This paper presents the results of a laboratory study concerning the effects of the geometric characteristics of aggregates on the fatigue response of bituminous paving mixtures with both asphalt content and percentage of air voids constant. Three coarse aggregates and two fine aggregates, representing both natural and crushed materials were used. The geometric characteristics of these materials were determined by the particle index test for positive, quantitative identification.
The aggregate materials were combined to form three different gradations, and mixed with 6 percent (by weight) of an 85–100 penetration grade asphalt cement. The fatigue response of the various mixtures was determined by subjecting beam specimens to reversed bending at 3 constant stress amplitudes. The test program was designed according to the scheme of a factorial experiment and the data were analyzed in terms of the variances of the factors involved.
The results of the investigation show that the fatigue life of the mixtures increased with the value of the particle index of the fine aggregate. The effect of the fine aggregate was the same for all levels of the applied stress, within chance variation as measured by experimental error. The fatigue behavior of the mixtures tested was not significantly affected by the geometric characteristics of the coarse aggregate, nor was it affected by the gradation of the aggregates in these mixtures.