scholarly journals Assessment of Alkali Activation Potential of a Polish Ferronickel Slag

2019 ◽  
Vol 11 (7) ◽  
pp. 1863 ◽  
Author(s):  
Konstantinos Komnitsas ◽  
Georgios Bartzas ◽  
Vasiliki Karmali ◽  
Evangelos Petrakis ◽  
Witold Kurylak ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Structural Integrity ◽  
Analytical Techniques ◽  
Curing Temperature ◽  
Alkali Activation ◽  
Inorganic Polymers ◽  
X Ray ◽  
Synthesis Conditions ◽  
Activation Potential ◽  
Ferronickel Slag

In this study, the alkali activation potential of a Polish ferronickel slag (PS), for the production of inorganic polymers (IPs), is investigated. The effect of the main synthesis parameters, i.e., strength of the activating solution, consisting of NaOH and Na2SiO3 solutions and affecting (SiO2 + Al2O3)/Na2O and other important molar ratios in the reactive paste, pre-curing period, curing temperature and time and ageing period was investigated. The structural integrity of the produced specimens was tested after their (i) immersion in distilled water and acidic solutions for a period of 7–30 days, and (ii) firing at temperatures between 200 °C and 1000 °C. Several analytical techniques including X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy, Differential scanning analysis-Thermogravimetry and Scanning Electron Microscopy were used for the characterization of the produced IPs. Results show that under the optimum synthesis conditions the IPs obtain compressive strength that exceeds 65 MPa. An innovative aspect of this study is that after heating at 400 °C, the specimens acquire compressive strength of 115 MPa and this indicates that they can be also used as fire resistant materials. This study highlights the potential of alkali activation for the valorization of a ferronickel slag and the production of IPs that can be used as binders or in several construction applications, thus improving the sustainability of the metallurgical sector.

scholarly journals Factors Affecting Alkali Activation of Laterite Acid Leaching Residues

Environments ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 4
Author(s):  
Konstantinos Komnitsas ◽  
Georgios Bartzas ◽  
Vasiliki Karmali ◽  
Evangelos Petrakis
Keyword(s):  
Compressive Strength ◽  
Environmental Sustainability ◽  
Structural Integrity ◽  
Acid Leaching ◽  
Sodium Silicate Solution ◽  
Curing Temperature ◽  
Alkali Activation ◽  
Curing Time ◽  
Synthesis Conditions ◽  
Alkali Activated

In this experimental study, the alkali activation of acid leaching residues using a mixture of sodium hydroxide (NaOH) and alkaline sodium silicate solution (Na2SiO3) as activators is investigated. The residues were also calcined at 800 and 1000 °C for 2 h or mixed with metakaolin (MK) in order to increase their reactivity. The effect of several parameters, namely the H2O/Na2O and SiO2/Na2O ratios present in the activating solution, the pre–curing time (4–24 h), the curing temperature (40–80 °C), the curing time (24 or 48 h), and the ageing period (7–28 days) on the properties of the produced alkali activated materials (AAMs), including compressive strength, porosity, water absorption, and density, was explored. Analytical techniques, namely X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and elemental mapping analysis were used for the identification of the morphology and structure of the final products. The experimental results show that the laterite acid leaching residues cannot be alkali activated in an unaltered state, and the compressive strength of the produced AAMs barely reaches 1.4 MPa, while the mixing of the residues with 10 wt% metakaolin results in noticeably higher compressive strength (41 MPa). Moreover, the calcination of residues at 800 and 1000 °C has practically no beneficial effect on alkali activation. Alkali activated materials produced under the optimum synthesis conditions were subjected to high temperature firing for 2 h and immersed in distilled water or acidic solution (1 mol L−1 HCl) for 7 and 30 days in order to assess their structural integrity under different environmental conditions. This study explores the potential of alkali activation of laterite leaching residues amended with the addition of metakaolin for the production of AAMS that can be used as binders or in several construction applications in order to enable their valorization and also improve the environmental sustainability of the metallurgical sector.

scholarly journals Properties of Inorganic Polymers Produced from Brick Waste and Metallurgical Slag

Minerals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 551 ◽  
Author(s):  
Soultana ◽  
Valouma ◽  
Bartzas ◽  
Komnitsas
Keyword(s):  
Compressive Strength ◽  
Ageing Time ◽  
Metallurgical Slag ◽  
Curing Temperature ◽  
Added Value ◽  
Size Analysis ◽  
Alkali Activation ◽  
Inorganic Polymers ◽  
Synthesis Conditions ◽  
Optimum Synthesis

