Introduction
The objectives of this theme are to develop: a more comprehensive understanding of the microstructures of cementitious materials on all scales; new understanding of their microstructure-property relationships; and, applications of novel microstructural probes for cement science and technology. As for most materials of technological interest, understanding the microstructures of cementitious materials is the key to understanding their physical and chemical properties, predicting performance, and developing methods to engineer materials with desired and controllable properties. Cement microstructures are in many ways more complex than those of other technologically important materials, both because of the presence of hydrous phases with locally variable compositions and microstructural characteristics, and because of the presence of an aqueous phase of variable composition in pores with sizes ranging over many orders of magnitude. Thus, relevant advances in understanding cement microstructures and microstructure-property relationships require this integrated research program involving the use of a wide range of modern analytical tools capable of probing cement microstructure on many scales. ACBM has already made significant advances in this regard, and is now well poised both to bring microstructural understanding of cements to a higher plane and to integrate this understanding with recent advances in understanding of the physical, mechanical, and electrical properties of cements. ^Top

Nanostructure of C-S-H
Understanding a material begins with comprehending its nanostructure (0.1 - 1.0 nm scale) and is an important project in this theme. An integrated investigation of the structure of amorphous C-S-H is being undertaken. As the major strength-forming phase in silicate cements, its formation and properties dominate the microstructure and chemical and mechanical behavior of these materials. Understanding its structure on all scales is essential to a comprehensive prediction of cement behavior. The nanoscale structure, is being probed using mass atomic spectroscopy (MAS), NMR, Ca X-ray absorption (XAS), micro-Raman, and infrared (IR) spectroscopies. In addition, small angle scattering techniques and electron microscopy studies will complement spectroscopic data. ^Top

Pore Structure
Pores are critical components of the microstructure and ACBM will continue to utilize new approaches to probe the pore structure in a non-invasive manner. New techniques utilizing NMRspectropscopy, impedance spectroscopy, and electro-mechanical properties are being used. These studies will now be directed towards a more detailed characterization of the intrinsic porosity of C-S-H and of its interaction with water. The way water freezes within the pore system is being explored in more detail, thereby independently verifying the pore size distribution. ^Top

Coordinator: R. James Kirkpatrick (University of Illinois)

The Nanostructure of C-S-H and Related Materials: An Integrated Investigation
PI: R. James Kirkpatrick (University of Illinois)

Small-Angle Scattering for Microstructural Characterization
PI: J. Francis Young (University of Illinois) and Douglas Winslow (Purdue University)

Pore Structure Characterization of Wet Cement Pastes
PI: William Halperin (Northwestern University)

Microstructure and Image Analysis of Cement-Based Systems
PI: Sidney Diamond (Purdue University)

Study of Shrinkage and Thermal Stresses in High Strength Concrete Containing Silica Fume
PI: Will Hansen (University of Michigan)

Synthesis of Organo-Silicate Composites
PI: J. Francis Young and Walter Klemperer (University of Illinois)