Wyniki wyszukiwania - BazTech

1

Possible use of selected types of fly ash in the technology of caving goaf sealing

Pierzyna Piotr

Zeszyty Naukowe Politechniki Morskiej w Szczecinie

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2024

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nr 77 (149)

63--68

EN

This article presents selected properties of mixtures produced from two types of fly ashes from one coal-fired power plant. Mixtures made of fly ashes from a conventional boiler without flue gas desulfurization products (10 01 02) and from a fluidized bed boiler with flue gas desulfurization products (10 01 82) are subjected to testing. The mixtures are prepared using mine water. The tested mixtures are characterized by a liquid consistency in terms of flowability in a range from 160 mm to 280 mm. The mixtures made of 10 01 82 ashes show twice as much water demand, shorter setting time, and higher strength than those made of 10 01 02 ashes, but, unfortunately, they have a much higher volume of excess water. Moreover, the mixtures of 10 01 82 ash do not undergo full slaking, in contrast to the mixtures of 10 01 02 ash (conventional boiler). The requirements of the PN-G 11011:1998 standard, relative to the discussed parameters, are met by the mixtures made on the basis of ash 10 01 82 originating from a fluidized bed boiler in terms of flowability of up to 240 mm. This is the ash type useable in sealing technology.

2

Wpływ rodzaju popiołu na wybrane właściwości wytworzonych na ich bazie mieszanin wodnych

Pierzyna Piotr

Rynek Energii

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2024

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Nr 1

69--74

PL

W artykule przedstawiono możliwość zastosowania w górnictwie podziemnym dwóch rodzajów popiołów lotnych pochodzących z energetyki zawodowej spalającej węgiel kamienny. Badaniom podano mieszaniny wytworzone z popiołów lotnych pochodzących z kotła konwencjonalnego bez produktów odsiarczania spalin (10 01 02) oraz kotła fluidalnego z produktami odsiarczania spalin (10 01 82). Mieszaniny sporządzono wykorzystując wodę kopalnianą o gęstości 1023 g/dm3. Badane mieszaniny miały konsystencję płynną o rozlewności w zakresie 160-280 mm. Mając na uwadze uzyskane wyniki badań oraz wytyczne normy PN-G 11011:1998 należy stwierdzić, że w zakresie omawianych parametrów mieszaniny wytworzone na bazie popiołu pochodzącego z kotła fluidalnego (10 01 82) spełniają jej wymagania w zakresie rozlewności 160-240 mm, jedynie w technologii doszczelniania. W technologii podsadzki zestalanej żadna z zbadanych mieszanin nie spełnia ww. normy. Ponadto stosując w górnictwie podziemnym mieszaniny z popiołu lotnego bez produktów odsiarczania spalin pochodzącego z kotła konwencjonalnego należy dokładnie rozważyć jego możliwość, technologię w której ma być stosowany, a przede wszystkim miejsce jego aplikacji.

EN

The paper presents the possibility of using two types of fly ash from utility power plants burning hard coal in underground mining. Mixtures made from ﬂy ash from a conventional boiler without ﬂue gas desulphurisation products (10 01 02) and a fluidised bed boiler with ﬂue gas desulphurisation products (10 01 82) were tested. The mixtures were prepared using mine water With a density of 1023 g/dm3. The tested mixtures were of liquid consistency with a ﬂowability of 160-280 mm Taking into account the obtained test results and guidelines of the PN-G 11011:1998 standard, it should be stated that, in terms of the discussed parameters, mixtures produced on the basis of ash from the ﬂuidised bed boiler (10 01 82) meet its requirements in the range of ﬂowability of 160-240 mm, only in the case of the backﬁlling technology. In solidifying backﬁll . technology, none of the mixtures tested comply with the aforementioned standard. In addition, when using ﬂy ash mixtures without ﬂue gas desulphurisation products from a conventional cat (10 01 02) in underground mining, careful consideration must be given to its feasibility, the technology in which it is to be used and, above all, where it is to be applied.