This paper explores the alkali activation potential of brick wastes and metallurgical slags. Inorganic polymers (IPs) were produced using an alkaline medium consisting of sodium hydroxide and sodium silicate solutions and the optimum synthesis conditions were determined. In this context, the variable parameters, such as solid to liquid (S/L) ratio, curing temperature (60, 80 and 90 °C) and ageing time (7 and 28 days) on the compressive strength and the morphology of the produced IPs were investigated. Specimens produced under the optimum synthesis conditions were subjected to high temperature firing and immersed in distilled water and acidic solutions for various periods of time, in order to assess their durability and structural integrity. The results showed that the IPs produced using a mix ratio of 50 wt % metallurgical slag and 50 wt % brick wastes, cured at 90 °C and aged for 7 days obtained the highest compressive strength (48.9 MPa). X-ray fluorescence analysis (XRF), particle size analysis, Fourier transform infrared spectroscopy (FTIR), mineralogical analysis (XRD), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) and thermogravimetric (TG) analysis also confirmed the optimum microstructural characteristics and the chemical reactions that took place during synthesis. The overall results of this study indicate that the co-valorization of different waste streams, which are produced in large quantities and cause environmental problems if not properly managed, is a viable alternative for the production of binders or secondary construction materials with higher added value.

scholarly journals Grinding Kinetics of Slag and Effect of Final Particle Size on the Compressive Strength of Alkali Activated Materials

Minerals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 714 ◽  
Author(s):  
Evangelos Petrakis ◽  
Vasiliki Karmali ◽  
Georgios Bartzas ◽  
Konstantinos Komnitsas
Keyword(s):  
Particle Size ◽  
Compressive Strength ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Ageing Time ◽  
Reduction Rate ◽  
Curing Temperature ◽  
Alkali Activation ◽  
Final Particle ◽  
Alkali Activated

This study aims to model grinding of a Polish ferronickel slag and evaluate the particle size distributions (PSDs) of the products obtained after different grinding times. Then, selected products were alkali activated in order to investigate the effect of particle size on the compressive strength of the produced alkali activated materials (AAMs). Other parameters affecting alkali activation, i.e., temperature, curing, and ageing time were also examined. Among the different mathematical models used to simulate the particle size distribution, Rosin–Rammler (RR) was found to be the most suitable. When piecewise regression analysis was applied to experimental data it was found that the particle size distribution of the slag products exhibits multifractal character. In addition, grinding of slag exhibits non-first-order behavior and the reduction rate of each size is time dependent. The grinding rate and consequently the grinding efficiency increases when the particle size increases, but drops sharply near zero after prolonged grinding periods. Regarding alkali activation, it is deduced that among the parameters studied, particle size (and the respective specific surface area) of the raw slag product and curing temperature have the most noticeable impact on the compressive strength of the produced AAMs.

Influence of Curing Temperature on Metakaolin-Based Geopolymers

2014 ◽  
Vol 775-776 ◽  
pp. 210-215
Author(s):  
Danúbia Lisbôa da Costa ◽  
Romualdo Rodrigues Menezes ◽  
Gelmires Araújo Neves ◽  
Sandro Marden Torres
Keyword(s):  
Room Temperature ◽  
Industrial Wastes ◽  
Curing Temperature ◽  
Inorganic Polymers ◽  
Flexural Test ◽  
X Ray Diffraction ◽  
Curing Conditions ◽  
X Ray ◽  
Natural Minerals ◽  
Application Potential

Geopolymers, also known as inorganic polymers, are aluminosilicates with cementing characteristics that have great application potential. They are produced by the alkaline activation of aluminosilicates precursors such as industrial wastes, calcined clays, natural minerals, among others and have their properties intimately associated to characteristics of the precursor materials and curing conditions. In this sense, this study aims to evaluate the mechanical behavior of geopolymers obtained from metakaolin according to the curing temperature. The geopolymerization was reached by the mixture of metakaolin with NaOH and the curing of the specimens was held at room temperature, 60°C and 100°C. The specimens were characterized by X-ray diffraction, mercury intrusion porosimetry, and SEM. The mechanical strength was determined by flexural test. The results show that the process of geopolymerization suffers a direct influence of the curing temperature used.

scholarly journals Study on the Pore Structure Characteristics of Ferronickel-Slag-Mixed Ternary-Blended Cement

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4863
Author(s):  
Won Jung Cho ◽  
Min Jae Kim ◽  
Ji Seok Kim
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Pore Structure ◽  
Mercury Intrusion Porosimetry ◽  
Chloride Transport ◽  
Blended Cement ◽  
Cement Matrix ◽  
X Ray ◽  
Mercury Intrusion ◽  
Ferronickel Slag

