Polymer-based and bacteria-based self-healing concrete
Prof. Dr. Ir. Nele De Belie
DEPARTMENT OF STRUCTURAL ENGINEERINGMAGNEL LABORATORY FOR CONCRETE RESEARCH
OUTLINE
• Introduction
• Polymer based self-healing concrete
• Bacteria based self-healing concrete
• Conclusions
Bridges, locks, wharfs, piers, tunnels, …
CRACKING IN CONCRETE POSES SEVERAL PROBLEMS
CRACKING IN CONCRETE POSES SEVERAL PROBLEMS
Cl-
Cl-
Cl-
Cl-Cl-
Chloride resistance of uncracked concrete
If concrete cover is big enough, not much problems
Chlorides diffusing in concrete
concrete rebarexposure solution
Chloride resistance of cracked concrete
Cl-
Cl-Cl-
Cl-
Cl-
concrete rebarexposure solution
High risk for fast & localized corrosion initiation
CRACKING IN CONCRETE POSES SEVERAL PROBLEMS
External treatments are expensive and time consuming
Replacement of contaminated concrete
Epoxy to fill up the cracks Additional coating
AUTONOMOUS SELF-HEALING MAY HELP SOLVE DURABILITY PROBLEMS
Inspired by nature: - not designed to withstand everything- in case of failure: rapid detection
& ‘massive’ & efficient action
3 approaches at the Magnel lab:
(i) use of embedded bacterial spores cf. Wang (2013)(ii) use of superabsorbent polymers (SAPs) cf. Snoeck (2015)(iii) use of encapsulated polymers cf. Van Tittelboom (2012)
• Van Tittelboom, K., De Belie, N. (2013). Self-healing in cementitious materials – A review. Materials, 6(6), 2182-2217.
• Ferrara, L., Van Mullem, T., Alonso, M.C., Antonaci, P., Borg, R.P., Cuenca, E., Snoeck, D., Jefferson, A., Peled, A., Ng, P.I., Roig Flores, M., Serna Ros, P., Sanchez, M., Schroefl, C., Tulliani, J.M., De Belie, N. (2018). Experimental characterization of the self-healing capacity of cement based materials and its effects on the material performance: A state of the art report by COST Action SARCOS WG2. Construction and building materials, 167, 115-142.
• A. Jefferson, E. Javierre, B. Freeman, A. Zaoui, E. Koenders, L. Ferrara. Research Progress on Numerical Models for Self-Healing Cementitious Materials. Advanced Materials Interfaces (2018) 170378 (19 pages). DOI: 10.1002/admi.201701378.
• De Belie, N., Gruyaert, E., Al-tabbaa, A., Antonaci, P., Baera, C., Bajare, A., Darquennes, A., Davies, R., Ferrara, L., Jefferson, T., Litina, C., Miljevic, B., Otlewska, A., Ranogajec, J., Roig, M., Paine, K., Lukowski, P., Serna, P., Tulliani, J.-M., Vucetic, S., Wang, J., Jonkers, H.A. (2018). Review on self-healing concrete for damage management of structures. Special Issue “Self-healing materials”, Advanced Materials Interfaces. 1800074, 28 p.
REVIEWS
OUTLINE
• Introduction
• Polymer based self-healing concrete
• Bacteria based self-healing concrete
• Conclusions
Thin brass plate(thickness = 300 µm)
PVC mold
Nylon wire
Capsule filled with PU precursor
PhD Bjorn Van Belleghem, UGent, 2018
Chloride ingress in small samples with preplaced capsules
Department of Structural Engineering
Cracks cause increase in chloride concentration up to 18 times higher compared to uncracked concrete
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7 weeks 19 weeks 52 weeks
Department of Structural Engineering
Crack healing causes a reduction of chloride ingress through cracks up to 75%
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Department of Structural Engineering
Chloride profiling with EPMA
Uncracked
Cracked
Chloride ingress beyond the crack tipChloride ingress perpendicular to the crack face
Healed
• PMMA capsules by extrusion • Wall thickness controlled by conveyor speed• Øouter = 6.5 mm, w.t.= 0.7 mm, L = 50 mm• Healing agent: water repellent agent (WRA)• ~ 22 capsules per liter of concrete (3250 capsules)
(Adelaide Araujo, UGent)Chloride ingress in cracked concrete beams
• Beams of 2.5 m x 0.40 m x 0.20 m reinforced with four ribbed steel bars (Ø=10 mm)
• Cracks at 14 days formed by 3-point-bending• 6 cracks of variable width in each beam
Crack formation
• exposure to 3 wt% NaCl solution• flows over the beam for 24 h• once per week during 6 weeks
NaCl solution
Sides of beam waterproofed with
aluminum foil
Steel support
SH REF
Zones where WRA leaked out clearly visible
Durability testing: chloride ingress
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Macro-cell corrosion mechanism
Cl-
2Fe 2Fe2+ + 4e- 2H2O + O2 + 4e- 4OH-e-
H2O O2
2Fe2+ 4OH-
2Fe(OH)2
= anodic reaction = cathodic reactionMetal dissolution Oxygen reduction
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Reinforcement corrosion
Schematic test setup
Cl-
2Fe 2Fe2+ + 4e-
