A review of several past studies clearly shows the effect of reduced air voids on improved fatigue and rutting performance of asphalt mixtures, both in the laboratory and field. Depending on mix type and experiment (which included constant-stress bending beam fatigue testing and field results from WesTrack), fatigue performance improved between 8.2 and 43.8% with a 1% decrease in air voids. Lik...

The National Center for Asphalt Technology (NCAT) has undertaken a wide range of hot mix asphalt (HMA) related research projects. These projects have been funded by various agencies such as the National Cooperative Highway Research Program (NCHRP) of the Transportation Research Board, the Federal Highway Administration (FHWA), the Alabama Department of Transportation, the South Carolina Departm...

Background In the early 1970s, due to concern over asphalt cement supply issues and an anticipated over abundance of elemental sulfur, many organizations Société Nationale des Pétroles d’Aquitaine (SNPA), Gulf Oil of Canada, Sulfur Development Institute of Canada (SUDIC), Texas Chemical Company, U.S. Bureau of Mines, and the Texas Transportation Institute) began to evaluate the potential for su...

Fatigue cracking is an essential problem of asphalt concrete that contributes to pavement damage. Although stone matrix asphalt (SMA) has significantly provided resistance to rutting failure, its resistance to fatigue failure is yet to be fully addressed. The aim of this study is to evaluate the effect of crumb rubber modifier (CRM) on stiffness and fatigue properties of SMA mixtures at optimum...

Various models have been developed over the past several decades to predict the dynamic modulus /E*/ of hot-mix asphalt (HMA) based on regression analysis of laboratory measurements. The models most widely used in the asphalt community today are the Witczak 1999 and 2006 predictive models. Although the overall predictive accuracies for these existing models as reported by their developers are q...

Using a rejuvenator to improve the performance of asphalt pavement is an effective and economic way of hot asphalt recycling. This research analyzes the rejuvenating effect on aged asphalt by means of a Mortar Transfer Ratio (MTR) test, which concerns the ratio of asphalt mortar that moves from recycled aggregates (RAP aggregates) to fresh added aggregates when aged asphalt is treated with a re...

Reducing start and stop time without destroying the pavement surface is important in enhancing productivity of double-drum roller and compact quality of asphalt pavement, but it is difficult in confirming the maximum brake deceleration or start acceleration of double-drum roller. Dynamic analysis is used in studying these questions, and a mathematic model of double-drum roller is established, b...

The bearing capacity and service life of a pavement are adversely affected by the presence of undrained water in the pavement layers. In cold winter climates, such as in Iowa, this problem is magnified further by the risk of frost damage when water is present. Therefore, wellperforming subsurface drainage systems form an important aspect of pavement design by the Iowa Department of Transportati...