Question

We're seeking affordable reinforcement with corrosion protection for new poured-concrete porch decks, columns, and tie beams.

Asked by Mike
Merritt Island, FL

Our "new-build" home is bordered by brackish lagoon water and is located approx. 1.5 miles from the Atlantic Ocean in a Florida coastal area with HVHZ wind loads. 5000-psi concrete has been spec'd for the high-exposure structural areas. MMFX (long lead-times), "2205 SS" stainless steel rebar, and hot-dipped galvanized rebar are three options being considered. The 2205 SS rebar initial cost estimates are over eight times the comparable prices of the other two options. Hence, SS seems MUCH less affordable (even when factoring in lifecycle costs). Thanks in advance for any help deciding on an affordable corrosion protection approach.

Answer

Answered by Glenn Summers

Indian Harbour Beach , FL

ConselcoR, Inc

July 17, 2010

Mike, the 2205 SS bar is very expensive! Galvanized or epoxy-coated is significantly less, however still an added expense to your construction.

Epoxy-coated bar is also subject to being compromised with handling on installation. A number of case histories reveal that epoxy-coated bar that has a nick in the coating corrodes much more agressively at that location and can account for a structural failure. Basically, the electrochemical reaction that might normally occur over the entire bar surface area is concentrated at the coating breach and will completely sever the steel at one point!

The most affordable concrete preservation is a product called StableCrete, a liquid penetrating sealer that is spray, brush or roller-applied to the virgin concrete surface as soon as possible. It penetrates into the gel-pore/capillary system and reacts inside the concrete, filling these voids to waterproof the concrete without leaving a membrane on the surface that may cause a bond problem. Coatings, stucco, thin-set for tile or adhesives are placed without need for etching or sand-blasting to prep or remove a membrane from the surface.

The first harmful event to a concrete is "carbonation" of the surface by exposure to the CO2 in the atmosphere. The longer the concrete is left untreated, the deeper the carbonation goes below the surface. This "carbonation" causes the pH of the concrete to decrease.

New concrete is 13+or- when poured. High-pH concrete that surrounds reinforcing steel forms a "passivating" layer on the steel and as long as that high pH is maintained steel cannot corrode. Corrosion cells begin to form once the pH drops below 11.5. This is why it is so important to waterproof before the pH levels at any depth are allowed to drop.

StableCrete waterproofs the concrete, which starves a concrete interior of moisture and oxygen, two of the four essentials necessary for corrosion to commence on steel. The combination of maintaining a high pH and a low/no moisture/oxygen interior will protect the reinforcment. 15-year warranty for waterproofing with a material cost of around $0.35 a square foot.

A treated surface is now stabilized with no chemicals migrating out to a surface to cause paint peeling/burn or conditions like ASR or efflorescence to appear. Perfectly safe for interior use with an extremely low VOC content (13 g/L). You live in the corrosion capital of the United States and are very wise to protect the concrete!

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