3

Management of fly ash from biomass combustion

Maj Izabella

Rynek Energii

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2024

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Nr 1

75--81

EN

The efficient management of biomass fly ash is a key factor for the circular economy. Fly ash is produced in large quantities during biomass combustion and may be utilized for various applications, for both environmental and financial benefits. The main limitation of biomass fly ash utilization is its unrecognized potential caused by a lack of consistent law regulations. In this paper, possible paths of biomass fly ash management are discussed. The compositions of 4 fly ashes derived from biomass combustion in Polish units are presented, together with 2 examples of phosphorous-rich ashes. The five most promising ways of management are elaborated: concrete and cement production, phosphorous recovery and fertilizers, composites, ceramics, and sorbents. The latest state-of-the-art research regarding each path is briefly reviewed and current law regulations are introduced. Limitations for the safe management of biomass ash are also discussed.

PL

Zagospodarowanie popiołów lotnych z biomasy jest ważnym elementem gospodarki o obiegu zamkniętym (GOZ). Popiół lotny powstaje W znacznych ilościach podczas spalania biomasy, a jego odpowiednie zagospodarowanie może przynieść zarówno korzyści dla środowiska, jak i oszczędności finansowe. Głównym ograniczeniem wykorzystania popiołów lotnych z biomasy jest brak odpowiednich uregulowań prawnych, co powoduje również słabe rozpoznanie możliwości użycia popiołów. W artykule przedstawiono składy 4 popiołów lotnych pochodzących ze spalania biomasy W polskich obiektach energetyki zawodowej oraz 2 przykłady popiołów szczególnie bogatych w fosfor. Omówiono pięć najbardziej obiecujących sposobów wykorzystania: produkcja betonów i cementu, odzysk fosforu i zastosowanie jako nawozy, składnik kompozytów, materiały ceramiczne oraz sorbenty. Przedstawiono aktualne regulacje prawne oraz dokonano krótkiego przeglądu najnowszych badań dotyczących poszczególnych ścieżek. Omówiono także ograniczenia w zakresie bezpiecznego zagospodarowania popiołów z biomasy.

4

Aktywowany alkalicznie popiół lotny jako zamiennik cementu w mieszankach betonowych

Zieliński Krzysztof, Herbowska Martyna, Krawczyk Jacek

Materiały Budowlane

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2024

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nr 5

5--8

PL

W artykule zaprezentowano wyniki badań betonu wykonanego przy użyciu spoiwa mineralnego geopolimerowego. Betony wykonane zostały na bazie aktywowanego alkalicznie popiołu lotnego krzemionkowego bez dodatku cementu. Wykonano trzy rodzaje betonu geopolimerowego. Rolę aktywatora w sporządzonych mieszankach pełniła mieszanina zasady sodowej oraz szkła wodnego. Przygotowano trzy roztwory zasady sodowej o narastającym stężeniu molowym: 6M, 9M oraz 12M. Przygotowany roztwór mieszano ze szkłem wodnym w proporcji wagowej 1:1. Dla każdego stężenia wykonano pomiary w temperaturze dojrzewania 20°C i po utwardzaniu przez 24 h w 60°C. Wykonano badania wytrzymałości na ściskanie oraz na zginanie po 28 dniach dojrzewania oraz badanie nasiąkliwości i mrozoodporności. Analiza uzyskanych wyników badań wykazała, źe beton geopolimerowy może znaleźć zastosowanie w budownictwie, jako alternatywne rozwiązanie dla standardowych cementów powszechnego użytku, generując znacznie mniejszy ślad węglowy niż standardowe cementy.

EN

The article presents the results of tests on concrete made using a geopolymer mineral binder. The concretes were made on the basis of alkaline-activated silica fly ash without the addition of cement. Three types of geopolymer concrete were made. The role of the activator in the prepared mixtures was played by a mixture of sodium base and water glass. Three solutions of sodium alkali with increasing molar concentration were prepared: 6M, 9M and 12M. The prepared solution was mixed in a 1:1 weight ratio with water glass. For each concentration, measurements were made at a ripening temperature of 20°C and after hardening for 24 hours at 60°C. Compressive and bending strength tests were performed after 28 days of maturing, as well as water absorption and frost resistance tests. The analysis of the obtained test results showed that geopolymer concrete can be used in construction as an alternative solution to standard common cements, generating a much smaller carbon footprint than standard cements.

