of irregularities in laser beam welded joints are based on classic micrographs as set out in the standard ISO 13919-1:2019. Compared to classic micrographs, computed tomography enables a non-destructive, three-dimensional and material-independent mode of operation, which delivers much more profound results. Even in building material testing, methods with limited informative value can be checked and supplemented by CT examinations.
Polymers with intrinsic microporosity (PIMs) are gaining attention as gas separation membranes. Nevertheless, they face limitations due to pronounced physical aging. In this study a covalent organic framework containing λ5-phosphinine moieties, CPSF-EtO were incorporated as a nanofiller (concentration range 0-10 wt%) into a PIM-1 matrix forming dense films with a thickness of ca. 100 μm. The aim of the investigation was to investigate possible enhancements of gas transport properties and mitigating effects on physical aging. The incorporation of the nanofiller occurred on aggregate level with domains up to 100 nm as observed by T-SEM and confirmed by X-ray scattering. Moreover, the X-ray data show that the structure of the microporous network of the PIM-1 matrix is changed by the nanofiller.
As the molecular mobility is fundamental for gas transport as well as for physical aging, the study includes dielectric investigations of pure PIM-1 and PIM-1/CPSF-EtO mixed matrix membranes to establish a correlation between the molecular mobility and the gas transport properties. Using the time-lag method the gas permeability and the permselectivity were determined for N2, O2, CH4 and CO2 for samples with variation in filler content. A significant increase in the permeability of CH4 and CO2 (50 % increase compared to pure PIM-1) was observed for a concentration of 5 wt% of the nanofiller. Furthermore, the most pronounced change in the permselectivity was found for the gas pair CO2/N2 at a filler concentration of 7 wt%.
Future lunar exploration will be based on in-situ resource utilization (ISRU) techniques. The most abundant raw material on the Moon is lunar regolith, which, however, is very scarce on Earth, making the study of simulants a necessity. The objective of this study is to characterize and investigate the sintering behavior of EAC-1A lunar regolith simulant. The characterization of the simulant included the determination of the phase assemblage, characteristic temperatures determination and water content analysis. The results are discussed in the context of sintering experiments of EAC-1A simulant, which showed that the material can be sintered to a relative density close to 90%, but only within a very narrow range of temperatures (20–30 °C). Sintering experiments were performed for sieved and unsieved, as well as for dried and non-dried specimens of EAC-1A. In addition, an analysis of the densification and mechanical properties of the sintered specimens was done. The sintering experiments at different temperatures showed that the finest fraction of sieved simulant can reach a higher maximum sintering temperature, and consequently a higher densification and biaxial strength. The non-dried powder exhibited higher densification and biaxial strength after sintering compared to the dried specimen. This difference was explained with a higher green density of the non-dried powder during pressing, rather than due to an actual influence on the sintering mechanism. Nevertheless, drying the powder prior to sintering is important to avoid the overestimation of the strength of specimens to be fabricated on the Moon.
FenicsXConcrete
(2023)