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Stains & colors or discoloration on concrete surfaces: this article provides a catalog of types of stains found on concrete surfaces: walls, floors, ceilings, including un-wanted stains from various causes & deliberate concrete coloring processes, stains, or acid treatments.
Methods for removing un-wanted discoloration or stains from concrete. Catalog of research on causes & cures of concrete staining. Concrete stain products & product sources are also provided.
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[Click to enlarge any image]
At above right the concrete floor was "stained" using an acid treatment. The light patches in the left of the photo indicate foot-traffic wear through the acid-treated concrete surface . (Rigby 2006).
Wear on a stained concrete floor will be increased by any of the following
See these diagnostic articles
Reader Question: what are these black stains on our concrete porch?
Rhonda, the black marks in your photo (shown here so that others may comment) may be due to moisture variations in the slab, moisture from below, or moisture entering the house-slab juncture, possibly bearing staining contaminants. But most likely we're looking at a combination of variation in concrete hardness and moisture level.
This comment was originally posted at MOLD APPEARANCE - STUFF THAT IS NOT MOLD
Research References on Stains on Concrete Surfaces
Causes of stains on concrete; diagnosis & removal of concrete stains & discoloration
Reader Question: what are the different concrete stains & markings shown in these photographs?
Please offer me your expert opinion on what is going on with my structural walls. I am working on a project located on Eko Atlantic Lagos Nigeria. And despite all our efforts we keep getting bug holes as shown below. C.I., Nigeria, 7/2/2014
Reply: a catalog of concrete surface markings & stains
I'll be glad to try to assist, with the warning that I am not a concrete engineer, though I do have experience in the subject.
Commenting on your photos in order [Click to enlarge any image]
1. Your photograph of "bug holes" in the concrete wall photo above look to me like small voids due to air bubbles in the concrete pour, probably due to poor mixing;
On larger & commercial concrete placement projects concrete contractors use a vibrator to remove these bubbles and avoid the voids. In my photograph below, taken at the Vassar College building project in New York in 2014 you can see workers using the vibration tool as a large floor slab is being poured.
Only if these "bug holes" are in very great number would one expect there to be a structural concern. I can't evaluate that from a photo - you'd need an onsite expert. Usually for an important pour of structural concrete an expert checks the mix and the slump and the placement of reinforcing steel.
It's worth noting that entrained air has been intentionally included in some concrete placement operations for a very long time as a partial protection against freezing effects, salt scaling and other forces, as described in these research citations where proper air entrainment procedures are explained. As you'll see in our citations given below, Powers (1969) has written extensively on this topic.
2.Photograph of holes & chip marks in a concrete wall (above) looks like chipping or spalling where concrete form ties were removed (cosmetic)
3. Photograph of the dark horizontal lines in a concrete wall (photo above) look like concrete form ties; the horizontal lines seem to mark boards used for the concrete forms. I suspect that moisture variations during wall curing or possibly accumulation of water in irregularities in the form-wall caused the darkness.
The rippled surface in the lower right corner of the photo above (enlarged just below) suggests the mix contained excessive water or that plastic had been placed against the inner surface of the concrete form, but that's just an OPINION and we'll be interested to see what some of our readers who are concrete experts can offer.
4. & 5. Photographs of dark lines and blotchy areas in the concrete walls in the two photographs below look like cold pour joints in the concrete wall.
In your last photo (below left) we see both cold pour joints and rough surface areas or surface voids in the poured wall as well as holes (in both photos) from form ties.
Concrete Stains from Rusting Inclusions or Exfoliating Steel
The lower photo also includes reddish stains that may be rust from either metal forms or from iron slag inclusions in the concrete mix.
See details about cold pour joints found at CONCRETE COLD POUR JOINTS
If you give permission for me to publish these photos I may be able to solicit more expert opinions for you - I can keep your identity information private or can publish it with your contact information - which ever you prefer.- DF
You reflected my thoughts as well. Thanks for the link on concrete cold pour joints it was insightful.
Below are a concrete batch report and a sketch of the concrete wall plan for our project.
[Click to enlarge any image]
Research citations on air entrainment in concrete & freeze-thaw effects
Continue reading at STAIN DIAGNOSIS on BUILDING EXTERIORS or select a topic from the More Reading links shown below.
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