5

Trace elements in solid residues from the thermal treatment of municipal solid waste, sewage sludge and hazardous waste

Kępys Waldemar

Gospodarka Surowcami Mineralnymi

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2024

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T. 40, z. 2

29--46

EN

In many countries around the world, the thermal treatment of waste plays an important role in the waste-management system. As a result, electricity and heat are produced. However, solid residues are produced in the form of bottom ash, fly ash (FA) and air pollution control (APC) residues. Alternative raw material resources are currently being sought, one of which may be anthropogenic materials from waste thermal treatment processes. This paper presents the results of a study on the trace element content of FA and APC residues from three different installations: municipal solid waste incineration (grate boiler), sewage sludge (fluidized bed boiler) and hazardous waste (rotary kiln). Research methods such as ICP-MS (inductively coupled plasma mass spectrometry), ICP-AES (inductively coupled plasma/atomic emission spectroscopy) and XRD (X-ray diffraction) were used. The results obtained indicate that the chemical composition of FA and APC residues depends mainly on the type of waste being converted, the thermal process and the flue gas treatment method. Ash from sewage sludge incineration in particular contains significant amounts of P and Sb - elements classified as critical raw materials (CRM). In addition, they also contain other valuable metals such as Ag and Zn, in amounts far exceeding the average crustal abundance. In addition, residues from the incineration of hazardous waste may pose a potential risk to the environment due to the presence of significant amounts of heavy metals such as Pb, Cd and Hg.

PL

W wielu krajach na świecie termiczne przekształcanie odpadów odgrywa istotną rolę w systemie gospodarki odpadami. W efekcie produkowana jest energia elektryczna oraz cieplna. Z drugiej strony powstają także stałe pozostałości w postaci popiołów dennych, popiołów lotnych oraz produktów oczyszczania spalin z gazowych zanieczyszczeń. Obecnie poszukiwane są alternatywne źródła surowców, jednym z nich mogą być pozostałości z procesów termicznego przekształcania odpadów. W artykule przedstawiono wyniki badań zawartości pierwiastków śladowych w popiołach lotnych (FA) i produktach oczyszczania spalin z gazowych zanieczyszczeń (APC), pochodzących z trzech różnych instalacji: spalających odpady komunalne (kocioł rusztowy), osady ściekowe (kocioł fluidalny) i odpady niebezpieczne (piec obrotowy). Zastosowano metody badawcze takie jak ICP-MS (spektrometria mas ze wzbudzeniem w plazmie indukcyjnie sprzężonej), ICP-AES (spektrometria plazmy sprzężonej indukcyjnie, atomowa spektroskopia emisyjna) i XRD (dyfrakcja rentgenowska). Uzyskane wyniki wskazują, że skład chemiczny FA i APC jest zależy przede wszystkim od rodzaju przekształcanych odpadów, procesu termicznego oraz sposobu oczyszczania spalin. Popioły, w szczególności ze spalania osadów ściekowych, zawierają znaczne ilości P oraz Sb - pierwiastków zaliczanych do surowców krytycznych (CRM). Ponadto zawierają także inne cenne metale jak Ag czy Zn, w ilości znacznie przewyższającej średnią zasobność skorupy ziemskiej. Z drugiej strony pozostałości ze spalania odpadów niebezpiecznych mogą stanowić potencjalne zagrożenie dla środowiska z powodu obecności w nich znacznych ilości metali ciężkich jak Pb, Cd i Hg.

6

Właściwości samozagęszczalnego betonu z popiołem lotnym poddanego wewnętrznej pielęgnacji

Shanmugapriyan J., Chinnaraju K.

