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National Institute of Standards and Technology
Building Materials Division, 226/B350
Gaithersburg, Maryland 20899 USA
There seems to have been some confusion in recent years regarding the stress and displacements induced in a concrete material when either the matrix, the aggregate, or a shell around the aggregate is expansive. The case of a single spherical aggregate, surrounded by a single shell of arbitrary thickness, all of which are embedded in a matrix, can be solved exactly for any combination of elastic moduli and expansive strains. Solutions of this problem under various choices of parameters are used to illustrate the features of stress, displacement, and expansive cracking that are possible. These solutions can then be used to help better understand the features seen under the microscope in concretes that have been damaged by different expansive forces.