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Geopolymer Concrete Production by Using Nano-Bauxite Binder

Salman Sadeq Dawood, Jubier Najwa J., Al-Zubaidi Aseel B.

Journal of Ecological Engineering

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2023

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Vol. 24, nr 10

305--314

EN

Iraqi bauxite ore was used in the manufacturing of geopolymer mortar and concrete. To de-hydroxylate and turn bauxite into an amorphous phase, it was heated to 650 degrees Celsius. Mixing bauxite nanoparticles with an active alkaline solution produces a geopolymer of high grade due to their high efficiency. The nano-bauxite geopolymer mortar is produced following ASTM C109 with various quantities of alkaline solution with molarity (8, 10, 12, and 14). At 3, 7, and 28 days, the maximum compressive strength of mortar with a molarity of 12 was 20.2, 49.7, and 65.3 MPa, respectively. The same quantity of molarity for the mortar was utilized for the production of geopolymer concrete using an alkaline solution. The weight of nano bauxite was substituted for the percentage of nano-glass and carbon nano-tubes that were included in the geopolymer concrete. This resulted in the utilization of nano-glass and carbon nano-tubes, the best ratios are 8% silica merge with 0.01% of carbon nano-tubes. At the age of 28 days, the water absorbency value was found to be 1.78%, and it was noted that the increased compressive strength reached 81.4 MPa. For the polymerization and performance hardening of samples at low temperatures (20±3 °C), geopolymers with nano-bauxite binders were manufactured without heat treatment. The increased compressive strength as well as resistance to freezing and thawing tests are a result of the superior performance and high requirements of nano-materials. XRD examination was performed, many geopolymer phases were generated, and the bond structures between alumina and silica were observed; these results confirm the development of geopolymer.

2

Study on Corrosion Behavior of Q235 Steel and 16Mn Steel by Electrochemical and Weight Loss Method

Quan Bianli, Xie Zhiping

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 2

531--540

EN

This study investigates the corrosion characteristics of Q235 steel and 16Mn steel in the sulfur-containing alkaline solution. The composition and the morphology of the corrosion products were analyzed by XPS and SEM respectively. The electrochemical behavior of Q235 steel and 16Mn steel was evaluated by potentiodynamic polarization curve and EIS. The results indicated that the corrosion rate of Q235 steel is greater than 16Mn steel in the early corrosion. Pitting and selective corrosion appeared on the surface of the two steels, and the surface product layer was granular and defective. XPS and EDS indicate that the structurally stable iron oxide is formed on the surface of the two steels. Electrochemical results show the corrosion kinetics of Q235 steel and 16Mn steel are simultaneously controlled by the charge transfer and ion diffusion, and the formation mechanism of corrosion products was clarified.

3

Use of waste paper ash or wood ash as substitution to fly ash in production of geopolymer concrete

Owaid Haider M., Al-Rubaye Muna M., Al-Baghdadi Haider M.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2021

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Vol. 30, No. 3

464--476

EN

Large quantities of paper and wood waste are generated every day, the disposal of these waste products is a problem because it requires huge space for their disposal. The possibility of using these wastes can mitigate the environmental problems related to them. This study presents an investigation on the feasibility of inclusion of waste paper ash (WPA) or wood ash (WA) as replacement materials for fly ash (FA) class F in preparation geopolymer concrete (GC). The developed geopolymer concretes for this study were prepared at replacement ratios of FA by WPA or WA of 25, 50, 75 and 100% in addition to a control mix containing 100% of FA. Sodium hydroxide (NaOH) solutions and sodium silicate (Na2SiO3) are used as alkaline activators with 1M and 10M of sodium hydroxide solution.The geopolymer concretes have been evaluated with respect to the workability, the compressive strength, splitting tensile strength and flexural strength. The results indicated that there were no significant differences in the workability of the control GC mix and the developed GC mixes incorporating WPA or WA. Also, the results showed that, by incorporating of 25–50% PWA or 25% WA, the mechanical properties (compressive strength, splitting tensile strength and flexural strength) of GC mixes slightly decreased. While replacement with 75–100% WPA or with 50–100% WA has reduced these mechanical properties of GC mixes. As a result, there is a feasibility of partial replacement of FA by up to 50% WPA or 25% WA in preparation of the geopolymer concrete.

4

Chemical activation effect on the mechanical response of mortars based on dune sand

Ladjel Djelloul, Zairi Moncef, Belagraa Larbi

Mining Science

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2020

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Vol. 27

61--71

EN

The main qualities sought for a mortar are usually; the high compactness, good sealing or impermeability, better mechanical strength and long-term durability. The different methods of accelerating setting and hardening of the mortar as well as the desired characteristics are of great importance with regard to the use of mortars and their different applications in civil engineering. This work is a contribution to improving the properties of mortars at fresh and hardened state by different activation techniques in particular chemical alkaline activators method. The properties of chemically activated mortars using alkaline solutions (KOH and NaOH) at dosages of 0, 2 and 4% was investigated in this experimental program using a based cement matrix with dune sand and blended cement type CEM II/ B grade 42. The results obtained showed the beneficial effect of the chemical activation modes mainly, an improvement of the mechanical response (compressive strength) at young age and in the long term.

5

A new solvent extraction method with gas chromatography–Mass spectrometry for bisphenol a determination in canned foods

Arar S., Alawi M.

