EFFECT OF AGGREGATE GRADATION AND TYPE ON HOT ASPHALT CONCRETE MIX PROPERTIES

Mineral aggregates make up 90 to 96% of a HMA mix by weight or approximately 75 to 85% byvolume. The properties of the mineral aggregates have significant affects in performance of ourroadways which offers the possibility of investment in these properties towards resisting differentranges of external applied loads and environmental conditions. Therefore, aggregate characteristicsdeeply affect the performance of asphalt pavements. Gradation is one of the importantcharacteristics of aggregates affecting permanent deformation of hot mix asphalt. The objective ofthis research is to investigate the impact of aggregate gradation variations on various properties ofasphalt concrete mixtures. Fine, medium and coarse gradation mixtures for different aggregate typeswere tested to investigate the effects of variation in the aggregate types and gradation on mixproperties. The asphalt contents of the mixes were maintained at the job mix design contents.Properties investigated were, Marshall Stability, Marshall Flow, unit weight, air voids, and voids inmineral aggregate. Analysis of the considering different aggregate type data revealed that the finecoarseand coarse-fine gradation variations had the greatest impact on mix.The research program concentrated on the Marshall Design criteria for bituminous mixes. Theresults indicated that optimum asphalt content (OAC) is different due to aggregate type A coarsegrading with 25 mm maximum size is found to give the most satisfactory result from the stand pointof stability, stiffness, and voids characteristics. Test results reveal that the bituminous concrete withWCA can give satisfactory results when they are constructed using coarse gradation.