Cement Wapno Beton

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2024

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R. 29, nr 1

2--15

PL

Właściwa pielęgnacja i optymalizacja procesu dojrzewania betonu mają znaczący wpływ na jego właściwości transportowe, co z kolei wpływa na jego właściwości mechaniczne i trwałość. W niniejszym artykule zbadano wpływ popiołu lotnego na wewnętrzną pielęgnację i właściwości mieszanki betonu samozagęszczalnego w różnych warunkach otoczenia. Do badań wybrano dwa materiały do wewnętrznej pielęgnacji: lekkie kruszywo keramzytowe [LECA] oraz polimer superabsorbujący [SAP]. Przedstawiono właściwości takie jak sorpcyjność, odporność na penetrację jonów chlorkowych oraz migrację jonów chlorkowych w próbkach betonów ze zmiennym udziałem procentowym popiołu lotnego w zakresie 30% ÷ 50% w różnych warunkach dojrzewania, mianowicie konwencjonalnym dojrzewaniu w warunkach otoczenia, dojrzewaniu z ograniczonym dostępem powietrza z dodatkami do wewnętrznej pielęgnacji oraz dojrzewaniu w warunkach otoczenia z dodatkami do wewnętrznej pielęgnacji. Wyniki wskazują, że szczelność betonu poprawiła się wraz ze zwiększeniem udziału procentowego popiołu lotnego dzięki obecności wody pochodzącej z wewnętrznej pielęgnacji, wpływającej na proces hydratacji oraz popiołu lotnego, który obniża ciepło hydratacji i skurcz spowodowany wysychaniem. Efektywność wewnętrznej pielęgnacji również poprawiła się wraz ze zwiększeniem udziału popiołu lotnego w próbkach. W warunkach otoczenia, mieszanki z zamianą popiołu lotnego powyżej 45% wykazały najlepsze właściwości mechaniczne, z powodu zmiany struktury porowatości prowadzącej do lepszych właściwości transportowych betonu [mniejszej przepuszczalności].

EN

Proper curing of concrete has a major beneficial effect on the transport properties of concrete which in turn influences its durability. This paper attempts to study the effect of fly ash on the transport properties of internally cured Self-Compacting Concrete specimens under ambient conditions. Two internal curing materials, Lightweight Expanded Clay Aggregates [LECA] and Superabsorbent Polymer [SAP] were chosen for the study. Properties such as sorptivity, resistance to chloride ion penetration and chloride ion migration specimens with varying percentages of fly ash replacement from 30% to 50% are presented under different curing conditions namely conventional curing, sealed curing with internal curing materials and ambient curing with internal curing materials. The results showed that the impermeability of concrete improved with an increasing percentage of fly ash replacements owing to the presence of internal curing water to improve hydration along with fly ash that moderates the heat of hydration and drying. The internal curing efficiency also improved with the increase in the percentage of fly ash replacement. Under ambient conditions, the mixes with fly ash above 45% replacement have shown very good mechanical and durability properties indicating a refined pore structure leading to enhanced transport properties.

7

Geopolimery: nadchodząca rewolucja czy ślepy zaułek?

Gołek Łukasz

Budownictwo, Technologie, Architektura

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2024

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nr 2

60--64

PL

Niniejsze opracowanie analizuje potencjał spoiw geopolimerowych jako alternatywy dla tradycyjnych cementów. Poprzez przegląd historii, właściwości i możliwości zastosowania geopolimerów, autor przedstawia ocenę zasadności ich produkcji w kontekście współczesnych wyzwań klimatycznych i technologicznych. Pomimo pewnych korzyści, jakie niosą za sobą geopolimery, istnieją poważne obawy dotyczące ich skuteczności i trwałości w porównaniu z konwencjonalnymi cementami, a przede wszystkim informacje dotyczące śladu węglowego, co często nieprawdziwie deklarowane jest jako ich główna zaleta.

EN

This study examines the potential of geopolymer binders as an alternative to traditional cements. By reviewing the history, properties and possible applications of geopolymers, the author presents an assessment of the viability of their production in the context of contemporary climatic and technological challenges. Despite some benefits that geopolymers bring, there are serious concerns about their effectiveness and durability compared to conventional cements, and above all, information about their carbon footprint, which is often falsely declared as their main advantage.

8

Fly ash from sewage sludge as a component of concrete mix resistant to environmental influence

Rutkowska Gabriela, Żółtowski Mariusz, Ogrodnik Paweł

Zeszyty Naukowe Politechniki Morskiej w Szczecinie

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2023

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nr 76 (148)

65--72

EN

The restrictions on carbon dioxide emissions introduced by the European Union encourage experimental work on new-generation materials containing smaller amounts of clinker. At present, silica fly ashes from the combustion of hard coal are widely used in the technology of cement and concrete in Europe and Poland. This research aims to assess the physical and chemical properties of fly ashes from the thermal treatment of sewage sludge for use in concrete technology in relation to applicable standards and determine their impact on the natural environment. The established concentrations of heavy metals are below the maximum values required when discharging sewage into the ground or waters and also meet the necessary leaching limits when inert waste is allowed to be landfilled and on substances particularly harmful to the aquatic environment. On this basis, it was found that the migration of heavy metals from concrete with the addition of ashes to the water environment is insignificant and should not be a major problem. In addition, the tests showed that the activity index did not exceed the limit value.

