On the crystallisation pressure of gypsum

Serafeimidis, Konstantinos; Anagnostou, Georg

doi:10.1007/s12665-014-3366-7

Cited by 20 publications

(20 citation statements)

References 16 publications

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“…With an interpolation between those points (Figure 1-11b), they consider the swelling law by Grob (1972) to be valid also for sulfatic rock. However, when plotting the curves from Figure 1-11b in a semilogarithmic diagram (Figure 1 -11c) and extrapolating their data linearly to zero strain (as is exemplarily indicated for three data sets, A2, A3d and A4d, where "A" stands for "Ablesung") the author obtains unrealistically high maximal stresses (in the case of A2 more than 100 MPa, which even exceeds the expected crystallization pressure of gypsum, see Serafeimidis and Anagnostou, 2014a, who consider a range up to about 50 MPa for the crystallization pressure in a closed system). Since in none of the cases the maximal swelling stress under constant volume was actually measured and not all load-steps were considered for the generation of the interpolated curves, these interpretations are considered questionable.…”

Section: Pimentelmentioning

confidence: 89%

“…Anagnostou et al (2014) then investigated, why anhydrite rather than gypsum is found at small depths of cover, which is usually the case in tunneling and came to the conclusion that the clay minerals and thus the low water activity are most likely responsible for the anhydrite to be the thermodynamically stable phase, rather than gypsum, thus preventing AGT prior to the excavation of tunnels. They used thermodynamic computations to determine the crystallization pressure of gypsum and found that the pressures are considerably lower in the case of low water activities (Serafeimidis and Anagnostou, 2014a). Serafeimidis and Anagnostou (2014a) furthermore show that the crystallization pressure is dependent on a number of factors, such as pore radius, temperature, water activity, and presence of foreign ions.…”

Section: Modelling Of Anhydritic Swelling Claystones -Theoretical Partmentioning

confidence: 99%

“…They used thermodynamic computations to determine the crystallization pressure of gypsum and found that the pressures are considerably lower in the case of low water activities (Serafeimidis and Anagnostou, 2014a). Serafeimidis and Anagnostou (2014a) furthermore show that the crystallization pressure is dependent on a number of factors, such as pore radius, temperature, water activity, and presence of foreign ions. Serafeimidis et al (2015) expanded their investigations to the macroscopic and the mega scale using a cavity expansion model for the interaction between the growing crystal and the surrounding clay matrix to explain why swelling pressures in the laboratory are far lower than the crystallization pressure of gypsum, yet higher than the swelling pressures in situ.…”

Section: Modelling Of Anhydritic Swelling Claystones -Theoretical Partmentioning

confidence: 99%

“…(cf. also Serafeimidis and Anagnostou, 2014aand 2014b. In this chapter, two factors are further discussed: the influence of the temperature (with which the AGT process can be prohibited or triggered, see Chapters 10.2.1 and 11.2.3) and influence of the water activity (which in the case of partially saturated rocks can be the reason for anhydrite to be the stable phase, see Chapter 10.2.2).…”

Section: Chemical Swelling Due To Agtmentioning

confidence: 99%

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Experimental investigations for the modelling of anhydritic swelling claystones

Wanninger¹

2020

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Anhydritic claystones are highly problematic for underground construction because of their swelling ability: When the rock comes into contact with water, the rock volume expands due to swelling of both clay as well as anhydrite. When the expansion is restricted, e.g., by an invert arch in tunneling, the swelling rocks can exert high pressures on the lining and damage the structure. The swelling behavior of purely argillaceous rock (containing solely swelling clays and no anhydrite) can be attributed mainly to osmotic processes and is well understood for the conceptual design of tunnels, as opposed to the swelling of anhydrite, where considerable knowledge gaps exist. Swelling of anhydrite is caused by chemical processes: The anhydrite dissolves when it comes into contact with water, and from the dissolved ions in the pore water gypsum precipitates. The volume of gypsum is greater than that of anhydrite by 61%. During Anhydrite to Gypsum Transformation (hereafter denoted as AGT) the rock mass expands and the pore volume can also increase, for example due to cracking of the rock induced by the pressure exerted by the growing crystals upon a rigid rock structure ("crystallization pressure"). This PhD thesis seeks to establish a better understanding and quantification of the coupled chemomechanical swelling processes due to AGT and creates a basis for developing chemo-mechanical models of the swelling of anhydritic claystones. The findings from the experiments verified kinetic models and assumptions related to AGT. Moreover, the systematic experimental investigations regarding the swelling behavior of anhydrite give an indication of a stress-strain relationship which can be implemented and used as a fundamental basis for future modelling of swelling due to AGT. This is necessary for practicing engineers in order to design underground structures in anhydritic rock. Furthermore, it was shown that the swelling due to anhydrite and clay can be de-coupled by varying the testing temperatures, which changes the equilibrium concentrations.

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Section: Pimentelmentioning

confidence: 89%

Section: Modelling Of Anhydritic Swelling Claystones -Theoretical Partmentioning

confidence: 99%

Section: Modelling Of Anhydritic Swelling Claystones -Theoretical Partmentioning

confidence: 99%

Section: Chemical Swelling Due To Agtmentioning

confidence: 99%

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Experimental investigations for the modelling of anhydritic swelling claystones

Wanninger¹

2020

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“…Crystallization in these types of environments frequently occurs in unsaturated conditions, where both a fluid and a vapor phase are present in pores. Numerous experimental (e.g., Noiriel et al, 2010;Tsui et al, 2003;Wolterbeek et al, 2017) and theoretical (e.g., Coussy, 2006;Flatt, 2002;Scherer, 1999Scherer, , 2004Serafeimidis & Anagnostou, 2014;Steiger, 2005aSteiger, , 2005b studies have been conducted in attempts to quantify the stresses involved, mostly in systems where crystallization occurs within a porous medium whose matrix does not participate in the reaction.…”

Section: Introductionmentioning

confidence: 99%

Competition Between Crystallization‐Induced Expansion and Creep Compaction During Gypsum Formation, and Implications for Serpentinization

et al. 2018

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Deformation caused by reaction‐driven volume increases is an important process in many geological settings. The interaction of rocks with reactive fluids can change permeability and reactive surface area, leading to a large variety of feedbacks. Gypsum (CaSO4·2H2O) is an ideal material to study these processes. It forms rapidly at room temperature via bassanite (CaSO4·[1/2]H2O) hydration and is commonly used as an analog for rocks in high‐temperature, high‐pressure conditions. We conducted uniaxial deformation experiments on porous bassanite aggregates to study the effects of applied axial load σa on deformation during the formation of gypsum. While hydration of bassanite involves a solid volume increase, gypsum exhibits significant creep compaction when in contact with water. These two processes occur simultaneously. Samples exhibited an initial phase of deformation followed by a slower secondary phase. A particular value of σa separates expansion from compaction during each of the deformation phases. At σa≤150 kPa, samples expanded initially; for σa≥230 kPa, samples compacted initially. Up to σa≈3.2 MPa, samples expanded after compacting initially, while for σa≥3.6 MPa, no further deformation or continued compaction occurred. This behavior implies that crystallization‐induced stresses depend on porosity and reaction extent such that larger stresses cannot be generated by the reaction. We explain aspects of the observed behavior with a model that predicts strain evolution using kinetic relationships for the reaction and creep rates and consider the implications of our results for reaction‐induced fracturing during serpentinization.

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