Dear Tim,

After having a few of my drive spall off some 3 years old. I have drove around town and to see just how bad the problem is. Talked to the ready mix companies and been on the internet.

What I have noticed is that all 3 Ready mix companies and just about all the concrete contractors have issues with spalling concrete even the City has its own crew pour concrete and they are not immune from this problem. Also all ages of concrete are affected.

I noticed that some driveways were deteriating worse than the side walk. Yet both were doing it after talking to the supplier they said that the sidewalk was machine poured and required a slump of 1-2 as it formed and poured at the same time. This is why many concrete Hiways have less spalling problems.

The contractors that the least of problems used a cureing sealer at finishing time.


All the suppliers snd most of the contractors all have agreed that concrete requires maintence.

Do not let snow or ice sit on concrete this allows many freeze thaw cycles poping top of concrete.

Sealing of concrete every fall will help protect concrete.

Driveways that dont get sun to dry out concrete will see more problems than south or west facing driveways. Also flater driveways will have more problems due to water staying on them longer.

Driveways should be rinsed off to get road deicers off of driveway.

My conclusion is that concrete will be poured all year long so talk to the contactor to make sure that He goes the extra mile to protect the concrete and uses cureing sealer. Then the customer needs to do their part to keep the driveway shoveled and seal in fall of every year.


Thanks

Mike

Mike,
You should read all of my columns on Deicing Salts and Concrete. There are many. Bottom Line: You can install concrete and NEVER have to seal it, and this concrete will NOT spall. Want to see some that is 20-years-old? Come to my house. It gets salt on it each winter, I rinse it off, it goes through countless freeze-thaw cycles, etc. My driveway apron looks like the day it was installed. Read all of my columns about Concrete Installation if you want to discover how I would install concrete at your house.

This sounds bogus. You make it sound like the concrete will absorb water and freeze ONLY if you put salt on it, but water's going to enter the concrete and freeze whether you put salt on it or not. There are always warm periods in between the cold ones, so the ice or snow will melt, soak into the concrete, and then freeze when it gets cold again. The only thing salt might do is cause it to melt during the months when it would otherwise be constantly frozen.

"Salt is also hygroscopic. It attracts water. It can cause concrete to become more saturated with water than it would otherwise."

This sounds wrong, too. Road salt is either sodium chloride or calcium chloride. Calcium chloride is hygroscopic, sodium chloride is not.

But I don't see why this would have any effect on the concrete. Calcium chloride's hygroscopy means that it ABSORBS water. It's commonly used as a desiccant to REMOVE water from nearby things. So putting it on your concrete would seem to make the concrete drier, not wetter.

Do you have references for any of this?

We had snow/ice last night and I noticed this morning some cracks in the concrete where I had put out salt on the driveway outside of our garage. I have never had issues before, and just found this article about it. What can be done to repair the cracks/holes that are forming on the driveway??

There are many things to take in consideration when dealing with any de-icing agent and concrete. Obviously, if you have a weaker concrete, you'll have a higher risk. For instance, I have clay pavers in my driveway, and clay might measure a P.S.I. at around 15,000. Much stronger than concrete. I don't seal them and I never have an issue with water or ice. However, clay pavers are more rigid than concrete, and are more susceptible to chipping, so that isn't the answer to raise the PSI because you can make things more brittle. Now as for de-icing, you have to remember a few things. First off, salt lowers the temperature at which water freezes. In other words, 32F degrees and water will freeze. Add rock slat and now water won't freeze until around 5F degrees or so. It gives the water that much more time to penetrate your concrete by absorption. Calcium chloride will even lower the temperature more than that of rock salt. The amount of time to penetrate into the concrete is also dependent upon wind speed for evaporation, wind chill, and the current humidity at that point in time. There isn't any clear cut answer as when you should or shouldn't use a de-icing agent. Water, on its own will be absorbed into concrete, but the water doesn't "damage" cured concrete, it is the expansion of it that is the problem. Salt gives the water more time to penetrate into the concrete because it can't freeze at 32F degrees anymore (redundant, I know). I think the most important thing to remember about salt and concrete is that the more readily available water you have with salt being used in freezing temperatures, and the amount of time involved in all aspects of the equation, the more of a chance you might have of concrete coming apart. Remember, concrete weighs in at 4000 P.S.I. and ice can cause an outward pressure close to that. So if water gets in your concrete during freezing temperatures, it can saturate the pore space available in the concrete, eventually freeze and expand at about/up to 9%. If you have a weak mixture of concrete, you might have a problem in the future. The only thing I can say is that if you have ice and are putting concrete above safety, remember your head splits open just as easy on solid ice and chances of slipping on dry concrete are not as likely. On another note, what salt does to soil is terrible. Above all else, I suggest using magnesium chloride. This stuff can actually cause a minor fertilizing effect on green space. So, you can reduce the burn on your turf areas next to driveways and such.

Hi
My husband used rock salt this year to de-ice the sidewalk at our apartment. The landlord claims that we have taken 40 years off of the life of the concrete. We are not sure when the concrete was put in, but probably over 10 years ago.
Is he right?

I would want to know exactly how he came up with any figure for any amount of time. Unless he had a lab analysis done upon installation to create a benchmark, and then has recently performed a non-destructive evaluation, he has nothing to base that on. In other words, he sounds like he is hustling for something. Tell hime to go pound salt. Did he tell you never to use salt? Who is responsible for snow and ice management at your residence?

what we would really like to know is, if we used salt a few times this past winter, how much damage could it really have done? How long would it take to actually damage the concrete?

I am concerned about the concrete at a small condo complex in which I own 2 of the 12 units. The complex was built in 1983. I managed the complex from about 1993 through 2006 at which time the owners agreed to turn the management over to a proprty management company. During the time I managed the complex, I used only high quality snow melt on the cement. The complex has a detached 2 level parking grage. The top level is cement. Up to the time of the proprty management company taking over, the concrete (terraced parking, steps and sidewalks) was in good conditon. However, as of today, piles of concret surfacing are around the terraced parking and steps are in poor condition. I sampled the product used on the snow and ice by the property management company and it was determined to be cheap road salt. Is this cheap road salt (apparently, used for 3 winters) causing the problems with the cemente falling apart? Is the proprty management company negligent for using road salt? What can be done, at this point, to salvage the cement on the terraced parking?

i'm a contractor readind you're article on rock salt you wrote that if concrete isn't correctly poured rock salt would effect concrete " what is the correct way to pour concrete to avoid the rock salt affect