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High-tech concrete technology has a famous past
National Institute of Standards and Technology (NIST) ^ | March 16, 2011 | Unknown

Posted on 03/17/2011 7:00:58 AM PDT by decimon

In the business of concrete making, what's old—even ancient—is new again.

Almost 1,900 years ago, the Romans built what continues to be the world's largest unreinforced solid concrete dome in the world—the Pantheon. The secret, probably unknown to the Emperor Hadrian's engineers at the time, was that the lightweight concrete used to build the dome had set and hardened from the inside out. This internal curing process enhanced the material's strength, durability, resistance to cracking, and other properties so that the Pantheon continues to be used for special events to this day.

But it is only within the last decade or so that internally cured concrete has begun to have an impact on modern world infrastructure. Increasingly, internally cured concrete is being used in the construction of bridge decks, pavements, parking structures, water tanks, and railway yards, according to a review* of the current status of the new (or old) concrete technology just published by the National Institute of Standards and Technology (NIST).

The virtues of internally cured concrete stem from substituting light-weight, pre-wetted absorbent materials for some of the sand and/or coarse aggregates (stones) that are mixed with cement to make conventional concrete. Dispersed throughout the mixture, the water-filled lightweight aggregates serve as reservoirs that release water on an as-needed basis to nearby hydrating cement particles.

According to one study cited in the review, bridge decks made with internally cured, high-performance concrete were estimated to have a service life of 63 years, as compared with 22 years for conventional concrete and 40 years for high-performance concrete without internal curing.

"As with many new technologies, the path from research to practice has been a slow one, but as of 2010, hundreds of thousands of cubic meters" of the lighter and more durable material have been successfully used in U.S. construction, write the report's co-authors, NIST chemical engineer Dale Bentz and Jason Weiss, Purdue University civil engineering professor.

Compared with conventional varieties, internally cured concrete increases the cost of a project by 10 to 12 percent, Bentz and Weiss estimate on the basis of bridge-building projects in New York and Indiana. The increased front-end cost, they write, must be evaluated against the reduced risk of cracking, better protection against salt damage, and other improved properties that "should contribute to a more durable structure that has a longer life and lower life-cycle costs," they write. "Further, this could have substantial benefits in a reduced disruption to the traveling public, generally producing a more sustainable solution."

The 82-page report summarizes the current practice and theory of internal curing, reviews project experiences and material performance in the field, and describes opportunities for research that could lead to enhancements in the material.

###

* D.P. Bentz and W.J. Weiss. Internal Curing: A 2010 State-of-the-Art Review (NISTIR 7765). Feb. 2011. Available at: www.nist.gov/manuscript-publication-search.cfm?pub_id=907729.


TOPICS: Business/Economy; History; Science
KEYWORDS: godsgravesglyphs
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Caption: X-ray microtomograph (left) shows pores (blue) that remain within lightweight aggregates (LWAs) after water has migrated from the pre-wetted materials during the first day of hydration. In the two-dimensional image (right), the emptied pores are superimposed over the original microstructure (hydrating cement paste is white, sand is light grey, and LWA is dark grey), illustrating the detailed pore structure of LWA particles.

Credit: NIST

Usage Restrictions: None

1 posted on 03/17/2011 7:01:01 AM PDT by decimon
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To: SunkenCiv

Don’t ask why ping.

I guess that Hadrian’s boys didn’t need to know why to know what worked.


2 posted on 03/17/2011 7:03:04 AM PDT by decimon
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To: decimon
That's right. My Italian ancestors invented concrete. We made things out of it. Aqueducts, Coliseums.......shoes
3 posted on 03/17/2011 7:04:29 AM PDT by massgopguy (I owe everything to George Bailey)
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To: decimon

Reardon Concrete?


4 posted on 03/17/2011 7:07:26 AM PDT by Harpo Speaks (Honk! Honk! Honk! Either it's foggy out, or make that a dozen hard boiled eggs.)
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To: massgopguy
That's right. My Italian ancestors invented concrete. We made things out of it. Aqueducts, Coliseums.......shoes

My Italian ancestors were Calabrian...hard heads...good with masonry. ;-)

5 posted on 03/17/2011 7:08:03 AM PDT by decimon
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To: Harpo Speaks
Reardon Concrete?

Reared on concrete? Well, I am a New Yorker. ;-)

6 posted on 03/17/2011 7:09:55 AM PDT by decimon
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To: decimon

So, you essentially take a ground, highly porous material, saturate it with water and use it as a portion of the fines?