Pore structure development in Portland cement, fly ash, or/and ferronickel slag (FNS) was investigated using mercury intrusion porosimetry and X-ray CT tomography. The progress of hydration was observed using X-ray diffraction (XRD) analysis and compressive strength while durability of concrete was monitored by chloride penetration resistance and chloride profiles. Mercury intrusion porosimetry (MIP) results suggested that the blended cement had a higher porosity while lower critical pore size. The major reason to this increased porosity was the formation of meso and micro pores compared to ordinary Portland cement (OPC). In terms of chloride transport, replaced cement, especially ternary-blended cement had higher resistance to chloride transport and exhibited slightly lower development of compressive strength. X-ray CT tomography shows that the influence of pore structure of ternary-blended cement on the ionic transport was strongly related to the pore connectivity of cement matrix.

Mechanical Characterization of Hybrid (Organic-Inorganic) Geopolymers

2013 ◽  
Vol 569-570 ◽  
pp. 119-125 ◽  
Author(s):  
Giuseppe Lamanna ◽  
Alessandro Soprano ◽  
Flavia Bollino ◽  
Michelina Catauro
Keyword(s):  
Compressive Strength ◽  
Polyethylene Glycol ◽  
Testing Machine ◽  
Experimental Tests ◽  
Alkali Activation ◽  
Inorganic Polymers ◽  
Direction Parallel ◽  
Water Curing ◽  
Compressive Tests

The mechanical properties of geopolymers can be obtained through different kinds of experimental tests: this paper is focused on the compressive strength (i.e. in a direction parallel to the loading axis) for the case of uniaxial compression. The compressive strength of such materials is traditionally characterized by the 28th-day value, but their strength is expected to increase in time at a continuously decreasing rate. The knowledge of the strength vs. time law is of importance when a structure is subjected to a certain type of loading at a later age. In this work inorganic polymers from activated metakaolin (alumina silicate inorganic polymers, obtained from alkali activation of powders containing SiO2+Al2O3 > 80%wt) are reported. In order to improve their compressive strength a percentage of polyethylene glycol has been added, thus obtaining a hybrid (organic-inorganic) geopolymer. Many factors can influence significantly the compressive strength of such materials e.g. w/c ration, aggregate content, water curing period, polyethylene/glycol ratio. Afterwards experimental compressive tests (performed in a Zwick-Roell® testing machine) have been carried out varying the polyethylene/glycol ratio and the main dimensions of the samples.

The Formation and Properties of Zeolite-A and Zeolite-X through Geopolymerisation of Metakaolin

2018 ◽  
Vol 273 ◽  
pp. 167-174 ◽  
Author(s):  
Subaer ◽  
Hamzah Fansuri
Keyword(s):  
Compressive Strength ◽  
Vickers Microhardness ◽  
Physical And Mechanical Properties ◽  
Molar Ratio ◽  
Alkali Activation ◽  
Zeolite A ◽  
X Ray Diffraction ◽  
Zeolite X ◽  
X Ray ◽  
O 10

This study was aimed at experimentally investigate the formation of zeolite-A and zeolite-X through geopolymerization routes. The samples were prepared by alkali-activation of metakaolinite at 70 °C with Si:Al = 1.04 and 1.25 and Na:A l= 0.6, 0.8, 1.0 while keeping the molar ratio of H2O:Na2O = 10. The physical and mechanical properties of the resulting materials were characterized by means of bulk density and porosity measurement, compressive strength and Vickers microhardness tests. Crystallinity level and the phase of the samples was examined by X-Ray Diffraction (XRD) while morphology and elemental composition of the samples were examined by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). It was found that zeolite-A and zeolite-X were able to produce through geopolymerisation of metakaolin. XRD and SEM-EDX analysis results showed that these materials were composed of zeolite-A or zeolite-X together with amorphous geopolymer. The zeolite X was only formed when ratio of Si:Al is 1.25 while zeolite A was formed at all ratio except ata Si:Al=1.25 and Na:Al=1.0. These materials have relatively low hardness and compressive strength, low density and high apparent porosity.

scholarly journals Use of Ceramic Sanitaryware as an Alternative for the Development of New Sustainable Binders

2015 ◽  
Vol 668 ◽  
pp. 172-180 ◽  
Author(s):  
Lucía Reig ◽  
M.V. Borrachero ◽  
J.M. Monzó ◽  
Holmer Savastano ◽  
Mauro M. Tashima ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Sanitary Ware ◽  
Pozzolanic Activity ◽  
Raw Material ◽  
Alkali Activation ◽  
X Ray ◽  
Amorphous Phases ◽  
Ceramic Sanitary Ware ◽  
Alkali Activated

