Gaurav N. Sant, Ph.D.

Associate Professor and Henry Samueli Fellow

Department of Civil and Environmental Engineering

Henry Samueli School of Engineering and Applied Science

University of California, Los Angeles -UCLA

Concrete, a mixture formed by mixing cement, water, and fine and coarse mineral aggregates is the primary structural material used in the construction of nuclear power plants (NPPs), e.g., to construct the reactor cavity concrete that encases the reactor pressure vessel (RPV) etc. In such environments, concrete may be exposed to radiation (e.g., neutrons) emanating from the reactor core. Until recently, concrete has been assumed relatively immune to radiation exposure. Direct experimental evidence acquired on Ar⁺-ion irradiated calcite and quartz indicates that, on the contrary, such minerals, which constitute aggregates in concrete, may be significantly altered by irradiation. Specifically, while quartz undergoes disordering of its atomic structure resulting in a near complete lack of periodicity, i.e., similar to a glassy silica, calcite only experiences random rotations, and distortions of its carbonate groups. As a result, irradiated quartz shows a reduction in density of around 15%, and an increase in chemical reactivity (described by its dissolution rate) of ≈3 orders of magnitude. Calcite however, shows little, if any, change in dissolution rate – but its density noted to reduce by ≈9%. These differences are correlated with the nature of bonds in these minerals, i.e., being dominantly ionic or covalent, and the rigidity of the mineral’s atomic network that is characterized by the number of topological constraints (n_c) that are imposed on the atoms in the network. The outcomes are discussed within the context of the durability of structural concrete elements formed using calcite or quartz containing aggregates in NPPs.

Biography:

Gaurav is an Associate Professor and Henry Samueli Fellow in the Department of Civil and Environmental Engineering, and a Member of the California Nanosystems Institute at the University of California, Los Angeles (UCLA). Gaurav received his B.S., M.S., and Ph.D. in Civil Engineering from Purdue University in 2006, 2007 and 2009 respectively. Gaurav has published over 90 papers in refereed journals and conference proceedings. Gaurav’s research which is focused at the interface of materials science and civil engineering seeks to develop new understanding of structure-property relations in material systems encompassing: cement, concrete, metals, glasses, synthetic and natural minerals and hard biological tissues. Specific emphasis is placed on understanding reaction processes at solid-solution interfaces – and the relevance of such processes in: dissolution, precipitation, corrosion, microstructure formation, and mass transport.