Rock alteration in alkaline cement waters over 15 years and its relevance to the geological disposal of nuclear waste

Moyce, E.B.A.; Rochelle, Christopher A.; Morris, Katherine; Milodowski, Antoni E.; Chen, Xiaohui; Thornton, Steven F.; Small, Joe S.; Shaw, Samuel

doi:10.1016/j.apgeochem.2014.08.003

Cited by 45 publications

(46 citation statements)

References 45 publications

(61 reference statements)

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“…This may be a sign of the pH reduction through continued fluid-rock reaction causing the initially formed CSH to become unstable, possibly itself breaking down to form other phases (such as CSH of a different composition or clays) as the pH of the system evolved. Longer-duration experiments would reveal if this were the case (see Moyce et al, 2014). The surface area of the reaction products increased relative to the starting material, reaching a maximum increase of 39% after 9 months reaction, though this later fell to a 30% increase after 15 months reaction.…”

Section: Reaction Of Bvg With Young Cement Porefluid (Ynfp)mentioning

confidence: 99%

“…Longer-duration experiments would reveal if clays were a stable reaction product as the pH decreased (cf. Moyce et al, 2014).…”

Section: Reaction Of Bvg With Young Cement Porefluid (Ynfp)mentioning

confidence: 99%

“…Following the rejection of the Nirex Rock Characterisation Facility (RCF) planning application in March 1997 and the consequent cessation of the NSARP in the late 1990s, the remaining experiments were left unopened, but they were kept running. Some of these experiments have now been examined after 15 years of reaction and are the focus of a companion paper to the one presented here (Moyce et al, 2014). The remaining experiments are still running, and will be sampled and analysed over the coming years.…”

Section: Introductionmentioning

confidence: 99%

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A long-term experimental study of the reactivity of basement rock with highly alkaline cement waters: Reactions over the first 15 months

et al. 2016

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A series of long-term laboratory experiments was started in 1995 to investigate longer-term dissolution/precipitation reactions that may occur in the alkaline disturbed zone surrounding a cementitious repository for radioactive waste. They consist of samples of UK basement rock reacting with either Na-K-Ca-OH water ('young' cement porewater) or Ca-OH water ('evolved' cement porewater) at 70°C. This paper summarises results of reactions occurring over the first 15 months. Experiments of both fluid types showed many similar features, though primary mineral dissolution and secondary mineral precipitation were more extensive in the experiments involving Na-K-Ca (younger) cement porefluids compared to more evolved (Ca-rich) cement porefluids. Dissolution of dolomite, and to a lesser extent silicates (most probably K-feldspar, but possibly also mica) occurred relatively rapidly at 70 °C. Dolomite dissolution may have been a key factor in reducing pH values, and may be a key mineral in controlling the extent of alkaline disturbed zones. Dissolution was followed by precipitation of brucite close to dolomite grains, at least two generations of CSH phases

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Section: Reaction Of Bvg With Young Cement Porefluid (Ynfp)mentioning

confidence: 99%

“…Longer-duration experiments would reveal if clays were a stable reaction product as the pH decreased (cf. Moyce et al, 2014).…”

Section: Reaction Of Bvg With Young Cement Porefluid (Ynfp)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A long-term experimental study of the reactivity of basement rock with highly alkaline cement waters: Reactions over the first 15 months

et al. 2016

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“…Fe 2 O 3 nanoparticles have been selected as a model of Fe colloids, as previous work regarding long-term rock alteration under ADZ conditions showed no evidence of the reduction of hematite (Moyce et al, 2014). In all the experiments, the colloid concentrations were 0.5 wt.% and 0.2 wt.% for silica and Fe 2 O 3 , respectively.…”

Section: Stability Of Synthetic Colloidsmentioning

confidence: 99%

Inhibition of the formation and stability of inorganic colloids in the alkaline disturbed zone of a cementitious repository

