Environmental and Biological Impact of Fly Ash and Metakaolin-Based Alkali-Activated Foams Obtained at 70°C and Fired at 1,000°C

Alkali-activated foams (AAFs) are inorganic porous materials that can be obtained at temperatures well below 100°C with the use of inorganic wastes as aluminosilicate precursors. In this case, fly ash derived from a Slovenian power plant has been investigated. Despite the environmental benefits per se, due to saving of energy and virgin materials, when using waste materials, it is of extreme importance to also evaluate the potential leaching of heavy metal cations from the alkali-activated foams. This article presents an environmental study of a porous geopolymer derived from this particular fly ash, with respect to the leachability of potentially hazardous elements, its environmental toxicity as determined by biological testing, and the environmental impact of its production. In particular, attention was focused to investigate whether or not 1,000°C-fired alkaliactivated fly ash and metakaolin-based foams, cured at 70°C, are environmentally friendlier options compared to unfired ones, and attempts to explain the rationale of the results were done. Eventually, the firing process at 1,000°C, apart from improving technical performance, could reinforce heavy metal cation entrapment within the aluminosilicate matrix. Since technical performance was also modified by addition of different types of activators (K-based or Na-based), as well as by partial replacement of fly ash with metakaolin, a life cycle assessment (LCA) analysis was performed to quantify the effect of these additions and processes (curing at 70°C and firing at 1,000°C) in terms of global warming potential. Selected samples were also evaluated in terms of leaching of potentially deleterious elements as well as for the immobilization effect of firing. The leaching test indicated that none of the alkali-activated material is classified as hazardous, not even the as-received fly ash as component of new AAF. All of the alkali-activated foams do meet the requirements for an inertness. The highest impact on bacterial colonies was found in samples that did not undergo firing procedures, i.e., those that were cured at 70°C, which induced the reduction of bacterial Enterococcus faecalis viability. The second family of bacteria tested, Escherichia coli, appeared more resistant to the alkaline environment (pH = 10–12) generated by the unfired AAMs. Cell viability recorded the lowest value for unfired alkali-activated materials produced from fly ash and K-based activators. Its reticulation is only partial, with the leachate solution appearing to be characterized with the most alkaline pH and with the highest ionic conductivity, i.e., highest number of soluble ions. By LCA, it has been shown that 1) changing K-based activators to Na-based activators increases environmental impact of the alkali-activated foams by 1%–4% in terms of most of the impact categories (taking into account the production stage). However, in terms of impact on abiotic depletion of elements and impact on ozone layer depletion, the increase is relatively more significant (11% and 18%, respectively); 2) replacing some parts of fly ash with metakaolin also results in relatively higher environmental footprint (increase of around 1%–4%, while the impact on abiotic depletion of elements increases by 14%); and finally, 3) firing at 1,000°C contributes significantly to the environmental footprint of alkaliactivated foams. In such a case, the footprint increases by around one third, compared to the footprint of alkali-activated foams produced at 70°C. A combination of LCA and leaching/toxicity behavior analysis presents relevant combinations, which can provide information about long-term environmental impact of newly developed waste-based materials

Environmental and Biological Impact of Fly Ash and Metakaolin-Based Alkali-Activated Foams Obtained at 70°C and Fired at 1,000°C

