After 30 years of studying the variable and illusive microstructure of cement-based materials, Jennings developed the first successful, fully quantitative model of the nanostructure of calcium silicate hydrate (C-S-H), the major component of hydrated cement. The model was originally based on highly scattered and contradictory surface area and density data mostly published in the 1950's and 60's.
The model has been further developed to form a basis for quantitatively predicting static properties, as measured for example by nanoindentation techniques, and linking these relationships to the design of new materials. Also, the model is being extended to larger scales, greater than 100 nm. It accounts for observation obtained by sophisticated techniques — cutting edge electron microscopy and small angle neutron scattering — that reveal a specific complex fractal structure. New phase diagrams have been proposed that rationalize disparate data published by Jennings' research group and by other workers during the last 50 years.
In addition, this research has laid the foundation for solving the 100-year-old question about the mechanism that controls the rate of hydration of cement. Jennings has also developed an analogy between the structure of C-S-H and a gel or precipitate. This facilitates an interpretation of changes in the microstructure induced during drying, as well as opening the door to applying new research results to colloids in general.
Awards and Honors
Copeland Award, American Ceramic Society, 2004
Fellow and Chartered Engineer, Institute of Materials, United Kingdom, 1994
Fellow, The American Ceramic Society, 1993
“A Constitutive Model for Drying of a Partially Saturated Porous Material,” (Ivan Vlahinic, Hamlin Jennings, and Jeffrey J. Thomas), Mechanics of Materials, 41, 319-328 (2009).
“Influence of Nucleation Seeding on the Hydration Mechanisms of Tricalcium Silicate and Cement,” (Jeffrey J. Thomas, Hamlin Jennings, and Jeffrey J. Chen, Journal of Physical Chemistry C, 113, 4327-4334 (2009).
“A Model for the Microstructure of Calcium Silicate Hydrate in Cement Paste,” (H.M. Jennings), Cement and Concrete Research, 30,  101-116 (2000).
“Simulation of Microstructure Development During the Hydration of a Cement Compound,” (H.M. Jennings and S.K. Johnson), Journal of the American Ceramic Society, 69  790‑795 (1986). Received Best Paper Award, 1986.
“Aqueous Solubility Relationships for Two Types of Calcium Silicate Hydrate,” Journal of the American Ceramic Society, 69  614‑618 (1986).