Acta Chromatographica

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2019

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Vol. 31, no. 1

71--78

EN

A new reliable simple solvent extraction method for the endocrine disruptor bisphenol A (BPA) in canned food was developed employing an aqueous basic extraction solution of 0.25 M K2CO3/0.10 M NaOH after spiking with BPA-d16 as internal standard. The BPA was next extracted into diethyl ether after solution acidification to pH = 4 and filtration. Homogenous acetylation at dry basic conditions (acetic anhydride as derivatization agent and solvent with sodium acetate as catalyst) after diethyl ether evaporation was carried out for 30 min at 110 °C. Detection of the acetylated BPA was carried out by gas chromatography–electrospray ionization/mass spectrometry (GC–EI/MS) in the selected ion monitoring (SIM) mode with pulsed split-less mode. The method was applicable in terms of eliminating the use of solvents like acetonitrile for the extraction step, where relatively long evaporation times may have been needed to evaporate acetonitrile. Also, removing lipids and precipitating most of the proteins at acidic conditions (pH = 4) prior to diethyl ether extraction can replace the often used heptane or hexane or solid sorbents. The method was tested linear with limit of linearity (LOL = 750 μg/L) and with coefficient of determination (R2= 0.998), repeatable with relative standard deviation (RSDr < 7%) with instrument detection limit (IDL) of 0.01 μg/L and limit of quantitation (LOQ) of 0.034 μg/L. The method detection limit (MDL) ranged from 0.3 μg/kg to 3.2 μg/kg based on 1 g sample (wet weight). Recovery ranged from 85% to 94% with the relative standard deviations of 2%–13%. BPA concentrations in tested canned foods from outlet stores ranged from

6

Alkaline leaching of amphoteric elements from powdered, overstoichiometric hydride material

Gęga J., Dymek M., Drulis H., Hackemer A., Indyka P., Bala H.

Ochrona przed Korozją

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2015

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nr 11

378--380

EN

The alkaline preferential dissolution of amphoteric elements from overstoichiometric, powdered hydrogen absorbing material of LaNi4.5Co0.5(AlZnSn)0.35 composition has been studied using ICP AES method. The observations of structure changes of the as received and leached material particles have been studied by XRD and TEM techniques. It has been shown that during 50 h exposure of the powder in 6 M KOH (38oC) over 50% of amphoteric elements are selectively etched from the tested material. At the same time, as a result of etching, the surface layers of powder particles undergo strong development.

PL

Metodą ICP AES analizowano preferencyjne wytrawianie pierwiastków amfoterycznych z nadstechiometrycznego materiału wodorochłonnego o składzie LaNi4.5Co0.5(AlZnSn)0.35. Zmiany strukturalne wyjściowych i trawionych cząstek materiału obserwowano za pomocą technik XRD i TEM. Pokazano, że 50-godzinna ekspozycja badanego proszku w 6 M KOH (38oC) prowadzi do selektywnego roztworzenia ponad 50% pierwiastków amfoterycznych obecnych w wyjściowym materiale. Jednocześnie, w wyniku wytrawiania proszku, powierzchnia zewnętrznych warstw cząstek ulega silnemu rozwinięciu.

7

Elektrochemiczna charakterystyka eutektycznego stopu La3Ni w środowisku 0,1M KOH

Kukuła I., Bala H., Marciniak B., Pavlyuk V.

Ochrona przed Korozją

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2009

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nr 4-5

202-204

PL

Dokonano charakterystyki elektrochemicznej eutektycznego stopu La3Ni w odpowietrzonym, silnie alkalicznym roztworze wodnym (pH = 13). Wykonano potencjokinetyczne krzywe polaryzacji w szerokim zakresie potencjałów (-2,0 do +2,0 V wzgl. NEK), stosując jego skaning w kierunku anodowym i katodowym. W oparciu o dane termodynamiczne dokonano interpretacji krzywych polaryzacji pod kątem prawdopodobnych produktów cząstkowych procesów elektrodowych. Zwrócono uwagę na powstawanie warstw powierzchniowych (wodorkowych i tlenkowych) na powierzchni stopu w procesie polaryzacji i zaproponowano interpretację krzywych z uwzględnieniem zależnych od potencjału przemian fazowych w obrębie warstw powierzchniowych.

EN

Electrochemical characterization of eutectic La3Ni alloy in deaerated, strong alkaline (pH = 13) aqueous solution has been made. Potentiokinetic polarization curves in wide potential range (-2.0 to +2.0 V vs SCE) have been measured. Electrode potential has been scanned both in anodic- and in cathodic direction. The polarization curves have been interpreted on the basis of thermodynamic data in order to determine the feasible products of partial electrode processes. Attention has been paid to the formation of superfi cial hydride- and oxide layers in the process of alloy polarization. Phase transformations within the superfi cial layers dependent on the potential have been proposed.

8

Separation of CO2 from flue gas in air-sparged hydrocyclone (ASH) reactor

Żurawska M., Hupka J., Aranowski R., Misiuk S.

Ars Separatoria Acta

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2006

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No. 4

43-49

EN

Laboratory results of an initial study on CO2 removal from gas mixture by means of the air-sparged hydrocyclone (ASH) technology are reported. The CO2 absorption rate into sodium hydroxide aqueous solution was studied on a laboratory and pilot scale. The air flow rate was 900 dm³/min and the alkaline solution flow rate was 15 dm³/min in the case of pilot scale. The influence of CO2 concentration, pH of the liquid phase, the gas flow rate, and the alkaline solution flow rate on the efficiency of the process was investigated. An increase in the alkaline concentration significantly enhanced the CO2 absorption. A very low distribution of bubble sizes enhanced the carbon dioxide absorption, too.