Cement Damage

cementman42

I have been doing small cement repair work for a few years, and I have started a small cement business. My brother lives in the city and someone is putting (he thinks it is his neighbor) something on his sidewalk and causing deep pockmarks in the cement. Over period of about six months there has been a lot of damage done on two or three sidewalk blocks. No, this is not normal wear and tear. I am thinking it is some kind of acid. He checks the sidewalk on dry days to see it there are any wet spots on the cement (from acid or something else being poured on it), but so far he has not seen any liquids on the sidewalk cement.

what would cause this? Any help would be greaty appreciated.

Thank You for any help in this matter.

concretemasonry

Where is the sidewalk? - City, climate

How old is the concrete?

Pictures could help.

Do they look like "popouts"?

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

cementman42

Yes, it looks like popouts, but there are too many at one time. I'll try to upload a picture. The city is Philadelphia Pennsylvania. the popouts are near the curb, but no on the curb. None of my brother neighbors have this problem and the cement is the same for all of the other row homes. The reason he suspects the neighbor is because the neighbor has done damge to his brick wall by causing big chips in the bricks in too many places to be a natural chip and some chips too big to be natural break off

I tried to send a photo. But it did not come up on this Message board.

concretemasonry

Acid will not cause deep damage or damage to a well defined area.

Acid does not damage brick or cause chips.

__________________
Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

Luke

This might be a stretch but here in Reading, many of the older concrete sidewalks were installed over a crushed iron ore material instead of stone and over time, the chemical effect of the metals and the concrete eventually bleed through to the top of the walks. I don't know if the walks you are talking about are that old or newer installations but I thought I'd throw it out there. I'm talking about walks that are at least probably fifty years old now. This isn't Gary Heidnick's old home is it........?

finlander

It is possible that the cement in question was never air-entrained.
All exterior slabs should have 6% air installed at the batch plant. It is possible that the air was missed on the batch in front of his house.

concretemasonry

Most of the suggestions will give a general area of failure and not lo,ited to a very small area like a pop-out.

It could be the aggregates used that has shale, chert or other expansive particles.

many jurisdictions require different concrete mixes and aggregates for critical with with more severed exposures like gutters than they do for cosmetic surfaces like sidewalks.

A photo would probably tell the story.

__________________
Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

cementman42

I tried to send a photo. I must have done something wrong.

Can someone walk me through sending a photo to this sight?

Cole

How to post a photo:
http://www.contractortalk.com/f45/how-attach-photo-post-6001/

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house bldr

Did this happen during winter months? Salt on concrete can cause pock marks especially on newer concrete.

Michaeljp86

I dont think this is the problem but a torch will make pieces pop out. Hold a torch on it and a chunk will come flying in your face.

I would say it could be from salt to.

Chris Johnson

Philidelphia - Definately winter rock salt, the brick wall, does he use a snow blower/thrower on that same walk and aim it at the wall?

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Chris

cementman42

I uploaded the picture and saw it in the message box that I pasted it into, but the picture did not show up in my thread

Metrojoebarbs

I would bet salt from the roads. Thats why it's near the curbs.

concretemasonry

Metrojoebarbs -

No damage to the curbs that can see more salt (especially in Philadelphia). - That should be a clue, unless the posted information is not accurate.

It really can't be a big problem since the poster does not even know if it is happening to 2 or 3 slabs (50% difference).

__________________
Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

Michaeljp86

Concrete is a animal all its own, anything can change it from being mixed right to the temperature when it was poured, how it was worked etc. Im sure we've all seen concrete look like it was poured yesterday and its 20 years old. Im sure weve all seen concrete 3 years old already comming apart.

That section could be softer then the sidewalk 2 feet away because it was poured on a different day or even if the sun was beating down on that piece it could make it more susceptible to damage.

Metrojoebarbs

Dick,
What I'm picturing is pop marks as when a HO runs out of calcium and decides to use rock salt for that winter because it's cheaper. We all know what happens then. The curbs will never be effected because they are usually vertical as upposed to the sidewalks were the moisture and salt can go to town on the flats. I was thinking rock salt mixing with the snow and then being pushed up by the plows. I think he said close to the curbs.

Either way... 90lb jack and a short load charge and you out.