Concrete Strength Variation

[yshij]

I alway think that fully cured concrete has different strength under different wet conditions. Is it true or not?

 

[Ron]

Yes. There are many variables that affect the strength of concrete and one of them is whether the concrete is in a wet environment.

Concrete that is continuously kept moist will continue to gain strength.

 

[yshij]

Thank you very much for your answer. However, after the concrete is fully cured, the strength of the concret under wet and dry conditions should not be the same? You cannot imagine that a concrete building in raining day is stronger (may be weaker) than sunshine dray day's.

 

[Ginger]

Ron is correct in his advice. All concrete will continue to gain in strength throughout its hardened life. This is in part due to to the unreacted cement particles within the mix. Not all of the cement reacts in the first 28 days and, in general, if water is in contact ith the concrete then it will migrate and react with any cement it can find. Andy Machon

 

[yshij]

Thank you very much, Ron and Ginger. If there is no cement left for continuous reaction with water, will the concrete have a constant strength? I thought that if the concrete constantly contacts with water such as bridge fundation, the strength would eventually decay over long period of time. Don't you think so?

 

[Ginger]

The only adverse effects of being underwater thatI can think of which would cause the concrete to degrade are:

1. Cracks in the concrete which expose the rebar to water. The ensuing corrosion will burst the concrete.

2. Chemical attack from minerals in the water (ie high levels of sulphates in the water).

3. Scour from abrasion due to flowing water or from undermining of the formation.

The fact that the concrete is dry does not really have any bearing on this in terms of strength gain.

Regards

Andy Machon

 

[Trussdoc]

In addition to the above, concrete and masonry which are somewhat porous will absorb water during rain. Thus, the load carried by the structure will be marginally higher, though the strength remains the same.