OR/14/048 Starting materials - Revision history

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	\|+ Table 1 Target compositions and recipes of the ‘young’ near-field porewater (YNFP), ‘young’ near-field porewater plus additional chloride (YNFP+Cl), and the ‘evolved’ near-field groundwater (ENFG) used in the experiments		\|+ Table 1 Target compositions and recipes of the ‘young’ near-field porewater (YNFP), ‘young’ near-field porewater plus additional chloride (YNFP+Cl), and the ‘evolved’ near-field groundwater (ENFG) used in the experiments

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	\|+ Table 1 Target compositions and recipes of the ‘young’ near-field porewater (YNFP), ‘young’ near-field porewater plus additional chloride (YNFP+Cl), and the ‘evolved’ near-field groundwater (ENFG) used in the experiments		\|+ Table 1 Target compositions and recipes of the ‘young’ near-field porewater (YNFP), ‘young’ near-field porewater plus additional chloride (YNFP+Cl), and the ‘evolved’ near-field groundwater (ENFG) used in the experiments

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	These were thoroughly mixed together over several minutes in a portable mixer to form fine slurry (Figure 1). A sufficient quantity (approximately 50 kg) of cement slurry was prepared in a single batch to provide an excess of material for use in the FORGE project. The cement was then poured into several plastic moulds and allowed to set (Figure 2). As the cement was prepared as a single batch, all the resulting cylinders of cement should have identical composition.		These were thoroughly mixed together over several minutes in a portable mixer to form fine slurry (Figure 1). A sufficient quantity (approximately 50 kg) of cement slurry was prepared in a single batch to provide an excess of material for use in the FORGE project. The cement was then poured into several plastic moulds and allowed to set (Figure 2). As the cement was prepared as a single batch, all the resulting cylinders of cement should have identical composition.

	[[Image:~~OR14048fig1~~.jpg\|thumb\|center\|350px\| '''Figure 1''' Adding the cement components to a portable cement mixer. ]]		[[Image:14048fig1.jpg\|thumb\|center\|350px\| '''Figure 1''' Adding the cement components to a portable cement mixer. ]]

	[[Image:~~OR14048fig2~~.jpg\|thumb\|center\|350px\| '''Figure 2''' Pouring the cement slurry into plastic moulds. ]]		[[Image:14048fig2.jpg\|thumb\|center\|350px\| '''Figure 2''' Pouring the cement slurry into plastic moulds. ]]

	Once in the moulds the cement was left to set at 40°C for 24 hours. The plastic moulds were then removed, and the cylinders of cement cured for 40 days immersed in water saturated with Ca(OH)<sub>2</sub> at 40°C and 1 bar pressure. The presence of the Ca(OH)<sub>2</sub> was to minimise the potential for the outer parts of the cement to dissolve in the water. Being immersed in water also allowed pores within the cement to be fully saturated, and also to uptake extra water as remaining high temperature clinker phases slowly hydrated. After curing, the cement was stored in Ca(OH)<sub>2</sub>-saturated water in a sealed container at room temperature (20°C) and 1 bar.		Once in the moulds the cement was left to set at 40°C for 24 hours. The plastic moulds were then removed, and the cylinders of cement cured for 40 days immersed in water saturated with Ca(OH)<sub>2</sub> at 40°C and 1 bar pressure. The presence of the Ca(OH)<sub>2</sub> was to minimise the potential for the outer parts of the cement to dissolve in the water. Being immersed in water also allowed pores within the cement to be fully saturated, and also to uptake extra water as remaining high temperature clinker phases slowly hydrated. After curing, the cement was stored in Ca(OH)<sub>2</sub>-saturated water in a sealed container at room temperature (20°C) and 1 bar.

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Ajhil at 10:48, 4 February 2016

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New page

__NOTOC__
{{OR/14/048}}
The cement composition used is that of the ‘Nirex reference backfill cement’ (NRVB) (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>. This was chosen so that the results from the present study would be comparable with different measured parameters/datasets from earlier studies. It is acknowledged however, that the compositions of backfill cements used in any future repository may well be different to the composition used in this study, but it is thought that many of the mineralogical reactions we may observe are likely to be common to a wide-range of cements.

