Nuclear Seminar

Use of the ¹⁵N(p,α,γ)¹²C Reaction for Nanoscale Studies of Cement Hydration

Professor Jeffrey S. Schweitzer
University of Connecticut

Thursday, April 19, 2007**   4:00 p.m.   NSH 124
(Refreshments served prior to seminar in NSH 124)

A better understanding of the mechanisms and kinetics of cement hydration during the induction period is critical to improved concrete technology.  During the induction period a characteristic pattern of reaction layers develops at and just below the surface of the cement grain.  To under-stand the processes that occur, it is necessary to study the time dependence of the reactions on a nanometer scale.  The ¹⁵N(p,αγ)¹²C reaction is particularly well-suited to measure the distribution of hydrogen with depth with a spatial resolution of a few nanometers.  Time-resolved measurement of the hydration profile is achieved by stopping the chemical reactions at specific times.  The mechanism controlling the induction period of tricalcium silicate is a semi-permeable layer on the grain surface.  The diffusion of the hydrogen cannot be represented by a simple Fickian profile, indicating that multiple diffusion and reaction processes are occurring.  The hydration profiles for other common components of cement are significantly different.  The effects of additives on the chemical reactions have also been studied.

**Note different day