characterisation, improvements and long term evaluation of cementitious waste products
DESCRIPTION
CHARACTERISATION, IMPROVEMENTS AND LONG TERM EVALUATION OF CEMENTITIOUS WASTE PRODUCTS – AN INDIAN SCENARIO. by R.G. Yeotikar*, R.R. Rakesh, Biplob Paul, T.P. Valsala, Ajay Shirole and Dilip Kumar Chaudhari Bhabha Atomic Research Centre, INDIA *E mail- [email protected]. - PowerPoint PPT PresentationTRANSCRIPT
CHARACTERISATION, IMPROVEMENTS AND LONG TERM EVALUATION
OF CEMENTITIOUS WASTE PRODUCTS – AN INDIAN SCENARIO
byR.G. Yeotikar*, R.R. Rakesh, Biplob Paul,
T.P. Valsala, Ajay Shirole and Dilip Kumar Chaudhari
Bhabha Atomic Research Centre,INDIA
*E mail- [email protected]
2
Layout of presentation
• Aims and objectives of CRP
• Works planning in details & future works to be carried out for CRP
• Practices followed for cementation
• Some of the results of cementation work
• Expected result / outcome of CRP
3
Aim & objectives of CRP-1
• Preparation of cement waste products (CWP) on laboratory and plant scale with different cement formulation from :
• Sluges from treatment of LLW• Intermediate level liquid waste• Ion exchange resins• Miscellaneous wastes
• Improvement of CWP
4
• Cement Waste Products (CWPs) for • Chemical durability• Compressive strength• Homogeneity• Micro structure• Biological interaction
• Back fill material
• Site specific material / parameter
• Engineering barriers
Aim & objectives of CRP-2 Long term evaluation
5
• Study of cementation and hardening of CWP in presence of
• Various wastes • Different cement compositions • Role of additives during cementation
Aim & objectives of CRP-3
6
Work planning
• Development of CWP having better leaching characteristics and which can have more activity loading.
• Preparation of CWP• Laboratory scale• Plant scale
• Characterization of CWP• Laboratory • Field
• Evaluation of backfill material
7
Preparation of CWP on Lab. Scale
Variable• Waste, cement and admixtures• Waste to cement ratio • Admixture to cement ratio• Water / waste to cement ratio
Method• Preparation of number of blocks for each variable at a
time• Casting in moulds • Curing : 28 days • Leaching for 6 to 12 months as per ANSI 16.1 in DM
Water• Leachant vol. /block vol.= 10
8
• CWP on 20 liter scale
• CWP on 200 liter scale
• Taking the sample of CWP during in-situ cementation
• Core drilling of few samples from in-situ cementation
Preparation of CWP on Plant Scale
9
TYPES OF CEMENTS
• Ordinary Portland cement (opc) • ASTM type 1. OPC
• Slag based cement (SBC)
• Fly ash cement
• High alumina cement
• Blended cements
OPC clinker + gypsum + admixtures
- ground together
Component Weight % in
OPC TYPE I
SLAG BASED
CEMENT
BLENDED CEMENT
SiO2 20-24 34.10 27.8
Al2O3 3-8 14.15 13.3
CaO 60-65 36.04 47.6
MgO 0-2 11.21 5.2
Fe2O3 3-8 0.56 2.3
SO3 1-4 1.20 1.2
Sulphide - 0.22 -
General composition of the different cements
11
ADMIXTURES• Inorganic admixtures
– Backfill material– Bentonite– Vermiculite– Silica fumes– Precipitated silica
– Clay – Rock powder
• Organic admixtures- water reducing chemicals such as – Platilcisers– Super plasticisers
12
Characterization of CWP
• Leaching characterization• Mechanical properties
• Compressive strength
• Homogeneity • XRD analysis• Pore size distribution• Microscopy –optical & SEM
• Others • Hydraulic conductivity• Accelerated diffusion test
• Instrumental methods
13
Instrumental methods of characterisation of CWPS
Aim • To correlate the compressive strength, porosity, diffusion coefficient, permeability and leaching characteristics with respect to composition
• To shortlist CWP for leaching test
• To track the mineralogical changes with time after simulated disposal in NSDF
• To identify mechanisms of hardening, strength development/ deterioration etc.