Alkali-activated foams (AAFs) are inorganic porous materials that can be obtained attemperatures well below 100°C with the use of inorganic wastes as aluminosilicate precursors. In this case, fly ash derived from a Slovenian power plant has been investigated. Despite the environmental benefits per se, due to saving of energy and virgin materials, when using waste materials, it is of extreme importance to also evaluate the potential leaching of heavy metal cations from the alkali-activated foams. This article presents an environmental study of a porous geopolymer derived from this particular fly ash, with respect to the leachability of potentially hazardous elements, its environmental toxicity as determined by biological testing, and the environmental impact of its production. In particular, attention was focused to investigate whether or not 1,000°C-fired alkaliactivated fly ash and metakaolin-based foams, cured at 70°C, are environmentally friendlier options compared to unfired ones, and attempts to explain the rationale of the results were done. Eventually, the firing process at 1,000°C, apart from improving technical performance, could reinforce heavy metal cation entrapment within the aluminosilicate matrix. Since technical performance was also modified by addition of different types of activators (K-based or Na-based), as well as by partial replacement of fly ash with metakaolin, a life cycle assessment (LCA) analysis was performed to quantify the effect of these additions and processes (curing at 70°C and firing at 1,000°C) in terms of global warming potential. Selected samples were also evaluated in terms of leaching of potentially deleterious elements as well as for the immobilization effect of firing. The leaching test indicated that none of the alkali-activated material is classified as hazardous, not even the as-received fly ash as component of new AAF. All of the alkali-activated foams do meet the requirements for an inertness. The highest impact on bacterial colonies was found in samples that did not undergo firing procedures, i.e., those that were cured at 70°C, which induced the reduction of bacterial Enterococcus faecalis viability. The second family of bacteria tested, Escherichia coli, appeared more resistant to the alkaline environment (pH = 10–12) generated by the unfired AAMs. Cell viability recorded the lowest value for unfired alkali-activated materials produced from fly ash and K-based activators. Its reticulation is only partial, with the leachate solution appearing to be characterized with the most alkaline pH and with the highest ionic conductivity, i.e., highest number of soluble ions. By LCA, it has been shown that 1) changing K-based activators to Na-based activators increases environmental impact of the alkali-activated foams by 1%–4% in terms of most of the impact categories (taking into account the production stage). However, in terms of impact on abiotic depletion of elements and impact on ozone layer depletion, the increase is relatively more significant (11% and 18%, respectively); 2) replacing some parts of fly ash with metakaolin also results in relatively higher environmental footprint (increase of around 1%–4%, while the impact on abiotic depletion of elements increases by 14%); and finally, 3) firing at 1,000°C contributes significantly to the environmental footprint of alkaliactivated foams. In such a case, the footprint increases by around one third, compared to the footprint of alkali-activated foams produced at 70°C. A combination of LCA and leaching/toxicity behavior analysis presents relevant combinations, which can provide information about long-term environmental impact of newly developed waste-based materials

Alternative alkali activators based on waste bottle glass and waste cathode-ray tube glass

Alkali-activated binders are an environmentally friendly alternative to Portland cement, particularly when locally-available raw materials are used. It is well known that alkali activation with a sodium silicate activator generates a hardened binder with higher compressive strength than a binder hardened with sodium hydroxide. As the alkali-silicate activators are produced through energy extensive processes, and their use can significantly increase the carbon footprint of the final products, it is of great significance to develop alternative alkaline activators based on locally-available waste materials. This article assesses the potential to apply waste bottle glass and waste cathode-ray tube (CRT) glass to synthesise alternative alkali activators by the hydrothermal method. Inductively coupled plasma-optical emission spectrometry (ICP-OES) was used to determine silicon and aluminium content in the alternative activators. The influence of dissolution process parameters (time, temperature, particle size) on the concentrations of silicon and aluminium in the alternative activators was investigated. The alternative activators with silicon concentration up to 19 g/L and aluminium concentration up to 0.9 g/L were prepared at T = 120 °C and boiling time 24 h. The alternative alkali activators and, for comparison, also commercial sodium silicate were used in the alkali activation of fly ash powder. The formed pastes were cured at 70 °C for 72 h. Mechanical strength measurements indicated that alkali activation of fly ash with the optimal alternative activator yielded hardened paste with compressive strength of 33 MPa. However, the compressive strength of hardened paste prepared from fly ash and commercial sodium silicate reached 70 MPa. Part of this difference can be ascribed to the lower density of hardened pastes prepared with alternative activators

Evaluation of locally available amorphous waste materials as a source for alternative alkali activators

The production of alkali-activated materials with excellent mechanical performance requires the use of waterglass, which has a significant carbon footprint. Such materials can have a lower carbon footprint if we replace water glass with alternative activators sourced from waste. In this study, we assessed the suitability of locally available amorphous waste materials (stone wool, glass wool, bottle glass and cathode-ray tube glass) as a source for the preparation of alternative alkali activators. We quantified the amount of silicon and aluminium dissolved in the activator solutions via inductively coupled plasma-optical emission spectrometry. The alternative activators were then used to produce alkali-activated fly ash and slag. The compressive strength values of alkali-activated fly ash specimens upon the addition of NaOH, water glass and the most promising alternative activator were 38.98 MPa, 31.34 MPa and 40.37 MPa, respectively. The compressive strength of slag specimens activated with alternative activators with the highest concentration of dissolved silicon (21 g/L) was, however, 70% higher than the compressive strength of slag specimens activated with only 10 M sodium hydroxide. The compressive strength of slag specimens with the addition of the most promising alternative activator was significantly lower (3.5 MPa) than the compressive strength of those that had been activated by commercial water glass (34.3 MPa)

