self-healing concepts for building materials · microencapsulated bacterial spores. cement and...
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Magnel Laboratory for Concrete Research – Department of Structural Engineering
Self-healing concepts for building
materials
1
Nele De Belie
Magnel Laboratory for Concrete Research
Cracking in concrete poses several problems……
Magnel Laboratory for Concrete Research
Bridges, locks, wharfs, piers, tunnels, …
Cracking in concrete poses several problems……
Infrastructure!
Magnel Laboratory for Concrete Research
NBN EN 1992-1-1 (2010): the allowable crack width in
reinforced concrete depends on the environmental class:
300-400 µm
Our results: 10 μm is the critical crack width
Cracking accelerates chloride penetration
Crack width ≤ 10 µm Crack width > 10 µm
Magnel Laboratory for Concrete Research
Cracking in concrete poses several problems……
Magnel Laboratory for Concrete Research
Self-healing concrete may help to solve
the crack-related durability problem
Inspired by nature:
- not designed to withstand everything
- in case of failure :
‣ rapid & autonomous detection
‣ ‘massive’ & efficient action
‣ “after” as strong as “before”
‣ ‘inexhaustable’
‣ cheap
Magnel Laboratory for Concrete Research
Autogenous self-healing
Autogenous healing © N. ter Heide
Magnel Laboratory for Concrete Research
Stimulated autogenous healing: hydrogels
Hydrogel swelling Sealing of the crack
de-swelling Binder hydration, CaCO3
precipitation and healing
& PBM
Magnel Laboratory for Concrete Research
SAPs induce macropores that reduce strength
9
macropore
SAP
micropores
Stimulated autogenous healing: hydrogels
Magnel Laboratory for Concrete Research
But… the macropores increase freeze-thaw resistance
10
w/c=0.5
w/c=0.45
SAP+add (0.45 + 0.05)
SAP (0.45)
AEA (0.45)0
2
4
6
8
10
0 14 28 42 56
Scaled material [kg/m²]
# cycles
with 3% NaCl solution
Amount of scaled material ↓ when using SAPs
(Data of D. Snoeck / RRT in RILEM TC-SAP, confirming work by Jensen and Lautsen)
(Laustsen, S., “Engineered Air-Entrainment of Concrete,” PhD thesis, Lyngby)
Stimulated autogenous healing: hydrogels
Magnel Laboratory for Concrete Research
Autonomous healing by bacteria
& LabMET
High
pH
No
water
Shear
force
Narrowing
pores
Biogenic CaCO3
fills the cracks
Magnel Laboratory for Concrete Research
+
Carrier materials
Wang, J., Van Tittelboom, K., De Belie, N.,
Verstraete, W. (2012). Construction and building
materials, 26, 532–540.
& LabMET
Autonomous healing by bacteria
Magnel Laboratory for Concrete Research 13
Distinct properties:
1) Flexible in wet state and brittle in dry state
2) Impermeable
Bacteria in microcapsules
WANG, J., SOENS, H., VERSTRAETE, W., DE BELIE, N. Self-healing concrete by use of
microencapsulated bacterial spores. Cement and concrete. research, 56, 139-152.
0d 3 weeks
1mm
Crack healing:
500 μm up to
1 mm
Autonomous healing by bacteria (SECEMIN)
Magnel Laboratory for Concrete Research 14
Bacterial spores
0
10
20
30
40
50
60
70
80
90
100
Heali
ng r
ati
o (
%)
R
N
H
HYU
HYUC
HSYU
HSYUC
0-50 50-100 100-150 150-200 200-250 250-300 300-350 350-400 400-700Initial crack width ranges (μm)
0d 7d 14d
Crack width 0.5mm
almost healed
within 7dHydrogel
remains
CaCO3
precipitation
Crack healing ratio in the
bacterial series was much
higher compared with R series:
(50% ~ 100%) / (1% ~ 7%)
Bacteria in SAPs (SECEMIN)
Magnel Laboratory for Concrete Research
Denitrifying ACDC produces
nitrite that inhibits corrosion
ERŞAN, Y.C., VERBRUGGE, H., DE GRAEVE, I., VERSTRAETE, W., DE BELIE, N., BOON, N.
(2016). CaCO3 precipitating bacteria survive in mortar and inhibit steel corrosion. Cement and
concrete research, 83, 19-30.
(ISHECO)
Neg control a1
Autonomous healing by bacteria
Magnel Laboratory for Concrete Research
Nutrients
tank
(10 L)
CH4 Air
Mass
flow
controllers
120 ml/min
for 1min
every 6 hours
Mixing point
Qin=0.2 m3 h-1
Filter bed (x 2 units):
Hbed=0.90 m
Vbed=2.6 l
EBRT= 48 s
E.C.=429.2 gCH4-C d-1m-3
Exit
flow controller
Recirculation
[CH4]in = 960 ppmv I.L.= 1854 gCH4-C d-1 m-3
MBF-B
MBF-A
atmosphere
Bacteria for consolidation and methane removal
(SECEMIN, G. Ganendra)
Magnel Laboratory for Concrete Research
Self-healing concrete based on encapsulated
elastic polymers as healing agents
& PBM
Crack formation
Autonomous release
healing agent
First reloading
Additional release
healing agent
repair
Second reloading
UNCR
REF
MAN-PU
SHC-PU
Crack healed
with semi-rigid
polymer
Healed crack after
reloading
(SECEMIN, A. Araujo, J. Feitera, E. Gruyaert)
Magnel Laboratory for Concrete Research 18
SHEcon: self-healing in sandwich panels
(with Naessens
construct & Recticel)
Magnel Laboratory for Concrete Research 19
Acoustic
Emission
AE Tomography
Optical Microscopy
Ultrasound Pulse
Velocity
Digital Image Correlation
-0,04 0,04εyy - % 0 2εxx - %
2500 wave speed (m/s) 4500
0 2εxx - %
4-point bending on concrete beam
Repeatable cracking & repair
3-point bending on pre-cracked concrete beam
Sealing & local mechanical repair
TDCB polymer
Stick-slip abnormal damage
The capsule breakages are located
into the fracture process zone
of the concrete beam under bending
The wave velocity is restored at the
autonomously healed cracks.
PZT piezoelectric
transducer is embedded into
concrete during casting.
P-wave velocity & damage
index to assess healing.
Experimental assessment of fracture & autonomous healing of concrete & polymer systems
Tsangouri E., Aggelis G. D., Van Hemelrijck D.
Vrije Universiteit Brussel - Dept. Mechanics of Materials & Constructions (MeMC)
Magnel Laboratory for Concrete Research
Reconstructed µCT image (UGCT)
Modelling of self-healing (MMS, UGent)
...or even the capsules
may detach prematurely,
weakening the overall
structure
Cracks may ignore the
presence of capsules…
Magnel Laboratory for Concrete Research
Autonomous crack healing: results (M. Maes)
Chloride diffusion for concrete with healed crack is in
between open crack and virgin concrete
Magnel Laboratory for Concrete Research
Effect of self-healing on service life
0,00
0,10
0,20
0,30
0,40
0,50
0 50 100 150
Pro
b.
of
fail
ure
Pf
[ -]
Time [years]
Pf = 0.1 CR - 0.3 mmREF PU - 0.3 mm (Min.)PU - 0.3 mm (Max.) PU - 0.3 mm (Mean)