14
Field test characterization • Disposal of CWPs in earth trench in NSDF• Removal of CWPs periodically (once in two
years) and examination for :– Surface for cracks, chip off, color change etc.– Rebound hammer test – Homogeneity – Compressive strength– Hydraulic conductivity – Porosity – Mineralogical changes– Chloride penetration– Depth of carbonation – Change in diffusion coefficient
15
Long term Leaching characterization of CWP
• Laboratory scale CWP blocks in DM water
• Leaching of 200 lit CWP block
• Dynamic leaching of CWP
• Simulation of radiolysis of water - leaching
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400 LITRE STEEL CONTAINER
200 LITRE CWP
LEACHANT 200 L;ITRES
WITH AND WITHOUT DECAYING WOO
LIFTING HOOKS
LID
SUPPORTS
LONG TERM LEACH TEST OF 200 LITRE CWP
PROPOSED SET UP
collector
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• At one such location – Trombay
• Simulated CWPs of different sizes have been disposed in 2001.
• The location is having sandy silt with appreciable content of montmorillonite clay
• Similar experiments have been planned in other locations having different strata such as black cotton soil and sandy soil.
Field test characterization-disposal CWP in NSDF
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Field test characterization-disposal CWP in NSDF
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20
20 litre blocks
0.2 litre blocks
basalt
degraded basalt
Clay
21
Characterization of CWPs after excavation
• Compressive strength,• MIP, XRD, SEM, • Analysis of soil adhering to CWP • Rebound hammer tests• Ultrasonic tests
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Depth (m) Type of soil/rock
0 - 2.0 Black cotton plastic soil
2.0 - 10.0 Weathered basalt
below 10.0 Hard igneous basalt
Geological Succession of the area
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A typical geological section of the RSMS area
Ref. : Rakesh, R. R., Yadav, D. N., Narayan, P. K. and Nair, R. N. (2005). – “Post Closure Safety Assessment of Radioactive Waste Storage and Management Site, Trombay”, BARC library report. BARC/2005/I/010.
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Parameters Values
Bulk density (g/cc) 1.7
Porosity (%) 30.0
Radionuclides Kd (ml/g)
137Cs 600 – 1000
90Sr 140 – 300
PHYSICAL AND GEO-CHEMICAL PROPERTIES OF THE SITE
The representative physical properties such as density and porosity has been presented in Table 1.
The distribution coefficient values of soil samples obtained from RSMS site[2] were analysed and are presented in Table 2.
Table 2: Distribution coefficient of the soil
Table 1: Physical Properties of the soil
Ref: Rakesh, R. R., Yadav, D. N., Narayan, P. K. and Nair, R. N. (2005). – “Post Closure Safety Assessment of Radioactive Waste Storage and Management Site, Trombay”, BARC library report. BARC/2005/I/010.
25
Property Soil sample
T1(at 1 m depth)
T2(at 2 m depth)
(g/cc) 1.60 1.88
w (%) 26.6 29.0
d (g/cc) 1.26 1.46
G 2.82 2.70
e 1.24 0.85
Sr (%) 60.5 92.1
Particle size distribution characteristics:
Coarse sand (4.75-2.0 mm.) 15 23
Medium sand (2.0-0.420 mm.) 29 25
Fine sand (0.420-0.074 mm.) 17 15
Silt size (0.074-0.002mm.) 21 16
Clay size (<0.002mm.) 18 21
Consistency limits:
L.L. (%) 41 49
P.L. (%) 17 35
P.I. (%) 24 14
S.L. (%) 30 26
Specific surface area (m2/g) 41 52
Soil classification SM SC
Ref: Rakesh R.R. 2005. Simulation of radioactive contaminant transport in unsaturated soils, Ph. D. Thesis. Dept. of Civil Engineering, Indian Institute of Technology, Bombay, India.
Properties of soil of RSMS, Trombay
26
LONG TERM EVALUATION OF CWPs- Non-Destructive Test (NDT) Procedures
•Ultrasonic Tests• Ultrasonic pulse velocity can be used to determine homogeneity, presence of voids, cracks of CWP • Basic data correlating ultra sonic pulse velocity with density,
porosity and strength will be generated by preparing and testing number of blocks.
