Westerville OH (SPX) Jan 05, 2011
Nearly one year after a 7.0-magnitude earthquake rocked the Republic of Haiti, engineering and concrete experts at Georgia Tech report that concrete and other debris in Port-au-Prince can be safely and inexpensively recycled into strong new construction material.
In a paper published in the Bulletin of the American Ceramic Society, researchers Reginald R. DesRoches, Kimberly E. Kurtis and Joshua J. Gresham say that they have made new concrete, from recycled rubble and other indigenous raw materials using simple techniques, which meets or exceeds the minimum strength standards used in the United States.
Most of the damaged areas of Haiti are still in ruins. The trio says their work points to a successful and sustainable strategy for managing an unprecedented amount of waste, estimated to be 20 million cubic yards.
"The commodious piles of concrete rubble and construction debris form huge impediments to reconstruction and are often contaminated," says DesRoches, professor and Associated Chair of Civil and Environmental Engineering at Georgia Tech. "There are political and economic dilemmas as well, but we have found we can turn one of the dilemmas - the rubble - into a solution via some fairly simple methods of recycling the rubble and debris into new concrete."
DesRoches, who was born in Haiti, traveled several times in 2010 to Port-au-Prince to gather samples of typical concrete rubble and additionally collect samples of two readily available sand types used as fine aggregates in some concrete preparation.
He and Gresham also studied the methods, tools and raw materials used by local laborers to make concrete mixes. DesRoches recalls they encountered no mixing trucks. "Instead, all of the construction crews were manually batching smaller amounts of concrete. Unfortunately, they were mixing volumes of materials 'by eye,' an unreliable practice that probably caused much of the poor construction and building failure during the earthquake," he says.
Before leaving, DesRoches and Gresham manually cast an initial set of standard 3-inch by 6-inch concrete test blocks using mixes from several different construction sites.
They returned to Georgia Tech with their cast blocks, sand samples and notes, where they were joined by Kurtis, also a professor and Chair of the American Concrete Institute's Materials Science of Concrete Committee.
They quickly discovered that the concrete test samples cast in Haiti were of poor quality. "The Haitian-made concrete had an average compressive strength of 1,300 pounds per square inch," says Kurtis. "In comparison, concrete produced in the U.S. would be expected to have a minimum strength of 3,000 pounds per square inch.
They then manually crushed the samples with a hammer to provide course aggregate for a second round of tests. In this round, they made concrete samples from mixes that combined the course aggregate with one of the two types of sands they had collected.
However, instead of "eye-balling" the amounts of materials, in this round of tests they carefully measured volumes using methods prescribed by the American Concrete Institute. The materials were still mixed by hand to replicate the conditions in Haiti.
Subsequent tests of samples made from each type of sand provided good news: The compressive strength of both of the types of new test blocks, still composed of Haitian materials, dramatically increased, showing an average over 3,000 pounds per square inch.
"Based upon these results, we now believe that Haitian concrete debris, even of inferior quality, can be effectively used as recycled course aggregate in new construction," says Kurtis. "It can work effectively, even if mixed by hand. The key is having a consistent mix of materials that can be easily measured. We are confident are results can be scaled up mix procedure where quantities can be measured using common, inexpensive construction equipment."
DesRoches is pleased because recycling eliminates two hurdles to reconstruction. "First, removing the remaining debris is nearly impossible because there are few, if any, safe landfill sites near Port-au-Prince, and the nation lacks the trucks and infrastructure to haul it away. It is better to use it than to move it.
"Second," DesRoches says, "Finding fresh aggregate is more difficult than getting rid of the debris. It is costly to find, mine and truck in."
The trio notes recycled concrete aggregate has been used worldwide for roadbeds, drainage, etc., and that many European Union countries commonly use 20 percent recycled aggregates in structural concrete. Published research by others has also demonstrated that the use of local-sourced recycled aggregate concrete production can be more sustainable.
Because of the urgency of quick and safe reconstruction, the researchers urge that recycling the debris quickly move from proof-of-concept to large scale testing. "More work must be done to characterize the recycled materials, test additional performance parameters and gauge the safest ways to crush the rubble. Seismic behavior and building codes must be studied. But, these tests can and should be done dynamically, during reconstruction, because the benefits can be so immediate and significant," says DesRoches.
DesRoches, Kurtis and Gresham say they plan on sharing their research with Haitian government officials and nongovernmental organizations working on reconstruction projects. DesRoches is hopeful that a debris strategy and infrastructure will eventually emerge from the government once the disputed presidential elections in Haiti are resolved. "Some think that many rebuilding projects have on hold for the past few months because of distraction from the elections. The next round of elections is this month, so it soon may be possible to accelerate reconstruction."
Share This Article With Planet Earth
the missing link Space Technology News - Applications and Research
Munich, Germany (SPX) Jan 04, 2011
Everyone has heard that carbon dioxide is responsible for global warming. But the gas also has some positive characteristics. Researchers are now impregnating plastics with compressed CO2 in a process that could lead to new applications ranging from colored contact lenses to bacteria-resistant door handles. CO2 is more than just a waste product. In fact, it has a variety of uses: the chemi ... read more
Microsoft sold 8 mln Kinects in first two months|
Yahoo! adding interaction to Connected TV
Motorola unveils tablet computer, the Xoom
Team Develops Functionally Graded Shape Memory Polymers
IBCS Completes Warfighter-Centered Design Exercises
Arianespace Will Orbit Sicral 2 Milcomms Satellites
Codan Receives JITC Certification For 2110 HF Manpack
Northrop Grumman Bids for Marine Corps Common Aviation CnC
Arianespace says it plans 12 launches in 2011
ILS and Satmex Announce The ILS Proton Launch Of Satmex 8
Ariane 5's Sixth Launch Of 2010
Europe launcher puts Spanish, S.Korean satellites into orbit
Privacy Push Will Impact Geolocation Sector
President Medvedev Sacks Space Officials Over Satellite Loss
Galileo Pathfinder GIOVE-A Achieves Five Years In Orbit
Launch Of New Russian Navigation Satellite Postponed To Next Year
China completes prototype of stealth fighter: reports
France 'confident' of winning Brazil plane contract
Clariant resumes aircraft de-icer output after winter halt
Cathay makes pay offer to pilots: report
Greenpeace ranks 'greenest' electronics
Better Control Of Building Blocks For Quantum Computer
S.Korea's Hynix says chip price slump will hit Q4 profit
Sat-nav turtles go on trans-ocean trek
Cyclone Tasha Adds To Severe Flooding Over Eastern Australia
Tidal Flats And Channels, Long Island, Bahamas
GOES Look Back At 2010
British local authorities rubbished over trash backlog
Britain's rubbish: cold and holidays pile up trash
Ombudsman probes 'outdated' Hong Kong air pollution rules
'250 billion' plastic fragments in Mediterranean
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2010 - SpaceDaily. AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement|