scholarly journals Hybrid Cements. Mechanical Properties, Microstructure and Radiological Behavior

Molecules ◽  
2022 ◽  
Vol 27 (2) ◽  
pp. 498
Author(s):  
Ana María Moreno de los Moreno de los Reyes ◽  
José Antonio Suárez-Navarro ◽  
María del Mar Alonso ◽  
Catalina Gascó ◽  
Isabel Sobrados ◽  
...  
Keyword(s):  
Spectrometric Method ◽  
Similar Reaction ◽  
Reaction Products ◽  
Curing Conditions ◽  
Naturally Occurring ◽  
Powder Samples ◽  
Alkaline Activator ◽  
Industry Sustainability ◽  
By Products ◽  
Alkali Activated

The use of more eco-efficient cements in concretes is one of the keys to ensuring construction industry sustainability. Such eco-efficient binders often contain large but variable proportions of industrial waste or by-products in their composition, many of which may be naturally occurring radioactive materials (NORMs). This study explored the application of a new gamma spectrometric method for measuring radionuclide activity in hybrid alkali-activated cements from solid 5 cm cubic specimens rather than powder samples. The research involved assessing the effect of significant variables such as the nature of the alkaline activator, reaction time and curing conditions to relate the microstructures identified to the radiological behavior observed. The findings showed that varying the inputs generated pastes with similar reaction products (C-S-H, C-A-S-H and (N,C)-A-S-H) but different microstructures. The new gamma spectrometric method for measuring radioactivity in solid 5 cm cubic specimens in alkaline pastes was found to be valid. The variables involved in hybrid cement activation were shown to have no impact on specimen radioactive content. The powder samples, however, emanated 222Rn (a descendent of 226Ra), possibly due to the deformation taking place in fly ash structure during alkaline activation. Further research would be required to explain that finding.

scholarly journals Microstructure Features of Ternary Alkali-activated Binder Based on Tungsten Mining Waste, Slag and Metakaolin

2020 ◽  
Author(s):  
Naim Sedira ◽  
João Castro-Gomes
Keyword(s):  
Sodium Silicate ◽  
Room Temperature ◽  
Mining Waste ◽  
Dense Matrix ◽  
Microstructural Properties ◽  
Reaction Products ◽  
Granulated Blast Furnace Slag ◽  
Alkaline Activator ◽  
Furnace Slag ◽  
Alkali Activated

This study determines the effect of ground granulated blast furnace slag (GGBFS) and metakaolin (MK) on the microstructural properties of the tungsten mining waste-based alkali-activated binder (TMWM). During this investigation, TMWM was partially replaced with 10 wt.% GGBFS and 10 wt.% MK to improve the microstructure of the binder. In order to understand the effect of the substitutions on the microstructure, two pastes were produced to make a comparative study between the sample contain 100% TMWM and the ternary precursors. Both precursors were activated using a combination of alkaline activator solutions (sodium silicate and sodium hydroxide) with the ratio of 1:3 (66.6 wt.% sodium silicate combined with 33.33 wt.% of NaOH 8M). The alkali-activated mixes were cured in oven at temperature of 60 °C in the first day and at room temperature for the next 27 days. The reaction products N-A-S-H gel and (N,M)-A-S-H gel resulted from the alkaline activation reaction process. In addition, a formation of natrite (Na2CO3) with needles shape occurred as a reaction product of the fluorescence phenomena. However, a dense matrix resulted from the alkline activation of the ternary precursors containg different gels such as N-A-S-H, C-A-S-H and (N,M)-C-A-S-H gel, these results were obtained through SEM-EDS analyses, as well FTIR tests. Keywords: Mining Waste, Alkali-activated, Microstructure, Slag, Metakaolin

scholarly journals Role of Curing Conditions and Precursor on the Microstructure and Phase Chemistry of Alkali-Activated Fly Ash and Slag Pastes

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1918
Author(s):  
Marija Nedeljković ◽  
Bahman Ghiassi ◽  
Guang Ye
Keyword(s):  
Fly Ash ◽  
Analytical Techniques ◽  
Limited Information ◽  
Reaction Products ◽  
Curing Conditions ◽  
X Ray ◽  
Phase Recognition ◽  
Phase Chemistry ◽  
Alkali Activated

