FRACTALS, FRACTURES, AND SIZE EFFECTS IN CONCRETE

Correlation between fractal dimensions and fracture properties in ceme ntitious material is reported. Wedge splitting tests of specimens as m uch as 1.52 m (5 ft) long and having 7.62-cm (3-in.) maximum size aggr egate were first performed to determine fracture toughness K(lc) and f racture energy G(F). Subsequently, one of the split parts was mapped u sing a profilometer to provide detailed one-dimensional profiles. Fina lly, the fractal dimension of the profiles was determined by a special ly developed computer program. The fracture surfaces are fractal over the measured range of scales, and the fractal dimension is independent of crack trajectory. There is a weak correlation between the fracture properties and the fractal dimensions. The implications of the fracta l nature of the cracked surfaces on the fracture energy G(F) are discu ssed, as is the relationship between a fractal analysis and the size e ffect law.