Releasing agent for concrete on metal

[RESORT2ME Senior Member Find all posts View Profile Close RESORT2ME]

Bought for $40 with 3 inches of concrete left in cement mixer... I can chip it out but wondered if there's a better way.

[bigfrank Administrator Find all posts View Profile Close bigfrank]

bang the outside with a hammer

[RESORT2ME Senior Member Find all posts View Profile Close RESORT2ME]

bang the outside with a hammer

thanks but afraid it would dent the metal

[T. R. Oglodyte Moderator Find all posts View Profile Close T. R. Oglodyte]

IOW - you bought a mixer that has three inches of hardened concrete inside of it. Correct?

There is nothing that is going to release the concrete from the metal. Cement binds very tightly to steel; if it didn't we couldn't reinforce contrete with steel.

Probably the only option is to chip as much of the concrete out of the mixer as you can. Concrete will dissolve in acid, so you can finish job by running the mixer with some weak acid solution. I would go to a swimming pool supply store and get some muriatic acid, dilute it down to a pH of about 5.5 and run that in batches inside the mixer, changing out when the solution pH increases to about 8. You don't want to put in an acid solution that is too strong, as that might attack some of the parts inside the mixer. It will probably take awhile for acid to dissolve the concrete; think in terms of days (or more likely weeks or months), not hours, for the cement in the concrete to dissolve.

It's possible that a solution of pH 5.5 might not be strong enough to work effectively. I've never done this before, so I'm just guessing about a solution strength that will work. I know from experience that a solution of pH 5.5 will dissolve the reacted cement in concrete given enough time.

[Elan Senior Member Find all posts View Profile Close Elan]

Hate to say it, but I think a pneumatic hammer w/chisel bit is probably going to be the best option. Best of luck!

[vintner Super Moderator Find all posts View Profile Close vintner]

Steve, wondering on the acid suggestion. I am guessing the acid required to degrade the concrete would be more mild than an acid that would affect the steel. Is muriatic acid, by nature, a mild acid and would it affect the steel? As a misguided youth, with a basement floor and a nearby stored battery, I learned a little about acid effects on concrete.

I think Elan's suggestion would certainly be a good way to go, but the idea of weakening the concrete though the acid solution sounds very interesting to me.

If using the acid, caution is aways the word.

Amost makes me wish I had his mixer to try that. I am sure it makes my wife very happy I don't have the mixer.

[RESORT2ME Senior Member Find all posts View Profile Close RESORT2ME]

IOW - you bought a mixer that has three inches of hardened concrete inside of it. Correct?

There is nothing that is going to release the concrete from the metal. Cement binds very tightly to steel; if it didn't we couldn't reinforce contrete with steel.

Probably the only option is to chip as much of the concrete out of the mixer as you can. Concrete will dissolve in acid, so you can finish job by running the mixer with some weak acid solution. I would go to a swimming pool supply store and get some muriatic acid, dilute it down to a pH of about 5.5 and run that in batches inside the mixer, changing out when the solution pH increases to about 8. You don't want to put in an acid solution that is too strong, as that might attack some of the parts inside the mixer. It will probably take awhile for acid to dissolve the concrete; think in terms of days (or more likely weeks or months), not hours, for the cement in the concrete to dissolve.

It's possible that a solution of pH 5.5 might not be strong enough to work effectively. I've never done this before, so I'm just guessing about a solution strength that will work. I know from experience that a solution of pH 5.5 will dissolve the reacted cement in concrete given enough time.

Yeah, I like challenges.
Thanks all.

[T. R. Oglodyte Moderator Find all posts View Profile Close T. R. Oglodyte]

… Is muriatic acid, by nature, a mild acid and would it affect the steel? As a misguided youth, with a basement floor and a nearby stored battery, I learned a little about acid effects on concrete. …

Muriatic acid is hydrochloric acid, so no, it's not a mild acid. Of course much depends on how concentrated the acid is.

I suggested muriatic because it is commonly available in less concentrated form as a swimming pool treatment chemical; if a pool is treated with hypochlorite acid must also be added to maintain pH, and muriatic is usually the acid of choice.

