OR/14/048 Implications for repository performance - Revision history

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	Many of the experiments showed decreases in dissolved Cl<sup>-</sup>, not just those pressurised with CO<sub>2</sub>. The NRVB cement appeared to be immobilising Cl<sup>-</sup>, especially at lower temperatures (in this study 20°C) where Cl<sup>-</sup> uptake was especially favoured. Smaller, but still significant, amounts of additional Cl<sup>-</sup> were taken up in equivalent experiments pressurised with CO<sub>2</sub>. The additional stability provided by the presence of CO<sub>2</sub> possibly suggests that it may exist as part of a solid- solution series with Cl- and CO<sub>3</sub>-endmembers.		Many of the experiments showed decreases in dissolved Cl<sup>-</sup>, not just those pressurised with CO<sub>2</sub>. The NRVB cement appeared to be immobilising Cl<sup>-</sup>, especially at lower temperatures (in this study 20°C) where Cl<sup>-</sup> uptake was especially favoured. Smaller, but still significant, amounts of additional Cl<sup>-</sup> were taken up in equivalent experiments pressurised with CO<sub>2</sub>. The additional stability provided by the presence of CO<sub>2</sub> possibly suggests that it may exist as part of a solid- solution series with Cl- and CO<sub>3</sub>-endmembers.

	Detailed mineralogical observations in the region around carbonation fronts revealed the presence of small amounts of two fine-grained, Cl-rich solid phases. One was a gel-like Cl-rich CSH, the other was only found in the 20°C experiments and occurred as fine-grained radial fibrous crystal aggregates of a calcium chloroaluminate phase, probably hydrocalumite (Ca<sub>4</sub>Al<sub>2</sub>O<sub>6</sub>Cl<sub>2</sub>.10H<sub>2</sub>O) (Rochelle ''et al.'', 2013<ref name="Rochelle 2013">~~ROCHELLE, C A, PURSER, G, MILODOWSKI, A E, NOY, D J, WAGNER, D, BUTCHER, A, and HARRINGTON, J F. 2013. CO<sub>2</sub>~~		Detailed mineralogical observations in the region around carbonation fronts revealed the presence of small amounts of two fine-grained, Cl-rich solid phases. One was a gel-like Cl-rich CSH, the other was only found in the 20°C experiments and occurred as fine-grained radial fibrous crystal aggregates of a calcium chloroaluminate phase, probably hydrocalumite (Ca<sub>4</sub>Al<sub>2</sub>O<sub>6</sub>Cl<sub>2</sub>.10H<sub>2</sub>O) (Rochelle ''et al.'', 2013<ref name="Rochelle 2013"></ref>; Milodowski ''et al.'', 2013<ref name="Milodowski 2013">MILODOWSKI, A E, ROCHELLE, C A, and PURSER, G. 2013. Uptake and retardation of Cl during cement carbonation. ''Procedia Earth and Planetary Science'', 7, 594–597.</ref>) (Figure 16).
	~~migration and reaction in cementitious repositories: A summary of work conducted as part of the FORGE project. ''British Geological Survey Open Report'', OR/13/004, 30pp.~~</ref>; Milodowski ''et al.'', 2013<ref name="Milodowski 2013">MILODOWSKI, A E, ROCHELLE, C A, and PURSER, G. 2013. Uptake and retardation of Cl during cement carbonation. ''Procedia Earth and Planetary Science'', 7, 594–597.</ref>) (Figure 16).

	[[Image:14048fig16.jpg\|thumb\|center\|380px\| '''Figure 16''' BSEM photomicrograph of radial fibrous secondary calcium chloroaluminate phase. This formed within altered cement just behind the leading edge of the carbonation front. ]]		[[Image:14048fig16.jpg\|thumb\|center\|380px\| '''Figure 16''' BSEM photomicrograph of radial fibrous secondary calcium chloroaluminate phase. This formed within altered cement just behind the leading edge of the carbonation front. ]]
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	The apparent likely occurrence of Cl-rich phases within cementitious repositories, raises the question of whether performance assessment calculations could include them (many current approaches assume conservative, i.e. non-reacting, behaviour of Cl<sup>-</sup>). Inclusion of such phases would likely retard the overall predicted migration of <sup>36</sup>Cl, lowering eventual releases to the biosphere, and hence improving safety calculations. Equally, they may allow for higher initial loadings of <sup>36</sup>Cl in the waste. It would be useful to investigate these Cl-rich phases further.		The apparent likely occurrence of Cl-rich phases within cementitious repositories, raises the question of whether performance assessment calculations could include them (many current approaches assume conservative, i.e. non-reacting, behaviour of Cl<sup>-</sup>). Inclusion of such phases would likely retard the overall predicted migration of <sup>36</sup>Cl, lowering eventual releases to the biosphere, and hence improving safety calculations. Equally, they may allow for higher initial loadings of <sup>36</sup>Cl in the waste. It would be useful to investigate these Cl-rich phases further.

