Size Effect in Concrete

Abstract

The present paper addresses the important question of the effect of size on the rupture strength of plain concrete by focusing on the underlying phenomena in the mesoscale of the material. The formulation is based upon the experimentally confirmed premise that the rupture strength depends on the probability that the preferentially oriented plane contains the largest defect. Since the defect size has been shown to be related to the aggregate size, a rational solution of the problem can be derived knowing the distribution of coarse aggregate sizes (sieve grading) in the concrete mix. The proposed model, based on the stochastic representation of the concrete mesostructure, uses some well‐known principles of the statistics of extremes to predict the concrete rupture strength. The actual failure of the specimen is shown to occur when the most preferentially oriented microcrack (oriented perpendicular to the applied tensile stress) overcomes the inherent energy barriers of the mesostructure and propagates in an unstable manner until it splits the specimen. Even though the derived solution is not adorned with additional fitting parameters, it readily replicates the experimentally observed trends. No constants or parameters are introduced that cannot be readily determined from an experimental procedure.