Laboratory evaluation of hedmanite and lime modified asphalt concrete mixes

Abstract

The area of asphalt additives and extenders is somewhat complex, a variety of products and suppliers exist, and the evidence of behavior and performance is largely scattered and inconclusive. For these reasons, prospective users in the Kingdom's highway agencies are facing a rather difficult task in sorting out this subject and assessing whether or not a particular additive or extended can be applied to their problem as per the environment and loading conditions, and with what technical and economic effectiveness.

In view of the situation this investigation was undertaken to evaluate the effectiveness of a new additive called "Hedmanite" (Rookwool natural fibers) as a filler in the local road paving mixtures. AbuHadriyah aggregates were used to pepare control mix as well as modifed mixes having different percentages of hedmanite and lime as a substitute to conventional crushed stone filler in the aggregate gradation. Optimum asphalt content was obtained by Marshall method for the control mix for both wearing coarse and base coarse gradation, and was used in all the modified mixes. Mixes were evaluated for engineering properties and it was found that certain percentages of both hedmanite and line are effective in improving the resilient modulus of the mixtures, while the marshall stability loss and tensile strength loss is higher in hedmanite mixes. Creep test shows no specific trend for the MOC gradation used in this study. Lime modified mixes shows better resistance to fatigue and rutting than the hedmanite modified mixes. Results indicates that high quality asphalt concrete mixes can be prepared using lime as a filler than the material hedmanite for the local aggregates.