The composition of the starting cement is as follows:
* Portland Cement (‘Ordinary Portland cement’, from Hanson) = 450 kg/m3
* Limestone flour (‘Superlon 100’, from Longcliffe Ltd) = 495 kg/m3
* Lime (‘Hydralime’, from Lafarge) = 170 kg/m3
* Water (mains tap water) = 615 kg/m3

These were thoroughly mixed together over several minutes in a portable mixer to form fine slurry (Figure 1). A sufficient quantity (approximately 50 kg) of cement slurry was prepared in a single batch to provide an excess of material for use in the FORGE project. The cement was then poured into several plastic moulds and allowed to set (Figure 2). As the cement was prepared as a single batch, all the resulting cylinders of cement should have identical composition.

[[Image:OR14048fig1.jpg|thumb|center|350px| '''Figure 1''' Adding the cement components to a portable cement mixer. ]]

[[Image:OR14048fig2.jpg|thumb|center|350px| '''Figure 2''' Pouring the cement slurry into plastic moulds. ]]

Once in the moulds the cement was left to set at 40°C for 24 hours. The plastic moulds were then removed, and the cylinders of cement cured for 40 days immersed in water saturated with Ca(OH)2 at 40°C and 1 bar pressure. The presence of the Ca(OH)2 was to minimise the potential for the outer parts of the cement to dissolve in the water. Being immersed in water also allowed pores within the cement to be fully saturated, and also to uptake extra water as remaining high temperature clinker phases slowly hydrated. After curing, the cement was stored in Ca(OH)2-saturated water in a sealed container at room temperature (20°C) and 1 bar.

==Aqueous solutions==
The fluids used in the experiments were of three types:

# A synthetic, young near-field porewater (YNFP) representative of the initial Na/K/Ca-rich pore fluid composition.
# A slightly modified version of the above with chloride added (YNFP+Cl) to represent a fluid having a composition intermediate between (1) and (3).
# A synthetic evolved near-field groundwater (ENFG) representative of the later Ca-rich pore fluid that will exist once local groundwater starts to perculate through the cement backfill.

The fluids used in this study were based on those reported in Francis ''et al. ''(1997)<ref name="Francis 1997"></ref>. They are representative of those anticipated in the vicinity of a cementitious waste repository, and are broadly similar to those used in previous experimental studies Rochelle ''et al.,'' 1994<ref name="Rochelle 1994">ROCHELLE, C A, BATEMAN, K, COOMBS, P, PEARCE, J M, and WETTON, P D. 1994. The evaluation of chemical mass transfer in the disturbed zone of a deep geological disposal facility for radioactive wastes. IX. Further reactions involving discs of Borrowdale Volcanic Group lithologies with synthetic evolved near-field groundwater. ''British Geological Survey Technical Report'' WE/94/44, 30p.</ref>, 1997<ref name="Rochelle 1997">ROCHELLE, C A, PEARCE, J M, BATEMAN, K, COOMBS, P, and WETTON, P D. 1997. The evaluation of chemical mass transfer in the disturbed zone of a deep geological disposal facility for radioactive wastes. X. Interaction between synthetic cement porefluids and BVG: Observations from experiments of 4, 9 and 15 months duration. ''British Geological Survey Technical Report'', WE/97/16C, 79p.</ref>, 1998a<ref name="Rochelle 1998a">ROCHELLE, C A, BATEMAN, K, COOMBS, P, PEARCE, J M, and WETTON, P D. 1998. The evaluation of chemical mass transfer in the disturbed zone of a deep geological disposal facility for radioactive wastes. VIII. Further reactions involving powdered Borrowdale Volcanic Group lithologies with synthetic evolved near-field groundwater. Nirex Report NSS/R393, 33p.</ref>, b<ref name="Rochelle 1998b">ROCHELLE, C A, BATEMAN, K, MACGREGOR, R, PEARCE, J M, PRIOR, S V, SAVAGE, D, and WETTON, P D. 1998. The evaluation of chemical mass transfer in the disturbed zone of a deep geological disposal facility for radioactive wastes. VI. The hydrothermal aging of discs of bulk rock and near-fracture Borrowdale Volcanic Group lithologies with a synthetic evolved near-field groundwater. Nirex Report NSS/R390, 34p, 1998.</ref>, c<ref name="Rochelle 1998c">ROCHELLE, C A, BATEMAN, K, MACGREGOR, R, PEARCE, J M, SAVAGE, D, and WETTON, P D. 1998. The evaluation of chemical mass transfer in the disturbed zone of a deep geological disposal facility for radioactive wastes. V. Reaction of powdered Borrowdale Volcanic Group lithologies with synthetic evolved near-field groundwater. ''Nirex Report'' NSS/R382, 24p.</ref> which in turn used compositions based upon previous modelling studies (Bond ''et al.'', 1995a<ref name="Bond 1995a">

BOND, K A, MORETON, A D, and TWEED, C J. 1995. Water compositions of relevance to a deep cementitious-based repository at Sellafield: Evaluation using thermodynamic modelling, ''Nirex Report'' NSS/R310, 25p.