	Carbonation features and secondary phases observed in these experiments using a relatively porous/permeable cement, bear many similarities to those found in far lower porosity/permeability borehole cements used in CO<sub>2</sub>-storage operations (e.g. Rochelle and Milodowski, 2013<ref name="Rochelle 2013">~~ROCHELLE, C A, and MILODOWSKI, A E. 2013. Carbonation of borehole seals: comparing evidence from short-term lab experiments and long-term natural analogues. ''Applied Geochemistry'', 30, 161–177.~~</ref>). There are also similarities to samples of naturally-occurring CSH phases which have been naturally-carbonated over prolonged timescales (Milodowski ''et al.'', 1989<ref name="Milodowski 1989">		Carbonation features and secondary phases observed in these experiments using a relatively porous/permeable cement, bear many similarities to those found in far lower porosity/permeability borehole cements used in CO<sub>2</sub>-storage operations (e.g. Rochelle and Milodowski, 2013<ref name="Rochelle 2013"></ref>). There are also similarities to samples of naturally-occurring CSH phases which have been naturally-carbonated over prolonged timescales (Milodowski ''et al.'', 1989<ref name="Milodowski 1989">

	MILODOWSKI, A E, NANCARROW, P H A, and SPIRO, B. 1989. A mineralogical and stable isotope study of natural analogues of Ordinary Portland Cement (OPC) and Cao-SiO2-H2O (CSH) compounds. United Kingdom Nirex Safety Studies Report, NSS/R240.		MILODOWSKI, A E, NANCARROW, P H A, and SPIRO, B. 1989. A mineralogical and stable isotope study of natural analogues of Ordinary Portland Cement (OPC) and Cao-SiO2-H2O (CSH) compounds. United Kingdom Nirex Safety Studies Report, NSS/R240.

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	# As some wastes contain <sup>14</sup>C, it provides a mechanism for released <sup>14</sup>CO<sub>2</sub> to be immobilised in secondary carbonate minerals.		# As some wastes contain <sup>14</sup>C, it provides a mechanism for released <sup>14</sup>CO<sub>2</sub> to be immobilised in secondary carbonate minerals.

	One less expected observation concerning solute migration was the enhanced localised uptake of dissolved chloride (Cl<sup>-</sup>) by the cement. <sup>36</sup>Cl presents particular issues within repositories, due to its long half-life, ease of uptake into biological systems, and relative mobility in many settings. Uptake of Cl<sup>-</sup> was most clearly revealed by significant decreases in dissolved Cl<sup>-</sup> in the experiments using more ‘evolved’ porewater compositions (i.e. porewaters reflecting interaction between saline groundwater and the cement) ([[Media:~~OR14048fig13~~.jpg\|''see'' Figure 13]]).		One less expected observation concerning solute migration was the enhanced localised uptake of dissolved chloride (Cl<sup>-</sup>) by the cement. <sup>36</sup>Cl presents particular issues within repositories, due to its long half-life, ease of uptake into biological systems, and relative mobility in many settings. Uptake of Cl<sup>-</sup> was most clearly revealed by significant decreases in dissolved Cl<sup>-</sup> in the experiments using more ‘evolved’ porewater compositions (i.e. porewaters reflecting interaction between saline groundwater and the cement) ([[Media:14048fig13.jpg\|''see'' Figure 13]]).

