This award supports members of the NSF Science and Technology Center for Advanced Cement-Based Materials at Northwestern University, headed by Professor Surendra P. Shah, to collaborate with members of the Department of Civil Engineering of the Technische Hochschule Darmstadt, Germany, directed by Professor Gert Koenig. They are joining their resources and expertise in experimental research to determine the factors that influence the strain softening response of concrete in uniaxial compression and tension. The research plan combines the expertise of TH Darmstadt in large-scale structural testing and design with the knowledge of materials science being developed at the Center for Advanced Cement-Based Materials. Recent advances in concrete technology have made it possible to make concrete with compressive strength more than double that of normal strength concrete. This high strength concrete is used more and more in current construction, because of perceived beneficial characteristics, but there is growing evidence that it is being used improperly in some cases. The increased strength is due in part to an improved bond between the cement-based matrix and aggregate in concrete. However this improved bond makes the high strength concrete more brittle than normal concrete. The failure mechanisms are poorly understood. Different failure mechanisms result in different strain softening response. A better understanding of the strain softening response will help to define the appropriate use of this new material.
