IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 _______________________________________________________________________________________ Volume: 04 Special Issue: 01 | NCRTCE-2014 | Feb-2015, Available @ http://www.ijret.org 178 COMPARING PROPERTIES OF BITUMINOUS CONCRETE MIXES PREPARED USING MORTH AND SUPERPAVE GRADATIONS P. Sarika 1 , A K Sandra 2 1 Post Graduate Student, University of Texas, Arlington 2 Manager, GMR Infrastructure Ltd., RGI Airport, Hyderabad Abstract Hot Mix Asphalt (HMA) consists of two basic ingredients: aggregate and asphalt binder. HMA mix design is the process of determining Optimum Binder Content which satisfies the Marshall Properties. In the mix design process, selection of suitable aggregate gradation plays an important role in performing the pavement during its service life. In India, MoRTH guidelines are to be followed in selecting the aggregate gradation. Sometimes, it is difficult to achieve the gradation specified by MoRTH due to restrictions in upper and lower limits. It was observed that the gradation specified in SuperPave Mix design which is followed by majority of countries worldwide has little flexibility as compared to the MoRTH gradation. Hence, in the present study Marshall Properties were studied by following two aggregate gradations MoRTH and Superpave. The results obtained from the laboratory experiments shown that the SuperPave aggregate gradation is superior than the MORTH aggregate gradation in almost all the criterions of strength and volumetric parameters. Keywords: Hot Mix Asphalt (HMA), MoRTH, Superpave --------------------------------------------------------------------***------------------------------------------------------------------ 1. INTRODUCTION The top layers of a flexible pavement, particularly the surface course has to withstand high stress conditions and wear and tear due to traffic loads. In addition, the surface course is exposed to adverse climatic factors including temperature variations, water, etc. Therefore, properly designed high quality hot bituminous mixtures are to be laid on the surface course of flexible pavement. The high quality bituminous mixes consist of well graded hard aggregates and suitable bituminous binder of correct proportion. In the bitumen concrete mixes, 95 percent by weight is occupied by aggregate and hence, the structure formation in terms of gradation plays an important role [1, 2]. The particle size distribution, or gradation, of an aggregate is one of the most influential aggregate characteristics in determining how it will perform as a pavement material. In Hot Mix Asphalt (HMA), important performance related parameters including stiffness, stability, durability, permeability, workability, fatigue resistance, frictional resistance and moisture susceptibility depends on aggregate gradation [3, 4]. In PCC, performance parameters including durability, porosity, workability, cement and water requirements, strength, and shrinkage depends on distribution of aggregate particles. Because of this, gradation is a primary concern in HMA and PCC mix design and thus most agencies specify allowable aggregate gradations for both. Since, the gradation has a propound effect on material performance, it is necessary to select the best gradation. In general, the best gradation is nothing but the gradation which produce the maximum density. This would involve a particle arrangement where smaller particles are packed between the larger particles, which reduce the void space between particles. This creates more particle-to-particle contact, which in HMA would increase stability and reduce water infiltration. In case of HMA mixes voids space is important to occupy the volume of bitumen and to coat over the aggregate. Also, some more void space is required to re- adjust the bitumen when it became soft during hot climate and due to re-adjustment of particles due to secondary compaction. Considering these factors a suitable aggregate gradation is very much essential. In the present study six aggregate gradings were designed, three as per Ministry of Road Transport and Highways (MoRTH) [5] and three as per SuperPave. At various bitumen content, Marshall Mixes were prepared and tested for its properties. 2. MATERIALS USED. 2.1 Asphalt Cement Asphalt cement of grade VG30 obtained from HPCL Visakhapatnam, AP, India, was used for the study. Table 1 shows the physical tests of the asphalt.