Word comprehension and expression in children from 24 to 47 months

Vocabulary development is a very important part of a child's language development process. In this regard, the biggest changes occur in the first years of the child's life, which is why focus on children aged between 2 and 4 in this survey. By the fourth year, however, children manage to pronounce an average of 1,000 words. Having a wider vocabulary allows children to form sentences with more words. As a matter of fact, researchers have found a stronger correlation between the breadth of vocabulary and connecting words into sentences than between the age of the child and connecting words into sentences. Most four-year-olds are able to pronounce all of the sounds, except for sibilants and /r/, and fewer simplifications of words can be perceived in their speech. Their speech is better understood even by people they do not know. Nevertheless, one ought to remember that vocabulary is influenced by a variety of environmental and genetic factors, as well as any special needs children might have. Our research dealt with the vocabulary of children aged between 24 and 47 months. The aim of our research was to analyze the results achieved by children in the field of word comprehension and in the field of word production. We were also interested in how successful children were in understanding and expressing nouns and verbs and if there were differences between boys and girls. In the empirical part, we used the first three tasks of the New Reynell Developmental Language Scale (NRDLS-SI) to analyze the results of 11 children (four boys and seven girls) with regular speech and language development. The survey showed there were statistically significant differences between the children's scores on tests of language comprehension and language production. We also found statistically significant differences on the test of comprehension and expression of nouns and verbs, which means that more nouns than verbs appear in the speech of children between the ages of two and four. We also examined the influence of gender on vocabulary development and found some minor gender differences between the sexes (especially in language production). Girls scored slightly higher than boys, but the gender difference was not statistically significant

SPORT ACTIVITIES AND EATING HABITS OF PRE-SCHOOL CHILDREN AT THE SEVNICA KINDERGARTENS

V diplomskem delu z naslovom Športna aktivnost in prehrambene navade predšolskih otrok v sevniških vrtcih je razvidno, kakšna je povezanost športne aktivnosti in prehrambenih navad predšolskih otrok. Namen diplomskega dela je bil ugotoviti, kakšne prehrambene navade imajo otroci, ki obiskujejo sevniški vrtec, kakšno vlogo imajo pri tem njihovi starši, kako pogosto so otroci, vključeni v sevniški vrtec, športno aktivni zunaj vrtca in katere so njihove aktivnosti. Teoretični del smo razdelili na dva dela, prehrano in motoriko. Pri prehrani je opisana zdrava prehrana, prehrana predšolskega otroka, organizacija prehrane v Vrtcu Ciciban Sevnica, pri motoriki pa gibalne sposobnosti otrok, gibalni razvoj, gibalne dejavnosti v kurikulumu za vrtce, vpliv prehrane na gibalni razvoj otroka in organizirane gibalno-športne dejavnosti za predšolske otroke v Sevnici. V empiričnem delu so predstavljeni rezultati raziskave. V raziskovalnem vzorcu je sodelovalo 50 staršev predšolskih otrok. V empiričnem delu so bile z deskriptivno metodo pedagoškega raziskovanja preverjene in ovrednotene zastavljene hipoteze. Iz rezultatov anketnega vprašalnika je razvidno, da se otroci, ki obiskujejo sevniški vrtec, zdravo prehranjujejo in da starši poznajo posledice nezdravega in nepravilnega prehranjevanja. Starši so z otrokom športno aktivni 2 — 3 krat na teden in da zelo malo otrok obiskuje organizirano športno vadbo. Na podlagi podatkov o teži in višini otrok ugotavljamo, da ima večina otrok normalno telesno težo glede na indeks telesne mase.SUMMARY In my diploma paper with the title »Sport activities and nutritive habits of pre-school children at the Sevnica kindergartens« the connection between sport activities and nutritive habits of pre-school children is visibly shown. The aim of my diploma work is to find out what the nutrition habits of pre-school children are, what influence on it have their parents, how often are these children physically active in out-of-school time and how intensive are these physical activities. Theoretic part of my diploma work is divided into two parts including nutrition and motoric. The part about nutrition includes healthy food, nutrition of pre-school children and providing and organising food supply in Sevnica kindergartens. The other part of my work about motoric deals on the other hand with motoric abilities of these children, their motoric developement, exercises used for their motoric developement included in curicculum for kindergartens, the influence of nutrition on motoric developement of a child, the organisation of motoric-sportive activities for pre-school children in Sevnica kindergartens. The results and analysis of my research are presented in the empiric part of my work. There were fifty parents included in my reserch. The hypothesis were presented and evaluated with descriptive methods of pedagogical research in the empiric part of my work. From the results of the questionnaire is evident, that pre-school children attending Sevnica kindergartens eat healthy food and their parents are acquainted with the consequences of irregular and unhealthy nutrition. Parents are physically active with their children 2-3 times a weekalso a very small part of children attends organised forms of sport activities. On the basis of the information about children’s normal weight and height is ascertained that the majority of preschool children have normal weight on the basis of body mass index