Understanding the role of curing conditions on the microstructure and phase chemistry of alkali-activated materials (AAMs) is essential for the evaluation of the long-term performance as well as the optimization of the processing methods for achieving more durable AAMs-based concretes. However, this information cannot be obtained with the common material characterization techniques as they often deliver limited information on the chemical domains and proportions of reaction products. This paper presents the use of PhAse Recognition and Characterization (PARC) software to overcome this obstacle for the first time. A single precursor (ground granulated blast-furnace slag (GBFS)) and a binary precursor (50% GBFS–50% fly ash) alkali-activated paste are investigated. The pastes are prepared and then cured in sealed and unsealed conditions for up to one year. The development of the microstructure and phase chemistry are investigated with PARC, and the obtained results are compared with independent bulk analytical techniques X-ray Powder Fluorescence and X-ray Powder Diffraction. PARC allowed the determination of the type of reaction products and GBFS and FA’s spatial distribution and degree of reaction at different curing ages and conditions. The results showed that the pastes react at different rates with the dominant reaction products of Mg-rich gel around GBFS particles, i.e., Ca-Mg-Na-Al-Si, and with Ca-Na-Al-Si gel, in the bulk paste. The microstructure evolution was significantly affected in the unsealed curing conditions due to the Na+ loss. The effect of the curing conditions was more pronounced in the binary system.

The iron(III)-catalyzed oxidation of EDTA in aqueous solution

1980 ◽  
Vol 58 (19) ◽  
pp. 1999-2005 ◽  
Author(s):  
Ramunas J. Motekaitis ◽  
Arthur E. Martell ◽  
David Hayes ◽  
Wayne W. Frenier
Keyword(s):  
Aqueous Solution ◽  
Elevated Temperatures ◽  
Iminodiacetic Acid ◽  
Nitrilotriacetic Acid ◽  
Similar Reaction ◽  
Reactive Intermediate ◽  
Reaction Products ◽  
Reaction Proceeds ◽  
Catalyzed Oxidation ◽  
By Products

At temperatures above 100 °C iron(III) oxidizes coordinated EDTA to ethylenediaminetriacetic acid in aqueous solution in the absence of molecular oxygen. The reaction proceeds with an activation energy of 28.6 kcal/mol, and its rate is directly proportional to the concentration of Fe(III) and inversely proportional to pH. At 125 °C, the halflife of Fe(III) in the presence of excess EDTA is about 3 h at pH 9.3, but increases to >70 h at pH 5.4. The reaction is stoichiometric and no other reaction products or by-products were detected by nmr, gc, and gc – mass spectroscopy. In the presence of oxygen iron catalyzes quantitative oxidation of ethylenediamine-N,N,N′,N′-tetraacetic acid (EDTA) to ethylenediaminetriacetic acid. The copper(II)–EDTA chelate undergoes a similar reaction but higher temperatures [Formula: see text] are required. Iron(III) also oxidizes nitrilotriacetic acid (NTA) to iminodiacetic acid (IDA) and glycine. The hydrolyzed species Fe(OH)EDTA is shown to be the reactive intermediate, and the well-known (Fe–EDTA)2O4− μ-oxo dimer is shown not to exist at elevated temperatures (above 100 °C). Probable mechanisms are proposed for these reactions and comparisons are made with earlier work.

scholarly journals Statistical Evaluation of Mechanical Properties of Slag Based Alkali-Activated Material

2019 ◽  
Vol 11 (21) ◽  
pp. 5935 ◽  
Author(s):  
Martin Sisol ◽  
Dušan Kudelas ◽  
Michal Marcin ◽  
Tomáš Holub ◽  
Peter Varga
Keyword(s):  
Industrial Wastes ◽  
Sustainable Construction ◽  
Industrial Processing ◽  
Granulated Blast Furnace Slag ◽  
Strength Tests ◽  
Alkaline Activator ◽  
Solution Parameters ◽  
Furnace Slag ◽  
By Products ◽  
Alkali Activated

