Implications of Pyrite Oxidation for Engineering Works

Hawkins, A. B.; John, Tom St

doi:10.1007/978-3-319-00221-7

Cited by 13 publications

(3 citation statements)

References 73 publications

(102 reference statements)

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“…Many experiments confirmed that these reactions are often tightly coupled at the mineral/fluid interfacial layer, − resulting in interfacial fluid supersaturated with respect to the replacing phase. The growing crystal (or precipitation) in contact with the supersaturated solution may produce high crystallization pressures exceeding 300 MPa, which is large enough to fracture the surrounding host rock in the upper 10 km of the Earth’s crust. , During the oxidative weathering of pyritic mudstone and black shale, some authors also observed the rock fracturing caused by crystallization pressure due to the replacement of calcite (molar volume = 36.9 cm 3 /mol) by gypsum (molar volume = 74.4 cm 3 /mol). − Based on the microscale (or single crack) model proposed by Røyne et al in 2011, the crack velocity can be controlled by the kinetics of crystal growth. In 2017, Malvoisin et al also described a micromechanical model to quantify the propagation of a single crack during the replacement reaction of olivine with water to form serpentine.…”

Section: Introductionmentioning

confidence: 99%

Gypsum-Crystallization-Induced Fracturing during Shale–Fluid Reactions and Application for Shale Stimulation

et al. 2018

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Spontaneous microfracture propagation caused by mineral crystallization or growth has been demonstrated in a variety of volume-increasing mineral replacement reactions. This brings a new look on the way microfractures may be generated in the shale formation. Because carbonates and pyrite are highly reactive minerals during shale–fluid reactions and may be the most common sources of replacement reactions, 10 wt % sulfuric acid (H2SO4) and 10 wt % ammonium persulfate ((NH4)2S2O8) solutions were used to react with the centimeter- and millimeter-sized shale samples, which have a reactive mineral composition of 2.2–4.7 wt % calcite (CaCO3) and 4.3–4.8 wt % dolomite (CaMg(CO3)2), and 1.8–2.7 wt % pyrite (FeS2). A deionized water experiment was performed as a replacement-free control. We monitored the reaction-induced fractures using X-ray tomography and scanning electron microscopy imaging. The related mineral dissolution and new mineral precipitation were also examined. Experiments showed that reactions of the unconfined shale samples with H2SO4 and (NH4)2S2O8 solution have a great potential for generating chemically induced fractures, because of the replacement of carbonate minerals by gypsum (CaSO4·2H2O) crystal. The replacement process was supposed to occur via an interface-coupled dissolution–precipitation reaction. It allows the gypsum precipitation in the immediate vicinity of the dissolving carbonate mineral surfaces. Because gypsum has a higher molar volume (74.4 cm3/mol) than calcite (36.9 cm3/mol) and dolomite (64.3 cm3/mol), the local replacement reactions can generate internal swelling stress that drives fracturing of the surrounding shale matrix. The reaction-induced stress is on the grain scale and derived from the crystallization pressure. Based on the calculation from the degree of supersaturation of CaSO4 solution, the crystallization pressure can easily exceed 30 MPa, which may provide a sufficient local swelling stress to cause intensive shale microfracturing. This implies that the replacement of calcite and dolomite grains by calcium sulfate crystals could provide an additional driving force to generate microfractures during shale hydraulic fracturing.