Word comprehension and expression in children from 24 to 47 months

Razvoj besedišča predstavlja zelo pomemben del v razvoju otrokovega jezika. Največje spremembe na tem področju se dogajajo v prvih letih otrokovega življenja, zato se bomo v raziskavi osredotočili na otroke med drugim in četrtim letom starosti. Ob četrtem letu otroci uspejo izgovoriti povprečno 1000 besed. Široko besedišče pa tudi omogoča, da otroci iz več besed tvorijo povedi. Raziskovalci so namreč ugotovili, da je močnejša korelacija med širino besedišča in povezovanjem besed v povedi kot pa starostjo otroka in povezovanjem besed v povedi. Štiriletniki v večini uspejo izgovoriti že vse glasove, razen šumnikov in /r/, prav tako se v njihovem govoru pojavlja manj poenostavljanj besed. Posledično je njihov govor bolje razumljiv tudi za nepoznane ljudi. Ne smemo pa pozabiti, da na besedišče vplivajo tudi mnogi okoljski in genetski dejavniki ter tudi morebitne posebne potrebe otrok. Naša raziskava se je ukvarjala z besediščem otrok v starosti med 24 in 47 mesecev. Cilj naše raziskave je bilo analiziranje rezultatov, ki so jih otroci dosegli na področju razumevanja in izražanja besed. Zanimalo nas je tudi, kako uspešni so bili otroci pri razumevanju in izražanju samostalnikov in glagolov ter če obstajajo razlike med dečki in deklicami. V empiričnem delu smo s pomočjo prvih treh nalog Nove Reynellove razvojne jezikovne lestvice (NRDLS-SI) analizirali rezultate 11 otrok (štirih dečkov in sedmih deklic) z značilnim govorno-jezikovnim razvojem. Raziskava je pokazala, da obstajajo statistično pomembne razlike med rezultati otrok na testih razumevanja besed in izražanja besed. Prav tako smo ugotovili statistično pomembne razlike na testu razumevanja in izražanja samostalnikov in glagolov, kar pomeni, da se v govoru otrok med drugim in četrtim letom pojavlja več samostalnikov kot pa glagolov. Preverjali smo še vpliv spola na besedišče in ugotovili manjše razlike med spoloma (predvsem pri izražanju). Deklice so dosegle malo višje rezultate, kot dečki, a razlika med spoloma ni bila statistično pomembna.Vocabulary development is a very important part of a child\u27s language development process. In this regard, the biggest changes occur in the first years of the child\u27s life, which is why focus on children aged between 2 and 4 in this survey. By the fourth year, however, children manage to pronounce an average of 1,000 words. Having a wider vocabulary allows children to form sentences with more words. As a matter of fact, researchers have found a stronger correlation between the breadth of vocabulary and connecting words into sentences than between the age of the child and connecting words into sentences. Most four-year-olds are able to pronounce all of the sounds, except for sibilants and /r/, and fewer simplifications of words can be perceived in their speech. Their speech is better understood even by people they do not know. Nevertheless, one ought to remember that vocabulary is influenced by a variety of environmental and genetic factors, as well as any special needs children might have. Our research dealt with the vocabulary of children aged between 24 and 47 months. The aim of our research was to analyze the results achieved by children in the field of word comprehension and in the field of word production. We were also interested in how successful children were in understanding and expressing nouns and verbs and if there were differences between boys and girls. In the empirical part, we used the first three tasks of the New Reynell Developmental Language Scale (NRDLS-SI) to analyze the results of 11 children (four boys and seven girls) with regular speech and language development. The survey showed there were statistically significant differences between the children\u27s scores on tests of language comprehension and language production. We also found statistically significant differences on the test of comprehension and expression of nouns and verbs, which means that more nouns than verbs appear in the speech of children between the ages of two and four. We also examined the influence of gender on vocabulary development and found some minor gender differences between the sexes (especially in language production). Girls scored slightly higher than boys, but the gender difference was not statistically significant

