Research Interests

[Development of Low-pH Concrete/Shotcrete for Deep Geological Disposal of High-Level Radioactive Waste and Identification of Cement-Bentonite Interaction]

The goal of this research is to: 1) develop 'alternative materials' for concrete plugs and shotcrete used in the engineered barrier system for the deep geological disposal of high-level radioactive waste, 2) conduct long-term performance assessments of the developed materials considering THMC coupled conditions, and 3) establish a predictive model for the performance/lifetime of cement-based materials in the engineered barrier system by identifying cement-bentonite interactions. In this context, the alternative materials are designed to have low pH (below 10-11) characteristics to prevent degradation of the bentonite-based buffer and backfill materials due to reaction with alkaline leachate.

[Development of innovative design details and strategic utilization of high-performance materials for enhanced performance of concrete structures]

We have tried to solve problems related to current design details for concrete structures and to provide innovative design methods for improved performance and lower construction costs. We also have focused our efforts in solving problems for the use of high-performance construction materials and to provide new design details for these materials. We have performed extensive research programs (especially large-scale structural testing), such as 1) bond characteristics of UHSC and UHPFRC/UHPFRC; 2) UHSC columns under concentric compression, eccentric compression, and combined axial and cyclic moments (simulated seismic loading) and; 3) axial load behavior of slab-column connections.

[Structural behavior of concrete under different strain rates of loadings (static, seismic, impact and blast loadings) and strategic design details to improve the response for these loadings]

Conventional concrete structures have been designed to resist static loading or seismic loading. However, bomb explosions and collisions of vehicles against structures are of great interest due to widespread terrorist activities in various parts of the world. There has been some research in these fields as well, but this area is still in its infancy. Carrying out research in such new areas provides many challenges. We are currently carrying out a research project that is aimed at understanding the behavior of reinforced concrete and ultra-high-performance concrete under extreme loading using the drop-weight impact testing machine, shock tube testing machine as well as field blast tests

[Development of innovative construction materials for structural applications by using experimental and microscopic approaches]

We have been heavily involved in the development of 200 MPa ultra-high-strength concrete in collaboration with Samsung Construction & Technology Corporation. This involved the making of a large number of concrete batches and testing to evaluate the mechanical properties of this concrete. Along with this experimental approach, we also performed analysis on particle size distribution of raw materials as well as the interfacial zone between the cement paste and aggregate. We are also trying to provide a fundamental understanding of the failure mechanisms of UHSC structural members to eliminate the extremely brittle failure modes. In assessing the response the Damage Rating Index (DRI) and the Stiffness Damage Test (SDT) are used.