Long-Term Aging Characteristics of Polyphosphoric Acid-Modified Asphalts

Abstract

An experiment involving three neat asphalts and their mixtures with 1.5 wt % of polyphosphoric acid (105%) was conducted to investigate the effect of polyphosphoric acid (PPA) on the long-term aging characteristics of asphalt binders. Analytical techniques including dynamic shear rheometry, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, and nuclear magnetic resonance (NMR) spectroscopy were performed on unaged and aged PPA-modified asphalts. Rheological properties of unaged and aged modified asphalts were measured with a dynamic shear rheometer at various temperatures. The concentration of carbonyl-containing compounds present in the various unmodified and PPA-modified binders was determined by FTIR spectrometry. The thermal properties of the unmodified and PPA-modified binder were obtained by using differential scanning calorimetry. The results indicate that PPA-modified asphalts reduce rutting potential by increasing initial stiffness and reduce fatigue or low temperature cracking, or both by improving the low-temperature flow properties. The correlation between rheological properties and chemical properties of unmodified and PPA-modified asphalts is also presented. The results show a linear relationship between physical properties and chemical properties of asphalt binders with respect to oxidative aging. However, addition of PPA to asphalt alters the linear relationship. NMR results showed no new chemical species formed in the asphalt-PPA mixture.

Effect of temperature and air void on mixed mode fracture toughness of modified asphalt mixtures

“…The optimum percentages of each additive and its mixing temperature with binder have already been obtained and proposed in previous research studies [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41]. The main specifications of each modifier are briefly outlined in the following.…”

“…PPA breaks the asphaltene agglomerates and creates the possibility for better distribution of asphaltene in the molten phase [28,29]. PPA is a mineral polymer in liquid form which is used in order to improve the rheological properties of the bitumen and the asphalt mixtures.…”

“…Thus, it will improve the performance of the asphalt mixture against cracking at low temperatures and against rutting under high temperature conditions. However, this influence significantly depends on the structure of the base bitumen and the used aggregates [28][29][30][31]. PPA consumption rate varies between 0.5 and 1 wt.% of bitumen [28][29][30][31].…”

Effect of Vacuum Residue on Rheological Properties of Low Viscosity Bituminous Binders for Road Construction

“…The importance of phase measurement in prediction of performance is given importance in US -SHRP performance based specification. The permanent deformation of bituminous surface can be controlled by a minimum value of [G*]/sinδ in the high service temperature range 11 . A maximum value of [G*].sinδ in the medium temperature range is important to reduce the risk of fatigue cracking.…”

The Interaction of Polyphosphoric Acid with Bituminous Binders

“…According to Masson, the existence of such areas is speculative, but not impossible. It has also been reported that after modification with PPA, no new chemical species, containing phosphorous compounds were formed in the bitumen-PPA mixture (Huang et al 2008 and.…”