Volumetric Mxer Using Type 3 2

[7515325]

Company just purchased a brand new Zimmerman Vol Mixer with the intent to mix rapid set concrete to use on highway project. Then the money people see the cost of rapid set material and want me to design a mix using Type III cement. I talked to a admix rep and the amount of liquid we will have to use does not sound like it will work. We need 3000 psi in 3to4 hrs. Has anyone seen a mix that will work using type III, I, or II using a Vol Mixer? Going to have a admix rep in the office wed to try to tell the big boys its going to be a night mare. I have a company that can supply the mix and meet the spec but after spending so much money on the mixer they feel the need to use it. Help

 

[Ron]

You won't get 3000 psi in 3-4 hours using Type III cement unless you make it incredibly hot...which will create durability and shrinkage issues.

The mixer has little to do with it.

 

[Hoaokapohaku]

7515325,

I have no experience with a similar specification, however I recently attended a seminar presented by a recognized expert in concrete pavement repair who presented the following information indicating required cure times for various concrete repair materials.

Blended cements 2-4 hours
Sulfo-aluminate cements 2-4 hours
Type III with accelerator 4-6 hours
Type I with accelerator 6-8 hours
Type III with water reducer 2-24 hours
Type I 24-72 hours

HOWEVER, the times indicated are to attain 1700 psi, the recommended required strength to open to freeway traffic on an 8" thick pavement. Determination of the precise time at which the repair may be opened to traffic is determined in the field by use of maturity meters.

I'm assuming you are doing highway concrete pavement repair work, although you didn't quite say that. If so, is there an unusual circumstance that prompts the 3000 psi in 3 hours requirement? If not, and if you have a good working relationship with the agency, perhaps the requirement could be revised. According to recommendations of the Portland Cement Association ("Design and Control of Concrete Mixtures", 2002, table 17-2 titled "Selected Properties of High-Performance Concrete", 3000 psi at 3 hours is the absolute maximum that may be specified for high-early concrete. Trying to meet the most difficult specification of it's kind with a brand new piece of equipment when you don't have experience either with the equipment or meeting these specs is a horror story waiting to happen.

Your problem reminds me so much of a similar problem of a friend and colleague of mine that I wonder if you are him! If so, we recently worked together on a 650 Flex pavement. Couldn't be, could it?

 

[7515325]

Its a Highway Project as said in my post. Thanks for the info. Not sure I am your friend, but I have worked with many. I have been working DOD projects for the last 20+ years. Live in Okla worked at Edwards AFB for many years. The trick so it seems to get the 3000 in 3 hrs is using a cure box to keep the heat in the test cylinders as close to whats being generated by the slab in place. Most do not agree that the cylinders setting on the side of the road are different than the slab that is surrounded by concrete on all sides. Putting them in a box under a control temp seems to work.

 

[Ron]

751...cylinders are not intended to represent the in-situ condition...they are intended to represent the mix design. It is difficult to replicate the in-situ condition with cylinders, however they may be cured in the field.

 

[Hoaokapohaku]

7515325,

Nope, you're not the guy I'm thinking of.

I realize you said it was a highway project, but I considered the concrete might be for some other aspect of a highway rather than a pavement.

The heat in cylinders vs. in place is why I mentioned the use of maturity meters. They measure and record the accumulated heat in the in place concrete itself rather than a test cylinder.

http://www.engius.com/web/special/rb-spotlight.aspx