If I want to tell my redimix plant to add plasticizer to ease the pour, which should I tell them to use, and in what proportion?

Gene,

In my opinion it is better to use an internal vibrator than to try to use a super plasticizer.  Much easier to handle and control.  We use a standard 3000 psi concrete mix with 57 stone at a 5" to 6" slump.  Consolidation is achieved with a 1" to 1.25" vibrator head on an electric vibrator.  Have striped  foam and know that we get concolidation through rebar and into corners. 

I agree that a 3000 or even a 3500 mix allows a lot of latitude in the flow. However, the redi-mix company should have someone on staff who could help you with your design. By the way, although you said plasticizer, I suggest you look at using a mid-range water reducer, if necessary!

There are way too many variables to just say one or two gallons per yard. Everything from wet sand and stone, temperature of materials, etc...all contribute as to the final proportion.
This stuff gets a little scientific in it's mix amounts, so it's important to have someone at the plant handle how much to give you what you want on site.

We had a load come in one time where they added Super P instead of the mid-range water reducer I sometimes use. It played hell because the lift wouldn't set up so we sent back the second truck and let it set awhile until we could proceed again. Added hours to a simple 47 yd pour

Gene, talk to your batch plant that you will get the concrete from, if they have ICF experience they have designed a mix especially for ICF. Ask them what their mix is composed of. We use a mid-range with pea-stone when were working in a area where we don't know the plant's reputation well.

Dave

Gene ,
stay away from super p.
A small aggregate mix at 3500 psi with a six inch slump at the pump will do just fine.
Plasticers or water reducers aare fine when everything goes exactly right but they will bite you if they get a chance. As a DIY you wont know somethings wrong until it is to late.
Regards,
Joe

Who's the DIY?

Gene:

 

I read your first post regarding the amvic interlock.  I may be reading in between the lines, but it seems that you have a decent level of experience with concrete and you are doing your research ahead of the actual building.  If you are familiar with the characteristics of super plasticizers (high range water reducer) and feel comfortable in using a high range rather than a mid range, it will work fine. 

Typically, the readymix producer only handles one brand of chemical since they have to have dispensers etc. for adding it to the concrete.  Essentially the only way you can get an answer to the question is to talk with the Quality Control person at the Readymix producer you are planning on using.

In the event that you have the opportunity to procure the admix apart from the concrete, you can usually discuss dosage rates with the sales rep or technical folks with the manufacturer and start conservatively from there.  We recently built five three story apartment buildings and decided that the best solution to such a thing was to add the chemical on site as needed.  This took some tweaking and turned out to be a good move.  By the size of your project, I'd guess that you are looking to place 30-50 yards.  In your case, any change in mix design or dosage rate by the readymix producer will not be instantaneous for you since you are likely to have two or three trucks on the road at the time you start placing concrete....you could delay trucks after the first one, but depending on batch and delivery time from the producer, you could take all day to place concrete as a result.  If you have stable temperatures, the readymix producer should be able to deliver a 5-6" slump mix design to you which will work.  Depending on the volume of reinforcing steel, this should suffice for your project (as previously mentioned, INTERNAL vibration is a smart move)  You can discuss with the QC representative to allow you to add as much as 20 gallons of water on site without destroying the integrity of the concrete, this way, you can adjust slump not only at the start of the truck, but possibly again should you place the concrete slow.  On a project like this, you realistically can attain a placement rate of 10-15 minutes per truck provided the pump operator can limit the mess and keep the hose over the wall.  If you can place concrete at a fairly fast pace, then you don't need to worry about loss of slump...this is where most people get lost...they don't know when to say "when" and stop, reslump the truck and carry on.  Your vibrator person is the person that you must listen to in this case.

I would also recommend that you get in touch with the amvic person that is going to be on your site to see if you can accompany him/her to other projects prior to your own so that you can get a hands on grasp of what takes place....without the risk of your own project.