ABM Project meeting 2012
The upcoming TR-11-06 report:
Content and mayor findings
Some thoughts about the continuation
Daniel Svensson
Content – The experiment
-The included clay materials and their origin
-The experimental configuration
-The test site
-Excavation procedure and sampling
Content - Hydromechanical tests
-Water content and density
-Swelling pressure and hydraulic conductivity
-Unconfined compression tests
Content – Chemical and mineralogical analysis - Reference materials
-Cation exchange capacity (CEC)
-Anion analysis
-Reductive dissolution extraction (CBD)
-Chemical data and evolved gas analysis
-Powder X-ray diffraction (XRD)
bulk and clay fractions
Content – Chemical and mineralogical analysis – Package 1
-Focus on MX-80, Asha, DepCAN and Calcigel
-Cation exchange capacity (CEC)
-Anion analysis
-Exchangable cations (EC)
-Chemical composition of bulk samples
-Powder X-ray diffraction (XRD) - bulk samples
Content – Microbiology - Reference materials
-Quantification of microbes by culturing
-Microscopy
-Identification of microbes
DNA extraction
Cloning and sequencing
- Special emphasis was put on aerobic heterotrophs and anaerobic sulphate
and iron reducers and autotrophic acetogens
Content – Microbiology – Parcel 1
Asha 505, Deponit CA-N and MX-80, were analysed with
focus on:
-Cultivable heterotrophic aerobic bacteria
-Heterotrophic sulphate-reducing bacteria
-Autotrophic sulphate-reducing bacteria
-Iron-reducing bacteria
Mayor findings – Hydromechanical I
The hydro-mechanical standard tests (water content, free
swelling, liquid limit and grain density) showed the large
diversity of the materials.
The liquid limit varies between 68 % (Friedland) up to 545 %
(MX-80).
There was also a clear difference between the different
materials regarding the grain density. Eight of the tested
materials had a grain density between 2678 and 2753 kg/m3
while three of the materials (Asha, Rokle and Friedland) had
a grain density between 2828 and 2940 kg/m3
Mayor findings – Hydromechanical II
Hydraulic conductivity, m/s
Hydraulic conductivity and
swelling pressures were
determined on MX-80, Asha
505 and Deponit CAN. No
change was identified.
MX-80 ref.
MX-80 ref (8mm)
MX-80 #2, inner
MX-80 #2, outer
MX-80 #2, inner trimmed (8mm)
MX-80 #2, inner crushed (8mm)
1.E-12
1.E-13
1.E-14
1200
1300
1400
1500
1600
1700
1800
Dry density kg/m3
Deponit CAN
1.E-11
Deponit CAN ref
Deponit CAN #15, inner
Hydraulic conductivity, m/s
At excavation the degree of
saturation was very close to
100% in all samples.
MX-80
1.E-11
Deponit CAN #15, outer
Deponit CAN #27, inner
1.E-12
Deponit CAN #27, outer
1.E-13
1.E-14
1100
1200
1300
1400
Dry density kg/m3
1500
1600
1700
Mayor findings – Hydromechanical III
A significant decrease in swelling pressure was seen on
Asha 505 and Deponit CAN. The largest deviation was
noticed on samples from the innermost part.
One possible explanation is the cation exchange process in
the clays.
Deponit CAN
Asha 505
1.E+04
Swelling pressure, kPa
Swelling pressure, kPa
1.E+04
1.E+03
Deponit CAN ref
Deponit CAN #15, inner
1.E+02
Deponit CAN #15, outer
1.E+03
Asha 505 ref
Asha 505 #14, inner
1.E+02
Asha 505 #14, outer
Asha 505 #24, inner
Deponit CAN #27, inner
Asha 505 #24, middle
Deponit CAN #27, outer
Asha 505 #24, outer
1.E+01
1100
1.E+01
1200
1300
1400
Dry density kg/m3
1500
1600
1700
1100
1200
1300
1400
Dry density kg/m3
1500
1600
1700
Mayor findings – Hydromechanical IV
Mechanical properties were determined by unconfined
compression tests on MX-80, Asha and Deponit CAN.
Reduced strain was observed on re-saturated specimens of
all three materials from the field experiment. Regarding
maximum deviator stress and compared to reference
material no large deviations was seen on specimens of
MX-80 and Deponit CAN while a decreased maximum
deviator stress was seen on Asha specimens and especially
on specimens taken from the innermost position.
Unconfined compression tests were also run on air-dried,
ground, re-compacted and re-saturated material of MX-80,
Asha and Deponit CAN from the field experiment. Those
tests showed strain of the same size or larger than observed
on the reference specimens while the maximum deviator
stress was of the same size.
Mayor findings – Chemistry and mineralogy - reference clays I
Most clays had a rather high CEC values
which is typical for bentonites. Friedland and
Callovo-Oxfordian was much lower in CEC which is
compatible with their different mineralogy.
The water extractable amount of sulphate and
chloride was not negligible. Ikosorb, Friedland and
Asha 505 had 0.2-0.3 wt% chloride. MX-80,
IbecoSeal, Deponit CA-N and Friedland had 0.3-0.5
wt% sulphate, the most likely source is gypsum
which is a water soluble hydrated calcium sulphate.
Fluoride and bromide are very low in all cases.
CBD-extracts showed elevated amounts of Mn in
Rokle indicate possible presence of undetected Mnphase. Rather high Si in Calcigel and Rokle
(compared to Kunigel that is low but high in quartz)
possibly indicates the presence of amorphous silica.
Mayor findings – Chemistry and mineralogy - reference clays II
The chemical data and evolved gas analysis confirmed the variety in the
clays regarding e.g. iron content. Kunigel with only 1.9 wt% Fe2O3 can be
compared to Asha 505 and Rokle with 12.2 and 13.7 wt% respectively.
