microsilica vs. DCI corrosion inhibitor

[JKStruct]

I'm working on an unbonded PT parking garage in chicaco. Our concrete spec calls for a microsilica admixture for corrosion protection. The contractor submitted an RFI asking if a Grace DCI corrosion inhibiting admixture would be an acceptable subsitute, on the basis that the microsilica mix requires a longer curing time. I have read some information on both systems, and it appears this might be acceptable. In your professional opinions, might this be acceptable? Are there any adverse repercussions that I am not considering? As a follow up question, from my understanding, the horizontal elements are more critical for corrosion protection of the reinforcement. Is it possible that the vertical elements (columns and shear walls) be poured with a separate mix devoid of this admixture? Or is that not general practice? I'm relatively new to the industry, and I would appreciate the thoughts of those more experienced. Many thanks.

 

[spagetti]

At our plant we have been using dci/cni for quite a while, as we are in Virginia and do alot of coastal parking deck, most of our jobs use 2 gals./yd. and occassionally with epoxy coated reinforcment and always in double t's where salt spray may be an issue. You do however realize a faster set time. we also use dci/cni in top mixes of face pours or insulated panels to allow finishers to get on the beds with trowel machines earlier. most all of our mixes run at about a 9 inch slump, the trick is to find the right time to put a broom finish on the double t's before it sets so much that it looks like you need a lint brush, or getting on it to early the finish will re-settle