concrete - black rot

[martinb]

Looking for the cause and remedy for "Black Rot" in concrete floor slabs - relating to high humidity areas e.g. Dominican Republic

 

[Ron]

I am assuming from your description that some type of deterioration is occurring to the concrete surface. One potential cause is an acid-producing bacteria or fungal residue.  Would need a description of the deterioration and its rate, though.  You can try an alkaline wash and see if it reduces the occurrence.  Cores taken from the slab can be examined under magnification to see the effects of the residue.  Assuming you have calcareous coarse aggregate and probably indigenous calcareous sands, the attack by a weak acid could be prominent.

 

[martinb]

Ron, many thanks for your reply. I am unsure of the exact problem - I received a call from people interested in using our building system for housing projects in the Dominican Republic and they mentioned that they had considerable trouble with "Black Rot". I suspect that you are correct and that the cause is a fungi growth. I was given to understand that the concrete 'powders' and that it may have been due to a form of fungal growth caused by high humidity. My first reaction was that it may have been another description for concrete cancer as I have not heard of the expression Black Rot before. We are contemplating the use of concrete slab floors in the project and of course are quite concerned to find a preventative media or process before moving forward.

 

[Imagineer]

Martin,<br>&nbsp;&nbsp;Could you elaborate on the term &quot;concrete cancer&quot;?&nbsp;&nbsp;I've not heard that term used and am interested.<br><br> <p> Imagineer<br><a href=mailto: > </a><br><a href= > </a><br>

 

[Ron]

Martin,<br>One other thought is the general quality and availability of good concrete in &quot;the islands&quot;.&nbsp;&nbsp;In my experience, the quality varies from awful to tolerable, unless you put some very specific controls and enforce them.&nbsp;&nbsp;If the concrete is weak (structurally and durability), then more susceptible to all sorts of attack, particularly surface affects.<br><br>Be hardnosed about the concrete quality and you might not experience the &quot;black rot&quot;.