Slag is one of the by-products of the energy industry, which is suitable for secondary industrial processing. Although slag has been successfully used in industrial production for several decades, its use does not achieve the level of its potential. Today, to achieve a sustainable construction industry, alternative types of cement have been extensively investigated. Geopolymer is a kind of material which is obtained from the alkaline activator and it can be produced from the industrial wastes or by-products. In this study, SiO2/Na2O ratio and the amount of Na2O in activation solution parameters of alkali-activated materials were tested how they affect the strengths of hardened geopolymers from ground granulated blast furnace slag (GGBFS). Compressive and flexural strength tests were conducted, and the results were analyzed by analysis of variance (ANOVA). Strengths were tested after 7, 28, and 90 days.

scholarly journals Alkali-Activated Binders Using Bottom Ash from Waste-to-Energy Plants and Aluminium Recycling Waste

2021 ◽  
Vol 11 (9) ◽  
pp. 3840 ◽  
Author(s):  
Alex Maldonado-Alameda ◽  
Jofre Mañosa ◽  
Jessica Giro-Paloma ◽  
Joan Formosa ◽  
Josep Maria Chimenos
Keyword(s):  
Bottom Ash ◽  
Physicochemical Characterization ◽  
Waste To Energy ◽  
Promising Alternative ◽  
Leaching Potential ◽  
Aluminium Recycling ◽  
Alkaline Activator ◽  
Alkali Activated Binders ◽  
Energy Plants ◽  
Alkali Activated

Alkali-activated binders (AABs) stand out as a promising alternative to replace ordinary Portland cement (OPC) due to the possibility of using by-products and wastes in their manufacturing. This paper assessed the potential of weathered bottom ash (WBA) from waste-to-energy plants and PAVAL® (PV), a secondary aluminium recycling process by-product, as precursors of AABs. WBA and PV were mixed at weight ratios of 98/2, 95/5, and 90/10. A mixture of waterglass (WG) and NaOH at different concentrations (4 and 6 M) was used as the alkaline activator solution. The effects of increasing NaOH concentration and PV content were evaluated. Alkali-activated WBA/PV (AA-WBA/PV) binders were obtained. Selective chemical extractions and physicochemical characterization revealed the formation of C-S-H, C-A-S-H, and (N,C)-A-S-H gels. Increasing the NaOH concentration and PV content increased porosity and reduced compressive strength (25.63 to 12.07 MPa). The leaching potential of As and Sb from AA-WBA/PV exceeded the threshold for acceptance in landfills for non-hazardous waste.

scholarly journals Anthocyanins Recovered from Agri-Food By-Products Using Innovative Processes: Trends, Challenges, and Perspectives for Their Application in Food Systems

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2632
Author(s):  
Henrique Silvano Arruda ◽  
Eric Keven Silva ◽  
Nayara Macêdo Peixoto Araujo ◽  
Gustavo Araujo Pereira ◽  
Glaucia Maria Pastore ◽  
...  
Keyword(s):  
Food Systems ◽  
Food Industry ◽  
Biological Properties ◽  
Extraction Techniques ◽  
Naturally Occurring ◽  
Current Review ◽  
Natural Colorants ◽  
Conventional Extraction ◽  
The Stability ◽  
By Products

Anthocyanins are naturally occurring phytochemicals that have attracted growing interest from consumers and the food industry due to their multiple biological properties and technological applications. Nevertheless, conventional extraction techniques based on thermal technologies can compromise both the recovery and stability of anthocyanins, reducing their global yield and/or limiting their application in food systems. The current review provides an overview of the main innovative processes (e.g., pulsed electric field, microwave, and ultrasound) used to recover anthocyanins from agri-food waste/by-products and the mechanisms involved in anthocyanin extraction and their impacts on the stability of these compounds. Moreover, trends and perspectives of anthocyanins’ applications in food systems, such as antioxidants, natural colorants, preservatives, and active and smart packaging components, are addressed. Challenges behind anthocyanin implementation in food systems are displayed and potential solutions to overcome these drawbacks are proposed.

scholarly journals Synthesis of Ambient Cured GGBFS Based Alkali Activated Binder Using a Sole Alkaline Activator: A Feasibility Study

2021 ◽  
Vol 11 (13) ◽  
pp. 5887
Author(s):  
Thandiwe Sithole ◽  
Nelson Tsotetsi ◽  
Tebogo Mashifana
Keyword(s):  
Silicate Solution ◽  
Environmental Footprint ◽  
Ambient Temperatures ◽  
Granulated Blast Furnace Slag ◽  
Naoh Solution ◽  
Alkaline Activator ◽  
Porous Morphology ◽  
Furnace Slag ◽  
Alkali Activated