9

Badania nad przygotowaniem nowego ekologicznego granulatu ceramicznego dla budownictwa

Wang Yifei

Przemysł Chemiczny

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2023

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T. 102, nr 8

795--798

PL

Poferment z fermentacji biomasy (DR) i popiół lotny (FA) zmieszano z biowęglem z osadów ściekowych (SSC) w stosunku 10:10:80 i spiekano w temp. 1050°C. Produkt został zgranulowany z przeznaczeniem na materiały budowlane i przetestowany zgodnie z chińskimi normami krajowymi. Wszystkie wskaźniki jakości granulatu spełniły wymagania chińskich norm krajowych dla granulatu budowlanego. Wskaźnik potencjalnego ryzyka ekologicznego związanego z obecnością metali ciężkich był niski, a produkt był bezpieczny.

EN

Biomass fermentation digestate and fly ash were mixed with sludge biochar in the ratio of 10:10:80 and sintered at 1050°C. The product was pelletized to building materials and tested according to China national stds. All the qual. indicators of the pellets met the requirements of the China national stds. for construction pellets. The potential ecol. risk index of heavy metals was low, and the product was safe.

10

Performance of self-compacting concrete cast in hot weather conditions

Khalil Hossam S., Abd Elhameid Mohamed W., Badawy Amal A.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2023

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Vol. 32, No. 3

284--302

EN

This work focused on how self-compacting concrete (SCC) performs in situ in hot weather conditions at an ambient temperature of about 35°C. Tests for the rheological properties and compressive and splitting tensile strength aspects were carried out. The results of SCC mix ingredients on the rheological and hardened features of SCC mix were studied. Variations in the amount of portland cement content (CC), water to cement ratio (w/c), coarse to fine aggregate ratio (C : F), chemical admixture ratio, and pozzolanic admixture ratio were considered. Optimum values were obtained for these ingredients, which satisfied the SCC rheological characteristics and gave a 28-day compressive strength of 42 MPa, and 52 MPa after 28 days and 56 days, respectively. These optimum constituent values were 450 kg·m–3 of cement, 0.45 water cementitious ratio, and a coarse to fine material ratio of 1 : 0.8, a high range superplasticizer of 2%, and a mineral admixture of either 5% silica fume or 25% fly ash as a substitute for a similar amount cement.

11

Wytrzymałość na zginanie oraz ściskanie materiałów geopolimerowych otrzymanych z wykorzystaniem odpadów poprodukcyjnych

Kaźmierowski Hubert, Prałat Karol, Koper Artur

Przegląd Budowlany

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2023

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R. 94, nr 7-8

147--150

PL

Artykuł przedstawia wstępne wyniki badań wytrzymałości na zginanie oraz ściskanie innowacyjnych materiałów geopolimerowych. Geopolimery zostały wykonane według dwóch receptur. Pierwszy produkt był próbą kontrolną (odniesienia), a drugi - próbą modyfikowaną (docelową). Przedstawione zostały również wyniki badań gęstości otrzymanych materiałów budowlanych. Wykazano możliwości zastąpienia czystych chemicznie substratów w procesie geopolimeryzacji materiałami odpadowymi.

EN

The article presents the preliminary results of bending and compressive strength tests of innovative geopolymer materials. Geopolymers were made according to two recipes. The first product was the control (reference) sample and the second was the modified (target) sample. The results of density tests of the obtained building materials were also presented. The possibilities of replacing chemically pure substrates in the geopolymerization process with waste materials have been demonstrated.

12

Semi-quantitative analysis study of the impact of microwave treatment on fly ash

Ma Xian Yun, Nie Yi Miao, Guo Jia Le, Chen Yang, Chang Zhen Jia, Wang Ling, Liu Shu Xian, Wang Long