	Many of the experiments showed decreases in dissolved Cl<sup>-</sup>, not just those pressurised with CO<sub>2</sub>. The NRVB cement appeared to be immobilising Cl<sup>-</sup>, especially at lower temperatures (in this study 20°C) where Cl<sup>-</sup> uptake was especially favoured. Smaller, but still significant, amounts of additional Cl<sup>-</sup> were taken up in equivalent experiments pressurised with CO<sub>2</sub>. The additional stability provided by the presence of CO<sub>2</sub> possibly suggests that it may exist as part of a solid- solution series with Cl- and CO<sub>3</sub>-endmembers.		Many of the experiments showed decreases in dissolved Cl<sup>-</sup>, not just those pressurised with CO<sub>2</sub>. The NRVB cement appeared to be immobilising Cl<sup>-</sup>, especially at lower temperatures (in this study 20°C) where Cl<sup>-</sup> uptake was especially favoured. Smaller, but still significant, amounts of additional Cl<sup>-</sup> were taken up in equivalent experiments pressurised with CO<sub>2</sub>. The additional stability provided by the presence of CO<sub>2</sub> possibly suggests that it may exist as part of a solid- solution series with Cl- and CO<sub>3</sub>-endmembers.
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	migration and reaction in cementitious repositories: A summary of work conducted as part of the FORGE project. ''British Geological Survey Open Report'', OR/13/004, 30pp.</ref>; Milodowski ''et al.'', 2013<ref name="Milodowski 2013">MILODOWSKI, A E, ROCHELLE, C A, and PURSER, G. 2013. Uptake and retardation of Cl during cement carbonation. ''Procedia Earth and Planetary Science'', 7, 594–597.</ref>) (Figure 16).		migration and reaction in cementitious repositories: A summary of work conducted as part of the FORGE project. ''British Geological Survey Open Report'', OR/13/004, 30pp.</ref>; Milodowski ''et al.'', 2013<ref name="Milodowski 2013">MILODOWSKI, A E, ROCHELLE, C A, and PURSER, G. 2013. Uptake and retardation of Cl during cement carbonation. ''Procedia Earth and Planetary Science'', 7, 594–597.</ref>) (Figure 16).

	[[Image:~~OR14048fig16~~.jpg\|thumb\|center\|380px\| '''Figure 16''' BSEM photomicrograph of radial fibrous secondary calcium chloroaluminate phase. This formed within altered cement just behind the leading edge of the carbonation front. ]]		[[Image:14048fig16.jpg\|thumb\|center\|380px\| '''Figure 16''' BSEM photomicrograph of radial fibrous secondary calcium chloroaluminate phase. This formed within altered cement just behind the leading edge of the carbonation front. ]]

	Element mapping clearly showed that these Cl-rich phases were found on the largely unreacted cement-side of the reaction front (Figure 17). It would appear that they are only stable under higher pH conditions (i.e. where CSH phases were still present). It is thought that they have progressively broken down as the carbonation reactions progressively consume the CSH around them. The released Cl<sup>-</sup> then diffused towards the remaining CSH and re-precipitated. This dissolution/precipitation process would continue until all of the CSH is reacted (in the case of a limited quantity of cement), at which point the Cl<sup>-</sup> would be released back into solution.		Element mapping clearly showed that these Cl-rich phases were found on the largely unreacted cement-side of the reaction front (Figure 17). It would appear that they are only stable under higher pH conditions (i.e. where CSH phases were still present). It is thought that they have progressively broken down as the carbonation reactions progressively consume the CSH around them. The released Cl<sup>-</sup> then diffused towards the remaining CSH and re-precipitated. This dissolution/precipitation process would continue until all of the CSH is reacted (in the case of a limited quantity of cement), at which point the Cl<sup>-</sup> would be released back into solution.

	[[Image:~~OR14048fig17~~.jpg\|thumb\|center\|500px\| '''Figure 17''' High resolution images of a cement carbonation front. Note the abundance of Cl on the partly-carbonated side of the reaction front, and its near absence in the fully-carbonated cement. ]]		[[Image:14048fig17.jpg\|thumb\|center\|500px\| '''Figure 17''' High resolution images of a cement carbonation front. Note the abundance of Cl on the partly-carbonated side of the reaction front, and its near absence in the fully-carbonated cement. ]]

	The uptake of Cl<sup>-</sup> in CO<sub>2</sub>-free cement systems concurs with observations undertaken as part of previous experimental buffer/backfill cement studies (Glasser ''et al.'', 1998<ref name="Glasser 1998">		The uptake of Cl<sup>-</sup> in CO<sub>2</sub>-free cement systems concurs with observations undertaken as part of previous experimental buffer/backfill cement studies (Glasser ''et al.'', 1998<ref name="Glasser 1998">

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__NOTOC__
{{OR/14/048}}
Information in the proceeding sections allowed identification and quantification of processes occurring during cement carbonation, and this will help inform predictive modelling of repository evolution. The buffer/backfill cement appears to have coped with carbonation well, generally remaining intact, with samples showing no evidence of overall shrinkage or swelling.

