High Performance Product Testing Goes Ballastic
- Written by CP Staff
Concrete mix technology and advanced reinforcement methods are spawning high performance products and building systems to meet escalating demand for blast resistance, greater security provisions, and more robust structural solutions in public and private construction. One formulation at advanced testing stages is Ducon micro-reinforced concrete.
Woodcliff Lake, N.J., security specialist Excend Inc. is adapting the German-developed material for the North American market. As the derivation of its name suggests, Excend officials note, Ducon [Ductile CONcrete] comprises a high-performance concrete whose patented design incorporates three-dimensional micro-reinforcement mats infiltrated with cementitious slurry. The matrix provides ductility and high compressive (13,000 psi to 29,000 psi) and flexural strength (2,300 psi to 11,000 psi) for extreme load resistance.
Accordingly, Ducon is said to enhance resistance to blast, ballistics, impact and fragmentation for the protection and fortification of vulnerable facilities, such as embassies, military installations, courthouses, data centers, and critical infrastructure. Moreover, product engineers affirm, high-strength, self-consolidating, flowable slurry lends the material an extremely fine matrix structure that renders Ducon resistant to abrasion and chemical invasion for a wide range of applications requiring impervious overlays, i.e., industrial floors, highway pavements, airport runways, gas stations, and loading areas.
In the first half of 2007, Excend undertook a three-phase effort to develop improved overhead cover solutions for the U.S. Department of Defense at deployed operations bases in the Near East and elsewhere. Fragment-simulating projectiles, 4.2-in. mortars, and bare C-4 explosive charges were used in 45 ballistic and 19 blast tests conducted at the Southwest Research Institute Ballistic and Explosive Range in San Antonio.
Ducon configurations demonstrating successful overhead cover performance included: (1) a standoff roof system comprising a metal panel separated from a 4.74-in. Ducon panel by a 5-ft. gap. Detonation of a 4.2-in. mortar positioned horizontally on the metal panel resulted in no fragment penetrations and minimal structural damage to the reinforced concrete panel; and, (2) A sandwich panel roof system wherein an 18-in. air gap separated 3.25-in. and 4.75-in. Ducon panels. A 4.2-in. mortar positioned horizontally and detonated on the top (3.25-in.) panel led to no fragment penetrations and minimal structural damage.
Bare C-4 charges were used to generate spall and breach at close contact, i.e., 6-in. and 12-in. standoffs. Exhibiting spall and breach resistance significantly greater than that predicted for conventional reinforced concrete, Ducon's superior spall performance was attributed to distributed mesh at the slab surface. Moreover, breach areas Û reduced by an average factor of 3.5 from that predicted for conventional concrete Û demonstrated improved breach resistance, likely due to increased energy absorption capability provided by distributed reinforcement.
Earlier research completed by Germany's Frauenhofer Institute demonstrated Ducon's superior performance against ordinary reinforced concrete of equal thickness. After comparative explosion load testing, Ducon maintained 70 percent of its structural capacity, while the ordinary reinforced concrete exhibited complete failure. Ducon's structural integrity was attributed to its resilience and ductility, which inhibited the type of catastrophic degradation observed at 1995 Murrah Federal Building bombing in Oklahoma City.
Additional testing of Ducon columns and conventionally reinforced concrete columns with Ducon jacketing has shown enhanced blast resistance as compared to that of ordinary concrete columns. Aiding the company as technical consultants were architectural/engineering/construction leaders Charles H. Thornton & Co. LLC, Thornton Tomasetti, and Turner Construction, along with Thornton Termohlen Group Inc. and Weidlinger Associates Inc. Test coordination and consultation were provided by Protection Engineering Consultants, organizer of previous Ducon trials.
Ducon is currently used in Europe to protect vulnerable buildings. Excend plans to license production to qualified precast producers and concrete contractors in North America. Additional information and test reports are available at www.excendinc.com.