Physicochemical Problems of Mineral Processing

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2023

|

Vol. 59, iss. 6

art. no. 174897

EN

Pre-processing provides an effective way for fly ash's high value-added utilization. However, the shortcomings of pre-processing methods such as grinding and flotation are apparent with many disadvantages that make it more challenging to use efficiently. Microwave heating helps the SiO2-Al.2O3 bond break, not only can make the structural change of the material can also promote the chemical reaction process. In the article, XRD, SEM, FT-IR, ammonia nitrogen adsorption, and other methods were used to analyze the changes in the properties of fly ash before and after microwave pre-treatment, the change in adsorption performance of fly ash before and after microwave treatment was analyzed. The study found that under microwave conditions of 600 W and 15 min, the adsorption rate of ammonia nitrogen by fly ash reached a maximum of 29.67%. The intensity of mullite and amorphous diffraction peaks decreased after 20 min at 600 W. The Si-O-(Si, Al) and Si-O-(Si) bonds showed significant changes at 15 min and 20 min under 600 W conditions. Based on the results, the microwave conditions were selected at 600 W for different periods, and semi-quantitative analysis was carried out by XRD-Rietveld, infrared peak fitting, and nuclear magnetic resonance. The XRD-Rietveld analysis showed that the amorphous phase content reached 46.18% at 15 min. In the infrared peak fitting, the fitting area at 1300-900 cm-1 and 600-400 cm-1 peaks at 56.92% at 25 min and 17.5% at 15 min, respectively. The silicon-oxygen network's degree of connection and polymerization was reduced after 15 min of microwave treatment for the nuclear magnetic resonance analysis. By combining specific surface area measurements, it was discovered that the maximum specific surface area attained a value of 3.122 m2/g at 15 min.

13

Wybrane właściwości gruntowych materiałów kompozytowych jako materiału konstrukcyjnego do budowy niskich nasypów obwałowań przeciwpowodziowych

Brzeziński Bartłomiej, Olchawa Andrzej, Wierzbicka Marianna

Materiały Budowlane

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2023

|

nr 6

32--36

PL

W artykule przedstawiono wyniki badań laboratoryjnych właściwości fizycznych i mechanicznych (zagęszczalności, ściśliwości, przewodności hydraulicznej oraz wytrzymałości na ścinanie) gruntowych materiałów kompozytowych stanowiących mieszaninę torfu, popiołu lotnego i wapna hydratyzowanego. W świetle uzyskanych wyników, parametry geotechniczne wszystkich kompozytów są porównywalne, co stanowi, że o przydatności materiału może decydować kryterium roboczego przedziału wilgotności.

EN

The paper presents the results of laboratory tests of physical and mechanical properties (compaction, compressibility, hydraulic conductivity, and shear strength) of ground composite materials made of peat, fly ash and hydrated lime. The results showed that the geotechnical parameters of the all composites are comparable. Given to these properties it may be accepted that range of working moisture is most usefulness parameter to assessment of composite as an embankment construction material.

14

Residual fly ash from pyrometallurgical processes as a partial replacement for Portland cement in mortars: a study of structural evolution and determination of compressive strength

Juarez-Tapia J. C., García-Ortiz H., Pérez-Labra M., Romero-Serrano J. A., Reyes-Pérez M., Hernández-Ramirez A., Acosta-Sanchez V., Teja-Ruiz A. M., Reyes-Dominguez I. A.

Materials Science Poland

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2023

|

Vol. 41, No. 4

120--131

EN

Mortar mixtures were prepared by partial replacement of Portland cement with 0%, 10%, and 15% of residual fly ash to determine the structural evolution and compressive strength at 3, 7, 14, and 28 days. Portlandite, calcite, ettringite, iron oxide, silicon oxide, and sillimanite were identified in the standard mortar, and, additionally, magnetite was identified in the mortar with 10% and 15% fly ash. X-ray diffraction peaks corresponding to portlandite and ettringite increased in intensity with increasing curing time as a result of the consolidation of mineral species. The SEM analysis revealed that the standard mortar contained mainly portlandite and ettringite at 28 days, while the samples with 10% and 15% fly ash contained particles of fly ash coated with portlandite and ettringite, particles with a smooth surface, and particles of fly ash with signs of attack on their surfaces. The sc increased when the age of the mortar and the substitution of Portland cement by fly ash was increased from 3 to 28 days and from 0 to 15%, respectively.

