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“Upside-down” concrete
Topic Started: Nov 30 2010, 01:57 PM (437 Views)
brenda
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..............
http://www.cts.umn.edu/Publications/ResearchENews/2010/10/index.html#concrete


Even if further research shows this product does not work well in Minnesooota, it could work very well in warmer climates.

"Upside-down" concrete intrigues pavement researchers
Quote:
 
From a pavement engineer’s point of view, “everything is upside-down” in the world of pervious concrete. Unlike standard concrete, pervious concrete is specially formulated to contain myriad tiny pores that allow water to drain through to the subgrade instead of running off into storm drains. It offers potential benefits in stormwater management, especially in large paved areas such as parking lots. University of Minnesota civil engineering professor Lev Khazanovich, a leading expert in pavement analysis and modeling, has been studying the drainage properties and durability of pervious concrete, and presented some of his team’s findings at a CTS seminar on October 28, 2010.

Among the most important issues related to pervious concrete, Khazanovich explained, are drainage capacity and durability. Because pervious concrete is not completely solid like conventional concrete, it has different physical properties including higher flexibility. Khazanovich’s research, sponsored by the National Ready Mixed Concrete Association, looked at how pervious concrete stands up to wear over time and how its drainage properties are affected by environmental conditions.

The effect of freeze-thaw cycles on pervious pavement is a particularly important question for paving projects in Minnesota. The researchers asked whether water freezing within the concrete matrix could damage the pavement, leading to cracking or a reduction of its drainage performance. But even without freeze-thaw damage, the porous nature of pervious concrete could, the researchers hypothesized, render it less resistant to repeated mechanical stress from heavy vehicles.

Although testing the mechanical properties of paving materials using small samples in the laboratory is a useful technique, Khazanovich noted that long-term monitoring and testing of real-world pavements is the best way to ensure accurate results. “What we see in the laboratory is not always how things are in the field,” he noted, due to the many environmental variables that affect pavement performance.

To study pervious concrete under real-world conditions, Khazanovich turned to the Minnesota Road Research project (MnROAD), which operates a dedicated experimental low-volume roadway for pavement testing. The researchers constructed several pavement sections using pervious concrete and monitored the pavement over time as it was exposed to precisely controlled vehicle traffic on the closed course.

Analyzing the wear and deformation of the pervious concrete proved problematic, however, because conventional pavement-coring techniques damage the porous matrix of the pervious material. The problem was solved by Kevin MacDonald of Cemstone, who realized that the concrete’s structure could be preserved by saturating it with a clear, non-viscous epoxy while taking the core sample. The epoxy fully penetrates the concrete’s porous structure and supports the pervious material as the coring bit cuts out a sample.

The researchers analyzed the pavement samples to determine how much permeability was affected by the accumulation of fine particles in the porous concrete matrix. They found that most fine particles accumulate within the top quarter-inch of pavement, and that even a small volume of particles can significantly degrade the concrete’s ability to drain water. Cleaning pervious concrete using vacuum devices is an important maintenance task that can restore much of the material’s ability to drain water; however, such cleaning methods are most effective in the uppermost one-eighth inch of pavement, making the removal of deeper particles a significant maintenance concern.

The majority of pervious concrete sections studied proved resistant to freeze-thaw damage, while a few fared significantly worse. However, the researchers were unable to identify consistent factors that made certain pavements more durable in the Minnesota climate. Khazanovich noted that the implications of freeze-thaw damage are not limited to pervious concrete—non-pervious pavements may experience similar effects but manifest damage in different ways due to the higher strength of standard concrete.

One unusual finding from the study was that pavements constructed later in the summer performed better than those constructed early in the season. Previous research has established that conventional concrete pavements tend to perform better when they are constructed earlier in the summer.

The researchers also asked whether the same engineering models used to design conventional concrete pavements could be relied on to predict the performance of pervious concrete given the material’s porous and relatively flexible nature. Khazanovich and Vancura compared the results of a traditional and widely used concrete model to the performance of their real-world samples using finite element modeling. They found that the model generally produced good predictions of pervious concrete performance.

The researchers also analyzed subgrade reaction using data from the MnROAD long-term pavement performance database. Model results for both rigid and pervious concrete pavements showed that the performance of both materials differed from the classical model’s predictions. Given that the performance of pervious concrete differs from the model in roughly the same way as rigid, non-pervious concrete, the researchers concluded that conventional models could be used in the design of pervious pavements.