7 posted on 03/17/2011 7:25:53 AM PDT by fso301
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To: massgopguy
That's right. My Italian ancestors invented concrete. We made things out of it. Aqueducts, Coliseums.......shoes.

LOL. One size fits all.

8 posted on 03/17/2011 7:39:47 AM PDT by USMCPOP (Father of LCpl. Karl Linn, KIA 1/26/2005 Al Haqlaniyah, Iraq)
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To: fso301
So, you essentially take a ground, highly porous material, saturate it with water and use it as a portion of the fines?

I don't know. There is a 5 meg PDF at the link for anyone sufficiently interested.

9 posted on 03/17/2011 7:41:19 AM PDT by decimon
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To: decimon

MN-DOT should hire Romans to build our bridges.


10 posted on 03/17/2011 7:56:48 AM PDT by WOBBLY BOB ( "I don't want the majority if we don't stand for something"- Jim Demint)
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To: fso301

It’s conventional lightweight structural aggregate — (regional — here in So Cali it’s expanded shale, but other areas may use slate or clay). So it’s not really “highly porous”, but it does absorb some percentage of water (say 5-15%) over a 24 hour period.


11 posted on 03/17/2011 8:20:47 AM PDT by absalom01 (You should do your duty in all things. You can never do more, you should never wish to do less.)
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To: decimon

One of the reasons concrete plants try to keep their aggregate stocks wet to the SSD (saturated, surface-dry) condition. The key, though, is knowing how much water content the aggregate has, because it has to be accounted for in the mix design.


12 posted on 03/17/2011 9:59:07 AM PDT by JRios1968 (Laz would hit it!)
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To: decimon; StayAt HomeMother; Ernest_at_the_Beach; 1010RD; 21twelve; 24Karet; 2ndDivisionVet; ...

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Thanks decimon.
Almost 1,900 years ago, the Romans built what continues to be the world's largest unreinforced solid concrete dome in the world -- the Pantheon.
That dome helped school the architects of the Renaissance.

To all -- please ping me to other topics which are appropriate for the GGG list.
 

· History topic · history keyword · archaeology keyword · paleontology keyword ·
· Science topic · science keyword · Books/Literature topic · pages keyword ·


13 posted on 03/17/2011 3:45:39 PM PDT by SunkenCiv (The 2nd Amendment follows right behind the 1st because some people are hard of hearing.)
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To: WOBBLY BOB
MN-DOT should hire Romans to build our bridges

Either that or don't stack so much equipment on the bridge when your resurfacing it.

14 posted on 03/17/2011 3:57:22 PM PDT by Sawdring
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To: SunkenCiv; decimon

Visiting the Pantheon was a highlight of my touring Rome. Because it has been continuously maintained it looks like it could have been built 100 years ago instead of 1900. It’s like stepping into a time machine and visiting ancient Rome. Totally awesome.


15 posted on 03/17/2011 3:59:25 PM PDT by colorado tanker
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To: decimon
",img src="http://www.engr.ncsu.edu/news/media/images/canoe80a.jpg">

NC State Concrete canoe in competition

16 posted on 03/17/2011 4:34:15 PM PDT by bert (K.E. N.P. N.C. D.E. +12 ....( History is a process, not an event ))
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To: bert

17 posted on 03/17/2011 4:52:54 PM PDT by decimon
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To: colorado tanker

Thanks colorado tanker. It’s strange to think how Rome would look today had it not burned in the reign of Nero.

This Pantheon was built to replace the somewhat earlier one that burned (it was brick and wood), but the original inscription was restored on a building Agrippa never lived to see.


18 posted on 03/17/2011 4:59:11 PM PDT by SunkenCiv (The 2nd Amendment follows right behind the 1st because some people are hard of hearing.)
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To: SunkenCiv
The fire enabled Nero to build his huge Golden House. And IIRC, Vespasian built the Colosseum on part of its grounds. Yes, big changes from the fire.
19 posted on 03/17/2011 5:37:25 PM PDT by colorado tanker
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To: colorado tanker

There is a brand new (a few year’s old) tall building here in Seattle made of concrete. Except it seems that some union worker skimped on some of the details, and did not coat the tips of most of the rebar in epoxy.

The rust problem started showing up right away. Repairs cost something like $1.5 million. But they still didn’t work. The tenents have all been moved out and demolition of the entire building (14 stories???) is forthcoming.

(For want of a nail, the shoe was lost.....)


20 posted on 03/17/2011 6:43:05 PM PDT by 21twelve ( You can go from boom to bust, from dreams to a bowl of dust ... another lost generation.)
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