摘要：

The objective of this study was to evaluate the engineering properties of two local unbound granular materials, with a focus on the gradation and especially the percentage of fines (aggregate passing the No. 200 sieve). Two materials were obtained from two local quarries for this purpose. The percentage of fines was varied in these mixtures. Each mixture was then put through a regime of tests to determine the effects that the gradation and fines content had on their properties. The tests used included moisture-density relationships, moisture susceptibility, triaxial tests, permanent deformation, and resilient modulus tests. The research approach, testing procedure, and results are presented and compared. From the tests performed it was found that increases in the amount of fines have a large impact on the engineering properties of the base materials. However, the results also showed that the percentage of fines used in the base material mixtures had a limit. This limit was found to be approximately 10%. In the range of 5 to 10% fines the base is less moisture susceptible, has higher compressive strength and a higher resilient modulus value. The Texas Department of Transportation (TxDOT)is the only DOT in the United States which does not control the -200 fraction of its flexible bases. It is not uncommon to find bases with between 20 and 25% passing the -200 sieve. The laboratory data presented in this study would suggest that TxDOT should conduct field investigations to determine if the low fines bases lead to improved field performance.

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