Carbonation was identifiable by a colour change of the cement samples (dark grey to light brown), and this progressed from the outside of the samples towards their centres. Carbonation was rapid, especially early in the experiments, with some samples showing at least partial carbonation through to the centres of the samples (12.5 mm minimum travel distance) within 40 days. Most of the carbonation observed was relatively uniform on greater than mm scales. However, a small number of (mainly diffusion) samples showed some evidence for carbonation along specific zones. This may have been aided in certain cases by heterogeneities within the samples. These appear to have been caused by segregation of cement grains during casting/setting. The coarser layers had their pore space filled with Ca(OH)2 and this was more susceptible to carbonation than the finer-grained CSH phases. Similar features could form in a repository setting, and could provide preferential routes for CO2 migration if they occurred on a large scale. Such cement heterogeneity could be minimised through the use of organic additives (superplasticisers) to enhance cement flow behaviour. However, Francis ''et al. ''(1997)<ref name="Francis 1997">FRANCIS, A J, CATHER, R, and CROSSLAND, I G. 1997. Development of the Nirex reference vault backfill; report on current status in 1994. ''Nirex Science Report'' S/97/014, United Kingdon Nirex Limited, 57p.</ref> and Young ''et al.'', (2013)<ref name="Young 2013">YOUNG, A J, WARWICK, P, MILODOWSKI, A E, and READ, D. 2013. Behaviour of radionuclides in the presence of superplasticiser. Advances in Cement Research, 25, 32–43 [DOI: 10.1680/adcr.12.00032].</ref> note that the presence of such organics may enhance the mobility of some radionuclides. Without them however, some degree of grain segregation and hetergoenious carbonation may be a feature within a repository. It will be important therefore, to consider carefully the pros and cons of adding additives to repository buffer/backfill cement.

In terms of bulk samples, carbonation was not associated with a sample volume change that meant that overall NRVB density increased. In detail however, this density change was not uniform. At microscopic scales carbonation resulted in a patchwork of low-density domains composed mainly of silica gel enclosed by higher density zones of secondary carbonate. The low-density domains had higher porosity, and the higher density zones had lower porosity. These higher density zones may have formed as the carbonation front moved through the sample, with initial local microcracking that was subsequently infilled by carbonate precipitation. Potentially, the many thin ‘walls’ of carbonate precipitate might reduce sample permeability (see Purser ''et al.'', 2013<ref name="Purser 2013">PURSER, G, MILODOWSKI, A E, HARRINGTON, J F, ROCHELLE, C A, BUTCHER, A, and Wagner, D. 2013. Modification to the flow properties of repository cement as a result of carbonation. ''Procedia Earth and Planetary Science'', 7, 701–704.</ref>; Rochelle ''et al.'', 2013<ref name="Rochelle 2013">ROCHELLE, C A, and MILODOWSKI, A E. 2013. Carbonation of borehole seals: comparing evidence from short-term lab experiments and long-term natural analogues. Applied Geochemistry, 30, 161–177.

</ref>). Reductions in permeability could be beneficial in terms of containment, as they would act to limit radionuclide migration. At a somewhat larger (millimetric) scale, there was some evidence that unconfined samples could develop stress cracking in the partly-carbonated cement close to the carbonation reaction fronts, though these features were very localised and could be filled by secondary carbonates as the reaction fronts moved through the sample. It is possible however, that there might be a dynamic zone of increased permeability that moves just ahead of the main carbonation front.

Carbonation resulted in a reaction zone several mm wide, within which were several reaction fronts delineating 4 main reaction zones. These were:

::Zone 1: Unreacted cement
::Zone 2: Partially carbonated cement
::Zone 3: Fully carbonated cement
::Zone 4: Leached cement (where slightly acidic CO2-rich water had re-dissolved some of the secondary carbonate)

The visually most apparent reaction front occurred between Zones 2 and 3. Note that Zone 4 probably formed relatively early in the experiment when waters surrounding the NRVB samples were not fully saturated with carbonate minerals, and as such may not occur in a repository setting. It is apparent however, that multiple reaction zones are likely to form within a repository setting as a consequence of carbonation.

