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This paper includes a summary of an extensive literature review and the experience of the author in researching the properties of surface aggregates. It confirms that to resist wear, the aggregate must be hard and tough, and to resist polishing and surface slipperiness, the aggregate must wear slowly and irregularly. Particle shape, size, and gradation are important characteristics in providing optimum pavement surfaces, but ultimate aggregate performance depends largely on the aggregate mineralogy. A high proportion of hard minerals well cemented in a softer or a porous matrix will provide both high skid resistance and acceptable wear resistance. Within an aggregate particle, grain shape and size contribute to improved performance—medium to large and angular to subangular crystalline grains outperform minute and rounded non-crystalline grains. The performance history of an aggregate provides the best key to its expected future performance. In the absence of experience with an aggregate or when it is to meet new requirements, commonly used tests combined with petrographic analysis should provide sufficiently dependable initial information on the expected aggregate performance. A table that includes suggested target values for properties that enhance aggregate skid resistance and wear resistance is included in the paper.
Professor of civil engineeringMember of ASTM, The Pennsylvania State University, Capitol Campus, Middletown, Pa.
Stock #: JTE10220J