Organic carbon was low in most cases, but higher in Callovo-Oxfordian (0.7)
and Friedland (0.5) wt%. The total sulfur content was very low (<0.2 wt %) in
Rokle, Ikosorb, Febex, Calcigel, Asha 505, low (< 0.5 wt %) in MX80,
Ibecoseal and Kunigel, and higher in Friedland (0.53) and Callovo-oxfordian
(0.68).
X-ray diffraction was used to show the variability in the crystalline phases of
the clays. Most clays were found to be dominated by dioctahedral smectites.
Mayor findings – Chemistry and mineralogy - reference clays III
Close up of the 060 region
Mayor findings – Chemistry and mineralogy - Parcel 1 - I
The distribution of chloride indicated that the wetting with groundwater
resulted in laterally and vertically smoothed and almost constant
concentrations.
The sulfate distribution displayed no consistent pattern, but some blocks had
a sulfate maximum at the heater, along with depletion in the peripheral parts,
indicating a lateral transfer of sulfate.
The test conditions also resulted in significant changes in the exchangeable
cation pool. Whereas lateral gradients within the blocks were insignificant, a
vertical gradient in the relative cation distribution had developed, dividing the
package into an upper, Ca-dominated, and a lower, Na-dominated part.
Mayor findings – Chemistry and mineralogy - Parcel 1 - II
The distribution of acid soluble carbon indicated carbonate dissolution close
to the heater in the carbonate-bearing bentonites.
The iron content had increased in several of the blocks
All four blocks examined displayed a deficit in magnesium in the peripheral
parts and a more or less distinct gradient towards to the heater.
The XRD-data for random powders provided no evidence of any significant
change of the smectite structure in any of the four blocks examined.
Supplementary analyses of clay fractions are, however, necessary for more
detailed evaluations.
.
Mayor findings – Chemistry and mineralogy - Parcel 1 - III
A tendency of increasing CEC towards the heater can be seen in particular in
calcigel (5) and Deponit CAN (27). Dissolution of carbonates in the samples
proximal to the heater was noted and could be one reason.
On the other hand, the incorporation of corrosion products of iron in the
bentonite would be expected to lower the CEC of samples closest to the Fetube due to the dilution effect. Alternatively it is also possible that corrosion
products may add to the CEC or reduction of smectite iron.
Block 2 MX-80
Block 5 Calcigel
Block 27 Dep CAN
70
88
86
84
82
87
68
CEC (meq/100g)
CEC (meq/100 g)
CEC (meq/100g)
90
66
64
62
0
2
4
6
8
Distance from Fe-tube (cm)
10
83
81
79
77
60
80
85
0
2
4
6
8
Distance from Fe-tube (cm)
10
0
2
4
6
8
Distance from Fe-tube (cm)
10
Mayor findings – Microbiology – Reference materials - I
A drastic difference in microbial abundance between the materials was
observed; Kunigel V1 was close to sterile while Friedland and Ibeco Seal M-90
contained high numbers of all microbes examined.
It was found that 200 – 84000 /g aerobic microbes were present in ten of the
eleven dry materials, while Kunigel V1 lacked detectable aerobic
microorganisms.
Iron reducers were detected in all examined materials, ranging from 10 (in
Kunigel V1) to 8000/g (in Ibeco Seal M-90).
Autotrophic acetogens was detected in the range of 20 – 60/g in the Febex,
Friedland and Ibeco Seal materials, and below 10/g in the other materials
examined.
Mayor findings – Microbiology – Reference materials - II
Sulphate reducers were detected in the range of 10 – 90/g in Asha 505,
Calcigel, Deponit CA-N, Febex, Friedland and Ibeco Seal M-90, and was below
10 g-1 in the other materials.
The dominant part of sulphate reducers and acetogens in the materials thrived
in the thermophilic temperature range and grew faster at 50°C than at 20°C.
A correlation between produced acetate and sulphide was observed, suggesting
that acetogenesis boosted the sulphate-reducing populations in the clay mineral
systems.
The studies showed that dry clay is a very potent media for long term survival of
both aerobic, anaerobic and thermophilic microbes and as it seems from
phylogenetic studies, not spore-formers only.
Mayor findings – Microbiology – Parcel 1
It was found that mesophilic aerobic bacteria were present in the range of 102 –
103 g-1wet weight (gww-1) in Asha 505, Deponit CA-N and MX-80.
All other bacteria were below detection in the materials.
Thus, the results showed that bacteria with potential corrosive or buffer
degradation properties were present in the raw materials, however failed to
survive after the high swelling pressure and temperatures of the experiment.
Some ideas about the continuation:
-Further evaluation of collected XRD bulk data
-Develop custom designed Siroquant diffraction profiles from observed
data on pure smectite fractions to provide good input to quantitative phase
analysis
Further evaluation of the clay fractions by:
-Evaluating the ethylene glycol samples by the Reynolds & Moore
method using Newmod
-Special pretreatment of samples with kaolinite and/or chlorite
to reduce uncertainties
-Evaluation of pre-saturation of bulk clay with divalent cations for
quantitative XRD and/or use of internal standard
-Search for new methods to further characterize the iron-bentonite zone
and to locate the iron-phase (s)
Availability
The 1st proof has been constructed.
A list of corrections is beeing assembled.
Probably printed and ready after the summer (?)
Acknowledgement:
We want to thank
Dietrich Koch
For all information about the clays and their origin.
And also for making a study visit to the clay mines in Landshut possible.
Stephan Kaufhold and Reiner Dohrmann
For reviewing the report and hence increasing its quality and readability.
And thank you all for your time!