•Rebound Hammer Test• Simple and quick method of obtaining correlation between compressive strength and rebound number • The force and pulse duration are critical parameters & will be used on various CWPs of 20 and 200 litre CWPs as quality control measure
•Will be used for disposed CWPs after their removal
27
Evaluation of admixture and clay
• Distribution coefficient
• Composition
• Physical properties,
• Chemical properties
TYPICAL SPECIFICATIONS OF VERMICULITE AND BENTONITE
Item Vermiculite Bentonite
Size -30 + 70 Mesh 90 % should pass through 200 mesh
True density (gm/cc) 2.6 – 2.7 2.4 – 2.6
Cation Exchange Capacity (meq/100gm)
40-50 70-100
Chemical Composition
SiO2 (%) 35-40 45-55
Al2O3 (%) 10-12 15-20
Fe2O3 (%) 6-8 3-6
MgO (%) 20-25 3-4
Na2O (%) --- 1-2
H2O (%) 10-15 10-15
Swelling (%) 20-50 100-250
Porosity (%) 50-60 40-60
Evaluations of admixtures for their sorption characteristics
Mineral Kd (ml/g) in Synthetic Granitic water
137Cs 85+89Sr
Bentonite 1460 665
Apatite 117 215
Calcite 111 237
Galena 7.6 420
Red mud 141 320
Pyrite 82 185
Vermiculite 4250 365
30
Evaluation of bentonite for particle size distribution
Majority of particles are in the range of 100- 500 microns
31
Evaluation of bentonite for swelling behavior
Bentonite
Type
Equilibrating media
Initial
Volume
(ml)
Final
Volume
(ml)
Swelling
%
Sodium Tap
water
10 30 200
Sodium Dist.Water 10 35 250
Calcium Tap
water
10 30 200
Calcium Dist.Water 10 38 280
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• Swelling is complete in 8-10hrs.• The swelling is of the order of 200-280 %.• The swelling is more in distilled water than in
service water : due to replacement of Ca ions from bentonite in the distilled by water molecule
• The swelling is more in case of calcium bentonite than sodium bentonite : Replcement of bigger Ca ions by water molecule
• Swelling gets enhanced due to exchange of Ca and Na ions with water molecule
Evaluation of bentonite for swelling behavior
33
Evaluation of bentonite for thermal stability
•The heat treated and un-heat treated bentonites in the range 300-500 oC show comparable swelling.
•In DTA run there are two major endo peaks at 100 and 450oC corresponding to free and bound water loss.
34
Evaluation of bentonite for water equilibration
Shaking time, hrs
pH Conductivity, microS/cm
Hardness as CaCO3 ppm
Sodium, ppm
Chloride
ppm
Silica,
ppm
4.5 7.55 4562 837 NA 310 NA
10 7.47 5750 962 NA 350 NA
15.5 7.48 6325 1075 NA 250 NA
22 7.7 6525 1185 NA 225 NA
27 7.78 7050 1500 NA 385 NA
37 7.66 6100 1400 700 300 25
49 7.46 6400 1380 720 300 35
61 7.16 6300 1390 790 305 35
73 7.7 7000 1620 730 300 37
85.5 7.8 6500 1350 720 350 35
87.5 7.85 6400 1370 750 300 35
Water gets saturated very fast and thereafter no marked change
35
Evaluation of vermiculite for particle size distribution
About 90 % of the particle size distribution is in the range of -16 to +80 ASTM mesh.
36
Evaluation of vermiculite for Cs loading
There is structural change in the vermiculite due to Cs loading.
37
Evaluation of vermiculite for thermal stability
DTA runs of as such and heat treated vermiculite indicate that the vermiculite is thermally quite stable.
