Influence of Aggregate Gradation and Nominal Maximum Aggregate Size on the Performance Properties of OGFC Mixtures

The effect of aggregate gradation and nominal maximum aggregate size (NMAS) on the performance properties of open-graded friction courses (OGFC) mixtures was investigated in this research. Several tests which included porosity, surface texture, indirect tensile strength (ITS), shear strength, and Cantabro abrasion loss were used to compare eight different aggregate gradations having two NMAS (9.5 mm and 12.5 mm) all from one aggregate source. For each NMAS, the gradations varied by adjusting the percent passing the No. 4 (4.75 mm) sieve. The results indicated that aggregate gradation does influence the behavior of OGFC mixtures. An increase in percent passing the No. 4 sieve showed significant decreases in porosity, which were more pronounced for the 12.5 mm NMAS compared with the 9.5 mm NMAS. Conversely, the increase in the percent passing the No. 4 sieve generally resulted in increases in the mixture performance properties as measured by the ITS, Cantabro loss, and shear strength. The results of this st...