</ref>, b<ref name="Bond 1995b">BOND, K A, and TWEED, C J. (1995). Groundwater compositions for the Borrowdale Volcanic Group, Boreholes 2, 4 and RCF3, Sellafield, evaluated using thermodynamic modelling, ''Nirex Report'' NSS/R397, 34p.</ref>) (see Table 1 for composition, and Appendix 1 for fluid chemical analytical results).

==Gases==
Two gases were used in the experiments: carbon dioxide (CO2) and nitrogen (N2).

''CO2'' 
The CO2 used in this study was sourced from high purity (99.99%) liquid CO2 (Air Products, 4.5 Grade). This liquid CO2 was obtained in a cylinder fitted with a dip tube and pressurised with 2000 psi (approximately 14 MPa) of helium. However, the actual experimental pressure was controlled by an ISCO syringe pump, which has its pressure transducer periodically ‘zeroed’ to minimise drift. As the liquid CO2 at room temperature was piped to the experiments in the incubator, the increase in temperature caused it to become a lower density (supercritical) phase. Recorded pressures were taken from the ISCO pump controller readout.

''N2'' 
The N2 used in this study was obtained from BOC Gases and classified as ‘oxygen free’ (99.998% pure). It was delivered in a cylinder pressurised to 230 bar (23 MPa). However, the actual experimental pressure was controlled by an ISCO syringe pump, which has its pressure transducer periodically ‘zeroed’ to minimise drift. Recorded pressures were taken from the ISCO pump controller readout.

<center>
{| class="wikitable"
|+ Table 1 Target compositions and recipes of the ‘young’ near-field porewater (YNFP), ‘young’ near-field porewater plus additional chloride (YNFP+Cl), and the ‘evolved’ near-field groundwater (ENFG) used in the experiments

| ! scope="col" style="width: 150px;" | '''Chemical component'''
| ! scope="col" style="width: 175px;" | '''YNFP (mol l-1)'''
| ! scope="col" style="width: 200px;" | '''YNFP+Cl (mol l-1)'''
| ! scope="col" style="width: 175px;" | '''ENFG (mol l-1)'''
|-
| pH
| c.13 (at room temperature)
| c.12.5 (at room temperature)
| 12.4 (at room temperature)
|-
| Na
| 7.1 x 10-2
| 7.1 x 10-2
| 3.9 x 10-1
|-
| K
| 9.3 x 10-2
| 9.3 x 10-2
| 3.9 x 10-3
|-
| Ca
| 3.6 x 10-3
| 3.6 x 10-3
| 5.2 x 10-2
|-
| Sr
|
|
| 3.0 x 10-4
|-
| Cl
|
| 1.64 x 10-1
| 4.3 x 10-1
|-
| Br
|
|
| 3.2 x 10-4
|-
| SO42-
|
|
| 1.1 x 10-2
|-
| SiO2
| 8.0 x 10-4
| 8.0 x 10-4
| 2.6 x 10-5
|}
</center>

<center>
{| class="wikitable"
| ! scope="col" style="width: 150px;" | '''Chemical component''' 
| ! scope="col" style="width: 175px;" | '''YNFP (grammes added per 2 litres of distilled de-ionised water)'''
| ! scope="col" style="width: 200px;" | '''YNFP+Cl (grammes added per 2 litres of distilled de-ionised water)'''
| ! scope="col" style="width: 175px;" | '''ENFG (grammes added per 2 litres of distilled de-ionised water)'''
|-
| CaO
| 0.3366
| 0.3366
| -
|-
| CaCl2.2H2O
| -
|
| 22.7739
|-
| NaOH
| 5.6249
|
| 3.7147
|-
| NaCl
| -
| 8.2988
| 37.5767
|-
| KOH
| 10.4344
|
|
|-
| KCl
| -
| 13.8660
| 0.5341
|-
| SrCl2.6H2O
| -
|
| 0.1602
|-
| SiO2
| † 96.125
| † 96.1738
| † 3.2019
|-
| Na2SO4
| -
|
| 3.1246
|-
| KBr
| -
|
| 0.0762
|}
†  g BDH 1000 mg l-1 standard SiO2 solution added.
</center>

==References==
<References/>
[[Category: OR/14/048 Results of laboratory carbonation experiments on Nirex Reference Vault Backfill cement | 05]]