Resistance of metakaolin-MSWI fly ash based geopolymer to acid and alkaline environments

Jin, Ming; Zheng, Zidan; Sun, Ye; Chen, Linwei; Jin, Zanfang

doi:10.1016/j.jnoncrysol.2016.07.036

Cited by 125 publications

(26 citation statements)

References 24 publications

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“…The increase in unconfined compressive strength of this study during the sulfuric acid immersion was not in agreement with the result of the study conducted in [25], wherein a loss in strength was recorded. The mechanism that may occur during sulfuric acid immersion involves an attack of acid on aluminosilicate bonding present in the geopolymer matrix.…”

Section: Unconfined Compressive Strengthcontrasting

confidence: 97%

“…Acid resistance is thus defined as the ability of the material to resist acid attack when exposed to such aggressive environment [32]. Hence, after curing for 28 days, the hardened soil geopolymer samples, SO-CFA-28 and SO-CFA-56, were immersed in a 5% (percentage by weight) sulfuric acid solution for 28 days and 56 days, respectively [19,25]. The unconfined compressive strength (UCS) was measured after the immersion.…”

Section: Acid Resistance Testmentioning

confidence: 99%

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Chemical Stability and Leaching Behavior of One-Part Geopolymer from Soil and Coal Fly Ash Mixtures

et al. 2018

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Aluminosilicate minerals have become an important resource for an emerging sustainable material for construction known as geopolymer. Geopolymer, an alkali-activated material, is becoming an attractive alternative to Portland cement because of its lower carbon footprint and embodied energy. However, the synthesis process requires typically a two-part system for alkali activation wherein the solid geopolymer precursor is mixed with aqueous alkali solutions. These alkali activators are corrosive and may be difficult to handle in the field-scale application. In this study, a one-part geopolymer in which coal fly ash was mixed with solid alkali activators such as sodium hydroxide and sodium silicate to form a powdery cementitious binder was developed. This binder mixed with soil only requires water to form the soil-fly ash (SO-CFA) geopolymer cement, which can be used as stabilized soil for backfill/foundation. This geopolymer product was then evaluated for chemical stability by immersing the material with 5% by weight of sulfuric acid solution for 28 days. Indication suggests that the geopolymer exhibited high resistance against acid attack with an observed increase of unconfined compressive strength even when the immersion time in acidic solution was increased to 56 days. The mineralogical phase, microstructure, and morphology of the material were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), respectively. Results not only confirmed the formation of gypsum due to acid attack but also indicated the dissolution of anorthite and albite that may have caused the microstructure to be composed of sodium aluminosilicate hydrate (N–A–S–H) and calcium (alumino) silicate hydrate (C(–A)–S–H) with poly(ferro-sialate-siloxo) and poly(ferro-sialate-disiloxo) networks. A column leaching test with deionized water was also performed on the soil-fly ash geopolymer to study the leachability of metals in the material. Results showed that arsenic exhibits higher mobility in the geopolymer as compared to that of cadmium, chromium, and lead.

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Section: Unconfined Compressive Strengthcontrasting

confidence: 97%

Section: Acid Resistance Testmentioning

confidence: 99%

Chemical Stability and Leaching Behavior of One-Part Geopolymer from Soil and Coal Fly Ash Mixtures

et al. 2018

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“…Specimen, prepared based on the parameters yielding highest UCS, was compacted in a cylindrical mold 50 mm diameter by 100 mm height and allowed to cure for 28 days. After curing, sample was immersed in 5% (w/w) sulfuric acid solution [17,24]. The compressive strength was measured after 28 days of immersion.…”

Section: Sulfuric Acid Resistance Testmentioning

confidence: 99%

Synthesis of a one-part geopolymer system for soil stabilizer using fly ash and volcanic ash

et al. 2018

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A novel approach one-part geopolymer was employed to investigate the feasibility of enhancing the strength of in-situ soil for possible structural fill application in the construction industry. Geopolymer precursors such as fly ash and volcanic ash were utilized in this study for soil stabilization. The traditional geopolymer synthesis uses soluble alkali activators unlike in the case of ordinary Portland cement where only water is added to start the hydration process. This kind of synthesis is an impediment to geopolymer soil stabilizer commercial viability. Hence, solid alkali activators such as sodium silicate (SS), sodium hydroxide (SH), and sodium aluminate (SA) were explored. The influence of amount of fly ash (15% and 25%), addition of volcanic ash (0% and 12.5%), and ratio of alkali activator SS:SH:SA (50:50:0, 33:33:33, 50:20:30) were investigated. Samples cured for 28 days were tested for unconfined compressive strength (UCS). To evaluate the durability, sample yielding highest UCS was subjected to sulfuric acid resistance test for 28 days. Analytical techniques such as X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscope/energy-dispersive X-ray spectroscopy (SEM/EDX) were performed to examine the elemental composition, mineralogical properties, and microstructure of the precursors and the geopolymer stabilized soil.