38
Micro organisms of interest for degradation Study on cement waste products
Micro organism Reactivity Effect on cement matrix
Nuclear waste matrix
Thiobacillus concretivorus, T. Thiooxidans and t. Ferrooxidan
Oxidation of sulphur compound to sulphuric acid
Calcium sulphate formation leads to increased volume and cracking
Cationic resin waste (R-SO3H)
incorporated into SBC
Pseudomonas cepacoa Heterotropic
Produce organic acid from decaying organic matter
Complex calcium in pore water
All CWPs disposed in NSDF in humid environment
Nitrosomonas and nitrobactor
Oxidise inorganic nitrogen compounds to nitric acid
Neutralise Ca(OH)2
in pore water
Anionic resin (R-CH2-N(CH3)3OH)
wastes incorporated in SBC
Bio-degradation of CWP
1. Identification of cement degrading bacteria in NSDF soils
2. Flow test on 60 ml size CWP &
3. Characterization of degraded CWP
39
Practices followed for Cementation of various types of Radioactive Waste in India
• Cementation is carried out at various locations for immobilization of – Sludge generated due to LLW treatment– Intermediate level wastes– Ion exchange resins– Miscellaneous wastes
• Techniques of Cementation at plant scale – In drum mixing – Conical Mixture Equipment and pouring the CWP in
200 lit drum.– In-situ cementation in 4000 lit capacity in CS tank in
RCC trenches.• Admixtures used - Vermiculite
40
In-situ Conditioning of ILW and Sludge of LLW in Cement Matrix at Tarapur
41
CONE MIXER ASSEMBLY USED FOR CEMENTATION
CURRENT CWPs FOR IMMOBILISATION OF NUCLEAR WASTES
WASTECEMENT TYPE WASTE TO
CEMENT RATIO
COMP. STRENGTH
( kg/cm2)
137Cs LEACH RATE
(g/cm2/d)
LLW SLUDGES/ ASHES/MOL. SIEVES
OPC 1.2 TO 10.4 TO 1
70 TO 100 Cs 10-4 Cs 10-6
HIGH Na ILW OPC/SBC BLENDED
1 ~ 1.2 TO 1 1.1 TO 1
45 TO 7095 TO 100
Cs 10-5
Cs 10-6
Na FORMATE ILW OPC/SBC 0.65 TO 1 95 TO 105 Cs- 10-5
IX RESINS* SBC 0.35 ~ 0.8 TO 1 50 TO 63 Cs- 10-4
IX RESIN PYROLYSIS RESIDUE*
OPC 0.6 TO 1 70 TO 75 Cs- 10-5
LUBRICATING OILS (ΑLPHA)
OPC 0.55 TO 1 30 TO 60 Cs- 10-5
α 10-7
TBP HYDROLYSIS PRODUCTS
OPC 0.6 TO 1 60 TO 70 β 10-6
α 10-7
ΑLPHA SLUDGES OPC 1.2 TO 1 50 TO 70 β 10-5
AVAILABLE FACILITIES
Cementation techniques Near surface disposal facility (NSDF)Radiological lab. Compressive strength testing unitAccelerated diffusion test unitXRD & XRF Optical microscope & SEM-EDXIon chromatograph & AASMercury intrusion porosity (MIP) unitPore water analysisFTIRImpedance spectroscopyGas chromatograph
44
Some of the results of cementation
• Evaluation of cement composition
• Optimization of waste to cement ratio
• Sampling of CWP during plant scale
• Evaluation of CWP from plant scale and comparison of result with laboratory
45
Block details OPC + 20 % Vermiculite
SBC Sample from conditioning tank
Core drilled sample from conditioning tank after 60 days
Cured for 14 days
Cured for 28 days
Leaching in DW
Leaching in GW
Waste to cement proportion 1:1.3 1:2 1:1.3 1:1.3 1:1.3 1:1.3
Diameter, cm 2.9 2.9 5.2 5.3 5.15 5.15
Height, cm 2.0 2.4 7.3 6.7 2.43 2.57
Surface area, cm2 31.20 35.06 156.75 155.7 80.93 83.2
Weight, g 24.1 28.99 264.0 257.0 80.0 83
Total βγ activity in the block, MBq
12.787 12.787 99.26 91.21 30.08 37.84
Contact dose rate, mSv/hr 1.0 1.0 2.82 3.0 1.0 1.1
Volume of block, cm3 13.2 15.8 154.95 147.74 50.59 53.5
Volume of leachant, cm3 315 350 1500 780 810 830
Compressive strength, kg/cm2 40-45 4.-45 20-25 35-40 35-40 35-40
Leach Rate, g/cm2/d x 10-5 1.25 2.01 1.9 0.94 1.25 1.0
Ref : A.S. Pente, U.S. Singh, C. P. Kaushik, R.G. Yeotikar, A. Mishra and S.S. Ali., “Cementation study of Intermediate Level radioactive liquid waste stored at Tarapur”, Proc.: Nuclear and Radiochemistry Symposium (NUCAR-2001), Department of Chemistry, University of Pune, Pune, India, Feb. 7-10, 2001, pp 540-541 .
