A rational asphalt concrete (A) mix de ign and analysi methodology wit developed. The term'rational''meant that the material properties evaluated in the mixture de ign and analysis could be u ed with a layered-ela tic pavement model and mcchanislicempirical formulation that relate to pavement performance. The procedures proposed in this srudy were intended to be u ed in conjunction wir11 the current Texas State Department of Highway and Publi Transp nation method or mix design in ac mptementary fa hion. Three 1nc1jor modes of pavement distrcs-(a) rutting,(b) flexural fatigue, and (c) low-temperature cracking-were addressed. In addition t'O mixture properties, structural~ trrangement of pavement layers and envir mnental ractors have signific~ nt effect, on the performance f A mixture. Therefore a comprehensive mix de ign sh uld nt be performed independent of pavement structural design. A phnlt mix design and pavement structural design p< tram ter· w re brought toge th r in an integrated fashion.

Hot-mix asphalt (HMA) mix design has long been a trial-anderror process. Two major empirical methods of mix design have emerged as those most commonly used by the asphalt community. The Hveem (ASTM D1560) and Marshall (ASTM D1559) methods have evolved over the past four decades. They are both regarded as empirical methods. There are many variations of these basic methods (see Figure 1) in use among state highway agencies (1). Texas State Department of Highways and Public Transportation (SDHPT) has its own unique method of mix design, which is basically a modified Hveem procedure (2).