ARTICLE - RECYCLED CONCRETE SAFE, STRONG

SCIENTISTS SUGGEST RECYCLED HAITIAN CONCRETE IS SAFE, STRONG, CHEAPER
(Sify News) - ANI

Concrete experts at the Georgia Tech have made new concrete, from recycled rubble and other indigenous raw materials using simple techniques.

"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," said Reginald R. DesRoches.

DesRoches and Joshua J. Gresham studied the methods, tools and raw materials used by local labourers to make concrete mixes.

Neither encountered any 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 said.

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.

Back at the lab, tests indicated that the Haitian-made concrete had an average compressive strength of 1,300 pounds per square inch, while US standards require it to be a minimum of 3,000 pounds per square inch.

Next, they manually crushed the samples with a hammer to provide course aggregate. Then 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 showed that 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," said Kimberly E. 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."

"Finding fresh aggregate is more difficult than getting rid of the debris. It is costly to find, mine and truck in," said DesRoches.

The trio said they plan on sharing their research with Haitian government officials and nongovernmental organizations working on reconstruction projects.

The study is published today in the Bulletin of the American Ceramic Society.