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I've seen roads in TN and MS where the interstate appears very red-tinted in the pavement; same with some other roads as well. Does anyone know why?
Likely for the same reason a lot of South Dakota roads appear to have a pink-to-lavender tint to them: Chip seal. The aggregate used for chip seal in TN and MS may have more red tint to it.
Quote from: brad2971 on May 18, 2020, 05:49:38 PM
Likely for the same reason a lot of South Dakota roads appear to have a pink-to-lavender tint to them: Chip seal. The aggregate used for chip seal in TN and MS may have more red tint to it.
I-40 east of Lehi, AR has the same red tint. Because of the color of the aggregate in the pavement as well.
The most common reason for this is iron compounds in the aggregate. So, broadly speaking, the pavement is red for the same reason your blood is.
Similarly the Mojave Desert has a lot iron content that ends up in asphalt mixes. The red hue is particularly prevalent in places like the Mojave Preserve.
I too noticed that Mississippi uses red aggregate for chip seal. It used to be more common in Arkansas going way back. Made the road look older, I thought as a kid. Now it's nearly nonexistent there.
Southeastern ID uses red lava rock as a snow treatment. Turns the pavement red.
Reading, MA has it, and possibly a few other towns, although I see it as purplish red.
It's all about where the paving contractor can get their materials for cheap, which almost always means the nearest supplier. It's the same reason you see limestone riprap in certain aprts of the country and granite riprap in others.
Remember the "red hills of Georgia" line from MLK's "I Have a Dream" speech? There's a lot of red soil in the south, and if it is used in road building, it tints the roads.
There are sections in the MI UP with red roads too, due to iron-bearing materials used.
I had always heard the red or brown aggregate was dredged out of the major barge-trafficked rivers (Tennessee and Mississippi Rivers). That may not be entirely correct, but thought I should at least throw it out there.
Maryland, especially the Panhandle, has a lot of red roads. For instance, when coming into Cumberland on US-220, there's no "Welcome to MD" sign, but you can always tell where the state line is by the color of the road.
The pavement fades as it ages from the sun and rain that is prevalent in the South. Pavement that starts out black loses a lot of color after a few years.
Ironically, I seem to remember that when the Interstates were first built in northern Mississippi the exit and entrance ramps were red -- on purpose. The ramps were concrete that had been intentionally colored red.
Quote from: wriddle082 on May 20, 2020, 07:31:57 AM
I had always heard the red or brown aggregate was dredged out of the major barge-trafficked rivers (Tennessee and Mississippi Rivers). That may not be entirely correct, but thought I should at least throw it out there.
I doubt the size of aggregates needed for most asphalt mixes comes from river bottoms. The biggest reason is it usually is too rounded to effectively bind with the other ingredients. Doesn't mean it didn't happen, but there is a large quarry just south of the I24/US41 interchange. Asphalt screenings are a byproduct of the primary crushing process. It should be cheaper to get them from there instead of a dredging process which would require additional processing (washing to remove impurities then screening to get he right sized aggregate.