Utilisation of industrial waste-based material to develop a novel binding material as an alternative to Ordinary Portland Cement (OPC) has attracted growing attention recently to reduce or eliminate the environmental footprint associated with OPC. This paper presents an experimental study on the synthesis and evaluation of alkali activated Ground granulated blast furnace slag (GGBFS) composite using a NaOH solution as an alkaline activator without addition of silicate solution. Different NaOH concentrations were used to produce varied GGBFS based alkali activated composites that were evaluated for Uncofined Compressive Strength (UCS), durability, leachability, and microstructural performance. Alkali activated GGBFS composite prepared with 15 M NaOH solution at 15% L/S ratio achieved a UCS of 61.43 MPa cured for 90 days at ambient temperatures. The microstructural results revealed the formation of zeolites, with dense and non-porous morphology. Alkali activated GGBFS based composites can be synthesized using a sole alkaline activator with potential to reduce CO2 emission. The metal leaching tests revealed that there are no potential environmental pollution threats posed by the synthesized alkali activated GGBFS composites for long-term use.

scholarly journals Process Design for a Production of Sustainable Materials from Post-Production Clay

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 953
Author(s):  
Michał Łach ◽  
Reda A. Gado ◽  
Joanna Marczyk ◽  
Celina Ziejewska ◽  
Neslihan Doğan-Sağlamtimur ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Waste Production ◽  
Sustainable Materials ◽  
Post Production ◽  
Rich Material ◽  
Jurassic Limestone ◽  
By Products ◽  
Alkali Activated

Alkali activated cement (AAC) can be manufactured from industrial by-products to achieve goals of “zero-waste” production. We discuss in detail the AAC production process from (waste) post-production clay, which serves as the calcium-rich material. The effect of different parameters on the changes in properties of the final product, including morphology, phase formation, compressive strength, resistance to the high temperature, and long-term curing is presented. The drying and grinding of clay are required, even if both processes are energy-intensive; the reduction of particle size and the increase of specific surface area is crucial. Furthermore, calcination at 750 °C ensure approximately 20% higher compressive strength of final AAC in comparison to calcination performed at 700 °C. It resulted from the different ratio of phases: Calcite, mullite, quartz, gehlenite, and wollastonite in the final AAC. The type of activators (NaOH, NaOH:KOH mixtures, KOH) affected AAC mechanical properties, significantly. Sodium activators enabled obtaining higher values of strength. However, if KOH is required, the supplementation of initial materials with fly ash or metakaolin could improve the mechanical properties and durability of AAC, even c.a. 28%. The presented results confirm the possibility of recycling post-production clay from the Raciszyn II Jurassic limestone deposit.

scholarly journals Leaching, carbonation and chloride ingress in reinforced alkali-activated fly ash mortars

2018 ◽  
Vol 199 ◽  
pp. 02025 ◽  
Author(s):  
Gregor J. G. Gluth ◽  
Petr Hlaváček ◽  
Steffi Reinemann ◽  
Gino Ebell ◽  
Jürgen Mietz
Keyword(s):  
Fly Ash ◽  
Visual Inspection ◽  
Electrochemical Behaviour ◽  
Transport Coefficients ◽  
Chloride Penetration ◽  
Chloride Ingress ◽  
Reaction Products ◽  
Steel Bars ◽  
Alkali Activated Binders ◽  
Alkali Activated

Alkali-activated fly ash mortars were studied with regard to durability-relevant transport coefficients and the electrochemical behaviour of embedded carbon steel bars on exposure of the mortars to leaching, carbonation and chloride penetration environments. The transport coefficients differed considerably between different formulations, being lowest for a mortar with BFS addition, but still acceptable for one of the purely fly ash-based mortars. Leaching over a period of ~300 days in de-ionized water did not lead to observable corrosion of the embedded steel, as shown by the electrochemical data and visual inspection of the steel. Exposure to 100 % CO2 atmosphere caused steel depassivation within approx. two weeks; in addition, indications of a deterioration of the mortar were observed. The results are discussed in the context of the different reaction products expected in highand low-Ca alkali-activated binders, and the alterations caused by leaching and carbonation.

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