Cement composition evaluation for immobilization of ILW*
* Specific activity of ILW : 1000 MBq/l
46
Properties of CWPs of immobilisation of various types of nuclear waste
WASTECEMENT TYPE WASTE TO
CEMENT RATIO
COMP. STRENGTH
( kg/cm2)
137Cs LEACH RATE
(g/cm2/d)
LLW SLUDGES/ ASHES/MOL. SIEVES
OPC 1.2 TO 10.4 TO 1
70 TO 100 Cs 10-4 Cs 10-6
HIGH Na ILW OPC/SBC BLENDED
1 ~ 1.2 TO 1 1.1 TO 1
45 TO 7095 TO 100
Cs 10-5
Cs 10-6
Na FORMATE ILW OPC/SBC 0.65 TO 1 95 TO 105 Cs- 10-5
IX RESINS* SBC 0.35 ~ 0.8 TO 1 50 TO 63 Cs- 10-4
IX RESIN PYROLYSIS RESIDUE*
OPC 0.6 TO 1 70 TO 75 Cs- 10-5
LUBRICATING OILS (ΑLPHA)
OPC 0.55 TO 1 30 TO 60 Cs- 10-5
α 10-7
TBP HYDROLYSIS PRODUCTS
OPC 0.6 TO 1 60 TO 70 β 10-6
α 10-7
ΑLPHA SLUDGES OPC 1.2 TO 1 50 TO 70 β 10-5
47
Cementation of IX resins
• Different Waste to cement ratio
• Properties of cement matrix• Homogeneity • Pore size distribution• Diffusion phenomenon• Leaching evaluation• Mineralogical examination
Mineral phases detected by XRD analyses of CWP using SBC incorporating IX resins
IX Resins Waste
Mineral phases detected
Cationic Calcium silicate hydrate, calcite, phosphate, silicate, sulphide
Anionic Calcium silicate hydrate, calcite, silicate,
Mixed Calcium silicate hydrate, calcite, phosphate, silicate,
PORE SIZE DISTRIBUTION OF CWP
ab
(a) IX RESINS IN SBC(b) ILW IN BLENDED CEMENT
1E-3 0.01 0.1 1 10 100
0
20
40
60
80
100
Per
cen
t T
ota
l
Pore Diameter (Micron)
Cationic Resin Aninic Resin Mixed Resins
1E-3 0.01 0.1 1 10
0
20
40
60
80
100
Blended Cement-ILW Matrix OPC-ILW Matrix
Per
cent
Tot
alPore Diameter (micron)
Void*
OPTICAL MICROSCOPY
CWPs incorporating IX resin
* FORMED DUE TO SHRINKING OF RESIN CAUSED BY LOSS OF WATER TO CEMENT HYDRATION
COMPARION OF 137CESIUM LEACHING WITH PHYSICAL CHARACTERISATION OF
CWPs INCORPORATING IX RESINS
IX Resins
137Cs Leach rate (g/cm2/d)
Diffusion Coeff. by 137Cs leaching (cm2/s)
Diffusion Coeff. by Ώ measure-ment (cm2/s)
Hydraulic condu-ctivity(cm/s)
Pore vol. by MIP (ml/g)
Comp. stren-gth(kg/cm2)
Mixed Resins
6.5x 10-4 5 x 10-9 3.12 x 10-8 3.21 X 10-9 0.20 56
K+ Resins
5 x 10-4 6 x 10-9 2.06 x 10-8 4.98 X 10-9 0.24 50
Borated Anionic Resins
3.6 x10-4 4 x 10-9 4.57 x 10-8 2.3 X 10-9 0.16 60
CHARACTARISATION OF FULL SIZE INACTIVE CWP INCORPORATING IX RESINS USING SBC
CORE DRILLED CWP
CORE SAMPLES
EXPECTED OUTCOME OF CRP WORK-1
• Development of improved cementitious waste products (CWP)
• Addition of admixtures• Modification of technique
• Complete characterisation of CWP• Understanding the mechanism of static and dynamic
leaching in presence of various components.• Finalisation of composition of cement for
immobilisation of various wastes e.g.• ILW• Sludge from treatment of LLW• Miscellaneous wastes• IX resins
54
EXPECTED OUTCOME OF CRP WORK-2
• Development of Instrumental techniques of characterisation of CWP
• Development and calibration of NDT Techniques for evaluation of CWP
• Ultrasonic tests• Rebound hammer tests
• Carry out field tests at different locations and co-relation of various results.
• Long term study of CWP with respects to following which can provide information for further improvement
• Bio degradation in various environment• Radiation stability
55
EXPECTED OUTCOME OF CRP WORK-3
• Understanding of behaviour of container material in presence of backfill and other geological material, e.g
• Soil • Ground water• Interaction with backfill, CWP and others
• Evaluation of various candidate container material• Evaluation of CWP source term for migration study• Understanding hardening and other physico-chemical
aspects of cementation which will be helpful for improvement
THANKS