However, Khazanovich noted the need to alter the model’s parameters to accommodate the new material’s modulus of elasticity to avoid overestimating stresses on the pavement. Currently, he said, there exists no fatigue model properly calibrated for pervious pavement, although the StreetPave model appears most relevant to the task. The base layers appear to contribute significantly to the flexural strength of pervious concrete, more so than in the case of rigid concrete. Further calibration of models for pervious concrete applications appears to be necessary to achieve the best results.
“Weeds are flowers, too, once you get to know them.”
~A.A. Milne
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Frank_W
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Resident Misanthrope
Sounds like this could pave the way for further, tougher research, as long as peoples' thinking doesn't become too rigidly set.
Anatomy Prof: "The human body has about 20 sq. meters of skin."
Me: "Man, that's a lot of lampshades!"
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Aqua Letifer
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ZOOOOOM!
Well, they'll need much mortar research before they start setting anything in stone.
I cite irreconcilable differences.
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Frank_W
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Resident Misanthrope
Perhaps they can begin to form up some initial opinions, though.
Anatomy Prof: "The human body has about 20 sq. meters of skin."
Me: "Man, that's a lot of lampshades!"
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ivorythumper
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I am so adjective that I verb nouns!
I like permeable surfaces, but I am not an early adopter of building technology.

That said, I'd love to do a project in translucent concrete.

Posted Image
The dogma lives loudly within me.
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ivorythumper
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I am so adjective that I verb nouns!
"In the aggregate, the quality of this thread is slumping. I have no idea how to cure that", he said with a gravelly voice.
The dogma lives loudly within me.
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brenda
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..............
ivorythumper
Nov 30 2010, 02:21 PM
I like permeable surfaces, but I am not an early adopter of building technology.

That said, I'd love to do a project in translucent concrete.

Posted Image
http://www.litracon.hu/product.php?id=9

Never seen it before. Cool!
“Weeds are flowers, too, once you get to know them.”
~A.A. Milne
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Frank_W
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Resident Misanthrope
I've got some neighbors who would look really good, in a pair of loafers made from that stuff. :)
Anatomy Prof: "The human body has about 20 sq. meters of skin."
Me: "Man, that's a lot of lampshades!"
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ivorythumper
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I am so adjective that I verb nouns!
"It matrix some of you, but not me" he replied with a reinforcing steel in his eyes.
The dogma lives loudly within me.
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ivorythumper
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I am so adjective that I verb nouns!
brenda
Nov 30 2010, 02:29 PM


Never seen it before. Cool!
MS did a project on it in her MBA course on future information technologies.

It was too cutting edge for the prof to get.
The dogma lives loudly within me.
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PattyP
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Senior Carp
ivorythumper
Nov 30 2010, 02:35 PM
brenda
Nov 30 2010, 02:29 PM


Never seen it before. Cool!
MS did a project on it in her MBA course on future information technologies.

It was too cutting edge for the prof to get.
Great idea! Would be fabulous for sidewalks at night time.

A tired dog is a good dog.

"Dogs' lives are too short...their only fault, really."
A.S. Turnbull
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Dewey
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HOLY CARP!!!
I considered it for the parking areas of a project here several years ago, but the issue of damage via freeze-thaw cycle, and the newness of the technology, led me to recommend that the client not use it. Plus, the ones I've seen are a bit tougher to traverse for women in high heels, if that's a concern.
"By nature, i prefer brevity." - John Calvin, Institutes of the Christian Religion, p. 685.

"Never waste your time trying to explain yourself to people who are committed to misunderstanding you." - Anonymous

"Oh sure, every once in a while a turd floated by, but other than that it was just fine." - Joe A., 2011

I'll answer your other comments later, but my primary priority for the rest of the evening is to get drunk." - Klaus, 12/31/14
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Axtremus
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HOLY CARP!!!
Dewey, it that was a multi-floor garage, perhaps you can consider recommending translucent concrete to make it easier for women with high heels?

Embedding optical fiber to make the material "translucent" ... may be Q can really make a translucent car for James Bond after all.
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Dewey
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HOLY CARP!!!
Heh, sorry Ax, it was a surface lot. ^_^
"By nature, i prefer brevity." - John Calvin, Institutes of the Christian Religion, p. 685.

"Never waste your time trying to explain yourself to people who are committed to misunderstanding you." - Anonymous

"Oh sure, every once in a while a turd floated by, but other than that it was just fine." - Joe A., 2011

I'll answer your other comments later, but my primary priority for the rest of the evening is to get drunk." - Klaus, 12/31/14
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Steve Miller
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Bull-Carp
ivorythumper
Nov 30 2010, 02:21 PM
I am not an early adopter of building technology.

Neither am I, and by the time this stuff has established a track record I'm willing to warranty I'll be too dead to use it.
Wag more
Bark less
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Frank_W
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Resident Misanthrope
Dewey
Nov 30 2010, 03:01 PM
Plus, the ones I've seen are a bit tougher to traverse for women in high heels, if that's a concern.
What??? What the hell is she doing out of the kitchen?! :veryangry:
Anatomy Prof: "The human body has about 20 sq. meters of skin."
Me: "Man, that's a lot of lampshades!"
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PattyP
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Senior Carp
Frank_W
Dec 1 2010, 06:04 AM
Dewey
Nov 30 2010, 03:01 PM
Plus, the ones I've seen are a bit tougher to traverse for women in high heels, if that's a concern.
What??? What the hell is she doing out of the kitchen?! :veryangry:
:lol2: :lol2: :lol2:

A tired dog is a good dog.

"Dogs' lives are too short...their only fault, really."
A.S. Turnbull
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