We thank the Partnership for High Performance Concrete Technology of the Building and Fire Research Laboratory for partial support of the work of EJG, and the National Science Foundation Science and Technology Center for Advanced Cement-Based Materials for supporting an annual computer modeling workshop (see http://ciks.cbt.nist.gov/garboczi/) at which the authors first began to formulate their new differential effective medium theory ideas. The work of JGB was performed under the auspices of the U. S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48 and supported specifically by the Geosciences Research Program of the DOE Office of Energy Research within the Office of Basic Energy Sciences, Division of Engineering and Geosciences.