Flow Properties of Fly Ash Modified Asphaltic Binders

Abstract

This paper investigated the influence of fly ash (FA) on the rheological properties of indigenous Trinidad asphaltic base binders: the world renowned Trinidad Lake Asphalt (TLA) and Trinidad Petroleum Bitumen (TPB). The intricate relationship between the chemical composition of the binder and its influence of the Fly ash additive was evident as changes in the phase angle, δ (a measure of elasticity) and the complex modulus, G* (a measure of stiffness) was not generalized but were different for the modified blends for each of the asphaltic base binders. Incremental additions of Fly ash (up to 8% wt.) to TLA and TPB resulted in a general increase in the complex modulus (G*) indicative of the stiffening of both materials: the stiffening effect being more significant with TLA compared to TPB. Incorporating incremental amounts of Fly ash to TLA resulted in a general decrease in the phase angle (δ): an increase in the elasticity of the blends. Incremental additions of Fly ash into TPB resulted in an opposite trend as the modified blends exhibited marginally decreasing elasticity (phase angle (δ) increasing). A significant finding of this study was the occurrence of a relatively stiffer and more elastic (high G* and low δ values) TLA blend containing 1% fly ash. The rheological property of loss modulus (G″) exceeded the storage modulus (G′) in all instances indicating that the asphaltic blends behaved like a viscoelastic liquid. This study has provided previously unavailable key information which can facilitate the creation of customized asphalt-Fly ash blends to suit special engineering applications thus offering an environmentally attractive option for improving the use of the world renowned TLA as well as refinery TPB.