modeling of hydration-lixiviation-mechanical coupling in ... · 27 October 2011. Plan ... (1:) 0 e...
Transcript of modeling of hydration-lixiviation-mechanical coupling in ... · 27 October 2011. Plan ... (1:) 0 e...
Modeling of leaching-mechanicalcoupling in concrete
Dawei Hu, Fan Zhang, Hui Zhou, Jianfu SHAO
27 October 2011
Plan
• Background and problem• Mchanical model• Leaching• Coupling model• Conclusions and perspectives
Where is the studied concrete?• Structures;• Seal material;• Stock cell of nulear waste B.
Representation of stock cell of nuclearwaste B [ANDRA]
Representation of closed tunnel [ANDRA]
Background
Which is the concrete subjected? • Thermal load;• Mechanical evolution;• Chimical degradation.
Problem
Implemented models in COMSOL for concrete Mechanical Leaching Leaching-mechanical coupling
mechanic leaching
temperature
( )( , , ) , 0p pp ij m mf d q p d Ks g h a g= + - =
( ) ( )0 01
( , )= 1p
pm m m pd d
b
ga g a a a
g
é ùê ú- + -ê úê ú+ë û
• Plastic characterization
Mechanical model1) Plastic damage modeling
1 2 13
RcRt Rc
23
Rt RcKRt Rc
: Uniaxial compression strengthRc
: Tension strengthRt
Criteron of Drucker-Prager
• Damage characterization
Mechanical model1) Plastic damage modeling
21 exp pm mcd d b
( ) 01 : eij m ijkl kld Cs eé ù= -ê úë û
• Effective modulus
ppij
ij
fd de l
s
¶=
¶
• Associated plasticity
Mechanical model1) Plastic damage modeling Plane stress module for plastic damage modeling
subdomain settings
Mechanical model1) Plastic damage modeling Plane stress module for plastic damage damage
scalar expressions
05
1015202530354045
0 0.005 0.01 0.015 0.02 0.025 0.03
axial stress (MPa)
axial stain
012345678
0 0.0002 0.0004 0.0006 0.0008 0.001
axial stress (MPa)
axial stain
Mechanical model1) Plastic damage simulation
Simulation of uniaxial compression and tension
0
0.2
0.4
0.6
0.8
1
0 0.002 0.004 0.006 0.008
axial stain
,pmd
0
0.2
0.4
0.6
0.8
1
0 0.0002 0.0004 0.0006 0.0008 0.001
axial stain
,pmd
Evolution of plastic hardening and softening function
Mechanical model1) Plastic damage simulation
1 0 1cpt mt mt m
Mechanical model2) Creep characterization
1 0 1cpc mc mt m
First creep Second creep
• Creep strainin compression
In tension
• Total strainElastic + Plastic + Creep
e p cpij ij ij ij
• Mass balance equation
2
2 22
solidCa Ca D Ca CatCa
Leaching model
Hydric source of calcium ion
Diffusion coefficient of calcium ion
• Diffusion coefficient with ammonium nitrate
2 2 23 2 eD Ca NO D Ca Ca
Acceleration parameter Diffusion coefficient of calcium ion
1) Leaching characterization
• Chemical damage
2+ 2+max 0
1 expc cd d Ca Ca
0
0
0
1
1
1
c
c c c
t t c
E E d
R R d
R R d
2) Leaching-plastic damage couplingLeaching model
• Chemical damage-mechanicalparameters
Test of micro indentation
2) Leaching-plastic damage simulationLeaching model
5 MPa
0 MPa
sound 18 months9 months
22 mol/m3
0 mol/m3
sound 9 months 18 months
2+Ca
Axial stress
Directe tension test after differentdegradation times (data after Camps 2008)
0
10
20
30
40
50
0 0.002 0.004 0.006 0.008
force (kN) CEM VF
displacement (mm)
sound
after 9 month leaching
after 18 month leaching
leaching surface
0
5
10
15
20
0 1 2 3 4 5
force (kN) CEM VF
flexility (mm)
sound
after 9 month leaching
after 18 month leaching
leaching surface
Flextion test after different degradation times (data after Camps 2008)
2) Leaching-plastic damage simulationLeaching model
1m e D mD d D d
1
1
1 compressive stress
1 tensive stress
cpc mc dc c
cpt mt dc c
mt d
mt d
1) Leaching-creep coupling characterizationCoupling Model
• Variation of diffusion coefficient with plastic damage
• Variation of creep strain rate with chemical damage
5×10-3
8×10-5
22mol/m3
0 mol/m3
0
500
1000
1500
2000
2500
0 100 200 300 400 500 600 700
strain (10-6)
time (days)
CEM VF
with leaching
soundleaching surface
2) Leaching-creep simulationCoupling Model
2+Ca
Axial
strain
Creep compression test with degradation(data after Camps 2008)
l
Concentration of calcium ion
Longitudinale strain
Ca2+
22 mol/m3
0 mol/m3
1×10-3
-2.5×10-3
2) Leaching-creep simulationCoupling Model
Creep flexion test with degradation (data after Camps 2008)
00.010.020.030.040.050.060.070.08
0 100 200 300 400 500 600 700
flexility (mm)
time (days)
CEM VF
with leaching
sound
leaching surface
Creep flexion test with degradation(data after Camps 2008)
2) Leaching-creep simulationCoupling Model
Conclusions and perspectives
Conclusions• Elastoplastic damage model and creep model can
describe the mechanical behavior of concrete inshort and long term.
• The coupling of mechanical and leaching candescribe the mechanical behavior subjected tochimic degadation in long term .
Perspectives• Temperature-leaching-mechanical coupling