2H2O + O2 + 4e- 4OH-
H2O O2
2Fe2+ 4OH-
2Fe(OH)2
anodic reactioncathodic reaction
e- e-
Connection of anode and cathode outside the beam to have a closed circuit
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Macro-cell corrosion mechanism
Schematic test setup Steel reinforced concrete prisms 120 mm x 120 mm x 500 mm
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Crack creation by three point bending
Every specimen is mounted into a steel frame in order
to keep the cracks open
- Cracked at 28 days- 48 h at 20 °C and 60% RH
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Test setup
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NaClCa(OH)2Ca(OH)2
Specimens subjected to weekly wet-dry cycles1 day wet, 6 days dry
for total period of 44 weeks
Measurements
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Other electrochemical parameters were measured weekly with potentiostats
Specimens are all connected to a current logging system
Imacro measured every hour automatically
Imacro =E0,C − E0,A
RP,A + RP,C + Re
internal Ag/AgClreference electrode, or external saturated calomel reference electrode (SCE)
Monitoring macro-cell corrosion current
020406080
100120140160180
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Week
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CR_EXT_A CR_EXT_B CR_EXT_C
Localized pitting corrosion on rebars of cracked samples
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Macro-cell corrosion current and potential
Service life prediction based on volume loss calculated by Faraday’s law
Volumetric mass loss of steel:3-6 mm³ 0.34-0.70 mm³/wk
Volumetric mass loss of steel:1-2 mm³ 0.03-0.05 mm³/wk
→ factor 14 lower
OUTLINE
• Introduction
• Polymer based self-healing concrete
• Bacteria based self-healing concrete
• Conclusions
Selection of micro-organisms
1. Ureolytic bacteria (ureum)2. Aerobic heterotrophic bacteria (e.g. lactate)3. Denitrifying bacteria (e.g. formate + nitrate)
Urea hydrolysisCO(NH2)2 + 2H2O + Ca(NO3)2 CaCO3 + 2NH4
+ + 2NO3-
Aerobic oxidationCa(CH3COO)2 + 4O2 CaCO3 + 3CO2 + 3H2O
Nitrate reductionCa(CH3COO)2 + 1.6Ca(NO3)2 2.6CaCO3 + 1.6N2 + 1.4CO2 + 3H2O
Self-healing bio-concrete: metabolic pathways
Axenic strains are delicate in harsh environments
They need protective carriers to survive the concrete environment +
They can avoid the need for protection if they collaborate
PhD Yusuf C. Ersan, UGent
Oosterweel: solving the traffic problems in Antwerp1st application of self-healing concrete in Belgium
Mixed UreolyticCulture (MUC)
Non-axenic culture, obtained by upgrading a side stream from the vegetable industry
before grinding after grinding PhD Filipe Silva, UGent
1st application of self-healing concrete in Belgium
1st application of self-healing concrete in Belgium
Mix design• CEM III/B
• 1m% vs cement weight of MUC+, added dry
• nutrients: urea and calcium nitrate tetrahydrate: dissolved in 40 l water
• agents were added via inspection hatchBUT took a long time high air content 4.7%
Age fcm
7 days 30.7 MPa 28 days 45.0 MPa 93 days 54.7 MPa
Compressive strength
Construction site: concrete casting
• E-mod specimens
• Tensile specimens with 1 bar Ø 16 mm(100x100x400 mm³)
• Capillary water absorption specimens(120x120x500 mm³)
• Water flow specimens (150x150x550 mm³)
Testing in the lab
Water flow setup to test water permeabilityBased on the test method designed in HEALCON
To monitor the water outflow from the (healed) crack in function of time (5 - 15 min)
Water-saturatedprism
• Cracked after 6 weeks in manual 3P bending
• until residual CW of 320 – 385 µm
• Sealing of the crack at the side surfaces
• Saturation for 5 days
• Initial water flow (1 bar)
• Repetitive cycle of 3 weeks healing and testing
Ø 10 mm
Ø 6 mm
6 cm
3 cm
Water flow setup to test water permeability
335 µm320 µm352 µm383 µm352 µm0
20
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WF [g/min]
Initial water flow
SE =𝑊𝑊𝐹𝐹𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖 − 𝑊𝑊𝐹𝐹𝑖𝑖
𝑊𝑊𝐹𝐹𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖� 100%
Sealing efficiency results
0%
20%
40%
60%
80%
100%
0 3 6 9 12 15 18week
Evolution of SE
1 (335 µm)2 (320 µm)3 (352 µm)4 (383 µm)5 (352 µm)
Up to date, no cracks have been noticed
Installation of roof plate
anoxic (denitrifiers)aerobic
• Sequencing batch reactor• Selective pressure (alkaline pH,
starvation, wash out)
Activated Compact Denitrifying Core (ACDC)Non-axenic cultures of NO3
- reducing bacteria encapsulated in bio-polymer and co-cultures.