2015

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The generation and stability of inorganic colloids have been studied under hyperalkaline conditions. For the generation of colloids, intact cores of Bromsgrove Sandstone were flushed with simulated cement leachates, and the eluates were ultrafiltered sequentially (12 µm, 1 µm, 0.1 µm and 30 kDa) for the separation of any colloids found. No colloid formation was observed during the experiments; however the analysis by ICP-MS of the eluates showed significant increases in Si and Al, indicating silicate mineral dissolution, as well as reduction of the concentration of Ca in the leachates indicating precipitation of secondary Ca-rich phases. Flow experiments with cement leachates spiked with tritiated water showed a noticeable reduction of the porosity of the sandstone as well as changes in the pore distribution. Additional stability experiments were carried out using model silica and Fe 2 O 3 colloids. The experiments indicated that the stability of the colloids was mainly controlled by the concentration of Ca in solution and that both types were unstable under the chemical conditions in the alkaline disturbed zone. The presence of cement additives such as superplasticisers could enhance the stability of the colloids.

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“…In the years that followed, alkaline alteration was evaluated for different materials comprising a wide range of commercial or natural clays and soils, as well as a combination of minerals, rocks and clay (Ramírez et al, 2002;Savage et al, 2002;Gaucher et al, 2004;Ramírez et al, 2005;Fernández et al, 2006;Savage et al, 2007;Yamaguchi et al, 2007;Rozalén et al, 2008;Fernández et al, 2009;Rozalen et al, 2009;Honty et al, 2010;Moyce et al, 2014). These studies demonstrated that the nature and extension of the modifications caused by the interactions of the minerals with the alkaline solution depend on the chemical/mineralogical composition of the initial solid material, the composition of the alkaline solution, and the alteration conditions, including temperature, period of exposure, and size of the solid sample (Gaucher and Blanc, 2006).…”

Section: Introductionmentioning

confidence: 99%

Impact of an Alkaline Solution on the Chemistry, Mineralogy, and Sorption Properties of a Typic Rhodudult Soil

Calábria

Cota

Ladeira

2017

Rev. Bras. Ciênc. Solo

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Abstract:The preferred option for disposal of short-lived low and intermediate level radioactive wastes is a near surface disposal facility in which soil is one of the barriers that avoid radionuclide migration outside the controlled area. For construction of that kind of facility, concrete is widely used, and its interaction with water induces its degradation, resulting in a high pH solution. The alkaline solution may affect the near-field environment of radioactive waste repositories, including the soil, promoting mineralogical alterations that result in significant changes in key properties of materials, compromising their performance as safety components. In this study, a sample of a Brazilian Typic Rhodudult soil, previously investigated concerning its performance for Cs sorption, was subjected to interaction with the alkaline solution for 24 h and for 7, 14, and 28 days in order to evaluate the impact on its chemical, mineralogical, and sorption properties. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), atomic absorption spectrometry (AAS), scanning electron microscopy (SEM), and electron microprobe analysis were performed before and after each alteration period. Results indicated dissolution of minerals, such as kaolinite and quartz, associated with incorporation of K and Ca from the alkaline solution, likely resulting in the formation of hydrated calcium silicate phases (CSH), which are expected to be worse sorbents for alkaline elements (e.g., Cs) than the original minerals. The Kd values for Cs in the altered samples also decreased according to the alteration period, demonstrating that alkaline interaction effectively modifies the soil sorption properties for Cs.

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Rock alteration in alkaline cement waters over 15 years and its relevance to the geological disposal of nuclear waste

Cited by 45 publications

References 45 publications

A long-term experimental study of the reactivity of basement rock with highly alkaline cement waters: Reactions over the first 15 months

A long-term experimental study of the reactivity of basement rock with highly alkaline cement waters: Reactions over the first 15 months

Inhibition of the formation and stability of inorganic colloids in the alkaline disturbed zone of a cementitious repository

Impact of an Alkaline Solution on the Chemistry, Mineralogy, and Sorption Properties of a Typic Rhodudult Soil

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