CONCRETE ADDITIVE QUESTION

[Guido]

Okay, We've got a problem here!!

A few months back we got in some concrete with fiberglass reinforcement in it (replacing the aggregate) for our airfield repairs. Our airfield stays pretty active so we really don't have time to let the concrete set normally. They sent us some accelerator and it worked great, set up really fast when we mixed 2 parts concrete to 1 part accelerator. Well the stuff I tested in the fall is all gone now and SUPPOSEDLY we got more, but its in a different kind/color bag then it was in before. I'm not even sure it was accelerator but we got a few he said / they told me stories, so we tried it. It took almost 24 hours to set-up enough to drive over it!! :(

So, I'm trying to find out if this was accelerator or some type of grout or morter they sent us (Thats what it smells like) I mixed some accelerator by itself (just a cup full) and it set up in about an hour or so.

My question is, should accelerator (powder not liquid) set up all by itself??

I would think there is a chemical reaction that takes place with the cement or something.

Please let us know what you know about this because its hard to find out anything about the product being here in Germany, they're always trying to pull stuff over on us.

Thanks in Advance! ;)

[paul]

With out seeing it it might have been a liquid plastizer, It's used to increase concrete strength. If it's not mixed enough it will not set very fast.

[osc]

I cannot really answer your question directly but here in Ohio, they use 1 or 2% calcium and it sets up really quick. Usually calcium is used as an additive in winter to prevent the concrete from freezing.

[parkwest]

Calcium Chloride is the most commonly used accelerator. It is rock salt. Salt lowers the freezing temp of water about 5 degrees plus it bonds with water molecules to speed up the removal of water from the mix.

Hope this helps.

[parkwest]

Originally posted by guido
They sent us some accelerator and it worked great, set up really fast when we mixed 2 parts concrete to 1 part accelerator.

It is reccommended never add more than 2% of CaCL by weight of cement. Too much may cause flash set, increase shrinkage(cracking), corrode reinforcement and weaken and discolor concrete. Did you really add 33% CaCl? How did it turn out? I guess you really won't know the answer for a couple of years.

[thelawnguy]

calcium Chloride is not the same as rock salt (Sodium Chloride).

I would double check as to which is to be used before possibly spoiling a load of mud.

[Guido]

If you read this thread tonight (Sunday/Monday) See if you can see what that stuff in the red bag is (the ONE bag thats left) and see what chemicals are in it and post here. I'm not sure what it even is. Thanks. If not I'll check tommorow night when I come in.

[parkwest]

Lawnguy,

Please check. I believe NaCl sodium Chloride is table salt.

[thelawnguy]

"Please check. I believe NaCl sodium Chloride is table salt."

Table salt and rock salt are the same thing, both sodium chloride just one has had the bugs and sticks sifted out of it and ground up finer. Go to a fancy french restaurant and watch em fill that fancy salt grinder with Halite lol.

Anyways, sodium chloride (salt) is different than calcium chloride (calcium) and I wonder if they do or do not have the same effect on concrete? Besides melting ice lol.

[Chuck Smith]

NaCl is Sodium Chloride
CaCl is Calcium Chloride
MgCl is Magnesium Chloride

~Chuck

[joe2106]

Calcium is fine, but don't use it if there is rebar inside b/c it will erode it. Use a non-chloride accelorator.

If you want fast setting concrete you have two options. One is to use Type III cement, which is high early strength, or use additives like calcium to speed the process. (Liquid is always better in my opinion with calcium)

If you only need a small amount of patch find a traffic patch or something in your area. I have mixed some of that stuff and you can literally drive over it within 15 minutes.

Email me any concrete questions. I have been in the ready mix industry my entire life.