The influence of immersing age of concrete in aggressive medium on its durability.
Please have a look at the work of my ex- and current students; Okiemute Roland Ogirigbo compared the effects of curing slag cements for 7 vs 28 days before immersion in a chloride solution. Meanwhile, Joseph Ukpata is currently looking at similar systems, but exposing them to combined sulphate-chloride solutions.
Yes, Dr. Doha M Al Saffar , I mean curing period of concrete in aggressive medium.
Durability is a long term study, it depends upon the period of curing and the medium of aggressive environment.
Please have a look at the work of my ex- and current students; Okiemute Roland Ogirigbo compared the effects of curing slag cements for 7 vs 28 days before immersion in a chloride solution. Meanwhile, Joseph Ukpata is currently looking at similar systems, but exposing them to combined sulphate-chloride solutions.
The immersing age also referred to the time duration of concrete commencing immediately after casting up to the formal curing. In a marine environment (aggressive medium), procuring of cement concrete can be done with either sea water of fresh water. The dissolved salts start reaching with the concrete affecting its rate of gain in strength properties when procuring is done with seawater.
Dear Dr. Leon Black , thank you so much for your interesting and valuable comments.
I would strongly recommend NOT to use seawater for mixing concrete. You will introduce aggressive species directly into the bulk of the concrete. If there is reinforcement then chlorides will be in contact with chlorides from day one, leading to corrosion. Secondly, sulphates in the seawater will also be aggressive, especially in the presence of magnesium ions which are also present in the seawater.
Dear Dr. Saleh
Kindly refer to the attached paper, the cyclic exposure of concrete to environment and deleterious materials is vital in the durability issue.
The curing will have a beneficial effect only when SCMs are incorporated in the mixes. Also, the effect will be more pronounced on exposure to medium where the ingress is by diffusion. However, in my opinion, curing and permeability related properties does not have a role on exposure to aggressive medium (For example, low pH acidic medium producing expansive salts of low solubility). In such cases, there could be direct attack also on CSH due to the reduction in the availability of buffer due to Portlandite.
Dear Dr. Saad Sarsam Yes the following suggested paper is very useful:
Bahrain 2013 Assessing durability.pdf
Dear Dr. Leon Black , Thank you so much for your interesting and valuable comments.
I completely agree with that, the curing will have a beneficial effect only when SCMs are incorporated in the mixes. Also, the effect will be more pronounced on exposure to medium where the ingress is by diffusion. However, curing and permeability related properties does not have a role on exposure to aggressive medium.
Dear Dr Ramaswamy, Thank you so much for your for your deep answer.
In addition to the destructive effects of chlorides and sulphates noted by Prof Leon Black and others, excessive liquid volume/solid ratio in the exposure environment may lead to decalcification of the calcium bearing phases of the cement causing loss of strength.
Dear Dr. Joseph O Ukpata , Thank you so much for your for your comment.
Yes, the durability is a long term study, it depends upon the period of curing and the medium of aggressive attack.
I agree with Professor Leon Black.
It is really a good question and good answers.
Regards,
Mostafa
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