I would like to ask the following regarding the Structural Waterproof Concrete:
-What is the terminology for Waterproof Cpncrete (and where is stated)
-What are the most practical laboratory tests for waterproof concrete (among the numerous that exists)
-What are the values on these tests that prooves impermeability (and how these values are corelated with service-life of the construction).
Best regards
Spiros Licoudis
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spiros licoudis
Spiros! Waterproof Concrete is a misnomer. It is concrete with low permeability. The permeability (typically water)of concrete can be reduced by refining its pore structure, using mineral admixtures like PFA, BFS, SF, MK and so on. The permeability of concrete is specified in the performance standard. It will be better to refer the national standard on the subject. http://www.drjdbapat.com
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Dr J D Bapat
Spiros,
Dr Bapat correctly called the expression or term "waterproof" concrete a misnomer. He also correctly focused on "refining" the pore structure. This refining is key to void control and requires careful managing and restructuring of the degree of residual voids, this determines the degree of porosity. Reducing your concrete voids is the first step to better resist liquids from being able to migrate through the matrix, but this is still not "water proof" or water tight or MVT controlled concrete.
The use of SCM's of various types are helpful but limited in creating the degree of void reduction for water tight (pore filling) to the degree you are looking for.
The other ingredients, not always adequately considered are better 1)cement 2)mix water utilisation. These need addressing as these also create voids when producing concrete. How? the mix water, when this exits, during the bleeding and drying phase. These are the most problematic voids and range from Macro to micro and are interlinked allowing for ease of migration for moisture.
Water needs to be utilized better during the hydration (of cement) phase. Additionally the cement needs to be better hydrated so as to consume more water. Then there is the additional consumption of the by-product hydrate Ca(HO)2 calcium hydroxide to futher increase paste production. If you understand how to utilise these you will also utilise better any SCM incorporated in your mix design.
The end result is ultra tight moisture resistent concrete, yet still breathable on the micro level. Healthy concrete.
If you require further info please contact eiitech@shaw.ca
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John Macdonald
Hi Spiros
The both responders are quite right, but not fully.
If SCM are used in concrete, they do indeed reduce the porosity of concrete, but they do not make concrete waterproof. By reducing the porosity they reduce permeability of concrete only.
Waterproofing actually means sealing concrete making it practically impermeable. It can be achieved with the use of waterproofing admixtures, either silicon, or crystal growth types. There are plenty of different brands are available in the market, they are widely used and are effective.
To see the difference between permeability reduction and waterproofing, a permeability test should be performed. I can't name a specific test, but am sure that ASTM would have one in their range, just Google it.
I don't think there are and would not expect to see any specific definitions or defined values for either waterproofing concrete, or concrete with reduced permeability. It all comes out of the specific requirements to a project.
Hope this was helpful.
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Michael Khrapko
Spiros,
For what purpose are you trying to make concrete meet a standard to be viewed as "water proof". Cement without needing any SEM but simply being efficiently hydrated will reduce even air permeability of 0.2 md
to 0.5 md. Would a SEM test report help.
Hydrated cement is a crystal growth process but OPC concrete is limited in achieving the degree of cement hydration due to hydrate shell development and needs only the additional help from a pozzolanic solution to reduce the micro pore structure to permanantly resist liquids.
We do it all the time. For proof please contact eiitect@shaw.ca
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John Macdonald
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