Coloring vs. Staining Concrete 2

[wancho]

I have a project involving a bridge replacement in which the USFS is requiring us (Public Works) to design the bridge to meet specific "scenic objectives". Basically they do not want a normal grey concrete bridge, they want it to somewhat blend into the forest scenery. I have contacted a few concrete contractors in the area and have been given conflicting statements on staining vs. coloring both cast in place structures and precast structures. One says staining requires more maintenance (seal eavery couple of years), while another says using stain is more permanent and not as maintenance heavy as the other stated.

So looking at both initial costs and maintenance costs, (we of course prefer the less maintenance aspect) would coloring be the better route? And does staining really require the maintenance of sealing every couple of years? Has anyone experienced a similar situation? Any input would be greatly appreciated!

 

[concretemasonry]

Does the bridge have just one type or two types (precast or cast in place)or is the exposed area of concern all the same type?

Are the local ready-mix suppliers capable and experienced with pigmented concrete? I assume a precaster has the experience and quality controls.

If you lump "staining" into one category, you are getting a wide range of products and processes. You may want to also research the stain suppliers instead of concrete contractors, since they usually have a wide range od applications under many conditions.

Dick

 

[wancho]

Thanks for the response, Dick.

The bridge will have cast in place abutments (3) and precast girders (2 spans).

I have a feeling the local redimix suppliers are capable, but not as experienced (small market area).

In your opinion, would using colored mix provide a better controlled result?

Steve

 

[civilperson]

Look at the bridges around the Las Vegas loop. Cement based paint used on recessed patterned concrete with 25 year life.

 

[wancho]

The paint would be an issue environmentally speaking. I don't think Vegas has the wetland/endangered fish supporting creeks worries this project is facing. As it is, looks like we're going to have to stage 3 cranes in the wetlands just to set the girders. So staining/dyeing prior to placement is preferred.

 

[cvg]

the color of the precast will not match the cast in place color if using a dye mixed into the concrete. It is best to have all concrete with color dye produced at the same time by the same plant in order to best match the resulting color. staining would probably produce a better color match. However, you will have to stain your abutments in-place which will have the same, if not additional impacts on the fish as the paint. My experience with stains, is that surface prep is essential to obtaining a uniform result and the same prep needs to be done on both the precast girders and on the abutments. this will probably require an acid etch on the abutments which will impact your stream also. I think pain has the least impact and greatest chance of matching.

 

[concretemasonry]

"dyes" should not be used to tint concrete.

In the international and domestic concrete industry, synthetic iron oxides are the most commonly used materials, especially in the range of colors usually desired and where ultra violet resistance is needed. They are readily available 1000's of yellows, reds, tans, browns and even in some blacks in addition to blended combinations. They warm the cold gray color of concrete. Normally, the sythetic (refined and processed) iron oxides are have the strongest tintin strength and are more consistant. The natural oxides and "umbers" are weaker and contain more imputities. For synthetic iron oxides, the maximum dosage is 10% of the cement content, with the average in the range of 1/2 to 3%.

For some other colors, there are other oxides (chrome as an example), but they are very strong and are for non-traditional tints.

Other types of "dyes" are better suited for other applications and uses. For practical opinions, I would think the producters of "tinted/colored" concrete and concrete products and the pigment suppliers (Bayer Chemical, Pfizer, Rockwell, and following entities) should be contacted in addition to local concrete contractor. The material suppliers and the producers have a much wider range of experience and the expertise, technical research and background in both factory produced and site cast concrete products)and it is a large part of their business.

Dick

 

[hokie66]

Oxide in the concrete, as Dick recommends, is the best solution. I would avoid just staining the surface. Any surface application will require maintenance.

 

[phuduhudu]

The problem with oxide in the concrete is that it can get quite expensive to colour the whole body of the concrete. Precasters sometimes add oxide just to the top layer but that affects the casting process and the moulds. You can do it by having a coloured batch which you spread in the mould say 100m thick and then another plain batch which goes in on top. Quite difficult to control though. Staining is usually done with acid which etches in the colour and as others have pointed out that can have environmental implications when the acid is washed off. Though if you are precasting then this could be done at the factory. The other option is to render with an oxide pigmented render. That would be maintenance free too. The other thing to investigate would be using lime oxide paint. It's basically a lime wash (whitewash) with oxide added in. It is very durable and much cheaper than synthetic paints. They could even be lime washed at the precasters yard. It doesn't give you a really even finish but it can look much more natural than synthetic paints and might fit in well.

Carl Bauer

http://www.bauerconsultbotswana.com

 

[wancho]

Thank you all for your comments/suggestions. Oxides are looking to be the front runner at this point, if the project goes forward.

 

[LCruiser]

We don't allow anything other than colored concrete. Quality control in the long run (usually after the contractor is gone) turns into a major issue. If you are concerned with the long term appearance, the color must be full depth.

 

[unclesyd]

You might want to look at this type product for any abutments, retaining walls, etc.

http://increte.doublematrix.com/vProduct.aspx?ID=2