Launch Slideshow

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Changing the Face of Construction

Changing the Face of Construction

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    About 30,000 square feet of reinforced concrete tilt-up walls at a facility in Phoenix were repaired with a hybrid carbon/S-gla ss wrap to provide seismic protection and lateral sheer reinforcement.

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    In testing sponsored by the Department of Defense, two unreinforced concrete masonry walls were constructed within a larger containment structure, with each wall being 8-ft. wide x 11-ft. high. One wall served as the control specimen, and the other was retrofitted with Blastek inside and outside.

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    A TNT explosive blast destroyed the control wall on the left, while the protected wall on the right remained intact.

Masonry applications

HJ3 focuses its research and development efforts on creating unique solutions for strengthening masonry. In 2005, the company introduced ArmorWall, which is designed to strengthen bowing and cracked foundation walls. The product is packaged in kits that include rolls of 4-inch-wide, pre-cured carbon straps and a single component epoxy that bonds the carbon straps to foundation walls. Each strap is less than 1/16-inch thick, but delivers tensile strengths equivalent to a 3/8-inch steel plate.

Like steel I-beams bolted to basement walls, the carbon straps counteract external soil pressure that causes walls to crack and bow. However, unlike steel I-beams, the carbon straps create minimal surface loss and easily blend into the wall surface, creating an aesthetically pleasing repair.

Another system—Blastek—is comprised of advanced carbon fiber composites specifically engineered to mitigatd and contain blast energy. “The concept is similar to retrofitting walls for earthquakes,” says Saadatmanesh.

“Most walls are not designed for the live loads created by impact or blast waves. The inertia from these events causes the walls to cycle back and forth, weakening the mortar joints and crushing the masonry, which leads to collapse.”

In testing sponsored by the U.S. Department of Defense at the Energetic Material Testing and Research Lab in New Mexico, 212 pounds of TNT were detonated 33 feet away from two unreinforced masonry walls—a control specimen and a wall retrofitted with Blastek. The explosion created a blast wave at the face of the un-reinforced masonry walls that measured a peak load of 180 psi.

Upon impact, the control specimen was obliterated, but the wall retrofitted with Blastek remained completely intact. The system allowed only 1.4 of the 180-psi force to transfer to the other side. Following the explosion, vibration in the wall quickly attenuated and it came to rest in the original position.

The application of high-strength composites to masonry in need of structural repair, retrofit, seismic upgrading, and blast protection represents the beginning of the transformation the materials could deliver to the construction industry. While the technology provides unprecedented benefits to standard masonry construction, it also offers solutions as the industry confronts new challenges, such as the damage caused by the earthquakes that sacked major cities in Iran, Pakistan, and Turkey, and the hurricanes that ravaged the South in 2005.