Any acid should work, even vinegar. (Same basic chemistry as cleaning scale out of a coffee pot). Perhaps someone who is better at material science than I can suggest an acid that can be used in a more concentrated form without attacking the steel. Maybe something with a pKa of about 5 would work better, but I don't know of any acids readily available to a homeowner (apart from vinegar (acetic acid), pKa = 4.75) that might fit that criterion.

++++++++++

edited to add: As I think about this more, I more in favor of trying vinegar before going to muriatic. If the vinegar works, then stick with it. Otherwise, move up to the muriatic acid. One advantage of vinegar is that the overall concentration of acid is higher, meaning that each treatment can dissolve more cement before needing to be changed out.

As vintner suggests, it might be a good idea to do some acid treatment before chipping. You would probably want to do this in several passes. Acid treat, chen chip to remove softened material. Acid treat again, remove softened material. Repeat as needed.

Needless to say, you want to wear safety glasses during chipping.

[RayAndrews Junior Member Find all posts View Profile Close RayAndrews]

All looks way too complicated to me, at $40 what's wrong with a few dents in the barrell or

How about buying another mixer without concrete?

[T. R. Oglodyte Moderator Find all posts View Profile Close T. R. Oglodyte]

All looks way too complicated to me, at $40 what's wrong with a few dents in the barrell or

How about buying another mixer without concrete?

We're guys. The fun is in finding a way to fix it make it work. This isn't a cement mixer. It's a toy.

If he wanted a cement mixer he would have bought a cement mixer. No, what he bought is a challenge in the form a cement mixer.

[Elan Senior Member Find all posts View Profile Close Elan]

I don't think it's important to get the drum completely clean. Once the drum is more or less in balance, a little residual concrete left inside shouldn't hurt anything.

BTW, muriatic acid should be available at Home Depot as it's commonly used for concrete floor (garage) cleaning and etching prior to application of epoxy. I have never used the stuff, but I'm guessing that a solution strong enough to be effective in this application is going to be a safety and disposal nightmare. As I said, JMHO.

[T. R. Oglodyte Moderator Find all posts View Profile Close T. R. Oglodyte]

but I'm guessing that a solution strong enough to be effective in this application is going to be a safety and disposal nightmare. As I said, JMHO.

That's why I recommended at least starting out at a pH of about 5. At that dilution it shouldn't be any more hazardous than Coca-Cola. The bigger factor is that at that pH there might not be much remaining acidity. Another reason why I'm now more inclined to try vinegar.

Speaking of vinegar, here's Leroy Vinnegar on bass with the Les McCann trio.

[Elan Senior Member Find all posts View Profile Close Elan]

That's why I recommended at least starting out at a pH of about 5. At that dilution it shouldn't be any more hazardous than Coca-Cola. The bigger factor is that at that pH there might not be much remaining acidity. Another reason why I'm now more inclined to try vinegar.

Speaking of vinegar, here's Leroy Vinnegar on bass with the Les McCann trio.

Well, I'm certainly willing to grant that you're more knowledgeable here than me. My chemistry education stopped years ago. I am just going off of the little research I've done recently regarding garage floor finishing. I'm going to pour a little vinegar on the slab behind my garage and see what happens.

As I stated previously, probably all moot as it's not critical to get the drum clean enough to eat out of -- unless the OP's going to mix up a party sized batch of margaritas....

[T. R. Oglodyte Moderator Find all posts View Profile Close T. R. Oglodyte]

Well, I'm certainly willing to grant that you're more knowledgeable here than me. My chemistry education stopped years ago. I am just going off of the little research I've done recently regarding garage floor finishing. I'm going to pour a little vinegar on the slab behind my garage and see what happens.

As I stated previously, probably all moot as it's not critical to get the drum clean enough to eat out of -- unless the OP's going to mix up a party sized batch of margaritas....

The reacted cement in concrete will dissolve if exposed to any acidic solution. The key question is how quickly the reaction will proceed. Weak acids will react more slowly than strong acids. If you pour vinegar on the garage floor you will probably not notice anything right away. You might not notice anything a day later. Let it sit for several months and you probably will.

Carbonic acid in rain dissolves the mortar between bricks. But it takes years to work.

[vintner Super Moderator Find all posts View Profile Close vintner]

If you care, you could take a q-tip, dip it in your auto battery's acid, then drip or write on the concrete. You will see a reaction quickly. Lots of power in that acid.