Carbonation resulted in the degradation of the high pH buffering capacity of the NRVB cement. Given that many metallic radionuclides have low solubility under alkaline conditions, but increased solubility as pH decreases, carbonation may potentially lead to increased metal corrosion rates and consequent increased potential for radionuclide migration. That said, if as seems likely, the repository contained an excess of cement that was more than sufficient to react with all the produced CO2, overall pH buffering to alkaline conditions could still be effective for many parts of the repository. Whilst we did not measure the porewater pH in the fronts directly, their presence can be determined by the abrupt nature of the reactions fronts and removal of portlandite and CSH phases due to the migration of lower pH conditions associated with the CO2.

In the experiments carbonation and uptake of CO2 increased the weight of the cement by up to 8.5%. This has two potential benefits:

# Reduction in potential for pressure increases due to gas production due to consumption of CO2.
# As some wastes contain 14C, it provides a mechanism for released 14CO2 to be immobilised in secondary carbonate minerals.

One less expected observation concerning solute migration was the enhanced localised uptake of dissolved chloride (Cl-) by the cement. 36Cl presents particular issues within repositories, due to its long half-life, ease of uptake into biological systems, and relative mobility in many settings. Uptake of Cl- was most clearly revealed by significant decreases in dissolved Cl- in the experiments using more ‘evolved’ porewater compositions (i.e. porewaters reflecting interaction between saline groundwater and the cement) ([[Media:OR14048fig13.jpg|''see'' Figure 13]]).

Many of the experiments showed decreases in dissolved Cl-, not just those pressurised with CO2. The NRVB cement appeared to be immobilising Cl-, especially at lower temperatures (in this study 20°C) where Cl- uptake was especially favoured. Smaller, but still significant, amounts of additional Cl- were taken up in equivalent experiments pressurised with CO2. The additional stability provided by the presence of CO2 possibly suggests that it may exist as part of a solid- solution series with Cl- and CO3-endmembers.

Detailed mineralogical observations in the region around carbonation fronts revealed the presence of small amounts of two fine-grained, Cl-rich solid phases. One was a gel-like Cl-rich CSH, the other was only found in the 20°C experiments and occurred as fine-grained radial fibrous crystal aggregates of a calcium chloroaluminate phase, probably hydrocalumite (Ca4Al2O6Cl2.10H2O) (Rochelle ''et al.'', 2013<ref name="Rochelle 2013">ROCHELLE, C A, PURSER, G, MILODOWSKI, A E, NOY, D J, WAGNER, D, BUTCHER, A, and HARRINGTON, J F. 2013. CO2
migration and reaction in cementitious repositories: A summary of work conducted as part of the FORGE project. ''British Geological Survey Open Report'', OR/13/004, 30pp.</ref>; Milodowski ''et al.'', 2013<ref name="Milodowski 2013">MILODOWSKI, A E, ROCHELLE, C A, and PURSER, G. 2013. Uptake and retardation of Cl during cement carbonation. ''Procedia Earth and Planetary Science'', 7, 594–597.</ref>) (Figure 16).

[[Image:OR14048fig16.jpg|thumb|center|380px| '''Figure 16''' BSEM photomicrograph of radial fibrous secondary calcium chloroaluminate phase. This formed within altered cement just behind the leading edge of the carbonation front. ]]

Element mapping clearly showed that these Cl-rich phases were found on the largely unreacted cement-side of the reaction front (Figure 17). It would appear that they are only stable under higher pH conditions (i.e. where CSH phases were still present). It is thought that they have progressively broken down as the carbonation reactions progressively consume the CSH around them. The released Cl- then diffused towards the remaining CSH and re-precipitated. This dissolution/precipitation process would continue until all of the CSH is reacted (in the case of a limited quantity of cement), at which point the Cl- would be released back into solution.

[[Image:OR14048fig17.jpg|thumb|center|500px| '''Figure 17''' High resolution images of a cement carbonation front. Note the abundance of Cl on the partly-carbonated side of the reaction front, and its near absence in the fully-carbonated cement. ]]

The uptake of Cl- in CO2-free cement systems concurs with observations undertaken as part of previous experimental buffer/backfill cement studies (Glasser ''et al.'', 1998<ref name="Glasser 1998">

GLASSER, F P, TYRER, M, QUILLIN, K, ROSS, D, PEDERSEN, J, GOLDTHORPE, K, BENNETT, D, and ATKINS, M. 1998. The

chemistry of blended cements and backfills intended for use in radioactive waste disposal. United Kingdom Environment Agency R&D Technical Report P98, ISBN: 1857 05 157 2, 332pp.

