AFRL Investigates Blast Response of Insulated Concrete Published Jan. 15, 2008 By Materials and Manufacturing Directorate AFRL/ML WRIGHT-PATTERSON AIR FORCE BASE -- AFRL researchers entered into a Cooperative Research and Development Agreement (CRADA) with the Portland Cement Association to research the response of insulated concrete products to explosive blasts. Under the CRADA, the Portland Cement Association will provide AFRL with insulated concrete products from several different trade associations, representing a wide range of product designs. AFRL will investigate material behavior and structural response to blast pressure loads. This research will provide valuable information concerning each product's ability to withstand explosive blasts; it will also help engineers accurately predict material behavior in the face of threats often included in the design criteria for government facilities. During Phase I of the agreement, engineers began investigating 13 mature products already in wide use throughout the commercial market, including two precast, prestressed sandwich panel products; four concrete masonry products; two tilt-up products; and five insulated, stay-in-place concrete forms. AFRL engineers constructed a three-story reaction structure to conduct the full-scale explosive experiments necessary for validating the engineering models developed to predict blast response for each insulated concrete product. Once validated, the models will facilitate the development of tools (e.g., range-to-effect charts) that engineers can use to determine whether a particular product can protect against a specified blast threat. In Phase II, engineers will focus on insulated concrete products that are recent additions to the market, using the same process of developing predictive models and conducting full-scale validation experiments. Determining validity is primarily a matter of measuring wall deflection and reflective pressures during the full-scale experiments. The goal is to achieve a 5%-15% over-prediction of deflection by the models, along with a good timing match between model response and gauges measuring peak deflection during the experiments. This over-predicted model deflection then yields engineering tools with inherent factors of safety desirable in all structural design decisions. Once the engineers are able to deem a model as an accurate predictor of blast response, they will begin Phase III of the CRADA. This phase will involve materials testing in the lab, combined with parametric studies that use Phase I and II computer models to identify material or design modifications capable of delivering improved blast protection. To validate model predictions, Phase III will also include essential full-scale experiments conducted on products manufactured according to any specified modifications.