SYMPOSIA PAPER Published: 01 January 2001

Effects of Fine Aggregate Angularity on VMA and Rutting of Kansas HMA Mixtures


With the recent introduction of Superpave, mix designers in Kansas have had difficulty meeting the voids in the mineral aggregate (VMA) requirements. To meet VMA, designers have been importing chat, a flaky fine aggregate of nearly pure chert produced as a by-product from lead and zinc mining, to boost VMA.

The objectives of this research were to evaluate the effect of fine aggregate angularity (FAA) on VMA and rutting. Two 12.5-mm Superpave gradations, one coarse and one fine, were developed using 100% crushed limestone. To change the FAA of the mix, the fine aggregate was replaced with natural sand and chat, a byproduct from lead and zinc mining. The resultant VMA and FAA of each blend was compared and samples were tested for rutting.

The results indicate that increased FAA results in greater VMA, after exceeding a minimum, and decreased rutting. Chat was shown to be effective at increasing VMA but reduced stability. Meeting Superpave mix requirements did not insure a stable mix.

Author Information

Cross, SA
University of Kansas, Lawrence, KS
Purcell, EM
University of Kansas, Lawrence, KS
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Developed by Committee: D04
Pages: 95–109
DOI: 10.1520/STP10802S
ISBN-EB: 978-0-8031-5457-5
ISBN-13: 978-0-8031-2892-7