</ref>). Cl- uptake in CO2-rich systems has also been previously noted as part of borehole stability studies for the deep underground storage of CO2. Rochelle ''et al. ''(2006<ref name="Rochelle 2006">ROCHELLE, C A, BATEMAN, K, MILODOWSKI, A E, KEMP, S J, and BIRCHALL, D. 2006. Geochemical interactions between CO2

and seals above the Utsira Formation: An experimental study. ''British Geological Survey Commissioned Report'', CR/06/069. 86 pp.</ref>, 2009<ref name="Rochelle 2009">

ROCHELLE, C A, MILODOWSKI, A E, LACINSKA, A, RICHARDSON, C, SHAW, R, TAYLOR, H, WAGNER, D, BATEMAN, K, LÉCOLIER, E, FERRER, N, LAMY, F, JACQUEMET, N, SHI, JI-Q, DURUCAN, S, and SYED, A.S. 2009. JRAP-14: Reactions between

CO2 and borehole infrastructure, report on laboratory experiments and modelling. CO2GeoNet project report for the European Commission, deliverable JRAP-14/3, 138p.

</ref>) found increased Cl- uptake in CO2-rich experiments compared to CO2-free experiments, and Carey ''et al. ''(2007)<ref name="Carey 2007">

CAREY, J W, WIGAND, M, CHIPERA, S J, WOLDEGABRIEL, G, PAWAR, R, LICHTNER, P C, WEHNER, S C, RAINES, M A, and

GUTHRIE, J. 2007. Analysis and performance of oil well cement with 30 years of CO2 exposure from the SACROC Unit, West Texas, USA. International Journal of Greenhouse Gas Control, 1, 75–85.

</ref> report a Cl-rich secondary phase in recovered samples of borehole cement that had been exposed to CO2-rich fluids for 30 years.

The apparent likely occurrence of Cl-rich phases within cementitious repositories, raises the question of whether performance assessment calculations could include them (many current approaches assume conservative, i.e. non-reacting, behaviour of Cl-). Inclusion of such phases would likely retard the overall predicted migration of 36Cl, lowering eventual releases to the biosphere, and hence improving safety calculations. Equally, they may allow for higher initial loadings of 36Cl in the waste. It would be useful to investigate these Cl-rich phases further.

Carbonation features and secondary phases observed in these experiments using a relatively porous/permeable cement, bear many similarities to those found in far lower porosity/permeability borehole cements used in CO2-storage operations (e.g. Rochelle and Milodowski, 2013<ref name="Rochelle 2013">ROCHELLE, C A, and MILODOWSKI, A E. 2013. Carbonation of borehole seals: comparing evidence from short-term lab experiments and long-term natural analogues. ''Applied Geochemistry'', 30, 161–177.</ref>). There are also similarities to samples of naturally-occurring CSH phases which have been naturally-carbonated over prolonged timescales (Milodowski ''et al.'', 1989<ref name="Milodowski 1989">

MILODOWSKI, A E, NANCARROW, P H A, and SPIRO, B. 1989. A mineralogical and stable isotope study of natural analogues of Ordinary Portland Cement (OPC) and Cao-SiO2-H2O (CSH) compounds. United Kingdom Nirex Safety Studies Report, NSS/R240.

</ref>, 2009<ref name="Milodowski 2009">MILODOWSKI, A E, LACINSKA, A, and WAGNER, D. 2009. JRAP-14: Reactions between CO2 and borehole infrastructure. Deliverable JRAP-14/2: A natural analogue study of CO2-cement interaction: Carbonate alteration of calcium silicate hydrate-bearing rocks from Northern Ireland. European Commission FP6 Project Number SES6-CT-2004-502816, Network of Excellence on Geological Storage of CO2 (CO2GeoNet), 28pp.</ref>, 2011<ref name="Milodowski 2011">MILODOWSKI, A E, ROCHELLE, C A, LACINSKA, A, and WAGNER, D. 2011. A natural analogue study of CO2-cement interaction: Carbonation of calcium silicate hydrate-bearing rocks from Northern Ireland. ''Energy Procedia'', 4, 5235–5242.</ref>). A number of common carbonation processes may be operating in all these systems, and consideration of all these sources of information is needed to help provide an overall picture of cement carbonation over a range of temporal and spatial scales.
==References==
<References/>
[[Category: OR/14/048 Results of laboratory carbonation experiments on Nirex Reference Vault Backfill cement | 11]]