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Description: This report presents in-depth results of laboratory testing comparing the impact resistance of residential concrete wall construction to conventionally framed walls. The damage inflicted on ten wall specimens subjected to the impact of a 15-pound wood stud "missile" traveling at up to 109 miles per hour is described. The study compares the differences in inherent resistance to debris driven by high winds, between concrete wall systems and standard residential construction. Only the concrete walls successfully demonstrated the strength and mass to resist the impact of wind driven debris. This report is also found on DVD021.
Debris driven by high winds presents the greatest hazard to homeowners and their homes during tornadoes and hurricanes. Insulating concrete form (ICF) wall systems provide much greater resistance to the impact of tornado debris than conventional frame construction. Recent laboratory testing at the Wind Engineering Research Center, Texas Tech University, compared the impact resistance of residential concrete wall construction versus conventionally framed walls. The frame walls failed to stop wind driven debris from penetrating. The concrete walls successfully demonstrated the strength and mass to resist the impact of wind driven debris. As a result, the disaster resistance of homes built with ICF wall systems is a significant advantage of this construction technology. Ten wall specimens were subjected to the impact of a 15-pound 2x4 wood stud traveling at speeds as high as 119 miles per hour. The Research Center has determined this to be equivalent to the weight and velocity of debris generated during a tornado with 250 mile per hour winds. Wind speeds are less in 99 percent of tornadoes occurring in the United States. Hurricane wind speeds will be less than the equivalent speeds modeled here. Missile testing designed to mitigate property damage losses from hurricanes use a criterion of a 9-pound missile traveling about 34 miles per hour. The wall specimens were representative of the type of construction now used to build frame homes and concrete homes in the U.S. Four of the test walls consisted of conventional wood or steel framing. Gypsum board was the interior finish for all walls. On the exterior, the specimens were clad in vinyl siding or brick veneer over 3/4" plywood sheathing, or synthetic stucco over gypsum board sheathing. Six concrete walls were constructed. Two were reinforced concrete walls built with removable forms. They were tested with no finishes applied. The remaining concrete walls were constructed with stay in place insulating concrete forms (ICFs). Steel reinforcing bars were placed at common intervals for ICF construction. A standard ICF concrete mix design was specified for the test: a 3000 psi compressive strength, a maximum aggregate size of 3/4", and a 6" slump. The Wind Engineering Research Center's compressed air cannon was used to propel a 2x4 wood stud debris "missile" at the test walls. At all velocities, the missile penetrated through the frame wall assembly. All of the concrete walls were subjected to at lest one impact, with two of the ICF walls tested twice, once on each of the front and rear faces. The velocities of the missiles fired at the concrete walls were all above 96 mph. No cracking, front face scabbing, or back face spalling was observed in any concrete wall tested.
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