Research Regarding the Partial Replacement of Aggregates in Concrete with a By-Product of Steel Industry

A continuous increase in demand for natural resources, in a high proportion for the construction sector, creates the necessity to search for alternatives. This work is intended to do so and the aim is the replacement of natural aggregates in some concrete samples with a metallurgical industry by-product. The replacement was gradual and only for one type of the three dimensions utilized. The results of the many tests conducted revealed the possibility of natural aggregate replacement in some extent, keeping the resulted properties of samples within the limits of the standards

Impacts of Nickel Nanoparticles on Mineral Carbonation

This work presents experimental results regarding the use of pure nickel nanoparticles (NiNP) as a mineral carbonation additive. The aim was to confirm if the catalytic effect of NiNP, which has been reported to increase the dissolution of CO2 and the dissociation of carbonic acid in water, is capable of accelerating mineral carbonation processes. The impacts of NiNP on the CO2 mineralization by four alkaline materials (pure CaO and MgO, and AOD and CC steelmaking slags), on the product mineralogy, on the particle size distribution, and on the morphology of resulting materials were investigated. NiNP-containing solution was found to reach more acidic pH values upon CO2 bubbling, confirming a higher quantity of bicarbonate ions.This effect resulted in acceleration of mineral carbonation in the first fifteen minutes of reaction time when NiNP was present. After this initial stage, however, no benefit of NiNP addition was seen, resulting in very similar carbonation extents after one hour of reaction time. It was also found that increasing solids content decreased the benefit of NiNP, even in the early stages. These results suggest that NiNP has little contribution to mineral carbonation processes when the dissolution of alkaline earth metals is rate limiting

Magnesium Chloride as a Leaching and Aragonite-promoting Self-regenerative Additive for the Mineral Carbonation of Calcium-rich Materials

Two approaches for the intensification of the mineral carbonation reaction are combined and studied in this work, namely: (i) the calcium leaching and aragonite promoting effects of magnesium chloride (MgCl2), and (ii) the passivating layer abrasion effect of sonication. The alkaline materials subjected to leaching and carbonation tests included lime, wollastonite, steel slags, and air pollution control (APC) residue. Batch leaching tests were conducted with varying concentrations of additives to determine extraction efficiency, and with varying solids-to-liquid ratios to determine solubility limitations. Aqueous mineral carbonation tests, with and without the use of ultrasound, were conducted applying varying concentrations of magnesium chloride and varying durations to assess CO2 uptake improvement and characterize the formed carbonate phases. The leaching of calcium from lime with the use of MgCl2 was found to be atomefficient (1 mol Ca extracted for every mole Mg added), but the extraction efficiency from slags and APC residue was limited to 26–35 % due to mineralogical and microstructural constraints. The addition of MgCl2 notably improved argon oxygen decarburization (AOD) slag carbonation extent under sonication, where higher additive dosage resulted in higher CO2 uptake. Without ultrasound, however, carbonation extent was reduced with MgCl2 addition. The benefit of MgCl2 under sonication can be linked to the preferential formation of aragonite (85 wt% of formed carbonates), which precipitates on the slag particles in the form of acicular crystals with low packing density, thus becoming more susceptible to the surface erosion effect of sonication, as evidenced by the significantly reduced carbonated slag particle size

Comparative Study Regarding the Design of a 3D Printed Hip Prosthesis

This work proposes the comparison of two models of 3D printed hip prostheses, using microscopic and chemical analysis, but also compression and bending testing. The comparison was made using a hip prosthesis designed in the Autodesk Inventor 2020 program and a model freely available on the Internet. The work includes some details about the virtual prototyping of prostheses and results from the chemical analysis of the components of the hip prostheses, carried out using an X-ray spectrometer to identify the elements contained in the PETG (polyethylene terephthalate glycol) material that was used to obtain the samples. The second method of analysis was the microscopic one and finally the samples were subjected to external forces, through bending and compression testing. This comparison aimed to demonstrate the dependence between the shape of the prosthesis and the mechanical properties of the analysed samples

Utilization of Carbonated BOF Slag as Partial Replacement of Aggregate in Cement Mortars

After direct mineral carbonation, a material rich in carbonates and with reduced quantities of free oxides is obtained. The aim of this work was to show that such materials can be used in the construction domain. Basic Oxygen Furnace (BOF) slag from the steelmaking process has been traditionally seen as unfit for bounded applications due to its propensity to swelling, resulting from hydration of its high free lime content. Here, BOF slag was crushed to suitable particle sizes, carbonated in an aqueous solution of carbonic acid, and utilized to replace 50% of natural sand aggregate in cement mortars. The mechanical and chemical properties of these mortars were compared to mortars containing non-carbonated slags, and a standard cement mortar as a reference. Tests were conducted to determine mortar flow and soundness, and cured mortar compressive strength and leaching tendencies. The results showed a satisfactory performance for all considered aspects (comparable with the reference) of the mortar sample containing 37.5 wt% (1.5 in 4 parts solids) carbonated BOF slag o

