General report

Summary

An understanding of the behavior of aggregates when used in concrete is necessary for that concrete to perform satisfactorily in service. There are as many as fifty aggregate properties that may have an influence on the properties of both freshly mixed and hardened concrete. The large number of papers presented at this session of the symposium is evidence of the desire for that understanding. Considerable progress has been made in the field of concrete technology. Since aggregates occupy approximately 75 percent of the volume of concrete, considerable investigations have been performed to improve selection, testing and evaluation of aggregates. In selecting new aggregate sources representative samples and detailed geological investigation are necessary. Petrographic analysis should be mandatory. However a petrographic analysis is far more meaningful if the petrographer recognizes the service condition to which the aggregates are to be used and the limitations of the concrete constituents to perform under those anticipated service condition. Also more detailed and new test procedures are needed to properly evaluate the aggregates used in concrete.