Use of Limestone Screenings in S-5 Surface Mixes: Final Report

About the report:

It is often practical to use limestone screenings in non-polishing S-5 surface mixes in some western areas of Virginia. Also, there has been some conjecture that limestone increases the durability of these mixes. Although the fine aggregate usually has a minimal effect on the skid resistance of bituminous pavements, there were no skid data available for S-5 mixes containing approximately 20% limestone screenings. The purpose of this study was to obtain such data and to determine if the limestone affects the durability of the S-5 mix. The durability was assessed by performing stripping tests and Marshall tests on several mixes containing various amounts of limestone screenings. The results of skid tests indicated that satisfactory skid resistance can be achieved using mixes with moderate levels of limestone screenings. The limestone did not significantly affect the Marshall properties; however, two of the three mixes tested showed an increased susceptibility to stripping. Thus, contrary to the supposition, limestone screenings did not improve the durability of the mixes.

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