Flying Debris Test


Texas Tech University Flying Debris Test

The Wind Engineering Research Center at Texas Tech University in Lubbock, Texas, tested Greenblock’s 6-inch insulating concrete walls and several other wall systems to determine their resistance to flying debris during a tornado or hurricane. The tests were performed using a compressed air cannon to propel a 15-pound 2×4 wood stud (missile) at over 100 miles an hour at the test walls. (It should be noted that the standard tests for building materials used in hurricane regions is a nine (9) pound object traveling at only 34mph!)

Greenblock’s 6-inch insulating concrete wall performed perfectly. After the 15 pound missile struck the wall at 119.9 mph the results showed “no cracking, front face spalling, or back face scabbing of the concrete core.” The missile splintered!

Wood or “Stick” framing failed miserably. A 2×4 wall with ¾ inch plywood AND a 4 inch brick veneer was penetrated at 64.9 mph with little damage shown on the missile.

CMU or “concrete block” testing also showed significant weakness. A standard 16 inch CMU contains two hollow cells. The missile penetrated the standard 6 inch block at 60 mph. Results comparable to Greenblock’s occurred only when a cell filled with concrete and supported by a #4 steel reinforcing rod was struck by the missile. Translation, for a 6 inch CMU product to compete with Greenblock’s strength, every cell must be filled and reinforced. Even an 8 inch CMU needs to have every cell filled with concrete and reinforcing rods every fifth cell to begin to compete with Greenblock’s strength. [1] Typically, CMU construction calls for a filled cell every 4 feet. That leaves lots of open cells vulnerable to penetration.

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[1] See FEMA’s Commentary on Debris Impact Performance Criteria for Safe Rooms