Postdoctoral Fellow (PREP0004134) Full-time

Postdoctoral Fellow

This position is part of the National Institute of Standards (NIST) Professional Research Experience (PREP) program. NIST recognizes that its research staff may wish to collaborate with researchers at academic institutions on specific projects of mutual interest, thus requires that such institutions must be the recipient of a PREP award. The PREP program requires staff from a wide range of backgrounds to work on scientific research in many areas. Employees in this position will perform technical work that underpins the scientific research of the collaboration.

Research Title: Understanding Concrete Foundation Deterioration by Modeling the Impact of Pyrrhotite

The work will entail: Damage to concrete structures in residential and commercial construction in central Connecticut has been attributed to the iron sulfide mineral pyrrhotite. Iron sulfides in concrete aggregate are not desirable as their relative instability results in decomposition with associated staining, expansion, and pop-outs near concrete surfaces or, in severe cases, cracking of the structure. There are no standardized test methods to assess pyrrhotite occurrence and abundance in aggregate or in concrete due to its low concentrations while still having a significant impact. Developing a standard test method, including a set of calibration reference standards will provide a means for accurate, consistent analysis of pyrrhotite in concrete. An improved understanding, based on modeling and experimental data, of the pyrrhotite/aggregate/concrete reaction types, reaction rates, and reaction product impact on concrete expansion, is needed so that the most deleterious reactions can be efficiently reduced or eliminated.

In this opportunity, the PREP researcher will develop models to better understand the microstructural characteristics relevant to the internal sulfate expansion phenomena, including its volume expansion.

Key responsibilities will include but are not limited to:

• Chemo-mechanical modeling to simulate the expansion and the damage in concrete
• Thermodynamic modeling to evaluate the reactions in cement phases due to pyrrhotite oxidation
• Crack progression modeling using Finite Element Model (FEM) to simulate cracking behavior due to internal phases expansion
• Moisture transport modeling that considers the distressed concrete due to pyrrhotite
• Surface coating simulation modeling
• Interfacing with NIST experimentalists to support and validate modeling work
• Analyzing modeling results and drafting manuscripts

Qualifications

• Ph.D. in Chemistry/ Physics/ Mechanical Engineering/ Chemical Engineering/ Civil Engineering
• Minimum of one year of experience of modeling pyrrhotite reactions and resulting damage in concrete with proof of peer-reviewed publications
• Knowledge of concrete durability, i.e., chemo-mechanical modeling, diffusion, thermodynamic modeling.
• Extensive knowledge of FEM, and programming skills in Fortran and C++.
• Strong oral and written communication skills
• Currently living in the United States
• U.S. citizenship is preferred