The Waffle-Crete precast panel system is being used for earthquake- and hurricane-resistant housing.
A cutaway of the Waffle-Crete mold.
More than one year after an earthquake ravaged Haiti and its capital, Port-au-Prince, more than 1 million people may still be homeless. They live in tent cities, on the streets, and anywhere else they can find temporary comfort.
Although exact figures will never be known, many estimate more than 200,000 people were killed and 190,000 homes destroyed in the earthquake that struck the Caribbean nation on Jan. 12, 2010. More than a year later, much rebuilding remains.
To put the task in perspective, The Washington Post reports it took five years to replace 139,000 homes that were destroyed on one island by the tsunami in Indonesia in 2004. Another source of concern is the pace at which rubble is being removed in Haiti. The newspaper reported that at the current pace, it will take at least three years to finish removing the crumbled buildings.
A precast concrete building solution is being called on to help in the rebuilding effort. The French construction company, Demathieu & Bard, has selected the Waffle-Crete portable precast building system as part of its strategy to secure a lead role in Haiti's reconstruction.
“Waffle-Crete is an ideal building system to meet Haiti's disaster resistance and cost objectives,” says Louis Charette, general manager of Technopref Industries, a U.S.-based subsidiary of Demathieu & Bard that is leading the company's effort there.
The system comes with many advantages. It has passed rigorous testing for extreme wind and seismic loads, ideal for an island located on a fault line and subject to hurricanes. The wall and roof panels can be cast directly on the jobsite one day and then erected the next.
“Another key is unskilled Haitian labor can be employed to do the casting and erecting,” says Larry Lightman, general manager of Waffle-Crete International, based in Hays, Kan. “This not only contributes to lower construction costs, but it also increases the number of locals who can participate and profit from the reconstruction process.”How it works
Waffle-Crete panels retain the design strength of traditional precast panels, but are up to 60% lighter than standard panels of the same thickness, says Stephen Andrews, an engineer with Professional Engineering Consultants, Topeka, Kan. Three system components make this possible: vertical ribs, horizontal ribs, and a thin shell called the skin.
The vertical rib acts as both a column to support compression loads and as a beam to withstand bending loads. As load requirements increase, the rib depth can be increased to compensate, but without a significant increase in material volume that a standard flat concrete panel would require.
Horizontal ribs provide lateral support to the vertical ribs and also help redistribute large loads throughout the panel. The skin ties the ribs together and allows the panel to act as a shear wall when required.
Waffle-Crete molds and curing covers are fabricated from ABS plastic and a rigid extruded aluminum frame. With reasonable care, the molds and covers can last for many years and hundreds of uses.
After a panel is cast, insulated Waffle-Crete covers help maintain optimal conditions for curing while also protecting the panel from the elements. The curing cover allows the panel temperature to climb up to 150° F while minimizing shrinkage and cracking. The next day, simply loosen the bolts at the corners of the mold, strip the panel using a Waffle-Crete demolding device, and stack it for erection. This panel design also simplifies installation of plumbing, electrical components, and insulation.
“Because of its structural capabilities, and when partnered with a design team that understands its strengths, the efficiency of precast concrete can save money by reducing the construction time-line. Controlled casting conditions can allow a more consistent product to be produced,” says Andrews. “In addition to these benefits, the reduced material requirements of the Waffle-Crete system gives producers another option to meet their design and cost objectives.”
Waffle-Crete has been used for cooling towers, retaining walls, and multistory hotels. Lightman says the system achieves the most economic and social value when used on disaster-resistant construction. So the company is focusing exclusively on this growing global need.
For more information and to see jobsite videos, visit www.waffle-crete.com.