Research as Related to the Development of Aggregate Specifications
Donald W. Lewis, K B Woods · Purdue e-Pubs (Purdue University System) · 1949
Not many years ago aggregates were considered inert materials which served as a filler and, when combined with certain cementitious materials, produced concrete.Years of laboratory study, combined with field experiences, have taught us that aggregates are not inert and that they are a very vital part of a bituminous-aggregate mixture or a portland cement-aggregate mixture.When it is considered that these ma terials constitute 75 percent of the total volume of a paving mixture, it is little wonder that engineers are considering the properties of aggregates with increasing interest.Field surveys of the performance of pavements-both bituminous and portland cement concrete-show striking correlations between the source of coarse aggregates and the performance of the pavement.These findings have been taken to the laboratory, where large-scale research projects have been set up in many sections of the country.The results of both the field and laboratory work indicate that the standard tests, which have been used for many years for acceptance or rejection of mineral aggregates, are not adequate for an accurate determination of the important physical and chemical characteristics of aggregates.The research data developed to the present time indicate that new methods of test are required and that new ideas in specifications are to be forth coming.The great number of reports that have appeared in the past ten years indicate that the major aggregate problems for which standard acceptance tests are inadequate are: (a) mapcracking, disintegration, and associated blowups of portland cement concrete in many sections of * A large part of this paper was presented by K. B. Woods at the Mississippi Valley Conference of State Highway Officials, Chicago, Illinois, March 10-12, 1949, under the title "Research as a Factor in the Development of Aggregate Specifications."** Figures in parentheses indicate references listed in the Bibliography, page 168.