COMPARISON OF VOLUMETRIC PROPERTIES OF MARSHALL AND SUPERPAVE FOR NHA MIXES

Abstract

Roads are the main mode of transportation in Pakistan. The aim of this research is the comparison of volumetric properties between Marshall and Superpave Mix design methods. Marshall Mix design method is in practice for many years. The new design method called the Superpave method has replaced the Marshall method for design of asphalt pavements in the USA. Roads in Pakistan are designed mostly on the basis of Marshall Mix design guidelines. The asphalt mixes made for the roads according to these specifications have failed to handle the traffic and environmental conditions in Pakistan. The impact compaction with Marshall Method does not allow mixture densification as it is commonly found in roads. The Marshall method doesn’t stimulate the field compaction, while Superpave design stimulates the field method of compaction. The Ideal condition should be if the mixtures to be tested are prepared and compacted as close to the field condition as possible, so that they can be representative of the mixtures to be produced and put in the field. Margalla hills aggregate was used procured from Taxilla. Binder was procured from Attock refinery. NHA gradation class A was used for the preparation of samples for both Marshall and Superpave Mix design method. Total of 15 samples were prepared for each grade (60/70 and 80/100) of binder using the Marshall method. The samples were prepared at (3, 3.5, 4, 4.5 and 5) percent binder content. Approximately 1200 grams samples were prepared for Marshall Method. The Optimum binder content was estimated for each grade of binder. The volumetric properties were estimated for each binder content and also at the optimum binder content. Similarly total of 9 samples were prepared for each grade of binder using the Superpave Method. Samples were prepared at (3.5,4 and 4.5) percent binder content. Volumetric properties were estimated for the Superpave method at all the binder contents and at the optimum binder content. The volumetric properties of Marshall and Superpave methods were compared graphically and statistically. The outcomes of the findings were.(a) Optimum binder content of the Superpave mix method is less than the Marshall mix method.(b) VMA calculated from the Superpave mix method is lower than that of Marshall Mix method at any binder content.