Large amounts of ceramic sanitary-ware waste are generated in both the production process and construction and demolition practices. This waste contains amorphous phases that may react with the Portlandite that originates during Portland cement hydration or with an alkali solution, leading to a low CO2-binding material. This study investigated the pozzolanic activity of ceramic sanitary-ware waste, together with its potential to form new binders by alkali activation. For this purpose, raw material was characterized by X-ray diffraction, X-ray fluorescence, particle size distribution, thermogravimetry (TGA) and scanning electron microscopy (SEM). Percentages of ceramic waste of 15 wt.% and 25 wt.%, to replace Portland cement, were used to assess the pozzolanic behavior of this material, and samples were cured at 20oC for different curing times. Alkali-activated samples, in which Ca (OH)2 was used as a source of calcium, and NaOH and sodium silicate solutions were utilized as activators, were cured for 7 days at 65oC. The microstructural evolution of the developed binders was assessed in pastes by SEM and TGA analyses, and mortars were used to evaluate the compressive strength behavior. While some strength gain was observed due to pozzolanic activity, compressive strength values within the 14-36 MPa range were obtained in the alkali-activated mortars in accordance with the activator concentration and the percentage of Ca (OH)2 addition.

scholarly journals Marble Waste Valorization through Alkali Activation

Minerals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 46
Author(s):  
Konstantinos Komnitsas ◽  
Athanasia Soultana ◽  
Georgios Bartzas
Keyword(s):  
Structural Integrity ◽  
Raw Materials ◽  
Curing Temperature ◽  
Alkali Activation ◽  
Environmental Footprint ◽  
X Ray Diffraction ◽  
Molar Ratios ◽  
Alkali Activated ◽  
Activating Solution ◽  
Marble Waste

In the present study, the valorization potential of marble waste in the presence of metakaolin via alkali activation was explored. The activating solution used consisted of NaOH and sodium silicate solutions. The effects of marble waste to metakaolin ratio, particle size of raw materials, curing temperature, and Na2O/SiO2 and H2O/Na2O molar ratios present in the activating solution on the main properties and the morphology of the produced alkali-activated materials (AAMs) was evaluated. The durability and structural integrity of the AAMs after firing at temperatures between 200 and 600 °C, immersion in deionized water and 1 mol/L NaCl solution for different time periods and subjection to freeze–thaw cycles were also investigated. Characterization techniques including Fourier transform infrared spectroscopy, X-ray diffraction, mercury intrusion porosimetry and scanning electron microscopy were used in order to study the structure of the produced AAMs. Τhe highest compressive strength (~36 MPa) was achieved by the AAMs prepared with marble waste to metakaolin mass ratio of 0.3 after curing at 40 °C. The results indicated that the utilization of marble waste in the presence of metakaolin enables the production of AAMs with good physical (porosity, density and water absorption) and mechanical properties, thus contributing to the valorization of this waste type and the reduction of the environmental footprint of the marble industry.

A Taguchi Approach for the Synthesis Optimization of Metakaolin Based Geopolymers

2014 ◽  
Vol 92 ◽  
pp. 44-49 ◽  
Author(s):  
Alexandros Tsitouras ◽  
Sotirios Tsivilis ◽  
Glykeria Kakali
Keyword(s):  
Compressive Strength ◽  
Synergetic Effect ◽  
Initial Mixture ◽  
Molar Ratio ◽  
Strength Development ◽  
Inorganic Polymers ◽  
Curing Conditions ◽  
Synthesis Conditions ◽  
Control Factors ◽  
Synthesis Parameters

There are several factors that affect geopolymerization, including the type and ratios of the starting materials as well as the curing conditions of the initial mixture. The effect of the synthesis parameters on the formation of inorganic polymers are usually examined by “changing one factor at a time”. In this study Taguchi experimental designing model was applied in order to study the synergetic effect of selected synthesis parameters on the compressive strength development of metakaolin based geopolymers. The experimental design involved the variation of three control factors in five levels. The selected factors and the corresponding level range were: i) the alkali to aluminum molar ratio in the starting mixture (0.5-1.5), ii) the kind of alkali ion (Na and/or K) and iii) the molar ratio of Si to alkali oxide in the activation solution (0-2.0). The compressive strength of geopolymers was measured and the final products were also examined by means of XRD, FTIR and SEM. As it is concluded, the optimal synthesis conditions for metakaolin geopolymers are R/Al=0.75, Na/(Na+K)=0.50 and [Si]/R2O=1.50, while the factor having the highest impact on the development of compressive strength is the [Si]/R2O ratio.

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