A Study on Indoor Particulate Matter Variation in Time Based on Count and Sizes and in Relation to Meteorological Conditions

An important aspect of air pollution analysis consists of the varied presence of particulate matter in analyzed air samples. In this respect, the present work aims to present a case study regarding the evolution in time of quantified particulate matter of different sizes. This study is based on data acquisitioned in an indoor location, already used in a former particulate matter-related article; thus, it can be considered as a continuation of that study, with the general aim to demonstrate the necessity to expand the existing network for pollution monitoring. Besides particle matter quantification, a correlation of the obtained results is also presented against meteorological data acquisitioned by the National Air Quality Monitoring Network. The transformation of quantified PM data in mass per volume and a comparison with other results are also addressed

Morphological and Chemical Characterization of Particulate Matter from an Indoor Measuring Campaign

The scientifically backed conclusion that pollution with particulate matter presents an important negative effect on human health is the driver of the present study. Not only are the results presented herein a completion, and to some small extent a confirmation, of a previous study, but these findings are also a confirmation of the need to further investigate the best way for monitoring particulate matter pollution in agglomerated areas throughout the world. This need is emphasized by the moderately positive results obtained in this measuring campaign that was carried out in an indoor location of an industrial city and near a heavily circulated road. The results presented in this study were obtained by utilizing advanced methods such as optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDX), and X-ray diffraction (XRD)

Recent developments and perspectives on the treatment of industrial wastes by mineral carbonation - A review

Besides producing a substantial portion of anthropogenic CO2 emissions, the industrial sector also generates significant quantities of solid residues. Mineral carbonation of alkaline wastes enables the combination of these two by-products, increasing the sustainability of industrial activities. On top of sequestering CO2 in geochemically stable form, mineral carbonation of waste materials also brings benefits such as stabilization of leaching, basicity and structural integrity, enabling further valorization of the residues, either via reduced waste treatment or landfilling costs, or via the production of marketable products. This paper reviews the current state-of-the-art of this technology and the latest developments in this field. Focus is given to the beneficial effects of mineral carbonation when applied to metallurgical slags, incineration ashes, mining tailings, asbestos containing materials, red mud, and oil shale processing residues. Efforts to intensify the carbonation reaction rate and improve the mineral conversion via process intensification routes, such as the application of ultrasound, hot-stage processing and integrated reactor technologies, are described. Valorization opportunities closest to making the transition from laboratory research to commercial reality, particularly in the form of shaped construction materials and precipitated calcium carbonate, are highlighted. Lastly, the context of mineral carbonation among the range of CCS options is discussed.status: publishe

Properties of Dental Zirconium Oxide and Metal-Ceramic: A Comparative Study

Zirconium oxide which is intended to be a material that is quite attractive due to its key characteristics, i.e. aesthetic appearance and mechanical resistance, compared to dental metal-ceramics, which to date it has proven to be a satisfactory solution for many of the requirements in the dental market. Understanding the characteristics and properties of these materials provides a starting point for new trends in the development or improvement of solutions for various medical conditions. The research topic of this work aims to understand the characteristics and properties of two categories of materials that are so competitive in the field of dental restoration. For this purpose, the behaviour of some dental  crowns made of zirconium oxide and metal ceramic was evaluated in order to obtain experimental data regarding microhardness, corrosion and roughness, before and at different time intervals of immersion in a solution of corrosion, respectively saline solution (3.5% NaCl)

Utilization of Nickel Nanoparticles as Catalytic Additive in Acceleration of the Mineral Carbonation Process

Carbon dioxide mitigation through mineral carbonation is still economically inefficient, despite the mounting knowledge pool on the subject. This inefficiency is due to high energy demand, slow reaction kinetics and low conversion degrees (and implicitly limited CO2 sequestration). Additive usage remains an interesting choice to accelerate CO2 absorption, especially if mild process conditions can be maintained. Most research conducted to date has sought additives to increase mineral dissolution and carbonate precipitation. This work presents a different approach regarding the use of pure nickel nanoparticles (NiNP) as a mineral carbonation additive. The mechanism of NiNP, of catalytic nature, is based on increasing the quantities of dissolved CO2 and dissociated carbonic acid in the process water, thus increasing the concentration of bicarbonate ions available to react with solubilised alkaline earth metals. This effect has the potential to reduce the time needed to reach a certain level of conversion through mineral carbonation. This study presents results and discussions regarding the effect of NiNP on the CO2 mineralization by four alkaline materials (pure CaO and MgO, and AOD and CC steelmaking slags), on the product mineralogy, on the particle size distribution, and on the morphology of resulting materials.status: publishe