• Granulation & drying at 60°C• 0.5 – 2 mm granules• 70 % bacteria, 30 % Ca-salts• Added to mortar: 0.5-1 wt-% vs cement
85 mg/L N reduced in 2 days
At pH 9.8 after 28 days in mortar
ACDC could revive between 3 to 7 days.
Survival in mortar0.5 % ACDC, 2 % Ca-formate, 3 % Ca-nitrate vs cement
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ERŞAN, Y.C., VAN TITTELBOOM, K., BOON, N., DE BELIE, N. (2018). Nitrite producing bacteria inhibit reinforcement bar corrosion in cementitious materials. Nature -Scientific Reports, 8: 14092.
a) plain mortar: standard sand (1350 g), CEM I 52.5 N cement (450 g) and tap water (225 g) (EN 196–1)
b) microbial test mortar with ACDC (0.5% wt/wt cement), Ca(NO3)2 (3%) and Ca(HCOO)2 (2%)
c) positive control: NO2– (1.6%) as a corrosion inhibitor in the
form of NaNO2 and Ca(HCOO)2 (2% wt/wt cement)d) abiotic control: nutrients, Ca(NO3)2 (3%) and Ca(HCOO)2 (2%) e) microbial self-healing control: CERUP (ureolytic) (0.5%) and
CO(NH2)2 (5%)
Materials
Corrosion inhibition test in concrete
• mortar specimens (40 mm × 40 mm × 160 mm) with a centrally positioned embedded smooth steel rebar (Ø=8 mm)
• artificial cracks with a depth of 20 mm and a width of ~300 µm created after 1 d
• cured for 28 d, 20°C, RH >90%
Methods
VAN TITTELBOOM, K., VAN BELLEGHEM, B., BOONE, M., VAN HOOREBEKE, L., DE BELIE, N. (2017). Use of X-ray radiography to […] judge the delay in corrosion through self-repair by encapsulated polyurethane. Advanced materials interfaces, 1701021, 10 p.
D
• six cracked and six uncracked pieces (38 mm × 40 mm × 15 mm) were sawn off
• cracked surface immersed in 0.5 M Cl– solution for 28 or 120 d
Results: healingplain mortar
positive control:NaNO2
abiotic control: NO3
–
microbial self-healing control: CERUP
microbial test mortar with ACDC
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Results: OCP (open circuit potential) monitored vs a saturated calomel electrode (SCE) for 120 days, data converted to standard hydrogen electrode (SHE)
16 d
Plain mortar and positive control with NaNO2
Microbial produced NO2- inhibits corrosion
44 d 28 d
18 d
Ca(NO3)2
NaNO2 ACDC
CERUP
Gravimetric mass loss of rebars due to corrosion
Conclusions
• Even small cracks may impair durability / self-healing improves durability• Durability of self-healing concrete has only scarcely been studied; mostly
indirect indicators such as water absorption / permeability are measured• Encapsulated low viscosity PU: mostly complete and consistent crack healing
o Reduction of chloride ingress up to 75% possibleo Significantly reduced corrosion propagation
• 1st application of self-healing concrete with MUC+ in Antwerp was successful; no cracks have been formed until now
• Bacterial ACDC granules provide concurrent corrosion inhibition & healing• Healing of 300 µm wide cracks was complete in less than 1 month time • During exposure to chloride solution, reinforcement protection was
comparable with that of cracked mortar containing chemical inhibitor or even uncracked mortar, due to the nitrite release by the denitrifying granules
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AcknowledgementsWith special thanks to:
PhD students and postdocs
FWO, IWT, SIM-Flanders, BOF-UGent, EC for financial support