38th Henry M. Shaw Lecture

What's the Matter with Concrete? A Multiscale Approach to the Development of Sustainable Materials and Structures

• February 5, 2009 (1:30 PM; 216 Mann Hall)
• Dr. Franz-Josef Ulm
  Professor of Civil and Environmental Engineering
  Massachusetts Institute of Technology

After water, concrete is the material the most consumed on Earth. The current annual rate of worldwide cement production stands at 2.4 billion tons, enough to produce one cubic meter of concrete per capita and year. But concrete faces an uncertain future due to the ecological footprint of cement production: Each ton of cement produced equates to one ton of CO2 released that is the equivalent of 5,000 car km of driving, or equivalent to the absorption capacity of a tree, absorbing CO2 over a 100 years! Despite the ubiquitous presence of this material forming the backbone of our societal needs for housing and infrastructure, the nanobehavior of concrete is still an enigma. In this talk, I present recent developments in nanoscience and nanoengineering of concrete. Evidence from an original statistical nanoindentation technique shows that the calcium-silicate-hydrate (C-S-H) phase, the hydraulic binding phase of all cementitious materials, has a unique nanomechanical signature.  This signature is characterized by unique low- and high-density packing arrangements of 5nm sized nanoparticles, found to be packed close to the random packing limit of spherical particles (64%), or packed around the ordered limit packing density of spherical objects (74%), similar to oranges in a grocery shop (Keppler's conjecture). Molecular Dynamic (MD) simulations provide evidence that these limit packings of nano-sized particles are necessary to stabilize an intrinsically metastable molecular structure. These conclusions do not only hold for concrete but for many other materials: clays, bones, etc. Furthermore, bridging between MD simulations and nanoindentation, I will conclude that this nanomechanical code of cement-based materials yields a new basis for the nanoengineering of sustainable concrete materials and structures. This will be illustrated through the recent design of the “bridge of the future”, a multiscale ultrahigh performance engineering design of the next generation of US Highway bridge girders.

After water, concrete is the material the most consumed on Earth. The current annual rate of worldwide cement production stands at 2.4 billion tons, enough to produce one cubic meter of concrete per capita and year. But concrete faces an uncertain future due

Biographical sketch: Franz-Josef Ulm is a Professor of Civil & Environmental Engineering at the Massachusetts Institute of Technology. He received his engineering degree from the Technical University Munich, Germany, in 1990, his Ph.D. from the Ecole nationale des ponts et chaussées, France, in 1994; and his abilitation Degree from the Ecole Normale Superiéure de Cachan, France in 1998. His current research focuses on experimental and theoretical nanomechanics of natural composites, microporomechanics, and biochemomechanics. Dr. Ulm has published over 80 scientific papers in peer-reviewed mechanics, materials science, and biomechanics journals, and four books; most recently ‘‘Microporomechanics’’ (co-authored with L. Dormieux and D. Kondo).