Mechanistic Enhancement of Asphaltic Materials Using Fly Ash

Background and Objective:The influence of the waste fly ash on the rheological properties of asphalt is unique and varies from material to material due to differences in the chemical composition of the binders.Previous studies show that the optimal fly ash dosages required for mechanical enhancement can range from 2-10% added fly ash.The lack of studies involving Trinidad Lake Asphalt (TLA) and Trinidad Petroleum Bitumen (TPB) has limited the use of fly ash as not only a possible performance enhance but an environmentally sustainable disposal method for the waste fly ash.Materials and Methods: Dynamic shear rheology was used to measure the rheological properties of complex modulus (G*) and phase angle (δ) of prepared blends and the fatigue cracking resistance and rutting resistance parameters (G*sinδ and G*/sinδ, respectively) were calculated.Results: The differences in rheological responses due to the addition of fly ash to the TLA and TPB are linked to the composition differences between the two materials.The fatigue cracking resistance of the TLA and TPB parent binders were superior compared with their fly ash modified blends.The TLA blends containing between 1-2% added fly ash exhibited particularly low cracking resistance as seen from the G*sinδ maxima.The rutting resistances of the TLA and TPB blends generally increased with incremental fly ash additions with the 1% TLA fly ash blend exhibiting the highest rutting resistance.Previous studies using other base asphaltic materials obtained higher optimal dosages between 2-10%.Conclusion: Fly ash additions to TLA and TPB generally improved rutting resistance while decreasing the fatigue cracking resistance at optimal dosages of fly ash below 2%.The study demonstrates the possibility to create customized Trinidad asphalt-fly ash blends to suit special applications and offers an environmentally attractive option for the reuse of waste fly ash.