Analysis of Foaming Properties of Asphalt Binder Through a Laser Based Non-Contact Method

Abstract

Water injected foamed asphalt application in warm mix asphalt (WMA) accounts for more than 90% of all WMA technologies in past several years in the United States (US). Among different asphalt foaming variables: foaming temperatures, foaming water content (FWC), and air pressure are the major controlling factors of foamed asphalt binder characteristics. Foaming induced binder volume expansion and durability of the expanded volume are two contributing factors of foamed asphalt binder properties and foamed mixtures workability. This study evaluates the effect of FWC on foamed asphalt binder properties through a non-contact method. A laser distance meter has been utilized to record the foaming induced binder volume expansion and subsequent foamed bubbles collapse rate. Recently developed four foaming parameters such as expansion ratio (ER), half-life (HL), foaming index (FI), and stability of semis-table foamed binder bubbles (k-values) have been evaluated to characterize foamed asphalt binder. It is seen that addition of higher FWC results in a higher expansion and durability of overall foamed bubbles. Foaming parameter analysis also shows that semi-stable foamed bubbles durability is fairly constant in higher FWCs. Foamed binder rheology is also found to be correlated with FWCs.