Determining the Relative Shear Behavior of Coarse Concrete Aggregate and Associated Matrix

A study of the bond characteristics of carbonate aggregates was made by applyirig shear stresses to 1/8-inch thick slices of highway concrete. It was found that aggregates can be classified as strong, indeterminate, and weak relative to the matrix of the concrete, when accurate lithological cataloging of the aggregates from the source quarry section is made prior to the shear study. Definite classification can only be made in older concretes ( 7-15 years in age) since newer concretes tend to fail in the aggregate-matrix bond zone, making it difficult to observe the relative aggregate strength. The method provides a basis for further study of the aggregates as classified, and a basis for correlating important factors revealed by the studies with the observed quality. Such studies might then be extrapolated to evaluate other quarry sections.