It is well known that permeability of concrete decreses with time, at least in its initial hardening phases (first few months). After these few months, what happens to the permeability of concrete when it has to face flowing water (e.g.) canals and conduits? To keep answer simple, assume there is no aggressive chemicals or abrasive materials in the water.
Will the concrete further harden and decrease its permeability? Or will the concrete soften due to constant presence of water and increase the permeability?
You will possibly get leaching, particularly of portlandite. It will depend on the nature of the concrete and on the flowing water. Hard water will reduce the extent of leaching, while the permeability of the concrete will also have an effect. Composite cements (so having lower portlandite contents) will be more resistant to change, as will concretes with low water/binder ratios.
Hi, Leon Black , are there any evidences reported?
As I mentioned in my question, assuming cement is OPC and water is neutral (say distilled water without any minerals), will there be any change in permeability? Will there be any leaching?
I did not find any paper on this.
Dear Nirmal Joshi
Distilled water (without any minerals) is one of the most efficient solvents, it will theorically leach CH until it reaches equilibrium concentration. When concrete specimen are submitted to water-submersed curing in some cases a loss of strength through time can be observed due to the leaching.
Hi Nirmal, I can't direct you to any specific work on precisely this topic, but we have a recent paper looking at freeze thaw attack where damage was much reduced when performing the test in lime water compared to deionised water. This was related to leaching of portlandite.
I'm away from the office just now so can't access the full publication, but the details are here:
https://www.researchgate.net/publication/320797267_Relationship_between_cement_composition_and_the_freeze-thaw_resistance_of_concretes?_sg=stvqdmAe9auNDc5IztS0ezI8nZNlJ4Cjgcdhk7zi8X_cfZasGsRK5yTP4AS0UuTG9CZXA6rmbWgEk-rb_uRw0vYgCZapZ5yn9N7r6P_A.e9xac-xpnu_Hitf4qht3Jt5zsWIGBfevQf7b_mobjlvYpq9pGKXS5h4UXpdxWdkVKowtCgVhNlHRYMdG9jOAYA
In addition to given responses,
Bottom and sides of canal cross-section may be faced to different leaching and efflorescence levels. At bottom part, water may help to further hydration of cement particles without any leaching, and thus concrete can result in less permeable structure due to gravity if there is no erosion or cavitation effect of water flow on concrete. However, its tidal zone and vertical sides can face to the leaching effect further. Additionally, you should consider abrasion, erosion and cavitation damage of water flow on concrete surface. The effects may be more destructive for concrete structures.
Hi Nirmal,
There are numerous studies in these topics for only leaching or only abrasion of such concrete structures. Comparison between leaching and wear effect reflects my senses from visual observations of the each effect by considering failure of concrete structures placed near river, sea etc. Ofcourse, combined effect of the leaching and abrasion is considered in field for many structures rather than pure leaching or pure abrasion effect. You can search what exactly you wonder by using technical keywords for each statement. I presents some searching examples in google scholar below
https://scholar.google.com.tr/scholar?hl=tr&as_sdt=0%2C5&q=cavitation+failure+of+concrete&btnG=
https://scholar.google.com.tr/scholar?q=abrasion+of+concrete+in+hydraulic+structures&hl=tr&as_sdt=0,5
https://scholar.google.com.tr/scholar?hl=tr&as_sdt=0%2C5&q=abrasion+of+concrete+in+canal+structures&btnG=
https://scholar.google.com.tr/scholar?hl=tr&as_sdt=0%2C5&q=leaching+of+concrete+in+canal+structures&btnG=
https://scholar.google.com.tr/scholar?hl=tr&as_sdt=0%2C5&q=leaching+of+concrete+in+tidal+zone&btnG=
good luck
Hi H. Süleyman Gökçe ,
Thank you for your time. Although my original question was about change in permeability due to flowing water, leaching and permeability are obviously interrelated.
Off-course leaching could result in higher permeability, but would that be the case in the canal which often only carries fresh water? Or a water tank where there is potentially no chance of abrasion except regular flow of fresh water (assume no chlorination). Has anyone really witnessed or measured the RATE of possible leaching? Image a senario after 10-15 years service life of these structures when the they may underperform due to such leaching.
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