15

Prediction of microstructural evolution in fly ash-modified cementitious system: A computational study

Yadeta Andualem E., Goyal Pradeep K., Sarkar Raju

Materials Science Poland

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2023

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Vol. 41, No. 4

68--77

EN

The intricate interaction between supplementary cementitious materials (SCMs) and cementitious systems profoundly influences the performance and sustainability of cementitious composites. This study explores the microstructural evolution of fly ash (FA)-modified cement paste by employing a three-dimensional cement hydration and microstructure development (CEMHYD3D) modeling package. Through comprehensive simulations, the influence of varying FA content on hydration phase evolution and pore structure within the cementitious system is revealed. As the proportion of FA within the cementitious mixtures increases, there is a substantial enhancement in the rate of hydration. Notably, the incorporation of FA introduces a significant augmentation in the hydration rate, a phenomenon with potential implications for the long-term performance of FA-modified cementitious materials. The prediction results also highlight that increasing FA substitution in cement leads to finer and more interconnected pore networks due to the pozzolanic reaction. These perceptions hold significant implications for optimizing cementitious mixes and advancing sustainable construction practices. The model-predicted results have been validated with experiments, and they are successful in predicting the microstructural evolution in FA-modified cement paste. In summary, the prediction model bridges the theoretical and practical implementation gaps by providing a thorough understanding of the microstructural evolution of FA-modified cement paste. Furthermore, it provides invaluable guidance for tailoring FA-blended cement compositions, thus promoting their enhanced performance and sustainability in the realm of cementitious materials.

16

Hydration, Microstructure, and Properties of Fly Ash-Based Geopolymer: A Review

Khawaji Mohammad

Materials Science Poland

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2023

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Vol. 41, No. 2

263--287

EN

Geopolymers have gained attention as a potential eco-friendly alternative to Portland cement, primarily due to their reduced carbon dioxide emissions and the opportunity to repurpose industrial waste materials. Fly ash (FA), a byproduct of coal combustion, has been favored as a raw material for geopolymer concrete owing to its widespread availability and high concentrations of alumina and silica. The development and application of fly ash-based geopolymer concrete can contribute significantly to production of sustainable construction materials. An in-depth analysis of fly ash-based geopolymer concrete has been conducted to explore its potential as a substitute for traditional concrete. This review encompasses the underlying reaction mechanism, strength, long-term durability, and microstructural characteristics of geopolymer concrete. The present review paper shows that adding the optimal quantity of fly ash improves the performance of fly ash-based geopolymer when exposed to extreme durability conditions, as well as improving strength properties. The microstructural analysis shows that when fly ash is added, the microstructure of the concrete matrix would be dense and packed. However, challenges remain in adopting fly ash-based geopolymer concrete for large-scale construction projects, as the existing literature presents inconsistencies in the reported strength, durability, and test results. Further research is necessary to consolidate knowledge on the behavior and mechanism of fly ash-based geopolymer concrete and to ultimately provide comprehensive data to support its widespread implementation in the construction industry.

17

Gravity and electrostatic separation of unburned coal from a selected fly ash

Wierzchowski Krzysztof, Klupa Agnieszka, Białecka Barbara, Całus Moszko Joanna

Journal of Sustainable Mining

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2023

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Vol. 22, iss. 1

33--40

EN

Unburned coal grains make it difficult to use fly ash economically, which causes energy losses in the fuel. The article presents the possibilities of separating unburned coal from selected fly ash. In order to assess the possibility of separation of unburned carbon, the analysis of grain density and ash composition was used. Unburned coal was separated by four methods – one wet gravity and three dry methods. It has been found that despite very fine ash grains, the quality and quantity of separation products are significantly dependent on the separation method used and the separated grains’ qualitative characteristics. The analysis of the coal grains under an electron microscope has revealed that they contain mineral inclusions. Their presence enables selective separation of carbon without first grinding the middling grains. The most advantageous results of the separation of unburned coal were obtained by the electrostatic separation method. Separated coal can be used in high-value carbon applications.

