Presented at the XXIV Nordic Concrete Research Symposium in Stockholm, August 17-19, 2022.

1. DTU Sustain
17 August 2022 Short term chloride binding and biofouling
Short-term chloride binding and
biofouling in calcined clay –
limestone binders exposed to
Øresund strait environment
Philip Haargaard Gyldenkærne, Wolfgang Kunther
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2. DTU Sustain
17 August 2022 Short term chloride binding and biofouling
Background
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(c) J.C. Svendsen

3. DTU Sustain
17 August 2022 Short term chloride binding and biofouling
Background
• Globally, artificial reefs are created specifically to improve local and regional fisheries
• Installing marine reefs requires engineering solutions that are socially, biologically and
technically meaningful.
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4. DTU Sustain
17 August 2022 Short term chloride binding and biofouling
What happens with:
if we add a layer of biology
to the ”usual processes”?
Research question:
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• Durabillity
• Service life & economy
• Carbon footprint
C-S-H
Ca(OH)2
Afm
Aft
OH-
OH-
OH-
OH-
OH-
pH=12-13 pH=8

5. DTU Sustain
17 August 2022 Short term chloride binding and biofouling
Test Set-up
• 3 different cementitious binders + granite reference
– PC
– Calcined clay and CaCO3 similar to EN 197-1 CEM II/B
– Calcined clay and CaCO3 similar to outside of EN 197-1 CEM II/B (44 % replacement)
• Strength measurements
• Surface characterization
• Assessment of succession (qualitative)
• Chloride profiles & apparent “diffusion” rates
• Microstructural changes
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6. DTU Sustain
17 August 2022 Short term chloride binding and biofouling
Concrete properties
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Ca(OH)2 %
of mass
CaCO3 %
of mass
11.8 4.7
4.1 8.2
1.3 15.3
• “CEM II/B” – 56: Binder = 56% OPC, 26 % calcined clay, 17 % grey microfiller
• CEM II/B – 65: Binder = 65% OPC, 26 % calcined clay, 9 % grey microfiller
• CEM I – 100: Binder = 100 % OPC
Concrete mix
Open
porosity
Compressive
strength MPa ±
SD
Surface
roughness
% ± SD Ra (mm)
CEM I-100 15.3 ± 0.3 36.3 ± 4.6 2,6
CEM II/B-65 15.9 ± 0.2 40.2 ± 3.7 1,1
“CEM II/C”-56 15.9 ± 0.2 37.5 ± 1.9 1,3
Granite - - 7,6

7. DTU Sustain
17 August 2022 Short term chloride binding and biofouling
Exposure site and treatment
• Exposure site
• Exposure rig
• Sample geometry
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Water analysis?

8. DTU Sustain
17 August 2022 Short term chloride binding and biofouling
Chloride profiles
& apparent “diffusion” rate
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𝐶 𝑥, 𝑡 = 𝐶𝑠 − 𝐶𝑠 − 𝐶𝑖 ∗ erf(
𝑥
4∗𝐷𝑎∗𝑡
)
Da = apparent diffusion rate
CS = initital chloride content
Ci: background chloride content
x= depth
65
56
100

9. DTU Sustain
17 August 2022 Short term chloride binding and biofouling
Some microstructural features after
28 days of exposure:
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500 mm 500 mm 500 mm
CEM I-100
CEM II/C-56 (WT)
NT WT

10. DTU Sustain
17 August 2022 Short term chloride binding and biofouling
Qualitative succession assessment
• Manual mechanical treatment to stress the biological development on surfaces
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CEM I-100 CEM II/B-56
CEM II/B-65
granite

11. DTU Sustain
17 August 2022 Short term chloride binding and biofouling
Other works: Influence of surface texture
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The Ecological Value of Concrete in the Marine Environment - The influence of surface
topography on colonisation of marine biota in littoral zones, MSc thesis DTU, J.W. Parkinson

12. DTU Sustain
17 August 2022 Short term chloride binding and biofouling
Summary
• No clear trends for promotion or regulation of the early biofilm were identified.
• Large abundance of diatoms on CEM I and granite compared to CEM II/B/C
type binders, grazing of gastropods (snails) was difficult to account for.
• Lower carbon emission (CEM II/B/C type concretes) are interesting in terms
of reduced chloride ingress/binding.
• Mineralogical changes after short exposure times.
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13. DTU Sustain
17 August 2022 Short term chloride binding and biofouling
Acknowledgements:
• MSc thesis:
– P.H. Gyldenkærne: Influence of mineralogical composition on the colonization of
concrete structures in the marine environment
• Exposure during autumn / winter 2018
– J.W. Parkinson: The ecological value of concrete in the marine environment - The
influence of surface topography on colonisation of marine biota in littoral zones
• Exposure during autumn / winter 2019
– M.N. Fugl: Nature inclusive concrete designs for surface texturing and its effect on
mineralogical changes and biological growth in maritime environments
• Exposure since spring 2021
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