The study of ecological impact of fly ash-based geopolymer binders on soil and aquatic biota

Vasilenko, Marina; Lebedev, M S; Гончарова, Е. Н.; Kozhukhova, N. I.; Kozhukhova, Marina

doi:10.1088/1757-899x/791/1/012049

Cited by 4 publications

(2 citation statements)

References 13 publications

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“…and FA67K 1,000. Differently from published results on FA-based AAMs, focused on fungicidal properties of some FA products ( Vasilenko et al, 2020 ), we investigated the effect on bacteria, either gram-positive ( E. faecalis ) or gram-negative ( E. coli ). Experimentally, we demonstrated that there is no obvious negative effect on bacterial growth, thus declaring a safe coexistence of the developed geopolymers with the ecosystem.…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2022

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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 alkali-activated 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 alkali-activated 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.

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Section: Discussionmentioning

confidence: 99%

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

et al. 2022

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“…Geopolymer concrete (GPC) has the advantages of environmental protection and energy savings, as well as mechanical properties close to or better than OPC concrete (OPCC) [ 16 , 17 , 18 , 19 , 20 ]. Besides, GPC will show higher temperature resistance on some structures, compared to OPCC [ 21 ].…”

Section: Introductionmentioning

confidence: 99%

Mechanical Properties of Nano-SiO2 Reinforced Geopolymer Concrete under the Coupling Effect of a Wet–Thermal and Chloride Salt Environment

Jin

Zhang

et al. 2022

Polymers

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In this study, the mechanical behaviors of nano-SiO2 reinforced geopolymer concrete (NS-GPC) under the coupling effect of a wet–thermal and chloride salt environment were investigated through a series of basic experiments, and a simulation on the coupling effect of a wet–thermal and chloride salt environment and SEM test were also included. During the experiments for the coupling effect of the wet–thermal and chloride salt environment, an environment simulation test chamber was utilized to simulate the wet–thermal and chloride salt environment, in which the parameters of relative humidity, temperature, mass fraction of NaCl solution and action time were set as 100%, 45 °C, 5% and 60 d, respectively. The content of nano-SiO2 (NS) particles added in geopolymer concrete (GPC) were 0, 0.5%, 1.0%, 1.5% and 2.0%. The result indicated that the mechanical properties of NS reinforced GPC decreased under the coupling effect of the wet–thermal and chloride salt environment compared to the control group in the natural environment. When the NS content was 1.5%, the cube and splitting tensile strength, elastic modulus and impact toughness of GPC under the coupling environment of wet–thermal and chloride salt were decreased by 9.7%, 9.8%, 19.2% and 44.4%, respectively, relative to that of the GPC under the natural environment. The addition of NS improved the mechanical properties of GPC under the coupling effect of the wet–thermal and chloride salt environment. Compared to the control group without NS, the maximum increment in cube compressive strength, splitting tensile strength and elastic modulus of NS–GPC under the coupling effect of the wet–thermal and chloride salt environment due to the incorporation of NS reached 25.8%, 9.6% and 17.2%, respectively. Specifically, 1.5% content of NS increased the impact toughness, impact numbers of initial crack and the ultimate failure of GPC by 122.3%, 109% and 109.5%, respectively.

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The Effect of Recycled Citrogypsum as a Supplementary Mineral Additive on the Physical and Mechanical Performance of Granulated Blast Furnace Slag-Based Alkali-Activated Binders

et al. 2023

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In the last decades, gypsum-bearing industrial wastes become one of the common globally produced industrial and domestic wastes that are currently recycled and further utilized. In this study, the gypsum-bearing waste citrogypsum was used as a Ca2+-containing component to modify the properties of alkali-activated cement (AAC) based on granulated blast-furnace slag (GBFS). Citrogypsum was used in different AAC mixes activated with three different alkaline components: Na2CO3, NaOH, and Na2SiO3. Laser granulometry was applied to assess the granulometric characteristics of citrogypsum and GBFS. Specific gravity (SG), compressive strength, and water resistance were tested to evaluate the effect of citrogypsum on the physical and strength performance of AAC. Experimental results obtained over 4-day to 28-day time periods for the studied AACs showed that the addition of citrogypsum had a detrimental effect on the properties of AAC mixes, where decreases in compressive strength between 1 and 100%, decreases in specific gravity between 4 and 30%, and decreases in water resistance between 12 and 100% were observed. It was determined that AAC mixes modified with citrogypsum cured in ambient conditions had compressive strength values 61% to 90% lower than those cured in hydrothermal conditions. In terms of strength performance, specific gravity and water resistance, citrogypsum showed the greatest effect on AAC mixes activated with NaOH, and to a lesser extent, on mixes activated with Na2CO3. The highest water resistance value of 0.77 was observed for the AAC mixes activated with Na2CO3 cured in ambient conditions, and when cured in hydrothermal conditions, the highest water resistance reached up to 0.84 for the AAC mixes activated with NaOH. It was observed that the type of alkaline activator and curing conditions are both crucial factors that govern the response of citrogypsum as a supplementary mineral additive in GBFS-based AAC mixes in regard to compressive strength, specific gravity and water resistance.

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The study of ecological impact of fly ash-based geopolymer binders on soil and aquatic biota

Cited by 4 publications

References 13 publications

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

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

Mechanical Properties of Nano-SiO2 Reinforced Geopolymer Concrete under the Coupling Effect of a Wet–Thermal and Chloride Salt Environment

The Effect of Recycled Citrogypsum as a Supplementary Mineral Additive on the Physical and Mechanical Performance of Granulated Blast Furnace Slag-Based Alkali-Activated Binders

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