18

Studies on Adsorption of Petroleum Products under Static Conditions

Sabadash Vira, Lysko Vitaliy

Journal of Ecological Engineering

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2023

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Vol. 24, nr 10

40--46

EN

This paper provides an overview of the adsorption of petroleum products, focusing on various aspects such as adsorbent types, mechanisms of adsorption, factors influencing efficiency, kinetics, equilibrium, practical applications, and environmental implications. It explores the properties and characteristics of adsorbents, including activated carbon, zeolites, clay minerals, silica gel, and others, highlighting their interaction with petroleum products. The article delves into the theories and mechanisms governing the adsorption process, discussing physical and chemical adsorption as well as the role of forces like van der Waals, hydrogen bonding, and electrostatic interactions. The results of experimental investigations were conducted to evaluate the adsorption capacities of various adsorbents for petroleum products. The adsorption performance, kinetics, and equilibrium behavior of different adsorbents were analyzed, providing insights into their effectiveness in removing petroleum contaminants from aqueous solutions. The adsorption kinetics and equilibrium studies were explored through mathematical models like Langmuir and Freundlich isotherms. The practical applications of adsorption in the petroleum industry were discussed, including removing pollutants from wastewater, gas and diesel purification, and desulfurization. The environmental implications of adsorption technology in mitigating oil spills and reducing petroleum-related pollution were addressed. The conclusion emphasizes the significance of these studies in enhancing understanding, developing efficient solutions, and addressing environmental challenges associated with the petroleum industry. Ongoing research in this field aims to further improve adsorption processes for a more effective and sustainable approach.

19

Characteristics of Silica Powder Extracted from Fly Ash of Coal Fired Power Plant – Effect of Heat Treatment Process

Nurmalita Nurmalita, Abdulmadjid Syahrun Nur, Setiawan Adi, Idroes Rinaldi, Jalil Zulkarnain

Journal of Ecological Engineering

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2023

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Vol. 24, nr 9

282--292

EN

Fly ash waste is a by-product of coal burning at PLTU Nagan Raya, Aceh Province, Indonesia. Since 2017, the coal used is a mixture of 90% Kalimantan coal (sub-bituminous) and 10% local Nagan Raya coal (lignite) which is still young so that the mineral ash content is still high. Silica is among the interesting minerals to be extracted from fly ash, given its wide range of benefits. This paper describes the process of extracting silica from fly ash at the Aceh power plant through the leaching method using a chemical solution and heating for 2 and 4 hours at a temperature of 100˚C. The difference in heat treatment aimed to study the changes in properties and obtain the best method in the silica extraction process. The effect of heat treatment on silica characteristics was studied based on X Ray Diffraction (XRD) test for phase identification, Scanning Electron Microscopy (SEM) test for morphological identification, Energy Dispersive X-Ray Spectroscopy (EDS) test for mineralogy element identification, Fourier Transform Infra-Red (FTIR) test for identification of functional groups and surface chemistry, and differential calorimetric analysis/ thermogravimetric (DSC/TGA) test for identification of thermal properties. As a result, it was found that fly ash still contains unburned carbon, which significantly affects its color, and has the potential for application as a hydrogen storage material because its pore diameter structure is larger than 0.7 nm. The silica extracted from fly ash is capable of achieving a purity of up to 87% and exhibits excellent thermal stability, especially at temperatures between 120–300 °C; thus, it has the potential to be a catalyst material in the adsorption-desorption reaction of hydrogen by magnesium, although further research is still needed.

20

Assessment of Fly Ash from Thermal Treatment of Sewage Sludge According to the Applicable Standards

Rutkowska Gabriela

Journal of Ecological Engineering

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2023

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Vol. 24, nr 3

20--34

EN

The restrictions on carbon dioxide emissions introduced by the European Union encourage experimental work on new generation materials containing smaller amounts of clinker. Currently, silica fly ash from the combustion of hard coal is widely used in cement and concrete technology in Europe and in Poland. Their wide application is mainly determined by their chemical and phase composition, especially pozzolanic activity, their high fineness, similar to cement. The aim of the research was to assess the properties of fly ash from thermal treatment of sewage sludge in terms of use in concrete technology in relation to EN 450-1, ASTM-C618-03 and ASTM C379-65T. The obtained test results confirm that the tested material has a different physicochemical composition and does not meet the requirements related to the use of ash in the production of concrete. In addition, the research showed the possibility of producing ordinary concrete, modified with fly ash from thermal treatment of sewage sludge. The average compressive strength for concrete containing 15% of ash from Cracow was set at 48.1 MPa and 49.2 MPa after 28 and 56 days of maturation, for ash from Warsaw at 42.0 MPa and 45.1 MPa, and for ash from Łódź at 36.2 MPa and 36.2 MPa. The determined concentrations of heavy metals are below the maximum values to be met when discharging waste water into the ground or water, the leaching limits required for accepting inert waste for disposal and for substances particularly harmful to the aquatic environment. On this basis, it was found that the migration of heavy metals from concretes with ash addition to the aquatic environment is insignificant and should not be a significant problem.