Abstract
The purpose of this investigation is to examine the effect of the strength and surface condition of coarse aggregate on the fracture of concrete under uniaxial compression. The two-phase model specimens consisted of a cylindrical coarse aggregate and mortar matrix were used to simplify the study. Three kinds of compressive strength and five kinds of surface condition were provided for coarse aggregates. The following conclusions were obtained by this investigation. 1) Regardless of the surface roughness of aggregate, the fracture process of model concrete with an aggregate whose compressive strength (Fca) is smaller than that of mortar matrix (Fcm) was as follows; (1) initiation of bond crack between aggregate and mortar matrix, (2) tensile cracking of mortar matrix and aggregate parallel to the longitudinal axis, (3) local compressive failure of aggregate and (4) failure of model concrete. 2) The fracture process of model concrete with an aggregate whose strength is larger than that of mortar matrix was as follows; (1) initiation of bond crack, (2) tensile cracking of mortar matrix, (3) local compressive failure of mortar matrix at the vicinity of aggregate and (4) failure of model concrete. 3) The compressive strength (Fcc) of model concrete increases with the increase of the value of Fca in the range of Fca/Fcm<1, but never increases in the range of Fca/Fcm>1, regardless of the surface ronghness of coarse aggregate.
