Volume 37, Issue 5 (September 2009)
Significance Evaluation of Material and Additive Factors Influencing Moisture Susceptibility of Asphalt Mixtures
Many factors have been identified to have influences on the moisture susceptibility of asphalt mixtures. This research study attempts to evaluate such factors as binder type, aggregate type, mixture type, additive usage, additive type, additive application approach, and additive organic nature. Tensile strength ratio (TSR) was tested on twelve asphalt mixtures of three types, with two binders and three aggregates, and with improving measures as three antistripping additives and two application approaches. Multiple variable statistical analyses were employed on the TSR data in assessing the significance of the factor. Test results and data analyses indicate that the extent of the influence varies considerably from one factor to another. The styrene-butadiene-styrene modified binder is superior to neat petroleum binder for producing asphalt mixtures subject to damp conditions. Granite, basalt, and limestone aggregates make asphalt mixtures that are least, in-between, and most resistant to moisture damage, respectively. Compared with dense graded asphalt concrete (AC) and stone matrix asphalt (SMA) mixtures, porous asphalt macadam (AM) mixtures are more prone to stripping. The usage of inorganic hydrated lime and Portland cement, and organic amine antistripping agent can substantially improve the moisture susceptibility of asphalt mixtures; the wet approach for applying the inorganic additives can result in better effects than the dry approach. Different additives show little difference in improving effects with mixed trends and the inorganic and organic additives are similar in performance with variations that are immaterial.