The effects of percent fracture and fines content on the laboratory performance of asphalt mixtures were investigated. The objective of this study was to develop an approach for the effective utilization of crushed aggregates in Alaskan highway and airfield pavements. In addition, current Alaskan specifications were evaluated in light of this laboratory testing.
The repeated load diametral test device was used to measure the mixture performance in terms of modulus, permanent deformation, and fatigue. Experimental variables included percent fracture, percent passing the 200 sieve, and aggregate source. Testing was conducted at temperatures representative of Alaskan environmental conditions.
Test results show optimum asphalt contents to be minimized at approximately 8%. At the temperatures tested, modulus changes could not be attributable to fracture levels. Significant reductions in laboratory lives were noted when fines contents were varied from the 6% level currently specified.
Laboratory testing indicates the current specifications for fines content is appropriate and, in fact, the mid-range value of 6% maximizes fatigue lives when standard Alaskan pavement sections were analyzed. At the temperatures tested, little increase in fatigue life can be attributed to increase in fracture.