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“…It also contained considerable amount of alkalis such as Na 2 O, K 2 O, and MgO. The high content of CaO and chlorine are the result of calcic adsorbent during the incineration process in order to control and neutralize the acidic gases such as sulphides and chlorides [23,24]. SiO 2 , Al 2 O 3 , Fe 2 O 3 are the main oxide in VA.…”

Section: Methodsmentioning

confidence: 99%

Characterization and Leachability Behaviour of Geopolymer Cement Synthesised from Municipal Solid Waste Incinerator Fly Ash and Volcanic Ash Blends

et al. 2018

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Municipal solid waste incinerator fly ash (MSWI-FA) was used synergistically with volcanic ash (VA) to synthesize Geopolymer cement. The effects of the incorporation of 0%, 30%, and 50% of VA and the alkalinity of activating solution on the structure and properties were studied by using the X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), field emission gun scanning electron microscopy (FEG-SEM), and mechanical testing. The encapsulation efficiency of the cements was carried out by using a toxicity characteristic leaching procedure (TCLP). The geopolymerization of MSWI-FA promoted the formation of new minerals such as Thernadite (Na 2 SO 4 ), Hydrocalumite (Ca 4 Al 2 O 6 (CO 3 ) 0.67 (SO 3 ) 0.33 ), C-S-H, and Faujasite-Na(Na 2 Ca) 0.075 (Al 0.3 Si 0.7 )O 2 (H 2 O) 0.22 . The Geopolymer cement synthesized with the addition of 50% of VA at 6M NaOH concentration, which exhibited the most compact microstructure. This was the highest strength with the best encapsulation ability. The microstructure analysis of the MSWI-FA-VA system revealed the coexistence of C-S-H and N-A-S-H phases as the main cementitious binders. The TCLP results of cement vis a vis raw MSWI-FA showed the leaching of metals reduced to a great extent. This was much lower than the permissible limit fixed by the United States Environmental Protection Agency (USEPA) for the toxicity characteristic. Furthermore, an attempt was made to correlate the microstructure with mechanical properties.Recycling 2018, 3, 50 2 of 14 of heavy metals content. Therefore, MSWI-FA is classified as a hazardous waste [3,4]. Owing to its chemistry, fine particle size, and pozzolanic behavior, MSWI-FA has the potential to be used as a mineral additive in cement. However, its high chlorine content restricts its application in construction material. Although the cement paste is not much affected by chloride except for increased solubilization of cement solids, chlorine is detrimental to the passivation of embedded steel [5]. To avoid this problem, some pre-treatment methods such as water washing and thermal treatment have been proposed [3,6,7]. These pre-treatments certainly eliminate the chlorides and inorganic salts in MSWI-FA but generate other wastes and increase the quantity of energy required for the synthesis and the total cost of the product. The efficient way to valorize MSWI-FA in construction is its use in the process, which displays limited signs of heavy metals leaching and the formation of the corrosion product in the presence of chlorine such as geopolymerization [8][9][10].Geopolymer cement are considered eco-friendly binder materials and potential alternative to Portland cement (OPC) in specific applications since they produce around 80% less CO 2 than Portland cement [11]. It has the potential to use alumina-silicate materials either from natural occurring waste, synthetic waste, or from industrial waste. Thus, varieties of alumina-silicate and industrial waste used for Geopolymer cement synthesis involve volcanic ash, glass powder,...

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Resistance of metakaolin-MSWI fly ash based geopolymer to acid and alkaline environments

Cited by 125 publications

References 24 publications

Chemical Stability and Leaching Behavior of One-Part Geopolymer from Soil and Coal Fly Ash Mixtures

Chemical Stability and Leaching Behavior of One-Part Geopolymer from Soil and Coal Fly Ash Mixtures

Synthesis of a one-part geopolymer system for soil stabilizer using fly ash and volcanic ash

Characterization and Leachability Behaviour of Geopolymer Cement Synthesised from Municipal Solid Waste Incinerator Fly Ash and Volcanic Ash Blends

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