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Section: Introductionmentioning

confidence: 99%

Gypsum-Crystallization-Induced Fracturing during Shale–Fluid Reactions and Application for Shale Stimulation

et al. 2018

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“…Whilst some arsenic bearing minerals (e.g., realgar, As 4 S 4 ; orpiment, As 2 S 3 ) react with a cyanide lixiviant, arsenopyrite oxidises very slowly and therefore has very little adverse effect on Au leaching [32]. Instead, arsenopyrite and remnant pyrite have also undergone surficial oxidation after heap leaching operations (Equations (8) and (9); [8,33]) resulting in localised low pH conditions. In turn, this has permitted galena oxidation (Equations (10) [8,34]).…”

Section: Heap Leach Pile Evolutionmentioning

confidence: 99%

Geoenvironmental Characterisation of Heap Leach Materials at Abandoned Mines: Croydon Au-Mines, QLD, Australia

Parbhakar-Fox

2016

Minerals

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Abstract:Heap leaching is a well-established metallurgical technology which allows metal recovery (e.g., Au, Cu, U) from low-grade ores. However, spent heap leach materials remaining at abandoned or historic mine sites may represent a potential source of contamination. At the Croydon Au-mines, heap leaching operations (1984)(1985) were performed on mineralized rhyolites hosting sulphides including pyrite, galena, arsenopyrite and minor sphalerite. Characterization of spent heap leach materials (n = 14) was performed using established geochemical and mineralogical techniques, supplemented by automated mineralogical evaluations. Whilst these materials contained low sulphide-sulphur (0.08 to 0.41 wt %) and returned innocuous paste pH values (pH 5.1 to 8.6), they were classified uncertain by net acid producing potential/net acid generating criteria. This was likely due to the reaction of secondary mineral phases (i.e., beudantite, hidalgoite, kintoreite and Fe-As-Pb oxides) during these tests. It is hypothesised that during heap leaching, gangue sulphides have differentially reacted with the cyanide lixiviant, pre-conditioning the formation of these complex secondary phases during surficial oxidation, after heap leaching termination. These materials are considered to represent a moderate geoenvironmental risk as dissolved Pb in basal leachates is in excess of the World Health Organization (WHO 2006) guideline values. Considering this, these materials should be included in ongoing rehabilitation works at the site.

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“…The effect of pyrite on building foundations is well discussed and documented in the literature. Hawkins and John report that oxygen and moisture are key factors that help pyrite crystallisation within most rock types, leading to swelling and thereby extensive damage to the concrete slab [6,7]. This damage may be observed either in the concrete itself as result of pyrite presence in the aggregate within the mix or in the soil underneath the slab.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Ground Penetrating Radar for Pyrite Swelling Detection in Soils

KhoderAgha,

Assaf

2024

Civ Eng J

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Pyrite swelling in soils below buildings is a major issue. It leads to severe deformations in floor foundations. A survey is carried out at a selected site in the city of Laval, Quebec, to assess the usefulness of ground-penetrating radar (GPR) to detect deformations that may be indicative of the presence of pyrite. Four soil samples are taken from the aforementioned site to determine the soil type below the concrete slab. The results indicate the presence of limestone, moor clay, and shale sediments, which are prone to pyrite swelling. The GPR data were collected using the GSSI SIR 4000 with a high frequency antenna and processed using RADAN software. The GPR data indicate the presence of severe deformation in many locations of the concrete slab. The most important wave reflections indicative of pyrite swelling are the rebar reflections, showing interesting pushed-up and dropped-down reflections. These reflections appear in two forms. The first is the attenuated reflections that may occur due to pyrite-rich materials. The second is the high amplitude reflections that occur because of the air void, which can be formed due to heaving the concrete slab because of pyrite swelling. As a result, GPR appears to be an effective method for assessing and mapping the effect of pyrite swelling below concrete slabs. Doi: 10.28991/CEJ-2024-010-03-05 Full Text: PDF

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Implications of Pyrite Oxidation for Engineering Works

Cited by 13 publications

References 73 publications

Gypsum-Crystallization-Induced Fracturing during Shale–Fluid Reactions and Application for Shale Stimulation

Gypsum-Crystallization-Induced Fracturing during Shale–Fluid Reactions and Application for Shale Stimulation

Geoenvironmental Characterisation of Heap Leach Materials at Abandoned Mines: Croydon Au-Mines, QLD, Australia

Assessment of Ground Penetrating Radar for Pyrite Swelling Detection in Soils

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