The deformation of alkali-activated materials at an early age under different curing conditions

The production of alkali-activated materials (AAMs) is known for its environmentally friendly processing method, where several amorphous-rich aluminosilicate material sources combine with an alkali media solution to form solid, ceramic-like materials. In terms of the Si:Al, Na(K):Al, and Na(K):H2O ratios, the theory of AAM formation is quite well developed, but some open questions in the technology process remain, especially with regards to the means of curing, where the generation of defects can be persistent. Knowing that deformation is extremely high in the early ages, this study investigates the effects of temperature and moisture on shrinkage behavior within the first 72 h of AA pastes made from ladle (LS) and electric arc furnace (EAF) slag and activated by sodium silicate (Na2SiO3). The method to determine the deformation of alkali-activated slag-based materials, in terms of both autogenous and drying shrinkage, was based on the modified ASTM C1698-19 standard for the measurement of autogenous shrinkage in cement pastes. Autogenous deformation and strain were measured in four samples, using the standard procedure at room temperature, 40 and 60°C. Furthermore, using an adjusted method, nine samples were characterized for strain and partial surface pressure, while drying at room temperature, 40, or 60°C at a relative humidity of 30 or 90%. The results show that the highest rate of autogenous shrinkage occurred at a temperature of 60°C, followed by drying shrinkage at 60°C and 30% relative humidity, owing to the fact that the rate of evaporation was highest at this moisture content. The study aimed to provide guidance regarding selection of the optimal curing set in order to minimize deformations in slag-based alkali-activated materials. In the present case, curing at a temperature of around 40°C under lower moisture conditions for the first 24 h provided optimal mechanical properties for the slags investigated. The methodology might also be of use for other aluminosilicate sources such as metakaolin, fly ash, and mineral wool–based alkali-activated materials

Particle size manipulation as an influential parameter in the development of mechanical properties in electric arc furnace slag-based AAM

Alkali-activated materials (AAM) have gained recognition as a promising alternative to technical ceramic and building materials owing to the lower energy demands for production and the potential to use slag as a precursor. In the present study, five sets of slag-based AAM pastes were prepared with different particle sizes (fractions d < 63, 63 < d < 90, and 90 < d < 125 μm in different mass ratios) under the same curing regime and using a fixed precursor to activator (water) mass ratio. Precursors and the hardened AAM are evaluated using BET, XRD, XRF, SEM, FTIR, reactivity of precursors by leaching, and mercury intrusion porosimetry (MIP). Chemical analysis indicated only marginal differences among the different-sized fractions of input materials, whereas the BET surface area and reactivity among the precursors differed significantly-smaller particles had the largest surface area, and thus, higher reactivity. The mineralogical differences between the precursors and hardened AAM were negligible. The results revealed that compressive strength was significantly influenced by particle size, i.e., a threefold increase in strength when the particle size was halved. Microstructural evaluation using MIP confirmed that the porosity was the lowest in AAM with the smallest particle size. The low porosity and high reactivity of the fine fractions led to the highest compressive strength, confirming that manipulation of particle size can significantly influence the mechanical properties

The deformation of alkali-activated materials at different curing temperatures

Alkali activation is a chemical process whereby materials rich in aluminosilicate, which dissolves in basic media at room temperature, form binding phases by polycondensation. The alkali- activated materials (AAM) are a promising alternative to binding materials such as cement or other products in civil engineering (van Deventer et al., 2012). This study investigates the early age shrinkage behavior of Slovenian ladle and electric arc furnace slag - based alkali activated materials at different curing temperatures. The dimensions of specimens cured at room temperature and elevated temperatures up to 90 °C were measured over the first 7 hours (every 10 min). The results show that the most shrinkage occurred at the highest temperature, owing to the highest rate of evaporation of liquid content. Loss of mass follows from the drying shrinkage